UNIVERSITY OF ILLINOIS LIBR RY AT URBANA-CHAMPA1GN AGRICULTURE I Characteristics, Classification, & Adaptation of in selected areas in SIERRA LEONE WEST AFRICA Bulletin 748 Agricultural Experiment Station College of Agriculture University of Illinois at Urbana-Champaign Bulletin 4 Njala University College University of Sierra Leone This bulletin is published as a cooperative effort between the University of Illinois at Urbana-Champaign and the Njala University College, Univer- sity of Sierra Leone. It is also included in the University of Illinois Interna- tional Publication Series I of the Office of International Programs and Studies and is Publication 2 in the Research Series of the University of Illinois Office of International Agricultural Programs. Urbana, Illinois November, 1974 c c laracteristJcs, assification & Adaptation o in selectedareas in SIERRA LEONE WEST AFRICA R.T Odell J. C Dijkerman, W van Vuure, S. W Melsted, A H. Beavers, P M. Sutton, L.T Kurtz, and R. Miedema During the preparation of this bulletin Professor R. T. Odell and Professor S. W. Melsted held joint appointments with the University of Illinois at Ur- bana-Champaign and the Njala University College, University of Sierra Leone. J. C. Dijkerman, former Senior Lecturer; W. van Vuure, former Lec- turer; P. M. Sutton, Assistant Lecturer; and R. Miedema, former Junior Re- search Fellow, were members of the staff at Njala University College, Uni- versity of Sierra Leone. Professor A. H. Beavers and Professor L. T. Kurtz are members of the Department of Agronomy, University of Illinois at Urbana-Champaign. no. Contents Acknowledgments ........................................... v SUMMARY ............................................. 1 INTRODUCTION ......................................... 2 SOIL FORMATION FACTORS ................................ 4 3:1 . Climate .......................................... 4 3:2. Parent Materials, Topography, and Time .................. 5 3:2:1 . Physiography ................................ 5 3:2:2. Geology and parent materials ................... 10 3:2:3. Topography ................................. 10 3:2:4. Time ...................................... 11 3:3. Living Organisms ................................... 11 3:3:1. Plants ...................................... 11 3:3:2. Animals .................................... 13 SOIL CHARACTERISTICS, GENESIS, AND CLASSIFICATION ......... 14 4:1. Soil Provinces in Sierra Leone and Relationships Among Soils in the Areas Studied ................................ 14 4:2. Major Processes Active in Soil Formation .................. 14 4:2:1. Accumulation of organic matter in the surface soil ..... 14 4:2:2. Mineral weathering, leaching of soluble substances, and formation of secondary minerals .............. 17 4:2:3. Illuviation of clay, iron, or organic matter ............ 18 4:2:4. Formation of gley, plinthite, and hardened plinthite glaebules ................................... 18 4:2:5. Formation of a gravel-free surface layer ............ 19 4:3. Amount and Characterization of the Clay Fraction .......... 19 4:3:1. Mineralogy of the clay fraction .................. 19 4:3:2. Total analyses and cation-exchange capacity of the clay fraction .................................... 24 4:3:3. Amount of water-dispersible clay ................. 24 4:4. Amount and Significance of Exchangeable Aluminum ........ 25 4:5. Area B* — Sandy Beach Ridges and Lagoons .............. 27 4:6. Area C* — Tidal Swamps ............................ 29 4:7. Area D* — Alluvial Floodplain Grasslands ............... 31 4:8. Area G* — Rokel River Series in the Njala Area ........... 33 4:8:1. Soils on upland erosion surfaces and steep hills ....... 33 4:8:2. Soils on colluvial footslopes and upper terraces and in swamps .................................... 36 4:8:3. Soils on stream terraces ........................ 42 4:8:4. Soils on alluvial floodplains ...................... 44 4:9. Area J* — Granite and Acid Gneiss, Makeni Area 46 4:9:1 . Soils on steep hills or inselbergs 47 4:9:2. Soils on upland erosion surfaces 47 4:9:3. Soils on colluvial footslopes and upper terraces and in swamps 51 4:9:4. Soils on alluvial floodplains 56 4:10. Area L* — Granite and Acid Gneiss in the Upper Moa Basin, Kenema Area 57 4:10:1. Soils on steep hills 58 4:10:2. Soils on upland erosion surfaces 59 4:10:3. Soils on colluvial footslopes and upper terraces and in swamps 62 4:1 0:4. Soils on alluvial floodplains 64 4:1 1. Comparison of Soils in the Boliland Region (Area I*) With Those in Adjacent Areas G* and J* 64 4:11:1. Comparison of soils in Area G* and Area I* 65 4:1 1 :2. Comparison of soils in Area I* and Area J* 65 4:1 2. Taxonomic Classification of Soil Series 65 4:1 2:1 . Diagnostic horizons 65 4:12:2. Comparison of the soil classification described in Soil Taxonomy with the FAO/UNESCO and French systems 67 4:1 2:3. Soil classification 69 5. ADAPTATION AND MANAGEMENT OF SOILS 76 5:1 . Important Factors in Soil Grouping 76 5:2. Capability Grouping of Soils 76 5:3. Soil Management Suggestions 77 5:4. Principles of Soil Fertility 82 5:4:1 . Well-drained and aerated soils 82 5:4:2. Poorly drained soils without excess sulfur 83 5:4:3. Tidal swamp soils high in sulfur 83 5:5. Management of Selected Crops 84 5:5:1. Rice 84 5:5:2. Maize 85 5:5:3. Plantation crops 85 5:5:4. Other crops 86 Literature Cited 86 Appendix A. Climatic Data for Selected Stations in Sierra Leone 89 Appendix B. Descriptions and Analytical Data for Selected Soil Profiles. . 97 Appendix C. Amount and Characterization of the Clay Fraction in Selected Soils in Sierra Leone 1 87 Appendix D. Established Soil Series in Sierra Leone, Soil Province in Which They Occur, Diagnostic Horizons, Thickness of Gravel-Free Layer, and INDEX for Soils Described in This Publication 193 ACKNOWLEDGMENTS Most of the cooperative work from which results are reported in this publi- cation was done between 1965 and 1972. It is impossible to mention everyone who has contributed to it, but the authors are deeply grateful to the following organizations and individuals who made special contributions to the soil survey field work, made laboratory analyses, or gave financial support: Njala University College Special thanks are due the administration of Njala University College for continuing support of this work. Messrs. T. N. J. Lamboi, J. M. Cawray, and their laborers were indispensable in the soil survey field work and contributed greatly to it. Mr. E. A. Okine kindly drafted the soil map of the Njala area. University of Illinois at Urbana-Champaign Messrs. Victor Gabriel, J. M. Parker, and Chusok Chavengsaksongkram did many of the laboratory analyses of the soil samples. Mr. D. R. Phillips drafted all the figures except the soil map of the Njala area. United States Agency for International Development Funds for part of the research and for printing this publication were provided through contracts USAID/Afr-293 and /Afr-648. Food and Agriculture Organization of the United Nations FAO supported the soil survey field work of Dr. S. Sivarajasingham and Mr. J. Stark in the Kenema area. Dr. Sivarajasingham's work was especially helpful in elucidating the genesis of soils in eastern Sierra Leone. Agricultural University of Wageningen, The Netherlands Messrs. H. Breteler, E. R. Jordens, and D. H. Westerveld, former Junior Re- search Fellows at Njala University College and former students from the Agricul- tural University of Wageningen, assisted with the soil survey field work in the Njala area and Torma Bum area. I. Summary The research results that are reported in this publica- tion have come from cooperative work by many indi- viduals and several institutions. Staff members of Njala University College, University of Sierra Leone, and of the University of Illinois at Urbana-Champaign have done most of the work, but important contributions were also made by other individuals and institutions, recog- nized in the Acknowledgments. This publication presents the results of recent research on important soils in six of the 16 recognized soil prov- inces in Sierra Leone. Soil maps are included for parts of five of the six soil areas that were studied. Major empha- sis is given 44 soil profiles, representing 34 soil series, for which detailed field and laboratory data are given. The genesis of the soils is discussed, and each of them is classified according to three systems: the comprehen- sive Soil Taxonomy system that is used in the United States of America and many other areas, the FAO/ UNESCO soil classification system, and the French soil classification system. The soils are grouped according to their suitability for agricultural use, and suggestions are given concerning their management. All this information is presented in a way that will help improve the manage- ment of Sierra Leone soils now, provide a framework in which to learn more about Sierra Leone soils and their proper management, and furnish a mechanism for ex- changing useful soils information with other countries in the humid tropics. On the basis of criteria in Soil Taxonomy, the soils belong to the following orders in progressively decreasing importance: Ultisols, Inceptisols, Oxisols, Entisols, and Spodosols. Many of the Ultisols and Inceptisols have oxic properties and, therefore, are near the Oxisol border. In the FAO/UNESCO soil classification system, the predominant soils are Nitosols, Cambisols, Ferralsols, and Gleysols. In the French classification system, many of the well-drained soils are Sols ferrallitiques and the poorly drained soils are often Sols hydromorphes, with smaller areas of other classes. The clay fraction of most of these soils is predomi- nantly kaolinite, which typically makes up 45 to 75 per- cent of this fraction. Other clay minerals in progressively smaller amounts are gibbsite, chlorite, illite, quartz, and goethite. There is also a unique suite of interstratified minerals composed of illite with chlorite or vermiculite in various combinations. These interstratified minerals are important only in soils that developed from sediments of the Rokel River Series in west-central Sierra Leone. There are marked differences among the soils and areas that were studied intensively. The soils on the beach ridges along the coast are very sandy and have very little agricultural value. They range from nearly pure quartz sand with few or no soil horizons to soils that have distinct horizons. The clayey soils that occur in tidal swamps along the coast and up adjacent stream estuaries have unique prop- erties and management problems. They contain excess sulfur, which may produce extreme acidity if there is too much drainage and oxidation. Under careful manage- ment, including proper water control, these soils can be used effectively for swamp rice production. The well-drained and moderately well-drained alluvial soils that occur on the floodplains of the larger streams are among the most productive soils in Sierra Leone. They are usually fine textured (clayey) and have favor- able physical properties, but they need to be fertilized to produce profitable yields. These soils are subject to occasional brief flooding. Because they are near water that can be used for irrigation during the dry season, they can produce up to three crops annually. On stream terraces and colluvial footslopes from the uplands, many soils are well drained and many are poorly drained. Some of these soils have hardened plin- thite glaebules of gravel size in their subsoils. The well- drained soils are adapted to a wide range of annual and perennial crops if fertilizers and other improved manage- ment practices are used. The poorly drained soils are well suited to swamp rice production, especially if water con- trol is practiced. Gravelly upland soils are the most extensive ones in Sierra Leone; in many inland areas, such as around Ken- ema, Makeni, and Njala, they compose approximately two-thirds of the landscape. These gravelly soils are low in productivity because they not only are low in fertility but also are droughty during the dry season as a result of low moisture-holding capacity. These soils are used to produce upland rice, cassava, and groundnuts in a tradi- tional slash and burn system of shifting cultivation. Their agricultural potential is low, however, and they are better adapted to tree crops and forestry. Steep bedrock hills, often of granite, are scattered throughout the upland in the eastern half of Sierra Leone. These areas of Rock Land have no value for agri- culture or forestry, but the natural vegetation should be maintained on them for watershed protection, wildlife use, recreation, and esthetic purposes. 2. Introduction This publication brings together the results of recent research on the soils in five areas in Sierra Leone near Torma Bum, Rokupr, Njala, Makeni, and Kenema (Fig. 1) . These represent six of the 16 soil provinces in Sierra Leone (Fig. 8), since the Torma Bum area represents two soil provinces. These areas occur between approxi- mately 7° 20' N to 9° 0' N latitude and 10° 16' W to 13° 0' W longitude. This cooperative work was done by staff members of the Agronomy Departments of Njala University College and the University of Illinois, except for the soil survey field work in the Kenema area, which was done by Dr. S. Sivarajasingham and Mr. J. Stark and supported by the Food and Agriculture Organization of the United Nations. Detailed soil reports have been prepared for the Torma Bum, Njala, Makeni, and Ken- ema areas, to which further reference will be made in the appropriate sections of this report. The size of these areas for which soil maps are available is as follows: Area Acres Torma Bum Njala Makeni Kenema 43,400 14,400 26,200 1,335,700 Hectares 17,600 5,800 10,500 540,550 A detailed soil map is included for the Njala area, and soil association maps are included for the other areas. These soil maps are based on detailed field observations of soils along traverses at appropriate intervals, plus interpretations of aerial photographs to extend soil boundaries into areas not seen directly. No soil map or report has been published for the Rokupr area. Of the soils identified in the areas studied, special em- phasis is given 44 soil profiles, for which detailed descrip- tions and laboratory analyses are given in Appendix B. The genesis of the soils is discussed. On the basis of field and laboratory data, the various soils are classified in Section 4:12 according to the comprehensive soil classifi- cation system (69) 1 used in the United States of America and in many other areas, the FAO/UNESCO soil classi- fication system (25) , and the French soil classification system (2,3} . Comparisons among these soil classification systems are made to facilitate the international exchange of information concerning tropical soils. The soils are grouped according to their suitability for agricultural use, and suggestions are given concerning their manage- ment (Section 5) . The primary objectives of this report are to consoli- date information from separate areas into an integrated whole; add data that were not available previously; pre- sent information on the characteristics, distribution, clas- sification, and adaptation of soils so that they can be used and managed efficiently; and provide a framework within which soils in other areas of Sierra Leone, West Africa, and the humid tropics can be studied and char- acterized in order to improve soil management and food and fiber production. Section 4:11 briefly summarizes the characteristics of soils in the Boliland Region, as reported by Stobbs (70). Of special interest are comparisons between these soils, which developed from Rokel River sediments under sa- vanna vegetation and seasonally swampy conditions, and soils in the Njala area, which developed in the same par- ent material (Rokel River Series) but under forest vege- tation and better drainage. 1 Italicized numbers in parentheses refer to entries in Litera- ture Cited. SECTION 2 0 IP 20 3O 40 50 Kilomttiri 0 10 20 30 MiltC ROAD RIVER AREA STUDIED BY THE AUTHORS BO LI LAND AREA STUDIED BY STOBBS (70) Figure 1. Location of areas studied in Sierra Leone, West Africa. 3. Soil Formation Factors Soils are formed by the alteration of parent material under the influence of climate and living organisms, as conditioned by topography over a period of time. These five soil-forming factors — climate, living organisms, par- ent material, topography, and time — differ in various parts of Sierra Leone, and so do the soils. These factors also strongly influence the suitability of a soil for agri- culture. 3:1. CLIMATE Sierra Leone has a hot, tropical climate with distinct rainy and dry seasons. Four main types of weather may be recognized : thunderstorms and squalls, steady rains, dry weather with high humidity, and dry weather with low humidity. They are distributed through the annual cycle as follows: Rainy season (May— November) Thunderstorms and squalls Steady rains Thunderstorms and squalls Dry season (December— April) Dry weather with high humidity Short periods of dry weather with low humidity (Harmattan) Dry weather with high humidity Thunderstorms and squalls occur from May through June and from October through November; that is, at the beginning and end of the rainy season. Thunder- storms accompanied by heavy rains travel east to west against the general wind direction. They are usually pre- ceded by a squall of easterly wind. These thunderstorms are responsible for most of the rainfall at those times of the year. Their intensity and frequency are highest in June and October. Towards the beginning and the end of the rainy season the thunderstorms decrease in fre- quency and intensity, and the weather is very changeable. The relative humidity throughout the rainy season is high. Steady rains occur from July through September; that is, during the middle of the rainy season. Rainfall is frequent and often heavy. Most of the annual rainfall occurs during this period. The wind is southwesterly. The sky is mainly overcast, and sunshine is rare. The relative humidity is between 95 and 100 percent. The temperatures are at their lowest, and the diurnal range of temperature is small. In some years, there is a short pause in the rainy season in July or August, characterized by clear and humid weather with little precipitation. Such a pause is more likely in extreme southeastern Sierra Leone than elsewhere in the country. Dry weather with high humidity occurs during most of the dry season. Skies are usually clear and, therefore, day temperatures are relatively high. The nights are also warm and very humid. Heavy dew and fog often occur during the night and early morning. Winds predomi- nantly come from the west. Short periods of dry weather with low humidity (Har- mattan) usually occur between late December and early February. The lengths of these periods vary from a few days to a number of weeks. The weather is characterized by a sudden drop in relative humidity from almost 100 percent to sometimes as low as 20 percent. This is caused by dry eastern or northeastern winds from the Sahara. The sky is clear but often obscured by a dust haze. The temperatures are relatively high during the daytime and low at night. The stability of the air prevents precipita- tion. Evapotranspiration is high because of the low rela- tive humidity and the high temperature. Although the annual cycle of the various types of weather discussed above applies to all of Sierra Leone, there are distinct differences in climatic data of various parts of the country. Details about the climate of Sierra Leone are presented in Sierra Leone in Maps (16) and the Atlas of Sierra Leone (72) and by Bartrum (4) and Gregory (35) . Appendix A in this publication contains a collection of rainfall, temperature, relative humidity, sunshine, and evaporation data for selected stations in Sierra Leone. Differences with respect to mean annual rainfall and wet and dry season rainfall are illustrated in Figure 2. The wet season is most extreme in the coastal area, with 120 to 200 inches (3,048 to 5,080 mm) or more of rain- fall, and least in the north, with rainfall of from less than 80 to 100 inches (2,032 to 2,540 mm). The dry season is most severe in the north, having less than 5 inches (127 mm) of precipitation, and least in the central east- ern part, with 10 to 15 inches (254 to 381 mm) or more of rainfall. The intensity of the rainfall is very high. For Bonthe, a maximum daily rainfall of 11.68 inches (297 mm) has been reported; Freetown has had a maximum hourly rainfall of 5.91 inches ( 150 mm) . Temperature data are illustrated in Figure 3. Febru- ary, March, and April have the hottest days with mean monthly maximum temperatures of 86° to 93°F (30° to 34°C) near the coast and 93° to 99°F (34° to 37°C) inland. July and August usually have the coolest days with mean monthly maximum temperatures from 81° to SECTIONS 3:1-3:2:1 MAY _ NO V. DEC _ APR Figure 2. Mean annual, wet season, and dry season rain- fall distribution in Sierra Leone (after Gregory, in J6). 83°F (27° to 28°C). Inland nights are coolest in Decem- ber, January, and February with mean monthly mini- mum temperatures as low as 57° to 68°F ( 14° to 20°C) . During the remainder of the year, minimum tempera- tures vary little from 68° to 74°F (20° to 23°C) but are depressed slightly in June, July, and August. Nights are much warmer along the coast, and reported mean monthly minimum temperatures range from 73° to 78°F (23° to 26°C) with the coolest nights in July and August. For the Njala station, some soil temperature data arc available. Soil temperatures at 6 and 12 inches depth show only slight variations. In 1966, 1967, and 1968, the mean annual soil temperatures were 81 °F (27°C) at 9 a.m. and 87°F (31 °C) at 3 p.m.; corresponding air tem- peratures were 69°F (21 °C) at 9 a.m. and 90°F (32°C) at 3 p.m. Thus, the mean soil temperature is closer to the maximum than to the minimum air temperature, and the daily range in soil temperatures is much smaller than that of the air temperatures. Relative humidity is very high, often close to 100 percent for the greater part of the day and night, espe- cially during the rainy season. However, during the Har- mattan, relative humidity may be as low as 20 percent. Mean monthly relative humidity at 3 p.m. in August ranges from about 90 percent along the coast to 75 per- cent in the northeast; in January it ranges from about 60 percent along the coast to 30 percent in the north- east. Evaporation data are scarce. Some open-pan and Piche evaporation data from weather stations at Njala, Torma Bum, and Makeni are given in Appendix A. Al- though some of these data may not be entirely reliable, the general trend is clear. Evaporation is highest during February and March and lowest in August. The same trend is shown in Figure 4 by the potential evapotrans- piration data as calculated according to Papadakis (60) . These data should be considered as approximations be- cause few parameters are used in the calculations. Ac- cording to these estimates, mean annual potential evapo- transpiration is relatively low at the coast — 37 inches (930 mm) at Freetown, for example — and increases with distance from the coast in a northeasterly direction : 74 inches (1,877 mm) at Musaia is an example of one of the higher values. The annual soil moisture regime depends on the dif- ference between evapotranspiration and precipitation throughout the year (see Fig. 4). During the dry season, potential evapotranspiration greatly exceeds the rainfall so that a distinct water deficit develops in most soils. The length of the period of soil moisture deficiency, which also depends on the available soil moisture-holding ca- pacity, ranges from 5 months to 1 month for well- drained to imperfectly drained soils and from 3 to 0 months for poorly to very poorly drained soils. During the rainy season, precipitation greatly exceeds evapo- transpiration. In soils where the excess water cannot be drained away quickly, waterlogging will occur and plant roots may suffer from oxygen deficiency. Soils dif- fer greatly in their ability to discharge excess water rapidly. Some soils are never waterlogged, while others are submerged for four to five months. The soil moisture regimes of various soils in selected areas of Sierra Leone are indicated in Section 4, and some of this information is summarized in Table 2 (pages 16 and 17). 3:2. PARENT MATERIALS, TOPOGRAPHY, AND TIME The geology and physiography of Sierra Leone have been described by Dixey (26, 27), Pollet (62), and in Sierra Leone in Maps (16). A geological map is pre- sented in Figure 5 and a physiographic map in Figure 6. 3:2:1. PHYSIOGRAPHY Sierra Leone consists of four broad physiographic re- gions: the Peninsula Mountains, the coastal plain, the interior plain, and the interior plateau and hill region. The Peninsula Mountains, located near Freetown, are the result of a large basic intrusive body of gabbro, prob- ably of Precambrian age. The present youthful topog- BULLETIN NO. 748 o o 0° 0 ro CM 2 o si i/. - 0 * z 5 B • I Z .. 0 ' 1 1 B • i . CO \\ 1 • •>• E / 1 1 /"/"T 3 CO I o _, z 7 T T E s ; ; ; Z ^ 4 ' c 1 \ TIT i - S •\ *\ \ • U. B • »• . •^ i i ^J- (O 00 O CM 0 CO (O 1 1 in to ULm 0 0 o 5 00 ro CM o o •• r ./ i / . • 0 !tt\! \ z o \ \ 1 " CO 7*T 0> I 7/*r a* » "c -> 0 / t \ o • • V CO 2 1 1 1 gin - Z 1 EV«V . u. -s <3" (O CO O CM 0 CO (O in ro o O o 0 0 0 ro CM 2 o B«» ' " O • 1 1 1 ° \T E - z ZITT z - o i >•» . CO \i "rr c o 41 I r?r rrr :rr il: o> *~ S w Ll. — -» r— *. X S u. ^> CO 00 O CM o CO CO in ro o o 1- 8° 8 2 o "' 7 r o x B • l» z o | I | S T T o • • i CO N\ 1 TTT § I /•/•r s •0 h- •z. • * ^ T> -> o ' / 1 • • «• s 5 / / 1 rgj \ z "\ *\ \ - ! 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G*,J*,L* L* L* G* I* J* J* I* I* G* I* J* L* L* L* J* L* I* G* I* J* G* I* J* L* Stream terraces and swamps 10-24 inches (25-60 cm) of gravel-free, fine- loamy alluvium over gravelly material or groundwater laterite or both Sandy alluvium Fine-loamy alluvium . Fine-loamy and clayey alluvium with a thick, dark surface Rock Land (5,0) Vaahun (3,'/2) Segbwema (3,0) Mandu(3,Vj) Momenga (4,0) Belia (4,0) Mabanta (5,0) Timbo (4,0) Diabama (4,0) War! (4,0) Njala (5,0) Batkanu (5,0) Makeni (5,0) Makoima (4,1) Mayanki(4,l) Waima (4,0) Mabassia (4,0) Baoma (4,0) Rosinth (5,0) Fanima (4,0) Manowa (4,0) Giema (3,0) Belebu (4,0) Ngelehun(3,0) Panderu (2,1) Mokonde (4,0) Batiema (3,3) Malinka (4,0) Matutu (4,2) Bonjema (4,'/j) Pelewahun (2,3) Mankahun (4,0) Masuri(4,1) Bosor(4,0) Tubum (4,0) Tisso (3,0) Masebra (3,3) Massimo (2,4) Madina (3,3) Romankne (2,4) Panlap(2,3) Mankane (0,4) Keya(0,4) Masheka (4,0) Masuba (3,0) Yumbuma (3,0) Pendembu (2,2) Kparva (0,3) Makonte (3,3) Kontobe (2,4) Babaibunda (2,3) Maroki (5,0) Mabang (4,0) Mara (4,0) Makoli (4,1) Mamalia (3,3) Malop (3,4) Matamba (3,2) Moyambaworo (3,2) Clayey sediments. D* G* G* Bali (4,0) Talk. (3,1) Naba (2,3) Nyawama (4,0) Kania (3,2) Taiama (2,3) Mamu (0,4) Bonganema (0,4) (Footnotes given at end of table.) SECTION 4:2:2 17 Table 2 (continued). Soil Moisture regime1' Physiography and parent material province (Fig. 8) 1 Well Moderately drained well drained Imperfectly drained Poorly drained Very poorly drained Alluvial floodplains 24-48 inches (60-122 cm) or more of gravel- free, clayey alluvium over gravelly material G* Mogbondo(3,lf) 1* Tabai (3,2) Fine-loamy alluvium G* Pujehun (3,'/jf) Mosunno (2 4) 1* Magbunga(3,Vif) 1* Bom (3,1) Fine-loamy and clayey alluvium D* Sewa (2,4f) 1* Rochin (2,3) Clayey alluvium D* Taso (2,'/jfl Torma Burntl 2f) fthnhnn (O ll S»n*him In 41 uuunan \u,j; oenenun \\jt*t D* Koyema (2,1f) Sang a ma (1,3f) G* Gbesebu (2,1f) Mokoll(l,3 f) I' Malansa (2,3) Rokel (2,4) 1* Mabole(2,4) 1* Mateboi(2,l) Seli (2,2) J* Makundu (2,'/if) L* Blama (0,3) Dowjo (0,4) L* Moa (l,'/2f) Sandy beach ridges and lagoons Sandy material with little profile development B* Sahama (5,0) Hahun (2,3) Mam (0,4) Sandy material with distinct profile develop- ment B* Gbamani (5,0) Tidal swamps Clayey sediments C* Rokupr (0,5) " Detailed data and discussion are given in the text for the soil series names set in heavy type. First number in parentheses after each soil series name indicates duration of soil moisture deficiency in months. Second number in parentheses indicates duration of waterlogging at the surface as follows: 0 = none 2 = 1 to 2 months 1/2 "- 1 'o 15 days 3 = 2 to 4 months, including submergence about 1 month 1 = 10 to 30 days, including occasional 4 -- = 3 to 5 months, including submergence • 1 month brief submergence 5 — floods daily at high tide unless protected by levees The letter "f" indicates soils flooded by river water with high oxygen content. ter content (see also Section 4: 12: 1). In the field, how- ever, it is difficult to distinguish between the kinds of epipedons because of the poor correlation between soil color and organic matter content in Sierra Leone. For instance, a young alluvial Gbesebu soil, N13, with 4.47- percent organic carbon in the A, horizon, has a color of 10YR 4/3 (ochric epipedon) ; by contrast, Nyawama, N100, a river terrace soil with 1.26-percent organic car- bon, has a color of 10YR 3/2 (umbric epipedon). The latter is darker colored because the organic matter more fully coats the smaller specific surface area of the Nyawama A: horizon, which is 23-percent clay, than the Gbesebu AI horizon, which is 46-percent clay. Soils of the young alluvial floodplains have the highest organic matter contents. Both umbric and ochric epipe- dons occur in these areas. The organic carbon contents of the Aj horizons range from 2.71 percent in the well- drained, sandy Pujehun soil under secondary farm bush to 13.48 percent in the poorly drained, clayey Gbehan soil under grass vegetation. The reasons for the high organic matter content in these floodplain soils are a relatively good moisture and nutrient supply and the low-intensity agricultural use thus far because of flood- ing hazards. In contrast, the surface horizons of soils of stream terraces and the colluvial footslopes have the lowest organic matter contents, ranging from 1.12-per- cent to 3.34-percent organic carbon. They may also have either ochric or umbric epipedons. Their low organic matter content is probably related to their frequent use for primitive agriculture in a shifting cultivation system with rather short fallow periods. The soils of the upland old erosion surfaces and steep hills have intermediate organic matter contents, ranging from 2. 01 -percent or- ganic carbon in the steep Segbwema soil to 4.19 percent in the more level Makeni soil. Although organic matter content here also depends upon the duration of the fal- low period, erosion is an additional factor on steep slopes. This is probably why soils on steep hills have ochric epipedons, while soils of the gently sloping upland erosion surfaces have ochric or umbric epipedons. Charcoal from partially burned vegetation occurs in variable amounts in many soil profiles, causing organic matter content to be somewhat erratic. 4:2:2. MINERAL WEATHERING, LKACHING OF SOLUBLE SUBSTANCES, AND FORMATION OF SECONDARY MINERALS Weathering of primary minerals is the result of in- stability under atmospheric conditions, especially those minerals that have been formed at much higher tempera- tures and pressures. The rate of weathering in Sierra Leone is rapid because of the high temperature and abundant rainfall. Most minerals in the soil are silicates. Weathering breaks down the crystalline structure of sili- cates, releasing silica, aluminum, iron, and bases. Bases, such as calcium and magnesium, and part of the silica 18 BULLETIN NO. 748 are in soluble form and are leached away by the abun- dant rainfall. The remaining silica combines with alumi- num and forms 1 : 1 clays. The surplus aluminum and iron may form gibbsite and goethite. Thus, the clay frac- tion of many soils in Sierra Leone consists mainly of 1 : 1 clays, gibbsite, and goethite and has a low cation-ex- change capacity. The remaining primary minerals, espe- cially quartz, are resistant to weathering and are concen- trated in the sand fraction. Two kinds of weathering horizons are common in the subsoils of Sierra Leone soils : a cambic horizon, which is slightly weathered, and an oxic horizon, which is strongly weathered and has a low cation-exchange ca- pacity and very few or no weatherable minerals (see 69 and Section 4:12:1). Well-drained cambic horizons oc- cur in soils on steep hills (Vaahun, Momenga). Erosion constantly exposes fresh weatherable minerals to the surface so that these minerals, and sometimes weathering bedrock, are present in the subsoil. The Segbwema soil, which also occurs on steep hills, presents a boundary case between a cambic and an oxic horizon. Cambic horizons also occur in some poorly drained soils such as Panlap, Mankane, etc. Strong weathering is prevented in these soils, probably because flooding during the rainy season prevents leaching. In soils of the young alluvial flood- plains, cambic or oxic horizons are present, depending upon whether or not the catchment area of the river contains a source of weatherable minerals. Soils such as Gbesebu and Pujehun, which have high amounts of mica in the sand and silt fractions but a low cation-exchange capacity, have cambic horizons. Oxic horizons, which occur in Gbehan, Makundu, and Moa soils, contain few weatherable minerals and have a low cation-ex- change capacity. The presence of oxic horizons in young alluvial floodplain soils is a good example of the impor- tance of preweathering of the parent material. 4:2:3. ILLUVIATION OF CLAY, IRON, OR ORGANIC MATTER Illuvial horizons may be formed when clay, iron, or organic matter is transported from the surface horizon and accumulates in the subsoil. In Sierra Leone the great surplus of rainfall over evapotranspiration in the rainy season promotes the mobilization and transportation of these materials through the soil profile. The pro- nounced dry season may be one of the essential factors for the subsequent deposition of the migrating materials. Two kinds of illuvial horizons, a spodic horizon and an argillic horizon (see 69 and Section 4:12:1), occur in Sierra Leone soils. A spodic horizon is a horizon of ac- cumulation of illuvial amorphous humus and aluminum, with or without iron. Soils with a spodic horizon (Gba- mani series) occur on the oldest sandy beach ridges along the coast in soil province B*. They have developed in very permeable, almost pure quartz sands. The argillic horizon is an illuvial horizon in which fine silicate clays, often with iron, have accumulated to a significant extent. Clay coatings are a characteristic fea- ture of argillic horizons. They are formed when, upon drying, water is drawn from the noncapillary pores and the clay is filtered out and deposited on the ped surfaces and on the walls of pores as clay coatings. During the field work in Sierra Leone, clay coatings were not de- tected except in the Pendembu and Pelewahun (N47) soils. Later, however, a micromorphological study1 on thin sections of nine soil profiles belonging to six different soil series indicated the presence of clay skins in Njala, Pelewahun, Makeni, and Taiama soils and their absence in Momenga and Gbesebu soils. As a consequence, sev- eral soils that formerly were considered to have a cambic or oxic horizon (25) were found to have an argillic horizon. Unfortunately, micromorphological data are available for only a few soils. By extrapolating the avail- able thin-section data to other similar soils and utilizing data about the clay distribution in soil profiles, the pres- ence or absence of argillic horizons in the other soil series has been inferred. Apparently, argillic horizons are wide- spread in Sierra Leone. They occur in many upland soils of the old erosion surfaces (Njala, Makeni, Man- owa, and Mabassia series) and in several of the soils of colluvial footslopes and stream terraces (Mokonde, Bon- jema, Pelewahun, Masheka, Bosor, Pendembu, Nya- wama, Kania, and Taiama series) . 4:2:4. FORMATION OK GLEY, PLINTHITE, AND HARDENER PLINTHITE GLAEBULES In seasonally wet soils in the presence of organic mat- ter, iron is mobilized by reduction because of low redox potentials. It is transported over relatively short dis- tances in the soil profile and oxidized in the form of reddish mottles along the biggest pores, where higher redox potentials prevail. Manganese, if present, under- goes similar changes but at different levels of redox po- tential. Thus a gleyed horizon develops that is charac- terized by reddish mottles in which iron has been concentrated and by grayish spots from which iron has been removed. Plinthite (69) is similar to gley but more strongly de- veloped and more highly weathered. It is a sesquioxide- rich, humus-poor, highly weathered mixture of clay with quartz and other diluents, and it occurs as a red mottled material that irreversibly hardens on exposure to re- peated wetting and drying. The high rainfall and dis- tinct dry season of Sierra Leone are optimum for the formation of plinthite. Saturated or nearly saturated water conditions in the soil during the rainy season cause segregation of iron, so that it crystallizes to goethite or similar minerals during the dry season (65). In many places, additions of iron from overlying horizons or from higher adjacent areas probably occur. The reddish parts of the plinthite, which contain much iron, harden ir- reversibly when exposed to repeated wetting and drying. The hardening process involves segregation and crystal- 1 Personal communication from Dr. E. B. A. Bisdom and Ir. R. Miedema of the Netherlands Soil Survey Institute and the Agricultural University, respectively, at Wageningen, The Netherlands. SECTIONS 4:2:5-4:3:1 19 lization of iron into a continuous assemblage that acts as a skeleton, thus ensuring induration (48). The hard- ening process is accelerated by the removal of the forest cover and by erosion, thus resulting in more intense wet- ting and drying cycles (/). If much iron is present in the parent material, the plinthite mottles may be so abundant that they become connected with each other and form a continuous phase that, upon hardening, de- velops into a massive ironstone hardpan. With less iron present in the parent material, the individual plinthite mottles are not connected with each other; upon harden- ing, therefore, these mottles develop into gravel-sized, indurated plinthite glaebules. Gley is present in poorly drained soils that are imma- ture or that do not have enough iron for plinthite de- velopment (such as the Keya and Kparva series). Plin- thite is present in many soils in Sierra Leone, especially in the imperfectly or poorly drained soils that are water- logged during the wet season but dry out completely during the dry season (Panlap, Mankane, and Mokoli series). Abundant plinthite is also present in soils of the colluvial footslopes and stream terraces (Mokonde, Bonjema, Pelewahun, Masuba, Nyawama, Kania, and Taiama series) ; in these soils, plinthite is most abundant on poorly drained sites that are waterlogged during the wet season. Waterlogging, however, is not absolutely necessary: plinthite mottles have also been observed, al- though only to a limited extent, in the subsoils of some well-drained upland soils that are never waterlogged (Njala and Momenga series) . In the soils of the young alluvial floodplain, few plinthite mottles have been re- ported in the moderately well-drained Taso and Ma- kundu soils, whereas abundant plinthite is present in the poorly drained Gbehan soils. Hardened plinthite glae- bules of gravel size are abundant in the well-drained upland soils such as the Momenga, Njala, Manowa, Makeni, Mabassia, and Baoma series; in these soils, as much as 80 percent of the total soil mass may be com- posed of gravels that are mainly hardened plinthite glaebules. Some of the soils of the colluvial footslopes and a few of the stream terraces (Mokonde, Bonjema, Pelewahun, Bosor, and Tubum series) have a very high gravel content in the subsoil, but the surface layer is gravel-free. Hardened plinthite in the form of a massive ironstone hardpan is especially abundant in areas with basic rocks high in iron, such as on the footslopes of the Peninsula Mountains near Freetown. 4:2:5. FORMATION OF A GRAVEL-FREE SURFACE LAYER On the gravelly upland soils such as the Njala, Ma- keni, and Manowa series, a gravel-free layer up to 10 inches (25 cm) thick may be formed by termite activity, especially by the Macrotermes species. These termites build numerous mounds as high as 10 feet (3m). The mounds consist entirely of material less than 2 mm in diameter, brought up by the termites from the gravelly subsoil. Since the termites leave the gravels in the subsoil, the gravel content of the gravelly layer progressively in- creases. The same kind of process has been reported in Nigeria (56, 57) and in Zaire (71). Evidences for the termite activity are the numerous termite mounds and the relatively small percentage of very coarse sand in the gravel-free surface layers as compared to the grav- elly layers, because in fact most termites usually do not carry particles larger than 1 mm in diameter. As soon as the mounds are abandoned by the termites, erosion dur- ing the rainy season spreads the gravel-free material over the surface, resulting in a gravel-free surface layer. The transition between this layer and the underlying gravelly soil is very sharp. On some relatively low places on the upland and on the colluvial footslopes, a thicker gravel- free layer may be present. This is the result of erosion of the gravel-free layer on higher ground and subsequent deposition on the lower sites. This explains why, on most upland soils, the gravel-free layer is very thin or absent and why this layer becomes progressively thicker down- slope. Consequently, a gravel-free colluvium up to more than -18 inches (122 cm) thick may be formed. In a toposequence from the summit of a hill to the valley bottom, the gravel-free topsoil gradually increases in thickness, so that the gravelly subsoil is found at pro- gressively greater depths. The gravelly subsoil gradually decreases in thickness and finally becomes a stone line that separates the colluvium from the residual material. This process of termite activity and subsequent colluvia- tion of the gravel-free topsoil, resulting in the formation of soils with a thick gravel-free surface layer overlying a gravelly subsoil, is widespread on the colluvial footslopes and upper river terraces (for example, Mokonde, Bon- jema, Pelewahun, Bosor, and Tubum series) . The streams also contribute to this process, especially on the upper river terraces, which are the result of both col- luvial and alluvial action. 4:3. AMOUNT AND CHARACTERIZATION OF THE CLAY FRACTION Clay is the most important fraction of many of the soils in Sierra Leone. In 44 soil profiles studied in detail, 18 to 69 percent of the fine earth (< 2.0 mm) is in the clay fraction in all except five soil series (Sahama and Gbamani on the sandy coastal beach ridges, Panlap and Mankane in the Makeni area, and Keya in the Kenema area) and in the surface horizons of a few other soils. Therefore, detailed analyses were made of the < 0.002 mm clay fraction to help understand the genesis of these soils and guide their use and management. 4:3:1. MINERALOGY OF THE CLAY FRACTION The mineralogy of the clay fraction of soils in the areas that were studied is discussed briefly here; more detail will be given later for individual soil profiles. De- tailed clay mineralogy values from Appendix C are presented as averages in Table 3 for areas and subareas. The soil areas discussed are shown in Figure 8. The kinds of clay minerals in the clay fraction of Sierra Leone soils vary widely. For the most part, these 20 BULLETIN NO. 748 •o 0) o I B •^ vt in •* cocooo *o CMCO >o co TJ OJ "5 1 . 0 1 e % 1 & uo u >->->.u uu u -C i i c 0) •*- •2 £^? •o-o-o o- OK"«-o is O-K n rs — 01 TJ s. £ o •— a o. 2 •o £ o .£• S .-Ife? COfJCO^ COCM>O CO CMCMCM CM J 0) 1 c _c o. 1 i ^ 4) ^ .*B SMS« •* tsoorjCM o Oco ~o — KKK *O ^ TJ X 1 o D M •^lOT) -^ OM5OK CO CO 1 o™ •— •— *- 1 c c a> a Iv O Ji J 1- o k. I & a; IS Os'0'*" • CO CO^-^ O ^ SS01^ ZZ§§ 0> °Z <" 5 c M _0> O. 1 "-•-ir o ppoo •- zo i- ._ 9-°-S^ »«** S °EJ "5 || < J tf-l-5 < 11 "* o "3 U 1 <*.*. o ££££ *£ E Q. I '6 '> M "8 •D ^ •— * CM- "O — >O CM CM •* O rs P> — C1 CM TfpJCOCO >>"uu'U' uuu uuo s. o o "C3 COCNV) >O CO M3 >O O CM i— 00 OlS^N M3-^IO>O >. E 2 = » --*—»— *— 2 CM u 6 O *™ O •o 1 O V c = .•§§ — 10 fO Tf 00"O-OCMCMP)-O —CM-*CM rMCOCOCO' S V y 1 D. TJ £ 0 1 i£^ •O |S CN IO ISM300COCMCMM3 CM^-^CO O>-^O«— •o t3 0 i- sS c o •£: g ? o- V •o 0 M •° t> to lO^CO CO * 5 fe? C0«- ^CSt CNCNCN«-CN-— f- CO •— "S 1 o • - ^ O N t 1 :i L UK = s O 0. VI 1 3 g S - rf ^ 5 o Average compo moisture regime o qz s a 1 I „ } ||s_ sg_ | „, |i! « to O P _Q 1 1 » * * * * £0 U O O si U 5 o 1 SE h- a. — SECTION 4:3:1 21 1 3 — — CM t— I) •D D o i i u i c -o i ,^ •» «0 10 >0 •« en '5i i 5 o -o 10 » >o -^ « a: C 0 54*5 — ^ a c o £"a''*'nS £ I || | -S Q. "o_ £ | ^« O ° £ ^ 41 Q. Q- 5 Ck ^ ^ i verm •1 1 TJ — ~ •— r-CO — CNF-CMCOO "5 O- — 11 s a — a 31 31 1 1 •^ . . C 8 -CM^^CM«0« ^f t C 8 C^CNO « -t !•* ° 1? °> ± CD ^ 1° ° •n O M •5 i 1 J 0 1 ~ '» § ••• "«^ t "6 ^-°° "5.'^'"o*~lr*oo "Q.CO = = 0) 3 C v | a ]i|S:1^^ii-i iljlrl-l 8 O $ f iljll llJl •* I o flofJMij it _0 £^ CO 11 £5 . clay fraction (glycolated) of selected horizons of some soils in the Njala area. and colluvial footslopes, have developed from sedimen- tary rocks such as sandstone, siltstone, and mudstone. The mineralogy of the clay fraction of these soils is varied and presents a combination of rare interstratified min- erals. X-ray diffractograms of the glycolated, Mg- and K-saturated clay fraction of Bonjema, N39, and Pele- wahun, N47, are given in Figure 10. These diffracto- grams show excellent examples of interstratification of 10 A illite with 14 A chlorite, vermiculite, or both, to give 10-14C and 10-14V minerals. In 10 soil profiles studied on the upland and colluvial footslopes in Area G*, the average content of interstratified minerals 10- 14C and 10-14V is from 10 to 25 percent of the clay fraction (Table 3), with more in individual horizons (Appendix C) . Kaolinite is the dominant mineral, averaging approxi- mately 45 to 65 percent; the better-drained soils contain slightly more kaolinite than their more poorly drained associates. These values for kaolinite content are dis- tinctly lower than those found for other soils studied in Sierra Leone, which average approximately 70-percent kaolinite. The chlorite content in the better-drained soils (six profiles) averages 8 percent, contrasting with 17- percent chlorite in the more poorly drained soils (four profiles). The illite content is relatively small (< 6 percent) in these soils, except in the Momenga profiles, which occur on steep slopes, and in the lower horizons of a few other soils (such as Pelewahun, N47) that extend nearly to the bedrock from which the illite comes. The most strik- ing sample (Lab. No. S29065) is from the IIC horizon of Momenga, N123, in which the clay fraction is 46- percent illite and 54-percent kaolinite (Appendix C). Among the soils studied in Sierra Leone so far, this sample is also unique in other properties, such as very high available water-holding capacity (Appendix B). 24 BULLETIN NO. 748 Gibbsite and quartz arc present in small amounts; goethite, if present, is found only in trace amounts. The diffractogram in Figure 10 for the Bonjema B]t horizon, sample S28652 Mg, shows a 6.8 A line for boehmite pres- ent in significant amounts, up to 10 percent. There are also less intense 6.8 A lines, indicating about 3-percent boehmite, in the two samples of Pelewahun, N47. Since boehmite was present in more than trace amounts only in these three samples, this mineral is not listed in Table 3 or Appendix C. Compared with soils on the upland and colluvial foot- slopes in Area G*, the soils on stream terraces contain very little interstratified minerals and less chlorite but significantly more kaolinite and gibbsite. In these respects the clay fraction of the soils on the Taia (or Jong) River terraces resembles the clay fraction of soils in upstream Area J*, which indicates that most of the material came from there rather than from the adjacent upland in Area G* (Table 3). The clay fraction of the well- drained Nyawama soils contains more kaolinite but less chlorite than their more poorly drained associates (Kania and Taiama) ; this is similar to the effect of drainage found in the clay composition of soils on the adjacent upland and colluvial footslopes in Area G*. The clay fraction of Pujehun, Gbesebu, and Mokoli soils in the alluvial floodplains of Area G* is unlike that in soils on the adjacent upland and colluvial footslopes (the alluvial soils contain very little interstratified min- erals and chlorite, but more kaolinite and gibbsite), but similar to that in soils in upstream Area J*, from which most of the materials probably came (see Fig. 8 and Table 3). The low content of illite in the clay fraction of these alluvial soils in Area G* is interesting, since there are many mica flakes in the silt fraction of the soils and probably in the sand fraction of Pujehun, N80 (see Appendix B) . Area J* — Granite and Acid Gneiss, Makeni Area. The soils on the upland and colluvial footslopes (10 profiles reported) have developed from granite and acid gneiss. The mineralogy of the clay fraction of these soils reflects their advanced age. Kaolinite, the predominant mineral, averages around 70 percent, except in Timbo, PI 9, which averages 52-percent kaolinite (Table 3). Gibbsite, the content of which is higher in these soils than in any other area studied, varies from 10 to 31 percent, with an aver- age of 17 percent for the 10 profiles. All other clay min- erals are present in amounts of less than 6 percent. Very small amounts of the interstratified mineral 10-14C are present in most of the profiles. The well-drained soils studied in the Makeni Area contain slightly less kaolinite and more gibbsite than their more poorly drained associates. The clay fraction of the Makundu soil, PI 04, on the alluvial floodplain of the Mabole River in this area merely reflects the same mineralogy as the soils on the adjacent upland and colluvial footslopes. Area L* — Granite and Acid Gneiss in the Upper Moa Basin, Kenema Area. The mineralogy of soil clays from seven soil profiles on the upland and colluvial footslopes and one profile on the alluvial floodplain in this area differs only slightly from the soil clays in Area J* from similar bedrock. The kaolinite content is almost the same, but the gibbsite content is slightly greater on the poorly drained soils in Area L* (see Table 3 and Fig. 11). Mineralogy of the Clay Fraction in Soils on Alluvial Floodplains. In Areas D*, G*, J*, and L*, the clay min- eralogy of the alluvial soils is strikingly similar (see Table 3 and the diffractograms for Taso, Gbesebu, and Moa in Figures 9, 10, and 11, respectively). These soils devel- oped in alluvium from the Sewa, Taia, Mabole, and Moa Rivers, respectively, all of which flow primarily from areas in which granite and acid gneiss predominate. With the exception of Pujehun, N80, all of these allu- vial soils are clayey (41 percent to 67 percent), with con- siderable silt and relatively low sand contents (Appendix B). Taso, T183, in Area D* and Makundu, P104, in Area J* are especially similar in that they have thick, dark surface horizons (umbric) and oxic subsoils (see Section 4:12). 4:3:2. TOTAL ANALYSES AND CATION-EXCHANGE CAPACITY OF THE CLAY FRACTION Total K2O, Fe2O3, A12O3, and TiO2 analyses of the clay fraction of selected soils are given in Appendix C. Total K2O content of the clay fraction is related to the content of illite as a clay mineral and as a constituent in the interstratified minerals. Total Fe2O3 content of the clay fraction is closely related to the natural drainage of the various soils. Total Fe2O3 in the well- and moderately well-drained soils ranged from 7 to 20 percent, whereas the poorly and very poorly drained soils contained 1 to 8 percent. In comparison with the < 0.002 mm clay frac- tion, total analyses of the < 2.0 mm fine earth (Ap- pendix B) of the same soil profiles indicate that the per- cent of total K2O tends to be similar, but total Fe2O3 content is usually smaller in the < 2.0 mm fine earth fraction than in the < 0.002 mm clay fraction. The cation-exchange capacity of the clay fraction ranges primarily from 15 to 25 milliequivalents (me) per 100 grams of clay, with the higher values more common among those samples which contain more illite, chlorite, and interstratified clay minerals. The cation- exchange capacity per gram of < 0.002 mm clay (Ap- pendix C) is usually about 2 to 3 times greater than in the < 2.0 mm fine earth (Appendix B) . 4:3:3. AMOUNT OF WATER-DISPERSIBLE CLAY Clays that are not dispersible in water are relatively stable and inactive. When less than 5 percent of the total clay in a subsurface horizon is dispersible in water, the horizon may be an oxic horizon, unless it lacks some other essential features or is part of an argillic horizon (see the definition of oxic horizon in Section 4:12:1). MANOWA 3.3 4.2 4.8 7.2 Angstroms 10 14 SECTION 4:4 KPARVA 3.3 4.8 7.2 Angstroms 10 14 MOA 3.3 4.8 7.2 Angstroms 10 14 Figure 11. X-ray diffractograms of the < 2/x clay fraction (glycolated) of selected horizons of some soils in the Kenema area. The lower horizons of Oxisols such as the Gbehan, Taso, and Makundu soils contain very little water-dispersible clay, as is indicated in Appendix C, even though their total clay content is high. 4:4. AMOUNT AND SIGNIFICANCE OF EXCHANGEABLE ALUMINUM The parent rocks from which most Sierra Leone soils developed include granite, schist, and gneiss. Common alumino-silicate minerals such as feldspars, hornblendes, chlorites, and micas (both muscovite and biotite) that make up these rocks weather and liberate large quanti- ties of aluminum. Exchangeable aluminum, as deter- mined with IN KC1, will usually exceed 1 me/ 100 g of soil in some or all horizons, with the highest values usu- ally in the lower portion of the profile. Soils with surface horizons having 2 to 6 me of exchangeable aluminum per 100 g of soil are not uncommon, and, in general, this contributes to the low productivity capacity of such soils. Soils that developed in Rokel River Series materials on the upland and colluvial footslopes in Area G* con- tain the largest amounts of exchangeable aluminum, typically in the range of 2 to 4 me/100 g, but Momenga soils contain up to nearly 13 me/ 100 g in their lower subsoils (Appendix B). The soils in Area J* contain the least exchangeable aluminum, usually less than 1 me/ 100 g of soil, and soils in Area L* are nearly as low — typi- cally about 1 to 2 me/ 100 g. Soils in both Areas J* and L* developed from granite and acid gneiss. The presence of large amounts of exchangeable alumi- num in soils usually increases their "unavailable" water content — water that is held against 15 atmospheres of tension. Clayey soils with 3 me/100 g, or more, of ex- changeable aluminum in the surface are difficult to cul- tivate when wet; when they undergo severe drying, as happens during the dry season, they become quite hard. These soils are the least desirable for plantation crops. Aluminum toxicity to crops is a potential threat on all unlimed soils in Sierra Leone. Toxicity may be suspected on almost all soils if the pH is below 4.8 or if the ratio of exchangeable Ca + Mg to Ca + Mg + Al drops be- low 0.100. For a crop like sugar cane, the critical ratio may be as high as 0.250, while for a tolerant crop such as cassava it may be as low as 0.050 before serious dam- age occurs. For other crops such as rice, groundnuts, corn, cocoa, oil palm, etc., the critical ratios probably fall somewhere between 0.100 and 0.200. Therefore, liming has two objectives: to raise the soil pH to at least 26 BULLETIN NO. 748 Table 4. Toxicity levels of aluminum in soils as determined by the ratio of exchangeable Ca + Mg to Ca + Mg + Al 5011 Soil series, Depth, Ca + Mg ^ Soil series, Depth, Ca + Mg pr°vin"' profile no. rig. o inches province, Ca + Mg + Al Fig. 8 profile no. inches Ca + Mg + Al B* Sandy beach ridges 0* Upland and colluvial footslopes (cont.) Sahama 0-6 .223 Bonjema 0-4 .620 T149 6-11 .178 N39 4-16 .233 11-20 .153 16-25 .072 20-31 .151 25-33 .062 31-40 .506 33-57 .065 40-55 .231 57-70 .029 Gbamani 0-16 .018 Bonjema 0-20 .158 T165 16-41 .006 N105 20-32 .114 41-48 .086 32-40 .087 48-80 .231 40-50 .173 80-120 .088 50-60 .075 Average .170 Pelewahun 0-1 1 .103 N47 1 1-17 .074 C* Tidal swamps 17-25 .054 Rokupr 0-5 .810 channel 25-41 .121 oxidized, Rl 5-22 .494 matrix 25-41 .080 22-57 .571 41-72 .082 Rokupr 0-3 .747 Pelewahun 0-15 .095 reduced, R2 3-26 .684 N106 15-26 .074 Average .661 26-41 .036 D* Alluvial floodplain grasslands Average 41-58 .060 .127 To so 0-6 .293 T183 6-12 .074 G* Stream terraces 12-22 .138 Nyawama 0-21 .083 35-50 .158 N100 21-31 .090 Gbehan 0-5 .082 31-42 .080 T187 5-11 .061 42-60 .148 11-14 .258 Nyawama 0-11 .101 23-52 .518 N71 11-17 .107 Average .198 17-26 .086 G* Rokel River Series, Niala area 26-50 .140 Upland and colluvial footslopes Nyawama N15 0-5 5-14 .886 .396 Momenga 0-3 .209 14-33 .192 N123 3-9 .094 33-50 .228 9-33 33-40 40-62 .030 .004 .085 Kania N70 0-12 12-16 16-24 .070 .080 .104 Momenga 0-6 .343 24-39 .092 N86 6-16 .107 39-56 .085 16-24 24-38 38-50 50-63 .108 .058 .050 .037 Taiama N101 0-13 13-31 31-42 42-63 .085 .072 .081 .065 Momenga 0-7 .867 Average .156 N44 7-15 .143 15-33 .039 G* Alluvial floodplains 33-42 .035 Pujehun 0-4 .101 42-57 .021 N80 4-12 .128 57-69 .021 12-31 .198 Njala 0-14 .176 31-55 .173 N109 14-21 .096 Gbesebu 0-4 .141 21-49 .229 N125 4-7 .134 49-62 .221 7-19 .115 Njala 0-4 .145 19-25 .182 N108 4-14 .113 25-63 .249 14-24 .101 Gbesebu 0-7 .536 24-35 .083 N13 7-42 .117 35-57 .131 42-50 .242 Mokonde 0-5 .267 Mokoli 0-6 .181 N42 5-15 .167 N14 6-15 .065 15-30 .050 15-27 .139 30-39 .115 27-60 .268 39-60 .064 Average .186 60-67 .058 SECTION 4:5 27 Table 4 (continued). Soil series, Depth, Ca + Mg So'1 Soil series. Depth, Ca +Mg pr°vmge' profile no. inches Ca + Mg + AI Fig. 8 profile no. inches Ca + Mg + Al J* Granite and acid gneiss, Makeni area J* Granite and acid gneiss, Makeni area (cont.) Timbo 0-12 .473 Mankane 0-6 .452 P19 12-19 .278 P8 6-21 .512 19-28 .463 21-25 .528 28-43 .509 Makundu 0-8 .916 43-70 .688 PI 04 8-16 .384 Makeni 0-10 .946 16-21 .178 P2 10-20 .500 21-28 .160 20-67 .903 28-43 .368 Mabassia, 0-7 .873 43-74 .236 shallow 7-25 .338 Average .444 P71 25-39 39-65 .308 * .344 Granite and acid upper Moa Basin, gneiss in the Kenema area Mabassia, deep P108 0-6 6-13 13-26 .791 .428 .267 Vaahun 145010 0-6 6-20 20-28 .965 .432 .462 26-35 .272 35-59 .750 Segbwema 0-13 .601 Bosor 0-9 .428 145005 28-60 60-94 .123 .126 P60 9-18 .114 18-26 .187 Manowa 0-10 .038 24-43 .321 Kpuabu 1 10-21 .067 43-51 .203 35-70 .106 Tubum 0-4 .644 Baoma 0-5 .249 P13 4-13 .321 144801A 5-23 .330 13-25 .290 23-43 .800 25-33 .168 43-67 .814 33-54 .246 Keya 5-11 .298 Masheka 0-16 .878 145041 21-33 .488 P49 16-26 .268 Pendembu 0-7 .022 26-38 .194 Kpuabu 2 7-18 .036 54-68 .219 37-54 .069 Masuba 0-7 .458 Kparva 0-9 .178 P9 7-22 .227 145042 9-39 .048 22-67 .261 39-66 .178 Panlap 0-11 .553 68-80 .158 PI 11-23 .618 Moa 0-6 .232 23-37 .693 Kpuabu 3 6-21 .073 37-60 .725 31-59 .188 Average .283 5.4 so that exchangeable Al++* is changed to hydrated aluminum oxide, Al2O;r3H2O; and to increase the Ca + Mg to Ca + Mg + Al ratio to above 0.300, where aluminum toxicity usually does not occur. The Ca + Mg to Ca + Mg + Al ratios for unlimed soils are given in Table 4. The ratio of exchangeable Ca + Mg to Ca + Mg + Al is lowest (average 0.127) in soils on the upland and colluvial footslopes in Area G* (Table 4), indicating that aluminum toxicity to crops is most likely in this area unless corrective liming is practiced for sensitive crops. On upland soils, the highest ratios are in Area J* (average 0.444), followed by Area L* (average 0.283), so that aluminum toxicity is less likely in these areas. The high ratios of the Rokupr soils in Area C* are associated with much higher exchangeable Ca and Mg levels in these tidal swamps than in the upland soils, even though Rokupr soils contain 1 to 5 me/ 100 g of exchangeable aluminum. 4:5. AREA B* — SANDY BEACH RIDGES AND LAGOONS Sandy beach ridges are present in the southern coastal part of Sierra Leone in a strip about 5 to 10 miles (8 to 16 km) wide adjacent and parallel to the Atlantic Ocean shore and including part of Sherbro Island, Turner's Peninsula, and a small coastal strip south of Shenge (Fig. 8). The ridges, Vz to 1 mile (about 1 km) wide, are separated from each other by sandy lagoons. The beach ridges and lagoons consist of Pleistocene and Re- cent beach sand that is more than 90 percent quartz. Geologically, it belongs to the Bullom Series. The annual rainfall in this area is between 140 and 160 inches (356 to 407 cm), 90 to 95 percent of which falls in the wet season. The vegetation is primarily coastal park savanna (3-feet tall grass and herbs with scattered trees) and farm bush; coastal scrub occurs near the ocean (17) . Three landscape units are present: young beach ridges, old beach ridges, and lagoons (25). The ridges closest 28 BULLETIN NO. 748 12° 5' W FIGURE 12. SOIL ASSOCIATION MAP OF THE TORMA BUM AREA, SIERRA LEONE LEGEND -7°30'N Soils On Sandy Beach Ridges And In Lagoons A-GBAMANI, SAHAMA B-HAHUN, MANI Soils On Alluvial Floodplains C-TASO, KOYEMA D- TORMA BUM, SANGAMA E-GBEHAN, SENEHUN Soils On River Terraces F-BALI G-TALIA H-NABA, MAMU TORMA BUM SOIL BOUNDARY VILLAGE, TOWN LIMIT OF SURVEY BAOMA 5 KILOMETERS * 3 MILES to the sea are the youngest and have soils that show little profile development. On the older beach ridges, there are two kinds of well-drained soils, Sahama and Gbamani, described below. In the lagoons, which are flooded dur- ing much of the year, Mani soils occur (Table 2). The soils in Area B* have sand or loamy sand textures. They are infertile and have extremely low water-holding ca- pacities. They are unsuitable for most agricultural crops, although coconuts and cassava grow reasonably well on the ridges. A small area of soils on sandy beach ridges and in la- goons was mapped by Dijkerman and Westerveld (25) near the Atlantic coast, along the Sewa River southwest of Torma Bum (see Fig. 12 and Table 5). SECTION 4:6 29 Table 5. Area of different soil associations in the Torma Bum area, as shown in Figure 12 Symbol on map Major soil series Area Percent of total area Acres Hectares A B C D E F G H Soils on sandy beach ridges and in lagoons 1 .700 690 3.9 3.9 15.0 24.9 4.9 32.7 6.9 7.8 Hahun, Man! 1,700 690 Soils on alluvial floodplains Toso, Koyema 6,500 2,640 Torma Bum, Sangama 10,800 4,380 Gbehan, Senehun 2,100 850 Soils on river terraces Bali 14.200 5.750 Talia ... 3,000 1,220 . . 3,400 1,380 Naba, Mamu Total . . . 43,400 17,600 100.0 Sahama Series. The Sahama soils are well drained and occur on the convex higher parts of sandy beach ridges. The vegetation is usually either secondary bush with many oil palms or tall and medium-height grasses. These soils are approximately 90- to 95-percent sand throughout their profiles. Sahama soils have three principal horizons with grad- ual boundaries between them. The very dark grayish- brown to dark brown surface soil is approximately 20 inches (51 cm) thick. It is usually dark enough and deep enough to be umbric, but the organic carbon content of the lower part of this horizon is often less than is specified for an umbric epipedon. The brown to dark yellowish- brown upper subsoil extends from about 20 to 40 inches (51 to 102 cm). The strong brown lower subsoil extends below 40 inches ( 102 cm) . Sahama soils are very strongly acid, low in available nutrients, and rapidly permeable, with no waterlogging during the wet season. They are very droughty with a very low moisture-holding capacity and low soil moisture content during about five months of the dry season (Table 2). In comparison with Gbamani soils (described below), Sahama soils are slightly better because of their somewhat finer sand and darker surface layer, which con- tains more organic matter. Despite such qualities, how- ever, Sahama soils are still very poorly adapted to any kind of productive agriculture. A detailed description and analytical data for a repre- sentative profile, T149, of the Sahama series are given in Appendix B. Gbamani Series. These are well-drained, coarse sandy soils that occur on the convex higher parts of beach ridges. Vegetation is similar to that on the Sahama soils. Gbamani soils typically have five horizons, of which the illuvial humus (B2h) and iron (B2ir) subsoil horizons are quite distinctive. There is usually a thin, very dark gray surface horizon (ochric epipedon) of coarse sand, unless it has been obliterated by mixing or removed by wind erosion. The dark gray, coarse sand A2 horizon is very thick — about 40 inches (102 cm). The dark red- dish-brown illuvial humus B2|, horizon occurs at approxi- mately 40 to 50 inches (102 to 127 cm) below the sur- face. It contains much more organic matter and has a higher cation-exchange capacity than any other horizon in the profile, but this organic matter is amorphous and does not decompose readily to release plant nutrients. Sometimes this horizon is slightly cemented and hence restricts root growth. The yellowish-red illuvial iron B2ir subsoil horizon (1.85-percent total Fe2O3) extends from about 50 to 80 inches ( 127 to 203 cm) below the surface. The loamy coarse sand C horizon below approximately 80 inches (203 cm) is yellowish brown with distinct strong brown mottles, which indicates that it is saturated with water for short periods of the wet season. Gbamani soils are very strongly acid, very low in avail- able nutrients in the solum, and rapidly permeable. They are distinctly droughty with a very low moisture-holding capacity and have a low soil moisture content during about five months of the dry season (Table 2) . Gbamani soils, among the poorest soils in this area, are unsuitable for most agricultural crops; however, coconuts grow rea- sonably well on these soils, although they suffer from in- adequate moisture during the dry season. Oil palms are numerous on the sandy beach ridges, but their yields are very poor. A detailed description and analytical data for a repre- sentative profile, T165, of the Gbamani series are given in Appendix B. The poorly drained Hahun and very poorly drained Mani soils (Table 2), which occur in lagoons adjacent to the beach ridges, are described by Dijkerman and Westerveld (25) . Laboratory data for these two soils are not available, however. 4:6. AREA C* — TIDAL SWAMPS Tidal swamps are present in Sierra Leone in a strip about 2 to 5 miles (3 to 8 km) wide along most of the coast from Mattru in the south to Rokupr in the north- west. Along the mouth of creeks and rivers they are present up to about 15 to 20 miles (24 to 32 km) inland. Soils in these swamps have formed in a salt- or brackish- water environment from recent marine and estuarine mud. Geologically, these sediments belong to the Bullom Series. The annual rainfall in this area ranges from 150 inches (381 cm) in the south to 110 inches (280 cm) in the northwest. Over most of the area, 90 to 95 percent of the rain falls between May and November; however, in the extreme northwestern part near Rokupr, more than 95 percent of the precipitation falls in that period. On the basis of vegetation, the coastal swamps can be divided into Rhizophora racemosa mangrove swamps, Avicennia nitida mangrove swamps, and sedge (Ele- ocharis dulcis) swamps (77, p. 9) . The two types of man- grove swamps are present near the coast and along tidal creeks; the sedge swamps occur between the mangrove swamps and the upland. 30 BULLETIN NO. 748 K Figure 13. Profile of Rokupr clay at the Rice Research Station, Rokupr. Figure 14. Mangrove (Rhizophora racemosa) vegetation at low tide. Rokupr clay soils often develop in coastal mangrove swamps. In the Rhizophora racemosa swamps, very poorly drained Rokupr soils occur, which are described next (see Fig. 13 and 14). These soils are waterlogged throughout the year and never dry out unless they are empoldered to exclude some water. They usually have a fibrous clay or silty clay surface soil over a very dark gray, soft-clay or silty clay mud. Upon empoldering and drying in a noncalcareous environment, they develop dis- tinct yellow jarosite mottles [KFe3(SO4) 2(OH)«] and become extremely acid (pH < 4) because of the oxida- tion of sulfur compounds to sulfuric acid (36, 37, 39, 74) . These soils are known as acid sulfate soils or cat clays. Reclamation is possible by leaching the excess acid with sea water (37) . The Avicennia nitida swamps have firmer, nonfibrous soils that are sandier or somewhat better drained than those of the Rhizophora racemosa swamps. Upon em- poldering and drying, these soils do not develop low pH (73, p. 46). Sedge swamps occur between the upland and the mar- ginal mangrove swamps of many rivers. They are flooded during the rains and remain more or less wet during the dry season. Stagnant fresh water conditions occur throughout most of the year because of a lack of creeks and small drainageways. Some of the sedge swamps were apparently once mangrove swamps, for large tree trunks identified as Rhizophora racemosa have been found be- neath the swamps. Soils of the sedge swamps have a dark surface horizon high in organic matter over a gray silty or clayey subsoil with red mottles. Most of the soils of the coastal swamps are fertile and can be used for swamp rice. The suitability of the land for rice is determined by the length of time that the swamp is covered by fresh water. The period during which the tidal water is harmfully saline decreases with distance from the sea. Areas for which the fresh water period is too short can be reclaimed by empoldering to exclude saline water so that rice can be grown as a rain- fed crop. A soil survey before empoldering is essential to determine whether any potential cat clays, which become very acid upon drying, are present. Such soils can be re- claimed but need special treatment (37). Sedge swamps have stagnant, fresh water throughout the year, but rice cannot be grown there because of excessive flooding. These soils can be reclaimed for rice growing by provid- ing drainage channels large enough to allow the tidal water to flood and drain from the land freely. A detailed description and analytical data are given in Appendix B for both an oxidized phase of Rokupr soils (profile Rl), which has been empoldered, and a reduced phase (profile R2), which floods daily at high tide. Both of these soil profiles were sampled on the Rice Research Station, Rokupr, where there has been much research concerning the characteristics and proper man- agement of these soils. A detailed soil map delineating the distribution of these and other kinds of soils in the Rokupr area is not available, but their general occur- rence along the Atlantic coast is shown in Figure 8. The Rokupr soils occur on nearly level tidal swamps and up adjacent stream estuaries. The parent material is recent marine and estuarine mud that is high in sulfur and usually high in organic matter. Textures are typically clay or silty clay — approximately 40- to 60-percent clay, 45- to 30-percent silt, and a relatively low sand content SECTION 4:7 31 (Appendix B). The surface horizon is very dark gray to very dark grayish brown ( 10YR 3/1-3/2) . In the subsoil, the color is very dark gray (10YR 3/1 -N 3/ ) under reduced conditions (profile R2) ; upon oxidation, promi- nent jarosite mottles develop, which become pale yellow (2.5Y 8/4) when dry (profile Rl). This yellowish mud and the smell of H2S when the soil is disturbed give rise to the term "cat clay." Under natural conditions, the Rokupr soils are very poorly drained and flood daily at high tide. Water control is necessary in order to use these soils for crops such as rice, but it must be done carefully so that excess drainage, oxidation of sulfur compounds, and the development of extreme acidity are avoided. Moisture relations, sulfur, organic matter, and iron are key factors in characterizing Rokupr soils and chemi- cal changes that occur in them. The total sulfur content is greater than 1 percent in all horizons of the two Rokupr soil profiles that were analyzed (Appendix B), reaching a maximum of 11.5 percent in the B2iK horizon of profile Rl. This is the highest total sulfur content en- countered by Chav engsaksongkram (15) in 22 acid sul- fate soil profiles from Southeast Asia, South America, southeastern United States, and Sierra Leone. Some typi- cal changes in sulfur that occur in these and related soils are outlined below. a. Soluble sulfates from sea water, in the presence of organic matter, are reduced to sul fides by sulfate- reducing bacteria. SO4 » S b. With time and available iron and sulfur, iron sul- fide recrystallizes to pyrite. FeS + S > FeS., c. With drainage and aeration, pyrite oxidizes and yields sulfuric acid, which causes extreme acidity down to pH 2.0 or even lower. 4FeS2 + 15O2 + 2H2O = 2Fe2(SO4)3 + 2H2SO4 Reactions a and b occur at neutral to alkaline reac- tions under waterlogged or reducing conditions. The B21K horizon of Rokupr profile Rl has the yellow jarosite mot- tles, high sulfur content, and very low pH that are char- acteristic of a sulfuric horizon in which reaction c occurs as a result of too much drainage and oxidation. Rokupr soils contain more exchangeable calcium than most other Sierra Leone soils because the calcium is re- plenished by sea water. Exchangeable Mg is nearly as high as Ca, except in the sulfuric B21); horizon of profile Rl (Appendix B). Cation-exchange capacity ranges from 20 to 26 me/ 100 g in the various horizons. At the time of measurement, pH ranged from 4.5 to 2.1; it is markedly influenced, however, by the status of reactions such as those described above. 4:7. AREA D* — ALLUVIAL FLOODPLAIN GRASSLANDS This area occurs in the Southern Province, along the lower reaches of the Sewa and Waanje Rivers (Fig. 8). The predominant grasses are Saccharum spontaneum and Chasmo podium caudatum (17). The annual rain- fall is approximately 140 inches (356 cm), of which 90 to 95 percent falls between May and November (see Appendix A data for Torma Bum) . The soils are formed from Pleistocene and Recent river alluvium of the Bul- lom Series. Unlike the tidal swamps in Area C*, there is no influence of marine or brackish water, because con- nection with the sea is blocked by the sandy beach ridges (Area B*) that make up Turner's Peninsula. These sandy beach ridges force the Waanje and Sewa Rivers to run parallel to the coast for 30 to 60 miles be- fore reaching the sea. Because these rivers lack an easy outlet to the sea, the alluvial floodplain grasslands are flooded every year as deep as 20 feet (6m). The soils on approximately 40,000 acres (16,220 hec- tares) were mapped by Dijkerman and Westerveld (25) west of Torma Bum and the Sewa River (Fig. 12 and Table 5). Distinctly different soils were found on the recent alluvial floodplain near the Sewa River and the older terrace farther away from the river. The recent alluvium, which occurs as a strip 2 to 4 miles (3 to 6 km) wide adjacent to the Sewa River, can be divided into a moderately well-drained natural levee (Appendix B, Taso profile T183) and poorly drained basins (Appendix B, Gbehan profile T187). The soils have clay or silty clay textures, a thick dark humus layer, and high water- holding capacities; however, they are low in nutrients and are so acid (pH 3.6 to 4.2) that aluminum toxicity is a serious problem. The older terrace is located farther away from the river, between the recent alluvium and the upland (Fig. 12). The soils are less productive than those that devel- oped in recent alluvium. They range from well to very poorly drained and have moderate humus content, low water-holding capacities, and sandy clay loam, sandy clay, and clay textures. They are very low in nutrients and very acid (pH 4). Aluminum toxicity is a serious problem. Detailed information concerning the Bali, Talia, Naba, and Mamu soils that occur on this older river terrace is not presented here but is available else- where (6, 25). The recent alluvial floodplain soils, especially those in the basins, can produce excellent rice crops. There are two main obstacles to the agricultural development of this area: the presence of coarse grass, which makes the preparation of a native farm a difficult job, and exces- sive flooding. Although the first obstacle has been solved by the introduction of a mechanical cultivation scheme, excessive flooding remains a problem. Generally, floating rice is grown; however, if after the flood begins to sub- side the waters suddenly rise again, the rice is greatly damaged ( 77, p. 42 ). Local water control by bunding is not possible because of the great height of the flooding. Digging a channel through Turner's Peninsula to pro- vide an outlet for the excess water has been suggested. When the floodwater rises to a predetermined level, the sluices would be opened and the surplus water would flow to the sea by the shortest possible route. If these flood-control and drainage improvements proved feasible and were installed, the soils on the recent alluvial flood- 32 BULLETIN NO. 748 plain not only would be more suitable for rice but also would have possibilities for other crops such as bananas, sugar cane, and pineapples. The soils on the older river terrace may well be used for rubber or oil palm, except in the poorly drained areas, which are more suitable for rice or dry season vegetables. Because of the low nutrient status of all soils of the alluvial floodplain grasslands, fer- tilization is essential. Lime, especially, is needed to cor- rect the low pH and aluminum toxicity. Taso Series. Taso soils occur on gentle convex slopes on natural levees adjacent to the Sewa River (Fig. 12). They are moderately extensive (Table 5), and they are important because they are better than most soils in the area. The parent material is recent clayey alluvium, con- taining approximately 45- to 60-percent clay, 45- to 30- percent silt, and small amounts of sand (25, and Ap- pendix B) . Textures are typically clay in the A horizon and silty clay in the B horizon, but this is not always true because of variable stratification. The AI horizon is about 6 inches (15 cm) thick, black (10YR 2/1), and is high in organic carbon (6 to 8 percent). The A3 horizon is ap- proximately the same thickness, very dark grayish brown (10YR 3/2), and contains about 4-percent organic car- bon. These two A horizons make up the umbric epipe- don. Colors of the upper subsoil, about 11 to 33 inches (28 to 84 cm), are yellowish brown (10YR 5/6 to 6/4) with strong brown (7.5YR 5/8) and yellowish-red (SYR 4/6) mottles. The lower subsoil is pale yellow (2.5Y 7/4), with mottles similar to those in the upper subsoil. Taso soils are well to moderately well drained, but they may be flooded from 1 to 15 days each year when the river level is very high (Table 2) . Available phosphorus and potassium and cation-ex- change capacity are favorable in the A1 horizon because of the high content of organic matter; they are fair in the A3 horizon but low at greater depths. Exchangeable Ca and Mg are low, about 1 me/ 100 g in the Aj horizon and much less in the deeper horizons. Exchangeable aluminum decreases with depth from approximately 4 to 1.5 milliequivalents per 100 grams of soil. Base saturation is low, ranging from 2 to 7 percent. The pH increases with depth in the profile (from 4.8 to 5.4 in H2O, and from 3.8 to 4.0 in KC1). Total K2O and Fe2O3 con- tents are greater in Taso soils than in corresponding hori- zons of the poorly drained Gbehan soils associated with them (see next soils discussed) . Taso soils receive deposition periodically, and erosion is not a problem except along stream banks. These soils are permeable because they have many to common mac- ropores. The available water-holding capacity is high because they contain more silt than most soils in Sierra Leone. The soil moisture content is low during only about two months of the dry season. Taso soils are among the most productive soils in this area. They have favorable physical properties and need only modest fertilization to produce satisfactory yields of the common agricultural crops. A detailed description and analytical data for a repre- sentative profile, T183, of the Taso series are given in Appendix B. Gbehan Series. Gbehan soils occur in concave basins and in old channels of the Sewa River floodplain (Fig. 12). The vegetation is water-loving grasses and sedges. These soils are of limited extent (Table 5). The parent material is recent clayey alluvium, containing approxi- mately 55- to 70-percent clay; most of the remainder is silt with very little sand (Appendix B) . Textures are typically clay throughout the profile ex- cept in the Al horizon, which is often silty clay. The black (10YR 2/1) At horizon is usually 5 to 10 inches (13 to 25 cm) thick and very high in organic carbon (13.5 percent). In Gbehan profile T187, however, the dark color does not extend deep enough to qualify as an umbric epipedon and, therefore, the epipedon is ochric (Appendix B) . The dark gray (10YR 4/1) sub- surface horizon extends from depths of about 7 to 13 inches (18 to 33 cm) and contains nearly 6-percent or- ganic carbon. It has strong angular blocky structure. The subsoil is light gray (2.5Y 7/2) with distinct yel- lowish-red (SYR 5/6) and strong brown (7.5YR 5/6) mottles. The structure is strong prismatic in the upper part and angular blocky in the lower part. Gbehan soils are poorly drained. They are waterlogged two to four months annually, including about one month of submergence (Table 2). Available phosphorus and cation-exchange capacity are favorable in the highly organic A horizon, but they are relatively low in the subsoil. Available and total potassium and total iron contents are lower in poorly drained Gbehan soils than in the better-drained Taso soils. Exhangeable Ca and Mg are low except in the lower subsoil, where they increase to more than 1 me/100 g of soil. Exchangeable aluminum ranges from approxi- mately 6 me/100 g of soil in the A horizon to 3 me/100 g of soil in the B horizon. Base saturation is low except in the lower subsoil, where it increases to 37 percent. The pH also increases (4.8 to 5.5 in H2O, and 3.6 to 4.2 in KC1) with depth in the profile. Gbehan soils receive deposition periodically, but they are not subject to erosion. They are moderately perme- able due to common macropores. Because of their high available water-holding capacity and low topographic position, these soils are not droughty. Gbehan soils are suitable for swamp rice production. With adequate drainage and fertilization they can be made moderately productive for other crops, but they would still be less productive than Taso soils under simi- lar management. A detailed description and analytical data for a repre- sentative profile, T187, of the Gbehan series are given in Appendix B. Detailed information concerning the Koyema, Torma Bum, Sangama, and Senehun soils, which also occur on this recent alluvial floodplain of the Sewa River, is not presented here but is available elsewhere (6, 25) . SECTIONS 4:8-4:8:1 33 4:8. AREA G* — ROKEL RIVER SERIES IN THE NJALA AREA This area occurs in the center of Sierra Leone in a belt about 20 miles (32 km) wide stretching from Bumpe to Yonibana (Fig. 8). Mean annual rainfall is about 108 inches (275 cm) in the Njala area (see Appendix A) , 90 to 95 percent of which falls between May and Novem- ber. The vegetation consists of secondary bush, but Lophira savanna or Chasmopodium grasses are present in some areas where secondary bush has been eliminated by too intensive farming (17). This area is part of the interior plain, a vast, gently undulating erosion surface with a few remnant hills (monadnocks) of earlier pla- teaus. The soils have developed from sandstones, mud- stones, and shales of the Rokel River Series (see Sec- tion 3:2). Because these rocks are poor in weatherable minerals, the soils developed from them have low nu- trient status. The monadnocks, such as the Kasabere Hills of the Kasewe Forest Reserve, consist of more re- sistant acid-volcanic rocks, which give rise to more fer- tile soils (62, p. 10) . Because of the low resistance of the local bedrock, extensive floodplains have developed, espe- cially along the Taia (or Jong) River. More recent changes in base level have made this meandering river cut down again, leaving the older terraces well above the modern floodplain (26, p. 48) . The presence of three deposition levels along the Taia River indicates that at least three changes in base level have taken place (24) . Four major landscape units in the area are the upland erosion surface, colluvial footslopes and upper terraces and swamps, stream terraces, and current alluvial flood- plains. The major soil series that occur on these land- scapes (see Table 2) are discussed in the remainder of Section 4:8, and additional information is published else- where (76). The distribution of various soils is shown on the soil map of the Njala area (Fig. 15), and the extent of each soil mapping unit is given in Table 6. 4:8:1. SOILS ON UPLAND EROSION SURFACES AND STEEP HILLS Upland soils on old erosion surfaces include the Njala and Momenga series. They are 35- to 75-percent hard- ened plinthite gravel, and the fine earth fraction ( < 2.0 mm) is usually sandy clay loam or sandy clay. The grav- elly Njala soils are low in available water-holding capacity and low in plant nutrients. Momenga soils are better in these properties but occur on steep slopes and contain harmful amounts of exchangeable aluminum, especially in the subsoil. Njala and Momenga soils are used for shifting cultivation, with upland rice and cassava as the main crops. A long fallow period is advisable. The strongly sloping areas are best adapted to tree crops and forestry. Momenga Series. The soils of the Momenga series usu- ally occur on steep escarpment slopes of the uplands, with slopes commonly ranging from 15 to 50 percent. These soils are of limited extent in the surveyed area (Table 6). Table 6. Area of different soil mapping units in the Njala area, as shown in Figure 15 Soil mapping unit Area No. on map Name Acres Hectares total area 1 108 44 0.7 2 1,895 767 13.1 3 5,432 2,199 37.7 4 Belebu 56 23 0.4 5 1,605 650 1 1.1 6 695 281 4.9 7 Pelewahun 724 293 5.0 8 855 346 5.9 9 200 81 1.4 10 1 1 Taiama 857 194 347 79 5.9 1.3 12 1,032 418 7.2 13 Mokoli 96 39 0.7 14 Gullied Land 18 7 0.1 15 51 21 0.4 16 Rock Land 6 2 0.1 17 140 57 1.0 18 15 6 0.1 19 Mogbondo 42 17 0.3 20 108 44 0.7 Borrow Pit 7 1 1 3 4 0.1 0.1 Water 260 105 1.8 Total 1 4,407 5,833 100.0 The parent material is a gravelly colluvium, usually overlying gravelly residual material, over weathered bed- rock (saprolite) , usually within a depth of 48 inches (122 cm). Hard bedrock may also be present. The colluvial plinthite gravels are rounded, hard, and dense and amount to approximately 50 percent by volume. The residual plinthite gravels, which formed in situ, are more irregular, relatively porous, and soft. Quartz veins may occur in the residual material. Quartz gravels may be present in the whole profile, being rounded in the topsoil and more angular in the subsoil. A gravel-free surface layer is only a few inches thick or absent. Tex- tures vary from gravelly sandy loam to gravelly clay in the upper few inches and are gravelly clay in the subsoil. The silt content of the subsoil often increases because of the presence of weathered bedrock pieces (Rokel River Series). The A! horizon is only a few inches thick (ochric epipedon) . The subsoil colors vary from very pale brown to strong brown and yellowish red (10YR 7/4, 7. SYR to SYR 5/6-6/8) with red and brown to white (sapro- lite) mottles. Topsoil colors range from dark grayish brown to dark yellowish brown ( 10YR 4/2 to 4/4) . The soils are well drained; however, profiles on the lower slopes close to the Taia River may occasionally be flooded during part of the rainy season, as is indicated in the water-table graph for profile N123 in Figure 16. BULLETIN NO. 748 V 2 s UJ D o •; UJ i- J — « "S ~ > >* c I si r i s ^ .^ i °' =' • * J .2, 5. ^ I ?i sis! 1-25* o "5 o o 03 a. A X I 1 ? g c ; 3 I I I 8 I I °l£ 1 g . ! 1 * • i - s „ f ^ > & 2 HllMili ujiis ! ZXH-mX g C OP X U O X « en iy> > ^•«w.--= • . . a: ^ O — j «; O «o S <•» — f^K» -^ TJ- in so -, ^* t i ! 1 o _ -g .. ~ „ 5 s « •? | s g s = a L ^_ o .« <\* *f*^ >* ; .^ s > 'c ^ 2 S^l .-=15 Si * o o- u_ I :i Figure 15 is in three sheets, on pages 34, 35, and 37. SECTION 4:8:1 35 1 I 1 § HI o UJ _Z- - $ I I i « '. j 1 1 1 1 i 1 ^ h i .2. a ~ .j ~ « » 5^*^tf2:o«»2S I in 36 BULLETIN NO. 748 Momenga soils are chemically poor, with a low nutri- ent content. The cation-exchange capacity is fairly high (varying from 10 to 20 me/100 grams of soil), often increasing in the subsoil. Contents of exchangeable Ca, Mg, K, and Na are low, and base saturation is very low except for the topsoil in a few occasions. In comparison with other upland soils (for example, the Njala series), exchangeable aluminum is high. The pH (KC1) is lower, and available water-holding capacity is higher. Organic carbon content is high (up to 4 percent) in the surface few inches but decreases sharply with depth. Total K2O is reasonably high and increases with depth. Total Fe2O:l is highest in the B horizon, lowest in the C horizon (pro- file N123), and intermediate in the A horizon. Because of the usually steep slopes, runoff is rapid and erosion is a serious hazard. Permeability is moderate. The soil moisture content is low during about four months of the dry season (Table 2) . Detailed descriptions and analytical data for three profiles of the Momenga series, N123, N86, and N44, are given in Appendix B. Njala Series. Njala soils are the most extensive ones in the surveyed area (Fig. 15 and Table 6) . They occur on nearly level ridgetops (map unit 2, on 0 to 3-percent slopes) and on moderate slopes (map unit 3, usually 3- to 15-percent gradient) downward toward the drainage- ways (Fig. 17). The parent material is a gravelly colluvium overlying gravelly residual material over weathered bedrock, which is always found at a depth of more than 48 inches (122 cm). The colluvial plinthite gravels are rounded, hard and dense, and dusky red to reddish black. The gravel content of the colluvial surface layer is usually 40 to 70 percent by volume ; the thickness of the layer varies from 30 to 60 inches (76 to 153 cm). The residual plinthite gravels are more irregular, relatively more porous and soft, and are formed in situ. Colors are brighter red ( 10R 4/6) . The gravel content varies from 35 to 45 per- cent, gradually declining with depth, and is replaced at about 8 feet (2.4 m) or more by red plinthite mottles in a light gray to white matrix. The total thickness of both colluvial and residual gravelly layers may be 10 feet (3m) or more. Quartz veins may be present in the resid- ual material. Quartz gravels may be present in the whole profile, being relatively rounded in the colluvial layers and relatively angular in the residual layers. A gravel-free surface layer is thin or absent (0 to 10 inches, or 0 to 25 cm), its thickness often depending upon topography. Textures are usually gravelly clay loam in the surface soil and gravelly clay loam to grav- elly clay in the subsoil (Fig. 18) . Topsoil colors are very dark grayish brown to dark yellowish brown (10YR 3/2- 4/4) . Subsoil colors are usually yellowish brown to yel- low, but strong brown and yellowish-red colors also occur (10YR-7.5YR-5YR 5/8-7/6). Red mottles may or may not be present. The soils are well to moderately well drained and are never waterlogged, as is indicated in the water-table graphs of profiles N109 and N108 (Fig. 19). The A! horizon is usually less than 10 inches (25 cm) thick (ochric epipedon), as it is in Njala profile N108, rather than more than 10 inches, as in N109 (Appendix B) . Njala soils have a very low nutrient status for plants. Except for the Aj horizon, the cation-exchange capacity is less than 10 me/100 g of soil. Exchangeable contents of Ca, Mg, K, and Na are low. In comparison with the Momenga soils, the exchangeable aluminum content is lower, pH (KC1) is higher, and the available water- holding capacity is much lower in Njala soils. The base saturation is very low. The organic carbon content of the A! horizon is moderate (about 3 percent) but declines sharply with depth to about 0.5 percent. Total K2O and Fe2O3 increase with depth in the soil profile. The erosion ha/ard is slight on nearly level areas (map unit 2) and moderate on sloping areas (map unit 3). Runoff is little to moderate; permeability is rapid. Njala soils are very low in moisture content during approxi- mately five months of the severe dry season (Table 2) . Detailed descriptions and analytical data for two pro- files, N109 and N108, of the Njala series are given in Appendix B. 4:8:2. SOILS ON COLLUVIAL FOOTSLOPES AND UPPER TERRACES AND IN SWAMPS On the colluvial footslopes and upper tributary ter- races and in swamps, soils such as Mokonde, Bonjema, and Pelewahun occur (Table 2). Downslope from the upland, the upper gravel-free layer becomes progressively thicker. On the upland footslope and highest terrace are the Mokonde soils, which have 10 to 24 inches (25 to 61 cm) of gravel-free material over a gravelly subsoil. At lower elevations are Bonjema soils, which have 2 to 4 feet (61 to 122 cm) of gravel-free material over a gravelly lower subsoil. In similar parent material, poorly drained Pelewahun soils develop in inland swamps. Mokonde Series. Soils of the Mokonde series occur on concave colluvial footslopes (2- to 8-percent gradient) and the upper river and tributary terraces. Mokonde soils are scattered throughout the mapped areas (Fig. 15 and Table 6). The parent material is a gravel-free colluvium, over- lying gravelly colluvium, over gravelly residual material, over weathered bedrock. The gravel-free colluvial top layer is 10 to 24 inches (25 to 61 cm) thick. The col- luvial plinthite glaebules are rounded, hard and dense, and dusky red to reddish black. The gravel content is usually 40 to 60 percent by volume; the thickness of this colluvial layer varies from 10 to 30 inches (25 to 76 cm) . The residual plinthite glaebules, formed in situ, are more irregular and relatively more porous and soft. Hard later- ite sheets are locally present at depths from 30 to 60 inches (76 to 153 cm) below the surface. The gravel content is high (40 to 80 percent by volume), gradually declining with depth and fading into the weathered bed- rock material (Rokel River Series). Quartz veins may be present in the residual material, and quartz gravels may be present in the whole profile. 0 I- 1 O 38 BULLETIN NO. 748 0 10 00 520 z 7 30 ^40 0 50 60 J.A.S.O.N.D J.F.M.A.M.J.J.A.S.O.N.DlJ.F.M.A.M.J .J.A.S.O.N.D J.F.M.A.M.J.J.A.S.O.N.D 0 25 w Q 51 | 76 | 102s 127 ° 153 Soil surface « NI23 - •. 4 « N86 4 IL -i fe 1 |S ] \ 1 1 i l - 1 ilj '| 4 jl f ' " I ' W T. irir~*v lift) l.-^-h-rM-'BMl" *"> ** W-". V N.I. , ,07.64 ,l,i, ,* ,", . , , , i P , i i i *, ',^,0^,66, "iXi i i l i i Ki D. T. 60 - Deeper than 60 inches (153 cm) N.R. = No reading Figure 16. Water levels in Momenga profiles N123, N86, and N44. Textures 'are sandy loam in the topsoil, changing into gravelly clay loam or gravelly sandy clay loam in the sub- soil. The A! horizon is thin, usually less than 10 inches (25 cm) thick (ochric epipedon). Surface soil colors are dark brown to dark yellowish brown (10YR 3/3- 4/3-4/4) ; subsoil colors are yellowish brown to yellow (10YR 5/6-7/6, sometimes 2.5Y 7/6). Prominent red- dish (2.5YR 4/8) mottles are usually present in the subsoil. The soils are moderately well drained and are seldom waterlogged, as is indicated in the water-table graph of profile N42 (Fig. 20). The chemical and physical properties of Mokonde soils can be compared with the Njala soils. The cation-ex- change capacity is less than 10 me/100 g of soil. Ex- changeable contents of Ca, Mg, K, and Na are low. Exchangeable aluminum is about 1 to 2 me/100 g, in- creasing in the subsoil. Base saturation is very low (ap- Figure 17. Njala soils on the upland in the background, and rice growing on Taiama soils in the valley in the foreground. Figure 18. Njala gravelly clay loam contains many hardened plinthite glaebules (gravels) throughout the profile. SECTION 4:8:2 39 1966 1967 1968 1969 J,A,S.O.N,D|J,F,M,A,M,J ,J,A,S,0,N.D|J,F,M,A.M.J .J.A.S.O.N.DJJiF.M.A.M.J .J.A.S.OiNiD Soil surface 10 t/1 IM 5 20 ' 30 Z 50 60 No water within depth of pit for profile N109 during the period of observation in 1967 and 1968 Depth of pit i i i i i i NI08 N-R'_-*- D.T. 60 D.T. 56 -X--N.-1----K D.T! 25 V) 51 £ U K 76 H -I02i O» 1*3 27° 153 D. T. 60 • Deeper than 60 Inches (153 en) Figure 19. Water levels in Njala profiles N109 and N108. N.R. = No reading J.A.S.O.N.DU.F.M.A.M.J.J.A.S.O.N.DlJ.F.M.A.M.J.J.A.S.O.N.D J.F.M.A.M.J.J.A.S.O.N.D Soil surface 10 -[, 25 „ g 20 il 51 | 30 - H| I 76 g u 40 50 UlI iiL 102 g 27 S 60 -11 111 „ N.R. JUUU1A v N.R. N.R „ M : 53 ^.T 63 A D.T 63 D.T. 63 i i i i i i i i i i i i i i i i i ii ii i i i i i i i i i i i D. T. 63 - Deeper than 63 inches (160 cm) N.R. = No reading Figure 20. Water levels in Mokonde profile N42. proximately 5 percent, except for the A, horizon) ; pH is very low (pH KC1 = 3.6; pH H2O increases with depth from 4.4 to 4.9) . Organic carbon content of the A! horizon is about 2 percent, sharply decreasing with depth to 0.5 percent and lower. Total contents of Fe2O3, K2O, and P increase with greater depth. Erosion danger is slight on the sloping Mokonde soils, runoff is little, and permeability is moderately rapid. The water-holding capacity is low. The soil moisture content is very low during four months because of the severe dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, N42, of the Mokonde series are given in Appendix B. Bonjema Series. The soils of the Bonjema series are part of the concave colluvial footslopes (2- to 4-percent gradient) and the upper terraces. Bonjema soils occupy a modest part of the surveyed area (Table 6). They occur near Njala and Mokonde soils on footslopes (Fig. 21 ) and on terraces of the Taia River. The parent material is a gravel-free colluvium or allu- vium, over gravelly colluvium, over residual material weathered from the local bedrock (Rokel River Series). The gravel-free upper layer is 24 to 48 inches (61 to 122 cm) thick. The gravelly colluvial layer is thinner than the corresponding layer in Njala and Mokonde soils and often has the character of a stone line less than 10 inches (25 cm) thick. The plinthite glaebules are rounded, hard, and dense; the gravel content varies from 30 to 60 percent by volume. The residual material has soft, more irregular, and relatively more porous glaebules, the number of which gradually decreases with depth. Quartz may be present in varying amounts. Textures are sandy loam to loam in the topsoil, chang- ing into sandy clay loam in the upper subsoil and grav- elly clay loam in the lower subsoil. The AI horizon is thin, usually less than 10 inches (25 cm) thick (ochric epipedon). The colors of the surface soil are very dark grayish brown to dark brown (10YR 3/2-3/3-4/3), changing with depth into yellowish brown (10YR 5/4- 40 BULLETIN NO. 748 Figure 21. Boundary between Njala soils (left), which contain many hardened plinthite glae- bules (gravels) throughout the profile, and Bonjema soils (right), which developed in gravel-free colluvium 24 to 48 inches (61 to 122 cm) thick over gravelly material. 5/6-5/8) ; by about 48 inches (122 cm) deep, the color usually changes into light brownish gray (10YR 6/2). Prominent red mottles (2.5YR 4/8) are usually present at depths of 20 inches (51 cm) or more. Bonjema soils are moderately well to imperfectly drained. They can be waterlogged at the surface and even submerged for a few weeks, as is indicated by the water-table graphs of profile N39 and N105 (Fig. 22). The submersion of profile N 105 in 1969 is considered to be exceptional. Bonjema soils are chemically rather poor. The cation- exchange capacity is low, varying from 6 to 8 me/ 100 g of soil in the topsoil, decreasing with depth to about 4 -. ^ •I me/ 100 g, then usually increasing again in the lower subsoil to values of 8 to 13 me/100 g. Exchangeable contents of Ca, Mg, K, and Na are low. Exchangeable aluminum is lowest in the topsoil (about 1 me/100 g), increasing with depth to about 3 to 4 me/ 100 g or some- times even higher. These values are lower than in Mo- inenga soils but are somewhat higher than in Njala soils. Base saturation is very low except for the upper few inches. The pH is very low (pH KC1 is about 3.4; pH H2O increases with depth from 4.3 to 4.8). Organic carbon content of the A, horizon is about 2 percent, sharply dropping with depth. Total contents of Fe2O3, K2O, and P increase with depth. 1966 1967 1968 1969 J,A.S.O.N,D|j,F,M,A.M,J.J,A,S.O.N.D|j,F.M,A.MiJ,J.AiSiOiN.D|j.FiMiAiMiJiJiAiSiOiNi D. T. 60 - Deeper than 60 Inches (153 cm) N.R. = No reading Figure 22. Water levels in Bonjema profiles N39 and N105. SECTION 4:8:2 41 1966 1967 1968 1969 J.A.S.O.N.D|J,F,M.A.M,J,J.A.S,0,N,D|J,F,M|A|M,J|J,A,SiOiNiDlJ,F,M,A,M,J,J|AiSiOi 3 X i.-.- DT60 D. T. 60 " Deeper than 60 inches (153 cm) Figure 23. Water levels in Pelewahun profiles N106 and N47. N.R. = No reading Erosion danger is slight, runoff is little, and permeabil- ity is moderately rapid. The available water-holding ca- pacity is medium but varies somewhat, depending upon the silt content. The soil moisture content is low during four months of the dry season (Table 2) . Detailed descriptions and analytical data for two pro- files, N39 and N105, of the Bonjema series are given in Appendix B. Pelewahun Series. The poorly drained Pelewahun soils occur in the drainageways or inland swamps that dissect the higher parts made up of Njala, Mokonde, and Bon- jema soils (Fig. 15). Usually, Pelewahun soils are found in the upper reaches of the drainageways; closer to the Taia River, they gradually fade into Taiama soils (Sec- tion 4:8:3). The terrain is nearly level to depressional, with concave slopes of 1 to 3 percent. Pelewahun soils occupy 5 percent of the mapped area (Table 6). The parent material is a gravel-free colluvium or allu- vium, over gravelly colluvium, over residual material de- rived from the parent rock (Rokel River Series). The gravel-free layer is 24 to 48 inches (61 to 122 cm) thick. The gravelly colluvial layer varies in thickness and can be compared with that of the Bonjema soils. Its gravel content ranges from 20 to 60 percent by volume, and often an important part (up to one-half) consists of quartz gravels. The transition to the underlying residual material is often obscure. Weathering bedrock (saprolite) may be found locally about 70 inches (178 cm) below the surface. Textures are loam to fine sandy loam in the topsoil, changing into clay loam in the upper subsoil, gravelly clay loam in the lower subsoil, and, as the bedrock is approached, clay. The silt content often increases in the lower subsoil, especially where saprolite is present. Clay coatings are present in the subsoil, which is argillic. The dark Al horizon ranges in thickness from 7 to 15 inches (18 to 38 cm) , so that both ochric and umbric epipedons are included. The surface soil colors are very dark gray to dark grayish brown (10YR 3/1-4/2). Subsurface soil colors range from yellowish brown to gray (10YR 5/4- 5/1) ; by a depth of 40 inches (102 cm) the color has changed to light gray (10YR 6/1-7/1). Prominent red mottles (2.5YR 4/6-4/8) are present in the subsoil, usually at depths of 20 to 30 inches (51 to 76 cm) or more. The Pelewahun soils are poorly drained. The water table is near, at, or above the soil surface during three to four months, as is indicated in the water-table graphs of profiles N47 and N106 (Fig. 23). In some years, the soils may be deeply flooded during more than one month. Pelewahun soils have poor chemical properties. The cation-exchange capacity is low, varying from 6 to 12 me/100 g of soil. Higher cation-exchange capacity values are due to a higher clay content in certain horizons. Ex- changeable Ca, Mg, K, and Na are low. Exchangeable aluminum is fairly high, ranging from about 2 to 3 me/ 100 g in the surface layer to 3 to 8 me/ 100 g in the lower subsoil. Base saturation is very low, ranging from 3 to 7 percent. The pH is very low (pH KC1 is about 3.3; pH H2O increases with depth from 4.3 to 4.8). Or- ganic carbon content in the A, horizon is 1 to 3 percent, sharply dropping with depth. Erosion is not a problem, and runoff is slow. Perme- ability is moderate. The water-holding capacity is high. The soil moisture content is low during about two months of the dry season (Table 2). These soils are suited for rice production during the rains and for vege- tables in the dry season. 42 BULLETIN NO. 748 Figure 24. Grass and shrub vegetation on Nyawama soils. Detailed descriptions and analytical data for two pro- files, N47 and N106, of the Pelewahun soils are given in Appendix B. 4:8:3. SOILS ox STREAM TERRACES The moderately well-drained Nyawama soils, imper- fectly drained Kania soils, and poorly drained Taiama soils (Table 2) are the major soils on the lower terraces of the Taia (or Jong) River (Fig. 15) ; they also occur in other areas. Although they are of only modest extent (Table 6), these soils are very important because they are gravel-free and they occur on topography that is favorable for intensive cultivation. A wide variety of crops can be grown, including oil palm, rubber, coffee, local food crops, feed grains, and vegetables. Many of the areas near the Taia River could be irrigated during the dry season. Nyawama Series. The Nyawama soils constitute an important part of the nearly level (0 to 3-percent slope) terraces within the large meanders of the Taia River (Fig. 15). The parent material is gravel-free alluvium of the Taia River or, in a few occasions, a deep gravel- free colluvium. The gravel-free material is always more than 48 inches (122 cm) thick. The natural vegetation is grass with scattered shrubs and trees (Fig. 24) . Textures are sandy clay loam to clay loam in the top- soil, usually changing towards clay or sandy clay in the subsoil. The clay content always increases with depth. The A, horizon is usually more than 10 inches (25 cm) thick (umbric epipedon). Surface soil colors range from very dark grayish brown to dark brown (10YR 3/2-3/3) . Subsoil colors are usually yellowish brown (10YR 5/4- 5/6-5/8). Mottling is typical for the subsoil, being dis- tinct and yellowish red (5YR 4/6-5/8) in the upper subsoil, and prominent, abundant, and usually red (2.5YR 4/8-5/8) in the lower subsoil. Nyawama soils are moderately well drained and never have waterlogging problems at the soil surface, as is in- dicated in the water-table graphs of profiles N100, N15, andN71 (Fig. 25). The Nyawama soils have poor chemical properties, but they are better than the soils discussed in Sections 4:8:1 and 4:8:2 — primarily because of the absence of concretions and the presence of a thick A! horizon with an organic carbon content of 1 to 3 percent. Or- ganic carbon content decreases rather gradually with depth. The cation-exchange capacity is low, ranging from 6 to 10 me/ 100 g of soil in the At horizon and 5 to 6 me/100 g in the subsoil. Exchangeable aluminum de- creases with depth from 2 to 1.2 me/100 g and is lower than in the gravelly soils. Base saturation is usually low, 3 to 6 percent ; much higher values are also possible, how- ever, with up to 35 percent in the Aa horizon and 8 to 15 percent at lower depths (profile N15). The pH is very low (pH KC1 is about 3.8; pH H2O usually in- creases with depth from 4.3 to 5.0), but it is slightly 1966 1967 1968 1969 J.A.S.O.N.DlJ.F.M.A.M.J .J.A.S.O.N.DlJ.F.M.A.M.J ,J,A,S.O .N.DlJ.F.M.A.M.J.J.A.S.O.N.D _ Soil surface • ^71 10 -^ f ;i - 520 z - 51 ,30 - r VfL fvlll *\ - 76 Q lif \ ffl , IlJI\ xi i! 102 50 — *™ 4' ^ j^ _5f \ * fit jA * | w Jl ^ v il'l ^ X V AJi n K 1 27 60 D.T.52 N.R \\ Juttjll^VD.T.60^ N'R- / ^ 1 ^f \5i '- N R A / 'D.T.52" Hi , r\ , Ail e-z | .DT6T^ , i6'.^. . . .^^'f , 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D. T. 60 - Deeper than 60 inches (153 cm) N.R. - No reading Figure 25. Wafer levels in Nyawama profiles N100, N15, and N71. SECTION 4:8:3 43 higher than in Bonjema and Pelewahun soils. Total Fe2O-j content ranges from 1.5 to 5 percent and increases with depth. Erosion is not a problem, and runoff is negligible. Permeability is moderate to rapid. The available water- holding capacity is medium. The soil moisture content is low during about four months of the dry season (Table 2). Detailed descriptions and analytical data for three pro- files, N100, N15, and N71, of the Nyawama series are given in Appendix B. Kania Series. Kania soils occupy the lower areas of the nearly level terraces of the Taia River (Fig. 15). They occur near drainageways on nearly level terrain, with slopes of 0 to 2 percent. These soils are of minor extent (Table 6). The parent material is gravel-free alluvium from the Taia River, or occasionally gravel-free colluvium. The gravel-free material is always more than 48 inches (122 cm) thick. Textures are sandy clay loam to clay. The clay con- tent increases with depth. The Aj horizon is more than 10 inches (25cm) thick (umbric epipedon). Surface soil colors range from black to very dark grayish brown (10YR 2/0-3/2), changing towards yellowish brown or pale brown ( 10YR 5/4-5/8-6/3) in the upper subsoil and towards light brownish gray to light gray (10YR 6/2- 7/1 ) in the lower subsoil. Mottling starts within 22 inches (56 cm) from the surface, being first strong brown (7.5YR 4/4-5/6) and gradually changing into distinct and prominent red (2.5YR 4/8) . Kania soils are imperfectly drained. They are usually waterlogged at the surface for about two months, includ- ing submergence of approximately one month, as is indi- cated in the water-table graph of profile N70 (Fig. 26). The Kania soils are slightly finer textured, darker colored, and have a higher cation-exchange capacity than Nyawama soils. The organic carbon content of Kania is approximately 3 percent in the thick Ax horizon and about 1 percent in the A3 horizon; below this, it gradu- ally declines with depth. The cation-exchange capacity is relatively high in the A! horizon (11 me/100 g) but drops sharply in the subsurface and subsoil to 4 to 7 me/100 g. Exchangeable Ca, Mg, K, and Na are low. Exchangeable aluminum increases gradually with depth from 1.3 to 1.9 me/100 g. Base saturation is very low, 2 to 5 percent. The pH is also low (pH KC1 is about 3.9; pH H2O is usually 4.3 to 5.0). Total Fe2O:! contents are within the range of those in the Nyawama soils. Runoff and erosion are negligible. Permeability is moderate. The available water-holding capacity is me- dium, and the soil moisture content is low during approx- imately three months of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, N70, of the Kania series are given in Appendix B. Taiama Series. Soils of the Taiama series occur in the drainageways of the terraces of the Taia River and in the downstream portions of its tributaries (Fig. 17). They are scattered throughout the surveyed area, next to Kania and Nyawama soils or, more frequently, near soils of the colluvial footslopes and uplands (Fig. 15). On tributaries of the Taia River, Taiama soils often occupy the downstream portion, and Pelewahun soils oc- cur upstream. The terrain is almost flat, with gentle slopes of 0 to 3 percent. Taiama soils occupy approxi- mately 6 percent of the area that was mapped (Table 6). The parent material is a gravel-free alluvium of the Taia River or a usually gravel-free colluvium and allu- vium of the tributaries. The gravel-free layer is more than 48 inches (122 cm) thick, except in a few areas where a thin (less than 10 inches or 25 cm) gravelly colluvial layer, consisting of plinthite and quartz, may be present within 48 inches (122 cm) from the surface. The thickness of the gravel-free layer is an important differ- ence between Taiama and Pelewahun soils (Section 4:8:2). 1966 1967 1968 1969 J.A.S.O.N.D J ,F,M. A.M, J , J.A^.O.N.O J.F.M. A.M, J , J . A.S.O ,N.D J.F.M, A.M, J. J,A, S,0,N, D n Soil surface V ry w U \ 10 I 1 • 25 „ 1 at g ^20 - . . 51 S UJ 1 3s 1C L1" n H 230 . V 76 % 1 o = 40 . I . 02 i Q_ 1 H LU a. °50 - . 27 ° t N.R. • 60 D.T 57' XD.T. 60 N.R. „ Iv D.T. 60 53 D.T. 60 D. T. 60 • Deeper than 60 Inches (153 cm) Figure 26. Water levels in Kania profile N70. N.R. = No reading BULLETIN NO. 748 1966 1967 1968 1969 J.A.S.O.N.D|j.F,M.A,M.J.J,A|SiO,N,D|j,F,M.A.M.J.J,A.SiO.N,D|j|F,IVI,A,M,J,J.A,S,0,N,D 10 o T. 10 20 J 30 40 50 60 Soil surface D.T.60 N.R. „ wdU D.t D.T.58 58 25 0 25 , [ [ 51 | 76 j -102: I 127' 153 D. T. 60 - Deeper than 60 inches (153 cm) Figure 27. Water levels in Taiama profile N101. N.R. = No reading Textures are usually clay loam in the topsoil, changing into sandy clay and clay in the subsoil. The Aa horizon varies in thickness, but it is typically more than 10 inches (25 cm) thick. It is usually an umbric epipedon, but in some of the upstream portions of the tributaries it does not always qualify. Surface soil colors range from black to dark grayish brown (10YR 2/1-3/1-3/2-4/2), chang- ing into dark gray to light brownish gray (10YR 4/1- 5/2-6/2) in the subsurface soil. In the subsoil, colors are light gray to white (10YR 7/1-8/1-2.5Y 7/2-8/2-8/0); chromas are 2 or less. Mottling starts at the surface or at shallow depths, being brownish and faint near the sur- face, changing rapidly towards distinct and prominent red or dark red (2. SYR 4/8-3/6) in the subsoil, and in- creasing in abundance with depth. Taiama soils are poorly drained. They have water- logging problems at the surface for three to four months during the rainy season, including submergence for more than one month, as is indicated in the water-table graph of profile N101 (Fig. 27). The chemical properties of the Taiama soils are simi- lar to those of the Kania soils. Organic carbon content is high in the topsoil (about 3 percent) ; below this, it decreases sharply with depth. The cation-exchange ca- pacity is highest in the Aa horizon, up to 14 me/100 grams of soil, but it drops sharply to 5 to 6 me/100 g in the subsurface and subsoil. Exchangeable Ca, Mg, K, and Na are low. Exchangeable aluminum ranges from 2 to 3 me/ 100 g, slightly more than in Kania soils. Base saturation is very low, 3 to 5 percent. The pH is also low (pH KC1 is about 3.3 in the subsoil; pH H2O ranges from 4.2 to 4.8) . Total Fe2O3 and K2O are lower in Tai- ama soils than in Kania soils. Runoff is slow, and erosion is not a problem. Perme- ability is moderate. The available water-holding capacity is medium ; the soil moisture content is low during about two months of the dry season (Table 2) . These soils can be used for rice during the rains and for vegetables in the dry season. A detailed description and analytical data for a repre- sentative profile, N101, of the Taiama series are given in Appendix B. 4:8:4. SOILS ON ALLUVIAL FLOODPLAINS Along the Taia (or Jong) River banks on the current floodplain, gravel-free soils occur that have loamy or clayey textures and still contain weatherable minerals, especially mica. These soils, which belong to the Puje- hun, Gbesebu, and Mokoli series (Table 2), are among the most productive in Sierra Leone. Their scattered oc- currence, difficult accessibility during the wet season, and the danger of occasional flooding have deterred the in- tensive use of these soils. Pujehun Series. Pujehun soils occur on very gentle, convex slopes on natural levees next to the Taia River (Fig. 15) . These soils are of limited extent (Table 6) . The parent material is gravel-free alluvium from the Taia River. Its textures are fine sandy loam to fine sandy clay loam in the topsoil, changing towards sandy clay- loam or clay loam in the subsoil. The sand fraction is dominated by the fine and very fine fractions (0.25-0.05 mm). There are many mica particles in the sand frac- tion. The silt content is low. The AI horizon is usually less than 10 inches (25 cm) thick (ochric epipedon). The colors of the surface soil are very dark grayish brown to dark brown (10YR 3/2- 3/3-4/3) . Subsoil colors are yellowish brown to brownish yellow or strong brown (10YR-7.5YR 5/6-5/8). Red mottles may be present in the subsoil, usually becoming more prominent and increasing in abundance with depth. Pujehun soils are well drained; they are seldom water- logged at the surface or submerged. However, the ground water fluctuates in the lower subsoil from 30 to 60 inches (76 to 153 cm) during the rainy season, under the influence of changes of the water level in the adja- cent stream, as is indicated in the water-table graph of profile N80 (Fig. 28). SECTION 4:8:4 45 1966 1967 1968 1969 J,A.S.O.N.D|J.F.M.A.M.J.J.A,S.O.N.D|J.F.M.A.M.J.J,A.S.O.N.D|J.F.M.A.M,J.J,A.S.O.N.D 0 10 ft 120 .30 E 50 60 Soil surface 0 25 £ 51 I H 76 § 102 == S 127° 153 N.R. 'D.T.6,6 /-*- D.T. 55 -X---* D. T. 60 - Deeper than 60 inches (153 cm) Figure 28. Water levels in Pujehun profile N80. N.R. » No reading Organic carbon content is nearly 3 percent in the thin A, horizon but decreases sharply with depth. Puje- hun soils have poor chemical properties. Cation-exchange capacity is low, varying from 3 to 9 me/100 grams of soil. Exchangeable Ca, Mg, K, and Na are very low. Exchangeable aluminum is comparatively low, 1 to 2 me/100 g. Base saturation is low (3 to 7 percent), as is pH. The pH KC1 is approximately 3.9; pH H2O ranges from 4.4 to 4.8, with the higher values in the lower sub- soil. Total K2O and CaO contents are greater in Pujehun soils, which are currently receiving deposition, than in other soils in the area. Permeability is rapid, and runoff is negligible. There may be occasional deposition by flowing water and occa- sional streambank erosion. Available water-holding ca- pacity is medium to high because of the fine sandy clay loam texture. The soil moisture content is low during about three months of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, N80, of the Pujehun series are given in Appendix B. Gbesebu Series. The soils of the Gbesebu series make up the major portion of the current alluvial floodplain of the Taia River (Fig. 15 and Table 6). They always occur near the river at slightly lower elevations than the associated Pujehun soils. The terrain is nearly level. The parent material is clayey alluvium, always more than 48 inches (122 cm) thick. Its textures are silty clay in the topsoil and usually clay in the subsoil. The silt content is moderately high, 35 to 45 percent, most of which is fine silt (0.02 to 0.002 mm). Mica flakes are nearly always present in varying amounts. The colors of the surface soil are very dark brown to brown (10YR 2/2-3/2-3/3-4/3). The At horizon varies in thickness. Although it is usually less than 10 inches (25 cm) thick (ochric epipedon), it is sometimes thick enough and dark enough to be umbric — for example, as in part of the area northwest of the bridge over the Taia River at Taiama. In the subsoil, the colors gradually change with depth towards yellowish brown, strong brown, reddish yellow, or yellow (10YR-7.5YR 5/6-5/8- 6/6-6/8-7/8). Mottles are usually present in the sub- soil, increasing in frequency and prominence with depth. Mottle colors are strong brown, yellowish red, and red (7.5YR-2.5YR 4/6-5/8). Gbesebu soils are moderately well drained to well drained. In most years, however, they are waterlogged at the surface for some time; local spots may briefly be deeply flooded by the Taia River. This is illustrated by the water-table graph of profile N125 (Fig. 29). Gbesebu soils have better chemical properties than most other soils in the Njala area. The organic carbon content of the At horizon is high, up to 4.5 percent. It decreases rapidly with depth but still is greater than in most other soils. The cation-exchange capacity of the A! horizon is also fairly high, up to 19 rne/100 grams of soil, whereas subsoil values range from 6 to 9 me/100 g, still somewhat higher than in Pujehun soils. Exchange- able aluminum is slightly higher in Gbesebu than in Pujehun soils. Base saturation is usually low, 3 to 9 per- cent, except in some AI horizons where it is higher. The pH is also low (pH KC1 is about 3.7; pH H2O ranges from 4.0 to 4.8, increasing with depth). Total K2O and CaO are lower in Gbesebu than in Pujehun soils, but the total Fe2O3 content of Gbesebu is higher. Runoff and erosion are negligible. Permeability is moderately rapid. The available water-holding capacity is high because of the relatively high content of silt in this soil. The soil moisture content is low during about two months of the dry season (Table 2). With proper fertilization, the Gbesebu soils can be used intensively to produce up to three crops annually. One crop, such as rice, can be grown from May to August during the rains; a second crop, such as maize, can be produced during the declining rains from September to December; and a third crop can be grown from January to April with ir- rigation water from the Taia River. 46 BULLETIN NO. 748 1966 1967 1968 1969 J,A,S,0|N.D|j.F.M.A,M.J,J.A.S.O.N,D|j,F,M.A,MiJiJ.A.S.OiNiD|j.FiM.AiMiJi J, A,S,0,N,D D. T. 60 = Deeper than 60 Inches (153 cm) N.R. = No reading Figure 29. Water levels in Gbesebu profiles N125 and N13. A detailed description and analytical data for two profiles, N125 and N13, of the Gbesebu series are given in Appendix B. Mokoli Series. The Mokoli soils occur in drainageways on the alluvial floodplain of the Taia River (Fig. 15). They are usually surrounded by Gbesebu soils or oc- cur between those and higher terrace soils such as Nyawama or Bonjema. Mokoli soils are of limited extent (Table 6). The terrain is nearly level and usually slightly depressed. The parent material is more than 48 inches (122 cm) of gravel-free alluvium from the Taia River. Its textures are silty clay to clay. The silt content is moderately high, 30 to 40 percent, most of it in the fine silt fraction (0.02 to 0.002 mm) . Mica flakes are usually present in varying amounts. The dark-colored A1 horizon varies in thickness; it may be less than 10 inches (25 cm) thick (ochric epipe- don) or sometimes more than 10 inches thick (umbric). The colors of the surface soil are black to dark grayish brown (10YR 2/1-2/2-3/2-4/2), changing with depth towards yellowish brown (10YR 5/4-6/4) in the upper subsoil and towards pale brown (10YR 6/3-7/3) in the lower subsoil. Reddish-brown to red (SYR 4/4-2.5YR 4/6) mottles may be present throughout the profile (with the exception of the Aj horizon), increasing in abun- dance and prominence with depth. Mottles with chromas of 2 or less may also be present. Mokoli soils are imperfectly to poorly drained. They are usually waterlogged at the surface and submerged as long as three months during the rainy season, as is in- dicated by the water-table graph of profile N14 (Fig. 30) . Natural drainage, subsoil colors, and mottles are the most important differences between Mokoli and Gbesebu soils. The chemical and physical properties of Mokoli soils and Gbesebu soils are somewhat similar, except those associated with organic matter content and moisture regime. The organic carbon content of the AI horizon (5.5 percent) is greater than in Gbesebu soils and de- creases regularly with depth. The cation-exchange ca- pacity is usually higher in the A, horizon of Mokoli soils, up to 23 me/100 grams of soil, gradually decreas- ing to 9 me/100 g in the subsoil. Exchangeable Ca, Mg, K, and Na are low. Exchangeable aluminum decreases with depth from 2.9 to 1.6 me/100 g. Base saturation is very low, 2 to 8 percent. The pH is also low (pH KC1 = 3.7; pH H2O increases from 4.5 in the topsoil to 5.0 in the subsoil) . Runoff is slow, and Mokoli soils are subject to slight deposition during periods of flooding. Permeability is moderate. Available water-holding capacity is high. Mokoli soils are low in moisture content during only about one month of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, N14, of the Mokoli series are given in Appendix B. 4 : 9. AREA J* — GRANITE AND ACID GNEISS, MAKENI AREA The interior plateaus and hills of the eastern part of Sierra Leone are separated from the low-lying interior plain to the west by an escarpment region in which the elevation increases from 250 feet (76 m) in the west to 1,000 feet (305 m) in the east. Area J* consists of that part of the escarpment region that is under secondary bush or forest. It consists of a northwest-southeast strip 15 to 50 miles (24 to 80 km) wide through central Sierra Leone, including the towns of Makeni, Magburaka, Yele, Bo, Blama, and Zimi. The escarpment is most abrupt in SECTIONS 4:9:1-4:9:2 47 1966 1967 1968 1969 J.A.S,0|N.D|j,F,M.A.M.J.J.A.S.O,N.D|j.F.M, A.M.J,J,A,S.O,N.D|j|F.MiA|M,JiJ|AiSiO.NiO wttawl \J, | . w II I I I I I III D. T. 60 " Deeper Chan 60 inches (153 en) Figure 30. Water levels in Mokoli profile N14. N.R. = No reading northern Sierra Leone. In central Sierra Leone, the ero- sion of the scarp is more advanced, and there are many large dome-shaped hills (inselbergs) near Makeni. Far- ther south, the escarpment region is much broader, more highly dissected, and less clearly defined than in the north. Annual rainfall ranges from 100 to 140 inches (254 to 356 cm), with 121 inches (308 cm) at Makeni (Appen- dix A) . In the northwestern part of this area, 90 to 95 percent of the rain falls from May to November; in the southeastern part, 85 to 90 percent of the precipitation falls during that period. Thus, the severity of the dry season decreases in a southeastern direction. The vegeta- tion consists mainly of secondary bush, but remnants of moist evergreen forest are present in the southeastern part, especially in the Gola Forest Reserve (17}. The bedrock is acid gneisses and granite and contains a moderate amount of weatherable minerals; thus, soils developed from it have a moderate nutrient status, espe- cially the soils on steep slopes where fresh minerals are exposed. A soil survey has been conducted in the northern part of this area, near Makeni. The four major landscapes in the mapped area are the steep hills or inselbergs of hard granite or gneiss designated "Rock Land," upland ero- sion surfaces, colluvial footslopes and upper terraces and swamps, and current alluvial floodplains. The major soil series occurring on these landscapes (Table 2) are dis- cussed in the remainder of Section 4:9; additional infor- mation is also available (75) . The distribution of various soils is shown in the soil association map of the Makeni area, Sierra Leone (Fig. 31), and the extent of each soil association is given in Table 7. 4:9:1. SOILS ON STEEP HILLS OR INSELBERGS Inselbergs, large dome-shaped granite hills with steep slopes (Fig. 32), predominate in the area designated "Rock Land" on Figure 31. However, some other areas with outcropping granitic bedrock are also included with Rock Land. Bedrock occurs on the surface or at very shallow depths. A thin layer of soil material up to 20 inches (51 cm) thick may occur locally, usually in small pockets. If a thin soil is present, its properties can be compared to Mabanta soils (see Table 2), described by van Vuure and Miedema (75) . Erosion danger is very great, especially on very steep slopes (up to more than 100-percent gradient). Because water must flow on the surface of the rock, runoff is very rapid. These areas of Rock Land have no value for com- mercial plant production and should be limited to uses for wildlife, water supply, recreation, or esthetic purposes. 4:9:2. SOILS ON UPLAND EROSION SURFACES On the uplands, there are deep gravelly soils (Makeni and Timbo), shallow soils over granite bedrock (Ma- banta, described in 75), and soils with gravel-free collu- vial surface material over gravelly subsoils (Mabassia). Timbo Series. Timbo soils, scattered throughout the mapped area (Fig. 31), occupy approximately 5 percent of the uplands (Table 7). They occur on moderate to steep slopes. Table 7. Area of different soil associations in the Makeni area, as shown in Figure 31 Soil association Area Symbol on map Name Acres Hectares total area J K Makeni, Timbo Mabanta and Mabassia, 14,400 1,900 5,765 764 54.9 7.3 L Mabassia, deep and very . 1,100 444 4.2 M 2,185 874 8.3 N O p Masheka, Bosor Makundu 315 540 5,040 126 217 2,022 1.2 2.1 19.3 R Rock Land 720 288 2.7 Total 26,200 1 0,500 100.0 48 BULLETIN NO. 748 Ld Z O LJ cc a: LJ CO LL) CC LJ LJ X H L_ O O O O CO CO < O CO ro cr o I kj ^l 1 CO CO 0 in a> •o < ial Footslop Terraces , TUBUM A, BOSOR O "a. T3 o 0 li_ o z> Bottoms E, PANLAP * < <§5 i - MABANT/ - MABASS > = >, §i c£ °H - MASUBA - MASHEK 3 c O - MAKUND a> o c - MANKAN Granite _J ^ O i i in ~3 * -i in ^ z U) O to a_ S" °t '5 "5 c "5 "6 .2? CO CO< CO CO CO /, % SECTION 4:9:2 49 Figure 32. Rock Land in the background and rice growing on Panlap soils in the valley in the foreground. The parent material is a gravelly colluvium, overlying gravelly residual material, over weathered bedrock (saprolite of granite or of acid gneiss). Partly decom- posed bedrock fragments, which contain some weather- able minerals, are encountered within 48 inches (122 cm) of the soil surface. The colluvial hardened plinthite glaebules, which are nodular, very hard, and relatively dense, amount to approximately 50 percent of the volume of this soil. The residual hardened plinthite glaebules, formed in situ, are more irregular, more porous, softer, and usually coarser. The gravel content decreases grad- ually with depth, whereas the proportion of weathered bedrock increases. A gravel-free surface layer is very thin (less than 10 inches or 25 cm) or absent. The tex- ture is gravelly sandy clay loam in the surface, subsurface, and subsoil. The clay content increases slightly with depth. The very coarse sand fraction is fairly high. The very dark gray to dark brown (10YR 3/1-3/3) A horizon is usually 10 to 20 inches (25 to 51 cm) thick ( uinbric epipedon ) . Subsoil colors vary in hue from 7.5YR to 2.5YR, with values of 4 or more and chromas of 6 or more. A common subsoil color is yellowish red (5YR 5/8). Mottles are usually absent in the subsoil but are common at greater depths (80 to 90 inches or 203 to 229 cm). Timbo soils are well drained and are never waterlogged at the surface (Table 2) . Timbo soils have low nutrient levels for plant growth. The cation-exchange capacity varies from almost 8 me/ 100 g of soil smaller than 2 mm in the A, horizon to less than 4 me in the subsoil. Exchangeable aluminum is fairly low, being highest in the A12 horizon (1.09 me/ 100 g) and gradually decreasing with depth to 0.24 me/ 100 g in the B22 horizon. Base saturation is rather low, being lowest in the A12 horizon (9.9 percent) and in- creasing markedly in the lower subsoil (21.4 percent). The pH is low, also, increasing slightly in the subsoil (pH KC1 is 4.2 to 4.6, and PH H2O is 4.6 to 4.9). Ex- changeable contents of Ca, Mg, K, and Na are low, being highest in the upper 12 inches (30 cm) and much lower in the underlying horizons; in the B22 horizon, however, higher contents are found again. Organic car- bon content is highest in the Aj horizon (2.34 to 1.87 percent) and much lower in the deeper soil layers; how- ever, the carbon content remains fairly high in the sub- soil. The water-holding capacity is very low, mainly be- cause of the high gravel content. Total contents of Fe2O3 are high in all horizons and increase with depth, but total K2O and CaO are low. Erosion danger is usually moderate, depending upon the degree of slope. Runoff is moderate, reflecting the soils' rapid to moderate permeability. Runoff and erosion are also affected by farming methods. Timbo soils are very low in moisture content during approximately four months of the severe dry season (Table 2) and are below the wilting point (15 atmo- spheres moisture content) in the A horizon in February and in the upper B horizon during March (Fig. 33 and Appendix B) . A detailed description and analytical data for a repre- sentative profile, PI 9, of the Timbo series are given in Appendix B. Makeni Series. The Makeni soils are by far the most extensive ones in the Makeni area, occupying approxi- mately 50 percent of the mapped area (Table 7 and Fig. 31 ). In area J on Figure 31, Makeni soils occupy the ridge summits and usually the gentle to moderate slopes with gradients not exceeding 15 percent, but they are occasionally interspersed with Timbo soils on some steeper slopes. The parent material is a gravelly colluvium, overlying gravelly residual material, over weathered bedrock (saprolite) ; the latter is always found at depths of more than 48 inches (122 cm). A very thin gravel-free surface layer of 0 to 10 inches (0 to 25 cm) may be present. The colluvial hardened plinthite glaebules are rounded and nodular, very hard and dense, and fine to medium sized, with red and yellow colors. The gravel content of the colluvial surface layer varies from 40 to 80 percent by 50 BULLETIN NO. 748 40 30 Interpolated line • 0-4 Inches (0-10 cm) depth X 12-16 inches (30-40 cm) depth • 24-28 inches (60-70 cm) depth A 35-19 Inches (90-100 cm) depth -40 w -30 ' SEPT. OCT. 1968 Figure 33. Moisture content in Timbo profile P19. 40 ' 30 120 i MAR APR 1969 • 0-4 Inches (0-10 cm) depth X 12-16 Inches (10-40 CGI) depth • 24-28 Inches (60-70 en) depth A 35-39 Inches (90-100 CM) depth -40 . • 30 Interpolated 11 JULY AUG. SEPT. OCT. NOV. OEC. JAN. FEB. MAR. APR. MAT JUNE JULY 10 0 25 E30 ' 51 Q i40 during the period of observstlon In 1968 snd 1969 102 gso • . 127 60 Depth of pit 53 Figure 34. Moisture content and water levels in Makeni profile P2. volume, and its thickness ranges from 20 to 60 inches (51 to 153 cm). The residual hardened plinthite glae- bules are medium and coarse nodular to angular; with increasing depth, they become relatively more porous and softer. They have been formed in situ. The gravel content is still very high, gradually declining with depth and being replaced at about 80 to 90 inches (203 to 229 cm) or more by red plinthite mottles in a light gray to white matrix that is often rich in quartz fragments and coarse sand particles. The total thickness of both colluvial and residual gravelly layers may be up to 10 feet (3m). The transition between the two layers is very diffuse. Textures of the fine earth (the fraction smaller than 2 mm) are sandy clay loam in the surface soil and sandy clay or clay in the subsoil. The A, horizon is very dark gray (10YR 3/1) to dark brown (7.5YR 4/4), 10 to 20 inches (25 to 51 cm) thick (umbric epipedon). Subsoil colors vary in hue from 7.5YR to 2. SYR, with values of 4 or more and chromas of 6 or more. A common subsoil color is yellow- ish red (SYR 5/8). Mottles are usually absent in the surface and subsurface soil but are common at greater depths (80 to 90 inches, or 203 to 229 cm) . Makeni soils are well drained and are never waterlogged at the sur- face, as is indicated in the water-table graph of profile P2 (Fig. 34). Makeni soils have a low nutrient status for plants. Compared with most other soils in the survey area, how- ever, and with other upland soils in Sierra Leone (for example, the Njala series, described in Section 4:8:1), the Makeni soils are relatively rich in nutrients. Except for the Aj horizon, the cation-exchange capacity is less than 10 me/100 g of soil smaller than 2 mm. Exchange- able aluminum is fairly low, varying from 0.16 to 1.05 me/100 g of soil. Base saturation is rather low, ranging from 14.5 to 36 percent, and the pH is also low (pH H2O is 4.7 to 5.2, and pH KC1 is 4.2 to 4.6). Exchange- able contents of Ca, Mg, K, and Na are fair in the At horizon but low in the subsoil. The organic carbon con- tent of the A! horizon is high (about 4 percent) but declines sharply in the B horizon. However, the carbon contents remain fairly high to considerable depths : about 1 percent at 70 inches (178 cm) is possible. The water- holding capacity is very low, because of the high gravel content. Total contents of Fe2O3 are high in all horizons and increase with depth. Total K2O is low, and CaO is low except in the Aa horizon. The erosion hazard is slight on nearly level summits and moderate on sloping areas. Runoff is little to mod- erate, depending upon slope and farming practices. Per- meability is rapid to very rapid. Makeni soils are very low in moisture content during approximately five SECTION 4:9:3 51 months of the severe dry season (Table 2). They were below the wilting point (15 atmospheres moisture con- tent) during January, February, and March, 1969 (Fig. 34 and Appendix B) . A detailed description and analytical data for a repre- sentative profile, P2, of the Makeni series are given in Appendix B. Mabassia Series. Mabassia soils occupy approximately 15 percent of the uplands or 10 percent of the total mapped area in the Makeni area (Table 7). They occur on relatively lower concave gentle slopes of the uplands, primarily in areas K and L on Figure 31. Mabassia soils have developed in colluvial material that is washed down from the neighboring higher areas; it can be aptly called "hill-wash." The colluvial layer is almost gravel-free and varies considerably in thickness. It is underlain by a gravelly subsoil (see description of Makeni series), which, in turn, gradually merges into the weathered bedrock (saprolite). The amount of hardened plinthite glaebules in the subsoil varies con- siderably; it may be slightly gravelly to very gravelly. Three phases of the Mabassia series have been recog- nized, based upon the thickness of the gravel-free collu- vium over gravelly subsoil: the very shallow phase, 10 to 24 inches (25 to 61 cm) gravel-free; the shallow phase, 24 to 48 inches (61 to 122 cm) gravel-free; and the deep phase, more than 48 inches (122 cm) gravel-free. Detailed descriptions and analytical data are given in Appendix B for soil profiles P71 and P108, which are representative of the shallow and deep phases, respec- tively, of the Mabassia series. Textures of the fine-earth fraction (< 2.0 mm) are sandy loam to sandy clay loam in the A horizon and sandy clay loam to sandy clay in the B horizon. The A! horizons range from very dark gray (10YR 3/1) to dark brown (10YR 3/3) in color and from 10 to 25 inches (25 to 63 cm) thick (umbric epipedon). Subsoil colors usually have a hue of 10YR or 7. SYR, with values of 5 or more and chromas of 4 or more. Typical subsoil colors are yellow (10YR 7/8) to reddish yellow (7. SYR 6/8). Mottles are usually absent. Mabas- sia soils are well drained and are never waterlogged at the soil surface (Table 2) . The nutrient status of Mabassia soils is low except in the An horizon, which contains more organic matter than the other horizons. The cation-exchange capacity ranges from 8 to 12 me/ 100 g of soil in the A horizon and declines to 2 to 4 me/100 g in the lower subsoil. Exchangeable aluminum is low, usually less than 1 me/ 100 g of soil. Exchangeable contents of Ca, Mg, K, and Na are low, being highest in the surface horizon and much lower in underlying horizons. Base saturation is approximately 30 percent in the An horizon, declines to 6 to 9 percent at depths of about 3 feet (1m), and then increases to 17.5 percent at greater depths. The pH is low (pH H2O is 4.7 to 5.2, and pH KC1 is 4.1 to 4.6) . Total contents of Fe2O3 are moderately high (5 to 12 per- cent). Total K2O is low, and CaO is low except in the An horizon. The available water-holding capacity is low for Mabassia, shallow phase, and medium for Mabassia, deep phase. Permeability is moderately rapid. Runoff and erosion hazards are slight. Mabassia soils are low in moisture content during approximately four months of the dry season (Table 2). During the dry season early in 1969, the Mabassia deep phase profile, PI 08, stayed above the wilting point in moisture content (Fig. 35 and Appendix B), but the Mabassia shallow phase profiles, P74 and P79, were below the wilting point (15 atmospheres moisture content) in the A horizon during January and February and in the B horizon during February, March, and into April (75) . 4:9:3. SOILS ON COLLUVIAL FOOTSLOPES AND UPPER TERRACES AND IN SWAMPS The well- and moderately well-drained soils that occur on colluvial footslopes and upper tributary terraces in- clude soils of the Bosor, Tubum, Masheka, and Masuba series (Fig. 31). Bosor and Tubum have gravel-free soil layers over gravelly subsoils; Masheka and Masuba soils developed in gravel-free, fine-loamy alluvium and colluvium (Table 2). In the poorly drained valley bottoms and swamps (area P on Fig. 31 ), rather extensive areas of Panlap and Mankane soils developed in coarse-loamy alluvium and colluvium (Table 2 and Table 7) . Bosor Series. Bosor soils occur in small areas on the older tributary terraces and colluvial footslopes, and oc- cupy about 1 percent of the area that was mapped (Fig. 31 and Table 7). They are on nearly level to sloping to- pography (2- to 8-percent gradient) near large streams. They occur on higher elevations than the Tubum soils and usually in different places in the survey area. Bosor soils consist of a gravel-free colluvial or alluvial layer 24 to 48 inches (60 to 122 cm) thick over a gravelly subsoil. The thick gravel-free layer originates from higher parts in the terrain and may be transported either from adjoining hills (hill-wash) or by a stream from other places. The gravel-free layer is fine sandy loam in the topsoil and fine sandy clay loam in the underlying layers. The lower subsoil is gravelly sandy clay loam. The A! horizon is very dark grayish brown (10YR 3/2) to dark brown (10YR 3/3) and is 10 to 20 inches (25 to 51 cm) thick (umbric epipedon). The subsoil colors are browner than those of Tubum soils; hues are SYR to 7.5YR, values are 4 or more, and chromas are 6 or more. Common subsoil colors are yellowish red to strong brown (SYR 5/8-7.5YR 5/8) . Bosor soils are well drained and are never waterlogged at the surface, as is shown in the water-table graph of profile P60 (Fig. 36). The nutrient status for plant growth is rather low. The cation-exchange capacity varies from about 7 me/100 g of soil smaller than 2 mm in the A! horizon to about 4 me in the subsoil. Exchangeable amounts of Ca, Mg, K, and Na are low. Exchangeable aluminum is fairly low, being highest in the lower A horizon (1.24 me) and de- 52 BULLETIN NO. 748 40 M 'SO "20 i I" • 0-4 Inches (0-10 cm) depth X 12-16 Inches (30-40 cm) depth • 24-28 inches (60-70 cm) depth A 35-39 Inches (90-100 cm) depth Interpolated line 1*0 »« 30 ' | 202 i .OS SEPT. OCT. 1968 Figure 35. Moisture content in Mabassia, deep profile P108. MAR. APR. 1969 • 0-4 Inches (0-10 en) depth X 12-16 Inches (30-40 cm) depth • 24-28 Inches (60-70 cm) depth A 35-39 Inches (90-100 cm) depth JUNE Interpolated 11 Soil surface JULY AUG. SEPT. OCT. NOV DEC JAN. FES. MAR. APR MAY JUNE JULY 1968 1969 30 > 20 S i 10- it. 40 £ SO 60 D.T 51 MAY JUNE JULY AUG. SEPT OCT. 1968 D. T. 51 - Deeper than 51 Inches 51 E30 - 76 s "40 - 102; £50 1 127 1 A A 3 60 - f^\ ^^*\W *J \ r*~ _. 153 " D.T62 DT 62 OT 62 D.T 62 1 1 1 1 1 1 1 1 1 1 1 1 1 MAY JUNE JULY AUG. SEPT D. T. 62 - Deeper than 62 inches (158 cm) 1968 Figure 38. Moisture content and water levels in Masheka profile P49. and pH H2O from 5.4 to 4.5). The organic carbon con- tent is high in the A, horizon (2.96 to 1.17 percent) ; in the subsoil, it gradually decreases to less than 0.5 percent. Total contents of Fe2O3 are relatively low (3.2 to 4.6 per- cent), and CaO is low except in the surface horizon. Total K2O content (1.1 percent) is higher than in many soils in higher rainfall areas in Sierra Leone. Masheka soils have a low available water-holding capacity. Permeability is moderate. Runoff and erosion danger are slight. Masheka soils are low in moisture content dur- ing approximately four months of the dry season (Table 2). During February, 1969, the moisture content of the topsoil and also of a subsoil layer at a depth of 35 to 39 inches (89 to 99 cm) in Masheka profile P49 was below the wilting point (Fig. 38 and Appendix B). A detailed description and analytical data for a repre- sentative profile, P49, of the Masheka series are given in Appendix B. Masuba Series. The Masuba soils occur on the lowest parts of recent tributary terraces, bordering larger streams and swamps in areas where Panlap and Man- kane soils predominate (Fig. 31). Masuba soils usually occur on gentle slopes of less than 4-percent gradient. They occupy approximately 4 percent of the area near Makeni in which soils were mapped (Table 7). The parent material is deposited by colluvial or allu- vial action or both, which has resulted in a gravel-free soil layer more than 48 inches (122 cm) thick, overlying gravelly or gravel-free residual material in the lower sub- soil. The texture is rather uniform sandy clay loam throughout the solum. Topsoil colors are very dark grayish brown or very dark brown (10YR 3/2-2/2). The dark A, horizon is usually 10 inches (25 cm) or more thick (umbric epipe- don), but in profile P9 it is only 7 inches (18 cm) thick (ochric epipedon) . Colors in the subsoil are characterized by hues of 10YR or yellower, chromas of 3 or more, and values of 5 or more, accompanied by distinct to prominent mottles (7.5YR or redder). Masuba soils are usually moderately well drained ; however, they gradually merge into almost imperfectly drained conditions in the transition zone to Panlap soils. Masuba soils never have waterlogging problems at the soil surface (Table 2) . Dur- ing the rainy season of 1968, groundwater fluctuated be- tween about 50 and 65 inches (127 and 165 cm) below the surface in profile P9, as is indicated in Figure 39. The nutrient status for plant growth in Masuba soils is very low. The cation-exchange capacity varies from nearly 6 me/100 g of soil in the surface horizon to 3 me in the subsoil. Amounts of exchangeable bases are low; exchangeable aluminum is approximately 1 me/100 g of soil throughout the profile. Soil tests for available K and P are very low, especially in the topsoil, when compared with Tubum, Masheka, and Bosor soils. Base saturation varies from 16 to 11 percent and remains somewhat higher than in Masheka and Bosor. The pH is low and nearly uniform throughout the profile (pH KC1 = 4.1 to 4.0, and pH H2O = 4.6 to 4.8). Organic carbon content is highest in the Ap horizon (1.25 per- cent), declining to 0.5 percent in the subsoil. The organic carbon content of the topsoil is less than in Masheka, Bosor, and Tubum soils. Total Fe2O3 content is low (2.7 to 3.2 percent), as is total CaO, but total K2O values (1.4 to 1.2 percent) are higher than in many soils in higher rainfall areas in Sierra Leone. Masuba soils have low to medium available water-holding capacity, which is better than the other soils mentioned : Tubum, Masheka, and Bosor. Permeability is moderate. Runoff and erosion danger are slight. Masuba soils are low in moisture content dur- ing approximately three months of the dry season (Table 2) . However, from July, 1968, to July, 1969, the moisture SECTION 4:9:3 55 Soil surface 10 in H PC £20 I -E f\ a. H Q S 40 cq I 60 MAR.20V MAY JUNE JULY 67 AUG. D. T. 67 « Deeper than 67 inches (171 cm) 1968 Figure 39. Water levels in Masuba profile P9. 67 67" SEPT. 25 £3 H H 51 76 102 127 153 OCT. NOV. content in two Masuba profiles, P33 and P55, did not drop below the wilting point (75) . A detailed description and analytical data for a repre- sentative profile, P9, of the Masuba series are given in Appendix B. Panlap Series. Panlap soils occur near streams throughout the Makcni area (Fig. 31) and occupy about 1 1 percent of the area that was mapped (Table 7) . Part of the so-called inland freshwater swamps belongs to the Panlap series. The terrain is nearly level, sloping less than 3 percent toward the streambed (Fig. 32). Panlap soils usually occur adjacent to and above Mankane soils and below Masuba soils. Panlap soils consist of a deep gravel-free layer more than 48 inches (122 cm) thick deposited by the streams. Colluvium from higher terrain may be present locally. The gravel-free alluvial or colluvial layers are sometimes underlain within a depth of 100 inches (254 cm) by kaolinitic residuum from the quartz-rich granitic bed- rock. The textures are sandy loam or loamy sand throughout the profile. Panlap soils are distinctly sandier than soils (such as Masuba) on the adjacent tributary terraces. The thick Aj horizon is black to very dark grayish brown (10YR 2/1-3.5/2), which qualifies as an umbric epipedon. The subsoil colors have hues of 10YR, values of 5 or more, and chromas of 2 (sometimes 3) or less, accompanied by prominent brown to red mottles (7. SYR or redder). Panlap soils are imperfectly drained (adja- cent to Masuba soils) to poorly drained. They are water- logged at the soil surface during four months, and partly submerged during about one to three months, as is indi- cated in the water-table graphs of soil profile PI (Fig. 40). The nutrient status for plant growth is very low. The cation-exchange capacity varies from 3.6 me/ 100 g of soil to less than 2 me, which is lower than in the tributary terrace soils. The amounts of exchangeable bases, espe- cially Ca and Mg, remain comparatively high, whereas exchangeable aluminum is low (0.8 to 0.3 me/100 g) . This results in a relatively high base saturation, from 31 percent in the topsoil to about 57 percent in the sub- soil. The pH is low and nearly uniform throughout the profile (pH KC1 = 4.2 to 4.0, and pH H2O = 5.0 to 4.7). Organic carbon content is highest in the An hori- zon (1.6 percent), sharply decreasing with depth to lower values than in the tributary terrace soils. Total contents of Fe2O3 (1.1 to 3.1 percent) and CaO are low, but total K2O content (1.0 to 0.8 percent) is medium. Panlap soils have a medium available water-holding capacity. Permeability is rapid, runoff is slow, and there is very little danger of erosion. Panlap soils are low in moisture content late in the dry season (April and May), but usually the soil moisture content does not fall below the wilting point (Fig. 40 and Appendix B). A detailed description and analytical data for a rep- resentative profile, PI, of the Panlap series are given in Appendix B. Mankane Series. Mankane soils are found in the low- est parts of some stream valleys and in most of the de- pressions that are sometimes referred to as inland fresh- water swamps (Fig. 31). They occupy about 8 percent of the mapped area (Table 7) . The terrain is nearly level or concave, often with a stream in the lowest part of the area. Panlap soils usually occur above and adjacent to Mankane soils. Locally, rock outcrops may be en- countered within this soil series. 56 BULLETIN NO. 748 40- N ' SO- 220 • i • 0-4 Inches (0-10 en) depth X 12-16 Inches (30-40 en) depth • 24-28 Inches (60-70 cm) depth A 15-39 Inches (90-100 cm) depth J I 1 AUG. SEPT OCT. NOV DEC JAN. FEB. MAR APR MAY JUNE JULY I96B 1969 VV --- Interpolated line JULY AUG. SEPT. OCT 1968 D. T. 67 • Deeper than 67 inches (171 cm) OT 1 67 -2S -51 -76 •102 IZ7 153 JAN FEB MAR APR 1969 Figure 40. Moisture content and water levels in Panlap profile PI. Mankane soils consist of a deep, gravel-free, alluvial layer more than 48 inches (122 cm) thick. Locally, col- luvium from adjacent higher terrain may be present. The gravel-free layers are locally underlain within a depth of 100 inches (254 cm) by kaolinitic residuum from the quartz-rich granitic bedrock. The textures are sandy loam or loamy sand throughout the profile, in which respect they are similar to the Panlap soils. The A, horizon is dark gray (10YR 4/1) or very dark gray (10YR 3/1) and ranges in thickness from 6 inches (15 cm), which is an ochric epipedon, to 12 inches (30 cm) or more, which is an umbric epipedon. The subsoil colors have hues of 10YR, values of 5 or more, and chromas of 2 or less, accompanied by brown to red mottles (7. SYR or redder). The depth of mottling and the amount of mottles are usually less than in Panlap soils. Mankane soils are very poorly to poorly drained (Table 2) . They are waterlogged at the soil surface dur- ing about five months and are even submerged for two to four months, as is indicated in the water-table graph of profile P8 (Fig. 41). The nutrient status for plant growth is very low. The cation-exchange capacity varies from 4.2 me/ 100 g of soil to less than 2 me, which is the same as Panlap soils. The amount of exchangeable bases is somewhat lower. The base saturation is lower than in Panlap soils but higher than the tributary terrace soils (18 to 25 percent) . Exchangeable aluminum is low (0.8 to 0.3 me/100 g). The pH is low and almost constant throughout (pH KC1 = 4.1 to 4.2, and pH H2O = 4.6 to 4.9). Organic carbon content ranges from 1.8 percent in the A, horizon to 0.4 percent in the C horizon. Total contents of Fe2O:i (2.2 to 0.5 percent) and CaO are low, but total K2O values (2.0 to 1.4 percent) are higher than in many other soils in Sierra Leone. Mankane soils have a low to me- dium available water-holding capacity. Permeability is rapid, runoff is very slow, and there is deposition rather than erosion on these soils. Because of their low topographic position, Mankane soils are never very low in moisture content, even during the dry season (Fig. 41 and Appendix B). A detailed description and analytical data for a repre- sentative profile, P8, of the Mankane series are given in Appendix B. 4:9:4. SOILS ON ALLUVIAL FLOODPLAINS On the alluvial floodplain and natural levees along the Mabole River, only one soil series, Makundu, was recognized (Fig. 31). It occupies 2.1 percent of the mapped area (Table 7) . Makundu Series. The Makundu soils occur in a strip of land approximately 650 to 1,650 feet (200 to 500 m) wide along the Mabole River, on the northern border of the mapped area (Fig. 31). The nearly level Ma- kundu soils on the alluvial floodplain are bordered by more sloping soils on the upland. Makundu soils consist of deep clayey alluvium de- posited by the Mabole River. The textures are very different from other soils in the Makeni soil survey area but are similar to other clayey alluvial soils such as Taso in Area D*, Gbesebu in Area G*, and Moa in Area L* (Fig. 8) . All of the horizons of Makundu soils are in the clay or silty clay textural classes, the clay content in- creasing from 47 percent in the At horizon to about 61 percent in the subsoil. Silt content is also high (34 to 42 percent), but sand content is low, especially in the subsoil. The A, horizon is very dark gray to very dark brown (10YR 3/1-3/2.5) and is usually 10 to 20 inches (25 to 51 cm) thick (umbric epipedon) . The subsoil colors have hues of 10YR or redder, values of 5 or more, and chro- mas of 6 or more, accompanied by common to many SECTION 4:10 57 «0 *4 ' JO f Kzo S 1° • 0-4 inches (0-10 cm) depth X 12-16 inches (30-40 cm) depth • 24-28 inches (t-C-70 en) depth A 35-39 inches (90-100 c«) depth Interpolated line 202 9. AUG. SEPT 1968 OCT. _v MAR APR 1969 V Interpolated line Depth of pit s Sso - 60- A. i_ MAR 20 ' MAY 25 Z 7 o •76 H -loz 5 AUG. SEPT OCT. 1968 JAN FEB. MAR. APR. 1969 Figure 41. Moisture content and water levels in Mankane profile P8. mottles with hues of 7.5YR or redder. A typical subsoil color is brownish yellow (10YR 6/6) . Makundu soils are moderately well to well drained (Table 2) but may be waterlogged at the soil surface or even flooded by the Mabole River during brief periods, probably for less than 15 days. The nutrient status for plant growth is fairly high, especially in the An horizon. In this horizon, the cation- exchange capacity ranks highest in the Makeni area (23.6 me/100 g of soil). With greater depth, the cation- exchange capacity declines rapidly, and reaches levels of less than 4 me in the subsoil. The amount of exchange- able bases remains at about the same level below a depth of about 16 inches (41 cm). In the upper 8 inches (20 cm) the base saturation is about 23 percent but declines rapidly to about 4 percent between depths of 16 and 28 inches (41 to 71 cm), then increases to 13 percent in the lower subsoil. Exchangeable aluminum ranges from 0.4 me/100 g of soil in the upper 8 inches (20 cm) to a high of 1.9 to 1.7 me between depths of 16 and 28 inches (41 to 71 cm). The pH is low (PH KC1 = 4.5 to 4.1, and pH H2O = 5.4 to 4.7), with minimum values in the upper B horizon and higher values both above and below in the profile, as was the case with base saturation. Organic carbon content is high in the topsoil (5 per- cent), gradually decreasing with depth to 0.4 percent in the lower subsoil. Total contents of Fe2O3 are high (10.4 to 11.8 percent) in all horizons, as is K2O (1.4 to 1.2 percent), but total CaO is low except in the An horizon. Makundu soils have a medium available mois- ture-holding capacity, ranking highest in this respect among the soils in the Makeni area. Their total moisture- holding capacity is very large (Fig. 42) because of their high clay content, but much of this moisture is held by the clay and is not available to plants. Permeability is moderately slow, and runoff is very slow. There is no danger of erosion except stream-bank cutting by the Mabole River. Makundu soils are low in moisture content during about two months of the dry season, but moisture content normally does not fall be- low the wilting point (Fig. 42 and Appendix B). A detailed description and analytical data for a repre- sentative profile, P104, of the Makundu series are given in Appendix B. 4:10. AREA L* — GRANITE AND ACID GNEISS IN THE UPPER MOA BASIN, KENEMA AREA In the southeastern part of Sierra Leone, erosion and denudation of the escarpment between the interior pla- teaus and hills in the northeast and the low-lying interior plain in the southwest have been so extensive that the scarp face is replaced by an undulating to gently rolling erosion surface. This is especially true in the Moa Basin, an area along the Moa River about 30 miles (48 km) wide and 75 miles (121 km) long that includes the towns of Kenema, Daru, and Pendembu. In this area (L* on Fig. 8 ) , the erosion surface rises from about 400 to 800 feet (122 to 244 m) above sea level and is broken by numerous monadnocks (isolated hills of earlier plateaus) of elevations generally between 600 and 1,000 feet (183 to 305 m). The area is underlain by granite and acid gneiss. Annual rainfall ranges between 100 and 120 inches (254 to 305 cm), with 101 inches (257 cm) re- ported at Daru (Appendix A). About 85 percent of the rain falls between May and November. The dry season is less severe in this area than in most of the rest of Sierra Leone. The dominant vegetation is secondary bush with some remnants of moist evergreen forest (17). The Moa Basin is the main cocoa-growing region in Sierra Leone. BULLETIN NO. 748 20 SEPT. OCT. 1968 JAN. Figure 42. Moisture content in Makundu profile P104. MAR. APR 1969 A soil survey conducted by Sivarajasingham (64) and Stark (66) included most of Area L* on Figure 8 and the extension of Sierra Leone east of Kailahun. The four major landscapes in the mapped area are steep hills, up- land erosion surfaces, colluvial footslopes and upper terraces and swamps, and current alluvial floodplains. Some of the major soil series that occur on these land- scapes (see Table 2) are discussed in the remainder of Section 4:10. Additional information concerning these soils and other soils in the Kenema area not discussed in this publication (such as Fanima and Waima in Table 8) is given by Sivarajasingham and Stark. The distribu- tion of various soils shown on the soil association map of the Kenema area, Sierra Leone (Fig. 43, in three sheets) , was adapted from soil maps they made. The extent of each soil association in Figure 43 is listed in Table 8. 4:10:1. SOILS ON STEEP HILLS Steep hills occupy one-half of the mapped area east of Kenema (Table 8). These include one land type, Rock Land, and two soil associations in which Vaahun and Segbwema soils are dominant. Many of the moderately steep and steep slopes have Segbwema and Vaahun soils, which contain weathering bedrock pieces in their sub- soil or even solid bedrock. Soils of this kind usually are fairly fertile, especially if the bedrock contains some weatherable minerals. They should not be used for up- land farms, however, because the erosion danger is great. They can best be put into forest or used for tree crops such as coffee, cocoa, or oil palm. Rock Land is unsuit- able for any agricultural use. Table 8. Area of different soil associations in the upper Moa Basin, Kenema area, as shown in Figure 43 Soil association Ar ea Symbol Name Acres Hectares total area on mop Q 288,000 1 16,550 21.6 R Rock Land 20,500 8,300 1.5 S Segbwema, Vaahun . 352,000 142,450 26.4 T Fanimo, Manowa 83,200 33,700 6.2 U Manowa, Fanima 211,200 85,500 15.8 W Waima, Baoma 108,800 44,000 8.2 X Pendembu, Waima 115,200 46,600 8.6 Y Keya, Kparva 67,200 27,200 5.0 2 Moa, Kparva 89,600 36,250 6.7 Total 1 335 700 540550 100.0 Rock Land. This is a land type used to delineate areas that are dominated by bedrock at the surface. Most of the Rock Land is steep granite domes (monadnocks) that rise above the surrounding areas. They occupy 1.5 percent of the mapped area (Table 8). They are widely scattered but tend to occur more frequently east of Kai- lahun (Fig. 43). Rock Land is unsuitable for the pro- duction of economic plants and should be left with its scanty natural vegetation for watershed protection, wild- life use, or esthetic purposes. Vaahun Series. Vaahun soils occur extensively near Kailahun and Koindu and on the northern and western margins of the mapped area (Fig. 43), but they are also widely scattered elsewhere (Table 8). They are most frequently associated with Segbwema soils and some Rock Land. Vaahun soils are associated with the steepest slopes on which soil develops, and their solum tends to be less than 36 inches (91 cm) thick. Vaahun soils develop in coarse-grained granite high in quartz and low in dark ferromagnesium minerals. Most of the fine gravel and sand is quartz. The fine-earth fraction (< 2.0 mm) is sandy clay loam in the surface horizon and clay in the subsoil. The very dark gray to dark brown ( 10YR 3/1-3/3) A, horizon is less than 7 inches (18 cm) thick (ochric epipedon). Subsoil colors are yellowish brown (10YR 5/6) with faint mottles in the lower part. Vaahun soils are moderately well drained or sometimes well drained. Although they occur on steep slopes with rapid runoff, the subsoil is somewhat slowly permeable and transmits seepage over the shallow bedrock. Erosion is a serious hazard. These relatively youthful soils have better chemical properties than some of the more highly weathered soils, but even this potential advantage is limited by their high quartz content. The cation-exchange capacity varies from approximately 19 to 15 me/100 g of soil smaller than 2 mm. Exchangeable bases are higher than in other soils in the area, with base saturation ranging from 39 percent in the surface horizon to 10 percent in the sub- soil. Exchangeable aluminum varies from 0.3 to 2.3 me/ 100 g of soil. The PH is low (pH KC1 = 3.8 to 4.4, and pH H2O = 4.8 to 5.3 ) . Total CaO is high ( 1 .2 to 0.6 per- cent), total content of Fe2O3 is medium (5.8 to 7.5 per- cent), and total K2O is low (0.7 to 0.25 percent). The available moisture-holding capacity is low. The soil mois- ture content is low during about three months of the dry season (Table 2) . SECTION 4:10:2 59 A detailed description and analytical data for a repre- sentative profile, 145010, of the Vaahun series are given in Appendix B. Segbwema Series. Scgbwema soils are the most ex- tensive ones in the mapped area (Table 8), being espe- cially common in the central and southwestern parts ( Fig. 43 ) . They are most frequently associated with Vaahun soils (described previously) and with limited areas of Rock Land and other soils. Segbwema soils oc- cur on moderately steep to steep slopes, typically with gradients less than those of Vaahun soils. Segbwema soils have developed in fine-grained grano- diorite, which is low in quartz and high in ferromag- nesium minerals and feldspars. In these soils, the textures are typically sandy clay loam in the A and C horizons and clay loam in the B horizon. Some detrital hardened plinthite gravel may be present in the upper layers. The strong brown (7.5YR 5/6) Aj horizon qualifies as an ochric epipedon. Subsoil colors are typically red (2.5YR-10R 4/6). Segbwema soils are well drained and are never waterlogged at the surface (Table 2). Levels of plant nutrients are low in Segbwema soils. Cation-exchange capacity ranges from nearly 1 1 me/100 g of soil in the surface horizon to 6 me in the lower subsoil. Exchangeable bases are low except in the A] horizon. Exchangeable aluminum is approximately 1 me/100 g of soil. Base saturation varies from 17 percent in the surface horizon to about 4 percent in the subsoil. The PH is low (pH KC1 = 3.8 to 4.0, and pH H2O = 4.7 to 5.5). The organic carbon content is 2 percent in the AI horizon and very low in the subsoil. Contents of total Fe2O.i, K2O, and CaO are medium to low. The available moisture-holding capacity is medium, which is the best among soils on the steep hills. Because of the moderately steep to steep slopes, runoff is rapid and erosion is a serious hazard. Permeability is rapid. The soil moisture content is low during approxi- mately three months of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, 145005, of the Segbwema series are given in Appendix B. 4:10:2. SOILS ON UPLAND EROSION SURFACES On the upland erosion surfaces of intermediate relief, the deep, very gravelly Manowa soils are most extensive; they are accompanied by smaller areas of redder, less gravelly Baoma soils. Both soils are described here. Other important soils on these upland erosion surfaces, Fanima and Waima, are described by Sivarajasingham (64) and Stark (66). Manowa Series. Manowa soils are the most extensive ones on the upland erosion surfaces, especially between Kenema and Pendembu (Fig. 43 and Table 8). They are often associated with Fanima soils (64, 66). Manowa soils usually occur on convex summits and convex upper slopes. Manowa soils have developed in very gravelly (usually more than 60 percent gravel by volume), reworked material. The gravels are predominantly dark-coated, dense, hardened plinthite glaebules. The fine earth (< 2.0 mm) is sandy clay loam in the At horizon, sandy clay in the upper subsoil, and clay in the lower subsoil. The AI horizon is usually low in gravel content. The very dark grayish-brown to dark brown (10YR 3/2-3/3) A horizon is usually 10 to 20 inches (25 to 51 cm) thick (umbric epipedon) . The subsoil is usually dark yellowish brown (10YR 4/4) to strong brown (7.5YR 5/8) . Manowa soils are moderately well drained and are never waterlogged at the surface (Table 2). Manowa soils are very low in plant nutrients. Cation- exchange capacity ranges from nearly 12 me/100 g of soil smaller than 2 mm in the surface horizon to 6 me in the subsoil. Exchangeable bases are very low, and base saturation is only 2 to 3 percent in the soil profile. Ex- changeable aluminum is 3.1 me/100 g in the Aj horizon and 0.7 me in the lower subsoil. The pH is low (pH KC1 = 3.8 to 4.2, and pH H2O = 4.3 to 4.8). The or- ganic carbon content is 2.7 percent in the A, horizon and occurs down into the very gravelly subsoil. Total con- tents of Fe2O3 are moderately high (8.1 to 11.2 percent), but total CaO is low (0.07 percent) and K2O is very low (0.2 percent). The available moisture-holding ca- pacity is very low because of the high gravel content. Permeability is medium and runoff is rapid. The ero- sion hazard ranges from slight on gently sloping summits to serious on steeper slopes. The moisture content is low during approximately four months of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, Kpuabu 1, of the Manowa series are given in Appendix B. Baoma Series. Baoma soils occur primarily in the central and western part of the mapped area (Fig. 43), associated with Waima (64, 66) , Manowa, and Seg- bwema soils. Baoma soils are similar in color (red) to Segbwema soils; in gravel content they are intermediate between Segbwema and Manowa soils. Baoma soils oc- cur on upper convex slopes of approximately 3- to 15- percent gradient. Cocoa and coffee plantations are com- mon on these soils. Baoma soils have developed in 24 to 48 inches (61 to 122 cm) of relatively gravel-free material over a red to dark red (10R 4/6-3/6) gravelly subsoil. The gravel, usually less than 50 percent of the subsoil volume, is dark-coated, dense, hardened plinthite glaebules plus weathered and fresh rock fragments. The hardened plinthite glaebules are probably transported material. Textures are sandy clay loam in the surface horizon, clay in the upper subsoil, and gravelly clay in the lower subsoil. Baoma soils are well drained and are never waterlogged at the soil surface (Table 2) . Baoma soils are similar to Segbwema soils in cation- exchange capacity, exchangeable bases, base saturation, and reaction, but exchangeable aluminum is lower in the Baoma subsoil. Baoma is extremely high in phos- phorus in all horizons. This may be due to local min- 60 BULLETIN NO. 748 •O -o c o 0) O) o a o CO •«t S! 3 O) * il i i •• 1 1 *1 Srf i . i 62 BULLETIN NO. 748 eralogy, location on .a former village or burial site, or possibly fixation of phosphorus by the very high con- tent of total Fe2O:) (16.4 to 19.0 percent). Total con- tent of CaO is low (0.1 percent) and K2O is very low (0.2 percent). The available moisture-holding capacity is low. Permeability and runoff are medium. The erosion haz- ard is slight. The moisture content is low during approxi- mately four months of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, 144801 A, of the Baoma series are given in Appendix B. 4:10:3. SOILS ON COLLUVIAL FOOTSLOPES AND UPPER TERRACES AND IN SWAMPS This group of soils includes imperfectly drained Pen- dembu on colluvial footslopes and upper tributary ter- races, poorly drained Kparva in stream valleys and around the edge of swamps, and very poorly drained Keya in the lowest parts of inland valley swamps. These soils are widely scattered along the drainage networks in the mapped area (Fig. 43) . Pendembu Series. Pcndembu soils are the most exten- sive ones on colluvial footslopes and upper tributary ter- races. They occupy approximately 5 percent of the mapped area (Table 8). They occur on gentle slopes between the upland and the alluvial floodplains or swamps. Pendembu soils have developed in fine-loamy collu- vium and alluvium. The textures are fine sandy loam in the surface horizon and sandy clay loam in the B horizon. The very dark gray (10YR 3/1) Aa horizon is usually 6 to 10 inches (15 to 25 cm) thick (ochric epipedon). Colors in the B horizon are yellowish brown (10YR 5/4) to yellow (2.5Y 7/6) with prominent red mottles in the lower subsoil. Pendembu soils are imperfectly drained because of seepage and are waterlogged at the soil sur- face during one to two months of the rainy season (Table 2). Pendembu soils are very low in plant nutrients. Cation- exchange capacity ranges from 9.4 me/100 g of soil in the A! horizon to 3.5 me in the lower subsoil. Exchange- able bases are very low, and base saturation is only 2 to 5 percent in the soil profile. Exchangeable aluminum ranges from 3.6 me/ 100 g of soil in the surface horizon to 1.2 me in the lower subsoil. The pH is low (pH KC1 = 3.6 to 3.9, and pH H2O = 4.1 to 4.7). Total con- tents of Fe2O3 (2.5 to 3.1 percent) and CaO (0.07 per- cent) are low, and total K2O is very low (0.2 percent). The available moisture-holding capacity is low. Permeability is moderately rapid, runoff is medium, and the erosion danger is slight. The moisture content is low during about two months of the dry season (Table 2). A detailed description and analytical data for a repre- sentative profile, Kpuabu 2, of the Pendembu series are given in Appendix B. Kparva Series. Kparva soils occur throughout the mapped area on nearly level terrain (slopes of less than 3 percent) around the edges of swamps and in low areas at the bottom of slopes from the upland to alluvial flood- plains (Fig. 43 and Table 8) . Kparva soils have developed in fine-loamy colluvium and alluvium. The textures are sandy clay loam in the surface horizon, sandy clay in the B horizon, and usually sandy clay loam in the substratum with occasional thin gravelly layers. The A, horizon is very dark gray to very dark grayish brown (10YR 3/1-3/2) and is usually less than 10 inches (25 cm) thick (ochric epipedon). Colors in the B hori- zon are brownish yellow (10YR 6/8) with light yellow- ish-brown (2.5Y 6/4) mottles in the upper part, and white (2.5Y 8/2) with strong brown (7. SYR 5/6) mot- tles in the lower part. Kparva soils are poorly drained and are waterlogged at the soil surface two to four months, including submergence of about one month (Table 2). Because of flooding, seepage, and the low topographic position of Kparva soils, the water table re- cedes slowly. Plant nutrient levels are low in Kparva soils but are slightly better than in the Pendembu soils. Cation-ex- change capacity varies from 5 to 1 1 me/100 g of soil. Exchangeable bases are low, and base saturation varies from 6.6 to 3.1 percent. Exchangeable aluminum ranges from 2.3 me/100 g in the upper part of the soil profile to 1 me in the lower part. The pH is low (pH KC1 = 3.7 to 4.2, and pH H2O = 4.4 to 5.0) . In the solum, the contents of total Fe2O3 (1.8 to 4.1 percent), CaO (0.10 to 0.08 percent), and K2O (0.4 to 0.6 percent) are low. The available moisture-holding capacity is low. Permeability is medium, and runoff is slow. Kparva soils are subject to deposition rather than erosion. These soils are not too dry for plant growth, even during the dry season (Table 2) . A detailed description and analytical data for a repre- sentative profile, 145042, of the Kparva series are given in Appendix B. Keya Series. Keya soils occur in depressions in the lowest parts of inland valley swamps throughout the mapped area (Fig. 43) . Though not extensive (Table 8) , they are important and easily-recognized features in the landscape. The vegetation is raphia palms, sedges, and other plants that tolerate very wet conditions. Keya soils develop in coarse loamy colluvium and alluvium transported from surrounding higher areas. Textures are variable, both vertically and horizontally, but are distinctly coarser than in the associated Kparva soils. Upper horizons of Keya soils are typically loamy sand, and lower horizons are usually sandy loam. The AI horizon is grayish brown to dark grayish brown (2.5Y 5/2-4/2) and is about 8 to 10 inches (20 to 25 cm) thick (ochric epipedon). The subsurface hori- zon is grayish brown (2.5Y 5/2), and the subsoil is white (N 8/ ). Keya soils are very poorly drained, being entirely waterlogged three to five months and sub- SECTION 4:10:3 63 64 BULLETIN NO. 748 merged more than one month (Table 2). Late in the dry season, the water table usually drops to depths of about 3 to 6 feet ( 1 to 2 m) . Cation-exchange capacity is very low (2.4 to 3.4 me/100 g) because of the low content of organic mat- ter (1.1- to 0.3-percent organic carbon) and of clay. Base saturation (13 to 24 percent) is better than in Kparva soils. The pH is low (pH KC1 = 3.9 to 4.0, and pH H2O = 4.5 to 5.0). Total Fe2O3 (0.1 to 0.7 percent) is very low, and total K2O (0.7 to 1.4 percent) and CaO (0.10 to 0.14 percent) are low. The available moisture- holding capacity is low. Permeability is rapid, but Keya soils are ponded be- cause they occupy the lowest position in the landscape and receive much water and some sediment from sur- rounding higher areas. These soils remain moist even during the dry season (Table 2) . A detailed description and analytical data for a repre- sentative profile, 145041, of the Keya series are given in Appendix B. 4:10:4. SOILS ON ALLUVIAL FLOODPLAINS Along the banks of many of the larger streams, clayey alluvial soils of the Moa series occur (Fig. 43). They occupy nearly 4 percent of the mapped area (Table 8). Moa soils are nearly level and occur slightly above the streams. These are the most productive soils in the area and are often used for cocoa production. Moa Series. Moa soils developed in clayey alluvium that is approximately 40- to 50-percent clay and 20- percent silt, the remainder being mostly fine sand. The very dark grayish-brown (10YR 3/2) Aj horizon is usually thin (ochric epipedon). Colors in the upper B horizon are strong brown to brown (7. SYR 5/8-4/4). Colors in the lower B horizon are variable but are often brownish yellow (10YR 6/8) with distinct mottles. Moa soils are considered to be moderately well drained (Table 2) with the upper part of the profile being better drained and the lower part more poorly drained. They may be flooded for brief periods of 1 to 15 days during the rains. Levels of available nutrients are relatively low. Cation- exchange capacity ranges from 13.8 to 6.5 me/100 g of soil. Exchangeable bases are low, and base saturation ranges from 7.5 to 6.0 percent. Exchangeable aluminum ranges from 2.8 to 1.2 me/100 g of soil. The pH is low (pH KC1 = 3.8 to 4.0, and pH H2O = 4.5 to 5.1). Con- tents of total Fe2O3, CaO, and K2O are medium to low. The available moisture-holding capacity is medium. Permeability and runoff are medium. These soils are not subject to erosion except by stream-bank cutting. The soil moisture content is low for only about one month during the dry season (Table 2) because the water table is relatively shallow and the moisture-holding capacity is favorable. A detailed description and analytical data for a repre- sentative profile, Kpuabu 3, of the Moa series are given in Appendix B. 4:11. COMPARISON OF SOILS IN THE BOLILAND REGION (AREA I*)' WITH THOSE IN ADJACENT AREAS G* AND J* The Boliland Region (Area I* on Fig. 8) is a season- ally swampy area in a belt about 20 miles (32 km) wide stretching from Yonibana through Batkanu to the Guinea border. It is a low-lying, flat or very gently un- dulating grassland area thought to be a former delta formed by the merging of the Mabole, Rokel, and Pam- pana Rivers at a period of higher sea level (70, p. 18). Medium (Fig. 44) and tall grasses are the most common vegetation in the swamps; savanna woodland and Lo- phira bush predominate on the uplands. Mean annual rainfall is between 110 and 120 inches (280 to 305 cm), with 109 inches (277 cm) at Batkanu (Appendix A). Approximately 90 to 95 percent of this rain falls between May and November. The soils in the Boliland Region are underlain by sandstones, siltstones, and mudstones of the Rokel River Series, similar to those in Area G* to the south (dis- cussed in Section 4:8). Stobbs (70) mapped the soils in the southern one-half of Area I* and made the following separations on his soil map : Upland peneplain drifts Map unit 1. Nearly bare exposures of ironpan Map unit 2. Red-brown concretionary drifts (Batkanu, Wari. Malinka, and Bella series) Map unit 3. Yellow-brown concretionary drifts (Matutu, Makoima, and Mayanki series) Upland colluvial drifts Map unit 4. Over concretionary weathered parent material (Mankahun and Masuri series) Map unit 5. Over nonconcretionary parent material Upland sedentary soils Map unit 6. Over locally weathered parent material (Dia- bama series) Alluvial deposits and local colluvial drifts Map unit 7. Over river terrace deposits: concretionary (Mara, Makoli, Matamba, Malop, and Mamalia series) Over river terrace deposits: nonconcretionary (Mabang and Maroki series) Map unit 8. Over contemporary levee deposits (Seli and Magbunga series) Map unit 9. Over old levee deposits (Tabai, Bom, and Mateboi series) Map unit 10. Over contemporary slough deposits (Rokel, Mabole, and Malansa series) Over old slough deposits or inland bolis (Masebra, Ma- dina, Makonte, Kontobe, Massimo, Romankne, and Babaibunda series) Map unit 11. Over old river channel deposits (Rochin series) Map unit 12. Developed in drainage grooves (complex of map units 7 and 10) Map unit 13. Mixed bottom soils (complex of map units 7 to 12) Map unit 14-. Recent alluvium SECTIONS 4:11:1-4:12:1 65 Figure 44. Short and medium grasses of the Anade/phia/ Rhyfachne association, which are characteristic of the seasonally flooded Boliland area. The soil series established by Stobbs in Area I* have been included in Table 2 (Section 4:1) with other soil se- ries in Sierra Leone. Comparing Stobbs' results with those reported herein indicates that they correspond closely. 4:11:1. COMPARISON OF SOILS IN AREA G* AND AREA I* The characteristics of soils in Area G* are discussed in detail in Section 4:8. The soils in both Areas G* and I* (Fig. 8) have developed over sandstones, siltstones, and mudstones of the Rokel River Series (see Section 3:2). The physiography in the two areas is similar except that in Area G* the better-drained upland and colluvial foot- slope soils predominate, whereas in Area I* imperfectly and poorly drained soils on old and contemporary ter- races and floodplains are more extensive. The soils on uplands and colluvial footslopes especially have many features in common; in fact, the following pairs of soil series may be so nearly alike that it would be desirable to correlate each pair as one series (see Table 2) : Soil series in Area G* Momenga Njala Mokonde Bonjema vs. vs. vs. vs. Soil series in Area I* Belia Batkanu Malinka Mankahun The range of soils on old and contemporary terraces and floodplains is greater in Area I* than in Area G*, but correlation of some soil series between the two areas may be possible. For example, the Mokoli series in Area G* and the Malansa series in Area I* are similar in many properties and should possibly be correlated into one series, especially in view of the similar mineralogy of the clay fraction in the clayey alluvial soils studied so far in Sierra Leone (see Section 4:3:1). More correla- tion needs to be done between these two areas in order to clearly establish relationships between soil series. 4:11:2. COMPARISON OF SOILS IN AREA I* AND AREA J* The characteristics of soils in Area J* are discussed in detail in Section 4:9. The physiography of this area is markedly different from Area I* (Fig. 8). Area J* con- sists of a highly dissected erosion surface with nearly level summits intersected by numerous swamps and streams; consequently, the proportion of sloping and nearly level uplands is much greater, and the swamps are much smaller, than in Area I*. The transition between the two areas is rather sharp and clearly marked by dif- ferences in topography and vegetation: the flat and tree- less bolilands (seasonally flooded grasslands) in Area I* contrast with the dissected topography and secondary bush in Area J* near Makeni. The parent rock in Area J* consists of granites and acid gneiss, which outcrops frequently. These "richer" igneous rocks result in a higher fertility of the upland soils in Area J* near Ma- keni, compared with the poorer sedimentary rocks of both Area I* and Area G*. The soil survey carried out by van Vuure and Mie- dema (75) northwest of Makeni in Area J* (Fig. 31) lies adjacent to the soils surveyed by Stobbs (70) in Area I*. Actually, there is a small overlap on the soil map of the boundary area (see Section 4:4 in 75), which was constructed by matching the soil maps of the two areas. Unfortunately, the boundary area could not be checked in the field, so the soil map of the boundary area should be considered as somewhat tentative. The texture of the soils near Makeni in Area J* is much sandier than most of the soils in Area I*. However, the terraces and levees on the alluvial floodplain of the Mabole River have similar textures in both areas. In fact, the Mateboi soils in Area I* and the Makundu soils near Makeni in Area J* may be similar enough that it might be desirable to correlate them as one series. 4:12. TAXONOMIC CLASSIFICATION OF SOIL SERIES In the previous portions of Section 4, the characteris- tics of 44 soil profiles, representing 34 soil series in Sierra Leone, have been described in detail. Their areas of oc- currence, physiography and parent material, moisture regime, and relationships among these and other soils in Sierra Leone are indicated in Table 2. In the rest of this section, the taxonomic classification of each of the 44 soil profiles listed alphabetically in Table 9 (pages 70 and 71) is discussed. Major emphasis is given to the soil classification system in Soil Taxonomy (69). This sys- tem, widely used in the United States and many other areas, is based on diagnostic surface and subsurface soil horizons, each of which has well-defined properties. 4:12:1. DIAGNOSTIC HORIZONS The most important diagnostic horizons that occur in Sierra Leone soils are described briefly here. More com- plete definitions are given in Soil Taxonomy (69). The diagnostic horizons in each soil profile are given with the description of the profile in Appendix B. 66 BULLETIN NO. 748 Ochric epipedon. This includes surface horizons that are either too light in color, too high in chroma, too low in organic matter, or too thin to be an umbric epipedon. The surface horizons of most of the soil series are ochric. Umbric epipedon. This includes dark-colored (Mun- sell color values darker than 3.5 and chromas of less than 4.0 when moist) surface horizons, 10 or more inches (25 cm) thick, with well-developed structure, an organic carbon content of at least 0.6 percent (1-percent organic matter) , and less than 50-percent base saturation. Only a few soil series have umbric surface horizons. Argillic horizon. This is a subsurface horizon (unless exposed by erosion) in which illuvial layer-lattice clays have accumulated to a significant extent. If an over- lying eluvial horizon remains, the requirements that a subhorizon be designated argillic are as follows: If the eluvial horizon contains 15- to 40-percent clay, the ar- gillic horizon should have at least 1.2 times as much clay as the eluvial horizon; if the eluvial horizon contains more than 40-percent clay, the argillic horizon should have at least 8 percent more clay than the eluvial hori- zon — for example, 50 percent vs. 42 percent. These clay increases should occur within a vertical distance of 12 inches (30 cm) or less. An argillic horizon should usually be more than 6 inches (15 cm) thick. The ratio of illu- vial to eluvial clay (I/E clay) for the various soil pro- files is given in Appendix C. Argillic horizons should show clay skins in fine pores or, if peds exist, on some vertical and horizontal ped surfaces. Thin sections should show approximately 1 percent or more of oriented clay coatings in some part of the argillic horizon. In many of the soils in Sierra Leone, clay content in- creases gradually with depth in the soil profile. However, the clay increases are often modest, and in many soils there is a lithologic discontinuity that precludes the pos- sibility of adequately evaluating the vertical changes in clay content. Clay skins are poorly developed and diffi- cult to observe in the field, except in a few imperfectly and poorly drained soils such as Pendembu and Pele- wahun (44) . Under these conditions, thin sections are often needed to determine where argillic horizons occur. Both field and laboratory data indicate that many of the soils in Sierra Leone have argillic horizons, but these horizons are often weakly developed; moreover, where clay skins do occur, they are frequently more evident in the lower part of the B horizon than in the upper part. Thin sections show that subsoils of the Pelewahun (44), Makeni, Njala, and Taiama series have enough clay skins to qualify as argillic horizons, but Momenga and Gbesebu do not. The ratio of clay in the illuvial horizon to the overlying eluvial horizon — where there is no lithologic discontinuity between them — also indi- cates that many Sierra Leone soils have argillic horizons but that others do not (Appendix B and Appendix C) . Cambic horizon. A cambic horizon is a slightly altered horizon between the A and C horizons but without enough evidence of illuviation to be an argillic horizon and with no cementation or induration. The evidence of alteration may include (a) stronger chromas or redder hues or higher clay contents than the underlying hori- zons, or (b) gray colors associated with a regular de- crease in organic carbon with depth. Cambic horizons have textures of loamy fine sand or finer in the fine- earth (< 2 mm) fraction; soil structure, or the absence of rock structure, in at least half of the volume; and significant amounts of weatherable minerals. They lack the dark colors, organic carbon, and structures that are definitive of umbric epipedons. Momenga soils have a cambic horizon (Appendix C), and the Pujehun, Gbesebu, and Mokoli series contain more than enough (> 6 percent) muscovite and other properties to qualify as having cambic horizons (see Sec- tion 4:12:3). Oxic horizon. This is a strongly altered subsurface ho- rizon (exclusive of the argillic horizon) at least 12 inches (30 cm) thick in which the fine-earth fraction consists primarily of a mixture of hydrated oxides of iron or aluminum or both, with variable amounts of 1 : 1 lattice clays and highly insoluble minerals such as quartz sand. An oxic horizon (a) contains more than 15-percent clay and has a texture of sandy loam or finer in the fine-earth fraction, (b) in some subhorizon has no more than 5 per- cent of its clay dispersible in water, (c) has a total of less than 10 milliequivalents per 100 grams of clay of bases extractable with IN NH4OAc and of aluminum extractable with IN KC1, (d) has an apparent cation- exchange capacity of the fine earth of 16 or less me/100 g of clay by NH4OAc, unless there is appreciable content of aluminum-interlayered chlorite, (e) has no more than traces of primary aluminosilicates, (/) has mostly gradual or diffuse boundaries between its subhorizons, and (g) has less than 5 percent by volume that shows rock struc- ture. The upper boundary of an oxic horizon is set at the least depth at which less than 5 percent of its clay is dispersible in water. Detailed information concerning items (b) , (c) , and (d) for each soil profile is given in Appendix C, Table I. Compared with the argillic horizon, the oxic horizon has few or no clay skins and either no increase or a gradual increase in clay content with depth. The oxic horizon has a lower cation-exchange capacity or smaller amounts of weatherable minerals than the cambic horizon. Some of the subsoils, such as those of the Njala, Ma- keni, Kania, and Taiama series, have the properties spec- ified for oxic horizons, including those listed in Ap- pendix C, except that they also have argillic horizons, as described above. Other soil series in Sierra Leone have some, but not all, of the properties specified for an oxic horizon. For example, Pujehun, Gbesebu, and Mokoli contain too much muscovite (more than 6 percent, as described in Section 4:12:3) to qualify as having oxic horizons, even though their lower subsoils meet the re- quirements for oxic horizons on the basis of the properties listed in Appendix C. SECTION 4,12:2 67 Spodic horizon. This is normally a subsurface horizon in which "active amorphous materials composed of or- ganic matter and aluminum, with or without iron, have precipitated" (69). The horizon usually lies below an eluvial mineral horizon. Typical spodic horizons are sandy and have weak or no structure. The upper bound- ary is abrupt, and colors change markedly with depth ; hues are usually redder than 10YR. Spodic horizons occur only in humid environments, primarily in cold and temperate climates but also in hot climates. In tropi- cal areas, spodic horizons may occur at depths of more than 3 feet (91 cm). So far, the spodic horizon has been found in only one soil series, Gbamani, in Sierra Leone (see Section 4:5) . Sulfuric horizon. This is a horizon "composed cither of mineral or organic material that has both (a) a pH of less than 3 (1:1 in water) and (b) jarosite mottles" (69) ; these mottles are iron sulfate that is the color of fresh straw in hues of 2.5Y or yellower and chromas of 6 or more. Sulfuric horizons form as a result of drainage and oxidation of sulfide-rich mineral or organic ma- terials. Sulfuric horizons are toxic to plants, and roots usually do not live in them. These horizons occur in some soil profiles, such as Rokupr, Rl, in the tidal swamps (see Section 4:6). Plinthite. This is "an iron rich, humus poor, mixture of clay with quartz and other diluents, which commonly occurs as dark red mottles" (69). This iron segregation occurs in horizons that are saturated with water at some season. "The mottles are not considered plinthite unless there has been enough iron segregation to permit irrevers- ible hardening on exposure to wetting and drying. Plin- thite in the soil is usually firm or very firm when the soil moisture is near field capacity and hard when below the wilting point. ... In moist soil, plinthite is soft enough that it can be cut with a spade" (69). After irreversible hardening, this material is designated ironstone rather than plinthite. Many of the soils in Sierra Leone contain plinthite, as indicated in the profile descriptions in Ap- pendix B and by the subgroup designations in Table 9. 4:12:2. COMPARISON OF THE SOIL CLASSIFICATION DESCRIBED IN Soil Taxonomy WITH THE FAO/UNESCO AND FRENCH SYSTEMS FAO/UNESCO System. The FAO/UNESCO system (28) is designed to define mapping units for the soil map of the world. The categories of this system are based on diagnostic surface and subsurface horizons, of which most definitions are almost identical to those in Soil Taxonomy (69) . A number of subsurface horizons, however, are defined in the FAO/UNESCO system that are not de- scribed in Soil Taxonomy. The additional horizons rec- ognized in Sierra Leone are briefly described below. The gleyic horizon "is indicative of pronounced wet- ness occurring within 50 cm of the surface and is re- flected by bluish colors (bluer than 10Y) that change on exposure to the air, and/or prominent mottling and dom- inant moist colors of low chroma in the soil matrix" (28) . Some poorly drained or very poorly drained soils such as Panlap, Mankane, and Keya have a gleyic horizon. The plinthic horizon "consists of a continuous phase of sesquioxide-rich, humus-poor, highly weathered mixture of clay with quartz and other diluents, which commonly occurs as red mottles, which changes irreversibly to hard- pans or irregular aggregates on repeated wetting and dry- ing. If textures are coarser than loamy very fine sand, more than half of the volume of the horizon shows dis- crete nodules, or disconnected, soft, red mottles" (28). The concretionary horizon "is a layer consisting of 60 percent or more, by volume, of oxidic concretions with other coarse fragments of hardened plinthite or iron- stone, with a thickness of at least 25 cm, the upper part of which occurs within 100 cm of the surface" (28) . The thionic horizon is indicative of an amount of sul- fides or elemental sulfur or a combination of the two that is high enough to cause acidification of the soil upon oxidation to a pH (KC1) of less than 3.5 within 100 cm of the surface. The Rokupr soils have a thionic horizon. French System. The French soil classification system is a purely pedogenetic system. It is based on soil properties that have resulted from soil-forming processes. Diagnostic horizons, as defined in Soil Taxonomy and the FAO/ UNESCO classification, are not mentioned in the French system (2, 3). Instead, the conventional ABC horizon nomenclature is used at the highest categorical level (classe) . Diagnostic criteria are often very different from the Soil Taxonomy and FAO/UNESCO systems. Fur- thermore, these criteria are not well defined in the French system. Although the classification of Sierra Leone soils according to the Soil Taxonomy and FAO/ UNESCO systems could be easily correlated, more diffi- culties were encountered with the French system, espe- cially at groupe and sous-groupe levels. Thus, the corre- lations listed in the right-hand column of Table 9 should be considered tentative. In the French system, four categories are distin- guished: classe (the highest level), sous-classe, groupe, and sous-groupe. A complete description of taxa can be found in Classifications des sols (2) and Projet de classi- fication des sols ferrallitiques (3). Brief explanations are given below for categories of soils believed to occur in Sierra Leone. Sols ferrallitiques. These are mineral soils with an ABC profile, usually very thick, with strongly decom- posed organic matter, very strong weathering, high in sesquioxides, dominated in the clay fraction by kaolinite (and sesquioxides), a low cation-exchange capacity, and usually a low base saturation. The most important sous- classe in Sierra Leone is the Sols ferrallitiques fortement desatures (en B) (ferrallitic soils strongly desaturated in the B horizon). They are characterized by an amount of exchangeable bases less than 1 me/100 g of soil, a base saturation less than 20 percent, and a pH (H2O) of less 68 BULLETIN NO. 748 than 5.5. The pH of the A horizon is usually lower than in the B horizon. A few profiles were classified as Sols ferrallitiques moyennement desatures en B (ferrallitic soils moderately desaturated in the B horizon) . These soils have an amount of exchangeable bases varying from 1 to 3 me/ 100 g soil, a base saturation of 20 to 40 per- cent, and a pH (H2O) of 4.5 to 6.0. The groupe typique indicates the central concept of the sous-dasse. Two sous-groupes of this groupe were found : hydromorphe, which' indicates slight hydromor- phism, usually reflected by mottling, and faiblement ap- pauvri, which means that some clay has disappeared from the A horizon but did not accumulate in the B horizon. The groupe lessive indicates that clay has disappeared from the A horizon and accumulated in the B horizon. Two sous-groupes were recognized: hydromorphe (see above) and indure, which indicates indurated ironstone. The groupe remanie indicates a change in the upper part of the profile, usually the addition of new material that has been weathered to the same degree as the origi- nal soil. A stone line is often present at the transition. Three sous-groupes were classified: jaune, indicating a yellow color; hydromorphe (see above) ; and modal, which is the most characteristic sous-groupe of the groupe. In the groupe penevolue the weathering still continues in the soil profile. This may be the result of additions of slightly weathered material, or erosion of the topsoil (leaving the less weathered subsoil close to the surface), or inadequate time of soil formation for removal of the weatherable minerals. Two sous-groupes have been dis- tinguished: hydromorphe (see above) and avec erosion et remaniement, which indicates a change due to erosion. Sols hydromorphes. Hydromorphism is considered the most important element of soil formation in this classe, which contains almost all the poorly and very poorly drained soils. One sous-dasse was recognized, Sols hydro- morphes mineraux, in which the soils have an organic matter content of less than about 10 percent, usually less than 4 to 5 percent, in the upper 20 cm (8 inches) . Hy- dromorphism is reflected by mottles, the presence of which indicates reduction, reoxidation after reduction, or the redistribution of iron and manganese compounds that are soluble under reduced conditions. This should be present in about the upper meter (39 inches) or, when very intense, also in the subsoil between 1 and 2 meters (39 to 79 inches). One groupe a gley was recognized, indicating gley phenomena in the profile. Two sous- groupes, Sols a gley de surface and Sols a gley de pro- fondeur, indicate gley characteristics at the soil surface or in the subsoil, respectively. Podzols. These soils are characterized by an ABC profile, with an enrichment of iron or humus or both in the B horizon. The one profile, Gbamani, classified as Podzol (see Section 4:5 and Table 9) belongs to the sous-dasse Sols a "mor" enrichis en sesquioxides sans hori- zon de gley en profondeur, which indicates podzols with "mor" humus and enriched with sesquioxides, without the influence of a groundwater table. The groupe that was recognized is Podzols, soils with a clear A2 horizon that has ash-like colors. The sous-groupe is Podzols humo- ferrugineux, which indicates the presence of a BI horizon enriched with humus, separated from the B2 horizon en- riched with iron. Sols peu evolues. Only one profile, Sahama (see Sec- tion 4:5 and Table 9), was classified in this classe, which refers to soils with an AC profile : the A horizon is either thin or low in organic matter, and the A and C horizons differ only slightly in degree of weathering. The sous- dasse is Sols peu evolues d'origine non dimatique: young or rejuvenated soils, not influenced by the atmospheric climate but under the influence of the pedoclimate. The groupe is Sols peu evolues d'apport, indicating soils usu- ally formed in recent alluvium. Sols mineraux bruts. These are soils with an (A)C profile. Two profiles (see Section 4:6 and Table 9) were classified in the sous-dasse Sols mineraux bruts d'origine non dimatique (see above), the groupe Sols bruts d'ap- port, and the sous-groupe marin. These soils are develop- ing in marine alluvium that is still being deposited. Relationships Among the Three Systems. Relationships among soils classified in the highest categories of the three soils classification systems are indicated below: FAO/UNESCO Soil Taxonomy (28): highest French system (69): order category (2, 3): classe Entisols Gleysols Sols hydromorphes Fluvisols Sols mineraux bruts Regosols Sols peu evolues Inceptisols Cambisols Sols ferrallitiques Gleysols Sols hydromorphes Fluvisols Sols mineraux bruts Spodosols Podzols Podzols Ultisols Nitosols Sols ferrallitiques Sols hydromorphes Acrisols Sols hydromorphes Oxisols Ferralsols Sols ferrallitiques Sols hydromorphes The most important soils in Sierra Leone are the Ulti- sols, Oxisols, and Inceptisols. Their FAO/UNESCO equivalents are Nitosols, Ferralsols, and Cambisols, re- spectively; in the French system, these are the Sols fer- rallitiques for the better-drained soils and the Sols hydro- morphes for the poorly drained soils. Hydromorphism is an important criterion in the French classification system. The classe of Sols hydromorphes has no equivalent in the Soil Taxonomy system, but degree of wetness is often seg- regated at the suborder category. Hydromorphism is also reflected in some names of the highest categories of the FAO/UNESCO system — for example, Gleysols, which belong to Entisols and Inceptisols of the Soil Taxonomy. SECTION 4:12:3 69 4:12:3. SOIL CLASSIFICATION In Table 9 the Soil Taxonomy subgroup name and family are given for each of the 44 soil profiles studied in detail, together with their FAO/UNESCO soil unit name and their subgroup name in the French classifica- tion system. These are further discussed in the following paragraphs of this section, with major emphasis being given to the Soil Taxonomy classification. In the family- name, the particle-size class is listed first, then the min- eralogy class, and finally the soil temperature class. Most of the detailed information that forms the basis for classifying the soil profiles is given in Appendix B and Appendix C. Data collected were not always sufficient to classify definitely whether some horizons were argillic, oxic, or cambic, according to the Soil Taxonomy and the FAO/ UNESCO classification systems. The presence and amount of clay skins, used to determine whether a hori- zon is argillic (see Section 4:12:1), are often difficult to distinguish in field observations. Additional informa- tion from thin sections is needed to more definitively determine whether some of these Sierra Leone soils are Ultisols, Oxisols, or Inceptisols. Some of the soil profiles for which thin-section data are available show the presence of an argillic horizon, although they also often have all the other properties of an oxic horizon (occasionally a cambic horizon). For example, the B22t horizon of Njala profile N103 (Ap- pendix C) is argillic, as is the horizon above it, but it also has all of the other properties of an oxic horizon. Because an argillic horizon is designated as taking precedence, however, Njala soils are classified as Ultisols rather than Oxisols, although they are very near the border between these two soil orders. Many Sierra Leone soils are near the border between Ultisols and Oxisols or between Ultisols and Incepti- sols, depending upon the presence of an argillic horizon. For some profiles, it was difficult to decide between Oxi- sol and Inceptisol because of inadequate information on the amount and composition of weatherable minerals. Most soils classified as Inceptisols are near the border with Oxisols. For soils in which the presence of an argillic or oxic horizon is not fully established, an alternate sub- group classification is given (in parentheses) in Table 9. Where appropriate, this is also done in the FAO/ UNESCO and French classification systems. The Baoma soils occur on the upland in eastern Sierra Leone. They are well drained and have developed in 24 to 48 inches (61 to 122 cm) of relatively gravel-free ma- terial over red gravelly subsoils. They have an ochric epipedon and, with an illuvial/eluvial clay ratio of 1.4 or higher in the profile (Appendix C), they probably have an argillic horizon. Therefore, they have been clas- sified as a member of the clayey over clayey-skeletal, kaolinitic, isohyperthermic family of Typic Paleudults. However, the entire B horizon also has the properties of an oxic horizon. If later thin-section study shows that the B horizon is not argillic, Baoma soils would be classified in the Tropeptic Haplorthox subgroup. Bonjema soils arc moderately well and imperfectly drained and occur on colluvial footslopcs and upper river and tributary terraces. They have a gravel-free layer 24 to 48 inches (61 to 122 cm) thick, overlying a gravelly subsoil. Bonjema soils usually are adjacent to Mokonde soils but have a thicker gravel-free layer. Both profiles N39 and N105 of the Bonjema series have an ochric epipedon, and there are many red plinthite mot- tles in the subsoil. Available evidence indicates that Bon- jema soils have an argillic horizon (Appendix C), and they have been classified as Plinthic Paleudults. Profile N39 is in the fine-loamy over clayey-skeletal, mixed, iso- hyperthermic family, whereas profile N105 contains less clay and is in the fine-loamy over loamy-skeletal particle- size class. If subsequent thin-section studies indicate that these soils have a cambic horizon instead of an argillic horizon, they would be classified as "Plinthic" Udoxic Dystropepts. The Bosor soils arc part of the well-drained older tributary terraces and the colluvial footslopes. They have a gravel-free colluvial or alluvial layer 24 to 48 inches (61 to 122 cm) thick, overlying a gravelly subsoil. They have an umbric epipedon and an argillic or a cambic horizon in the gravelly subsoil. The subsurface horizon has many properties of the oxic horizon, but the amount of water-dispersible clay is too high (Appendix C) . Bosor soils are classified as a member of the fine-loamy over loamy-skeletal, mixed, isohyperthermic family of Orthoxic Palehumults. If further study indicates that the B2 hori- zon is not argillic, Bosor soils would be classified as Udoxic Dystropepts. The well-drained, sandy Gbamani soils occur on beach ridges near the Atlantic coast. They have a thick ochric epipedon, characteristic of Podzols in the humid tropics, and a distinctive spodic horizon. Gbamani soils are in the sandy, mixed, isohyperthermic family of "Arenic" Tropohumods. The Gbehan soils are poorly drained and occur on the alluvial floodplain grasslands in southern Sierra Leone. Although these soils have a very dark A! horizon, it is not thick enough to be umbric and thus is an ochric epipedon. The lower subsoil has the properties of an oxic horizon (Appendix C). Therefore, Gbehan soils are a member of the clayey, kaolinitic, isohyperthermic family of "Plinthic Tropeptic" Ochraquox. Gbesebu soils are moderately well drained and occupy the major portion of the current alluvial floodplain of the Taia River. They present special classification prob- lems in the higher categories because they contain more than 6-percent mica in the fraction between 20 and 200 microns (see descriptions of profiles N125 and N13 in Appendix B), but in other properties their lower sub- soils have characteristics of oxic horizons (Appendix C). According to the current definition (69), this amount of mica excludes them from the oxic horizon, but they have 70 BUUETIN NO. 748 Table 9. Taxonomic classification of Sierra Leone soils according to three systems: Soil Taxonomy (69), FAO/UNESCO (28), and the French system (2, 3) Soil series and profile number Soil Taxonomy FAO/UNESCO French system Subgroup* Family1* Baoma 144801A Typic Paleudults (or Tropeptic Haplorthox) Clayey over clayey- skeletal, kaolinitic Humic Nitosols (or Humic Cambisols) Sols ferrallitiques fortement denatures lessives-modaux (ou remanies modaux) Bonjema N39 Plinthic Paleudults (or "Plinthic" Udoxic Dystropepts) Fine-loamy over clayey- skeletal, mixed Dystric Nitosols (or Ferralic Cambisols) Sols ferrallitiques fortement desatures lessives hydromorphes (ou penevolues hydromorphes) Bonjema N105 Same as Bonjema N39 Fine-loamy over loamy- skeletal, mixed Same as Bonjema N39 Same as Bonjema N39 Boior P60 Orthoxic Palehumults (or Udoxic Dystropepts) Fine-loamy over loamy- skeletal, mixed Humic Nitosols (or Humic Cambisols) Sols ferrallitiques fortement desatures lessives-modaux Gbamani T165 "Arenic" Tropohumods Sandy, mixed Humic Podzols Podzols humo-ferrugineux GbehanT187 "Plinthic Tropeptic" Ochraquox Clayey, kaolinitic Humic Ferralsols Sols hydromorphes a gley de surface Gbesebu Ml 25 Fluventic Udoxic Dystropepts Fine-clayey, kaolinitic Ferralic Cambisols Sols ferrallitiques fortement desatures penevolues hydromorphes Gbesebu N13 Same as Gbesebu N125 Same as Gbesebu N125 Same as Gbesebu N125 Same as Gbesebu N125 Konia N70 "Plinthic" Orthoxic Palehumults (or Plinthic Aquic Umbriorthox) Clayey, kaolinitic Humic Nitosols (or Humic Ferralsols) Sols ferrallitiques fortement desatures lessives hydromorphes (ou typique- ment hydromorphes; ou sols hydro- morphes mineraux a gley de profondeur) Keya 145041 Fluventic Tropaquents Coarse-loamy, mixed Dystric Gleysols Sols hydromorphes mineraux a gley de profondeur Kparva 145042 Aquic Paleudults (or Aquic Tropeptic Haplorthox) Clayey, kaolinitic Humic Nitosols (or Humic Ferralsols) Sols hydromorphes mineraux a gley lessives (ou gley de profondeur; ou sols ferrallitiques fortement desatures remanies hydromorphes) Mabassia, shallow P71 "Plinthic" Udoxic Dystropepts Fine-loamy, mixed Humic Cambisols Sols ferrallitiques fortement desatures penevolues hydromorphes Mabassia, deep PI 08 Makeni P2 Orthoxic Palehumults Typic Paleudults Clayey, kaolinitic Humic Nitosols Humic Nitosols Sols ferrallitiques fortement desatures lessives Sols ferrallitiques moyennement de- satures en B "lessives indure's" y y Makundu P104 Plinthic "Tropeptic" Umbriorthox Clayey, kaolinitic Humic Ferralsols Sols ferrallitiques fortement desatures penevolues hydromorphes Mankane P8 Plinthic Tropaquepts Coarse-loamy, mixed Dystric Gleysols Sols hydromorphes mineraux a gley de surface Manowa Kpuabu 1 Orthoxic Palehumults (or Typic Umbriorthox) Clayey-skeletal, oxidic Humic Nitosols (or Humic Ferralsols) Sols ferrallitiques fortement desatures lessives indures (ou remanies jaunes) Masheka P49 Orthoxic Palehumults (or Udoxic Dystropepts) Fine-loamy over loamy- skeletal, mixed Humic Nitosols (or Humic Cambisols) Sols ferrallitiques fortement desatures lessives hydromorphes (ou humiferes- modaux) Masuba P9 "Plinthic" Udoxic Dystropepts Fine-loamy, mixed Ferralic Cambisols Sols ferrallitiques fortement desatures typiquement hydromorphes Moa Kpuabu 3 Tropeptic Haplorthox (or Fluventic Udoxic Dystropepts) Clayey, kaolinitic Humic Ferralsols (or Ferralic Cambisols) Sols ferrallitiques fortement desatures penevolues hydromorphes Mokoli N14 Fluventic Udoxic Dystropepts Very fine clayey, kaolinitic Ferralic Cambisols Sols ferrallitiques fortement desatures penevolues hydromorphes Mokonde N42 Plinthic Paleudults (or "Plinthic" Udoxic Dystropepts) Coarse-loamy over loamy-skeletal, mixed Dystric Nitosols (or Ferralic Cambisols) Sols ferrallitiques fortement desatures lessives indures (ou penevolues hydro- morphes) Momenga N123 "Plinthic" Dystropepts Clayey-skeletal, oxidic Chromic Cambisols Sols ferrallitiques fortement desatures penevolues avec erosion et remanie- ment Momenga N86 Same as Momenga N123 Same as Momenga N123 Same as Momenga N123 Same as Momenga N123 Momenga N44 Same as Momenga Nl 23 Same as Momenga N123 Same as Momenga N123 Same as Momenga N123 * Names in quotation marks are suggested new subgroup designations not listed in Soil Taxonomy (69). All families belong to the isohyperthermic temperature class and acid reaction class. SECTION 4:12:3 71 Table 9 (continued). Soil series and profile number Soil Taxonomy FAO/UNESCO French system Subgroup* Familyb Njala N109 Orthoxic Palehumults Clayey-skeletal, oxidic Humic Nitosols Sols ferrallitiques fortement desatures lessives indures Njala N108 Plinthic Paleudults Same as Njala N109 Same as Njala N109 Same as Njala N109 Nyawama N100 "Plinthic" Orthoxic Pale- humults (or Plinthic Umbriorthox) Fine-loamy, mixed Humic Nitosols (or Humic Ferralsols) Sols ferrallitiques fortement desatures lessives hydromorphes (ou typique- ment faiblement appauvris) Nyawama N71 Same as Nyawama N100 Clayey, kaolinitic Same as Nyawama N100 Same as Nyawama N100 Nyawama N15 Plinthic "Orthoxic" Paleud- ults (or Plinthic Haplorthox) Same as Nyawama N71 Same as Nyawama N100 Same as Nyawama N100 Panlap PI Aerie Plinthic Tropaquepts Coarse-loamy, mixed Humic Gleysols Sols hydromorphes mineraux a gley de profondeur Pelewahun N47 Typic Plinth aquults Fine-loamy over clayey- skeletal, mixed Plinthic Acrisols Sols hydromorphes mineraux a gley de surface Pelewahun N106 Plinthic Paleaquults Fine-loamy over loamy- skeletal, mixed Dystric Nitosols Same as Pelewahun N47 Pendembu Kpuabu 2 Typic Paleudults Fine-loamy, mixed Humic Nitosols Sols ferrallitiques fortement desatures lessives hydromorphes Pujehun N80 Fluventic Udoxic Dystropepts Fine-loamy, mixed Ferralic Cambisols Sols ferrallitiques fortement desatures penevolues hydromorphes Rokupr Rl Typic Sulfaquepts Fine-clayey, kaolinitic Thionic Fluvisols Sols mineraux bruts d'apport marin Rokupr R2 Typic Sulfaquenfs Same as Rokupr Rl Same as Rokupr Rl Same as Rokupr Rl Sonoma T149 Typic Quartzipsamments Sandy, siliceous Dystric Regosols Sols peu evolues non climatiques d'apport-isohumiques Segbwema 145005 Tropeptic Haplorthox (or Udoxic Dystropepts) Fine-loamy, mixed Humic Ferralsols (or Ferralic Cambisols) Sols ferrallitiques fortement desatures penevolues avec erosion et remanie- ment Taiama N101 Plinthic Umbric Paleaquults Fine-loamy, mixed Humic Nitosols Sols hydromorphes mineraux a gley de surface TasoT183 Plinthic "Tropeptic" Umbriorthox Clayey, kaolinitic Humic Ferralsols Sols ferrallitiques fortement desatures penevolues hydromorphes Timbo PI 9 Typic Umbriorthox (or Udoxic Dystropepts) Fine-loamy skeletal, mixed Humic Ferralsols (or Humic Cambisols) Sols ferrallitiques fortement desatures p'enevolues avec erosion et remanie- ment Tubum PI 3 Udoxic Dystropepts Fine-loamy over loamy- skeletal, mixed Humic Cambisols Sols ferrallitiques fortement desatures penevolues Vaahun 145010 Typic Dystropepts Clayey, kaolinitic Dystric Cambisols Sols ferrallitiques moyennement de- satures en B penevolues avec erosion et remaniement " Names in quotation marks are suggested new subgroup designations not listed in Soil Taxonomy (69). l: All families belong to the isohyperthermic temperature class and acid reaction class. a cambic horizon with udoxic properties. These soils have an ochric epipedon and show evidence of stratification, including charcoal fragments deposited in various layers. Gbesebu soils are a member of the fine-clayey, kaolinitic, isohyperthermic family of Fluventic Udoxic Dystropepts. Kania soils are imperfectly drained and usually occur in somewhat lower areas of the nearly level terrace of the Taia River or in similar topographic positions. They developed in gravel-free, sandy clay loam to clay allu- vium. These soils have an umbric epipedon and usually have an argillic horizon and the properties of an oxic horizon (Appendix C). Analyses of other Kania profiles indicate that the ratio of illuvial to eluvial clay may not always be as great as in profile N70. Low chromas are present in the subsoil, and plinthite mottles are abundant. Kania soils have been classified as a member of the clayey, kaolinitic, isohyperthermic family of "Plinthic" Orthoxic Palehumults on the basis of available informa- tion. If thin-section studies indicate that the B horizon does not contain enough clay skins to be argillic, these soils would be classified as Plinthic Aquic Umbriorthox. The Keya soils are very poorly drained and occur in depressions in the lowest parts of inland valley swamps in eastern Sierra Leone. They are developing in coarse- loamy colluvium and alluvium that is transported from surrounding higher areas. They have an ochric epipedon but no other diagnostic horizons. Keya soils are classified as a member of the coarse-loamy, mixed, acid, isohyper- thermic family of Fluventic Tropaquents, although the colors do not entirely fit the definition for Aquents. 72 BULLETIN NO. 748 Kparva soils are poorly drained and occur on nearly level, low-lying areas in eastern Sierra Leone. They have an ochric epipedon and, with an illuvial/eluvial clay ratio of 1.8 in the profile (Appendix C), they probably have an argillic horizon. Therefore, they have been clas- sified as a member of the clayey, kaolinitic, isohyper- thermic family of Aquic Paleudults. Chromas in the B2t horizon are not as gray (Appendix B) as is characteristic of the aquic moisture regime (69), but saturation with water in the upper 30 inches (75 cm) of the profile is enough for this soil to be aquic. The B3l horizon has the properties of an oxic horizon. If subsequent thin-section study shows that the B horizon is not argillic, Kparva soils would be classified in the Aquic Tropeptic Haplor- thox subgroup, but this seems unlikely. The Mabassia soils are well drained and have devel- oped in a hill-wash that was deposited in relatively lower and concave parts of the uplands. The colluvial top layer may range considerably in thickness — from 10 to more than 48 inches (25 to 122 cm) — and consists of almost gravel-free sandy loam to sandy clay. The collu- vial layer is underlain by gravelly material. Mabassia soils usually have an umbric epipedon and some properties of an oxic horizon. The shallower phase, P71, has a cambic horizon and is classified as a member of the fine-loamy, mixed, isohyperthermic family of "Plinthic" Udoxic Dys- tropepts. The deep phase of Mabassia, P108, which probably has an argillic horizon (Appendix C), is classi- fied as a member of the clayey, kaolinitic, isohyper- thermic family of Orthoxic Palehumults. Both of these soil profiles are very close to the Oxisols. Makeni soils are well drained and occur extensively on both the summits and sloping sides of hills in the Makeni area. The soils consist of very gravelly colluvial and residual material, usually more than 10 feet (3 m) thick, overlying granitic bedrock. The main components are sesquioxides in the form of hardened to soft plinthite glaebules and mottles, quartz in sand grains and larger particles, and kaolinitic clay. The gravels consist mainly of hardened plinthite glaebules with some quartz. In the upper part of the profile, the hardened plinthite glae- bules are dense, dark-coated, and mostly rounded, prob- ably as a result of having been transported. With increas- ing depth, the glaebules become softer, more porous, and irregular because they are formed in situ. Below depths of 6 to 8 feet (2 to 2.5 m), red mottles of soft plinthite are present, having formed as a result of mobilization, displacement, and accumulation of iron in horizons that are seasonally saturated with water. With alternating wet and dry conditions, the plinthite mottles may irrevers- ibly harden into iron glaebules, even in well-drained up- land soils, under current climatic conditions in Sierra Leone. Soil fauna, especially termites and worms, are respon- sible for intensive biological homogenization of the soil profile. Termites are also partly responsible for a gravel- free surface layer up to 10 inches (25 cm) thick, which may occur on top of the gravelly layers. Termites, such as the genus Macrotermes natalensis, build numerous mounds as high as 10 feet (3m). These mounds consist entirely of material less than 2 mm in diameter, brought up from the gravelly subsoil by the termites. The gravels are left behind, and, as a result of these termite activities, the gravel content of the gravelly layers progressively in- creases. The termite mounds are chemically richer than the surrounding subsoils and often are richer than the topsoils (57 ) . Makeni soils are a member of the clayey-skeletal, ox- idic, isohyperthermic family of Typic Paleudults. They have an argillic horizon on the basis of the illuvial/ eluvial clay ratio (Appendix C) and on the basis of clay skins observed in thin sections. The clay skins appear to be relict rather than being formed currently, and they are weak enough that they were not described in the field. In fact, the B2at horizon of Makeni profile P2 has all the properties of an oxic horizon, and the soil would be classified as an Oxisol if it did not have an argillic horizon. The Makeni soils usually have an umbric epi- pedon, but a few profiles with too thin a dark surface horizon are classified as having an ochric epipedon. The Makundu soils, which occur on the alluvial flood- plain along the Mabole River, are moderately well to well drained. They are much finer textured than the soils with which they are associated. They have an umbric epipedon and a thick oxic horizon (Appendix C). Makundu soils are a member of the clayey, kao- linitic, isohyperthermic family of Plinthic "Tropeptic" Umbriorthox. The Taso soils along the Sewa River in southern Sierra Leone are a member of this same family, and the two series have many similar characteristics. Mankane soils occur in the lowest parts of the valley bottoms and are poorly to very poorly drained. They have sandy loam to loamy sand textures to depths of more than 48 inches (122 cm), often overlying white kaolinitic clay mixed with sand and quartz pebbles. The soils usually have an ochric epipedon and a cambic hori- zon. Mankane soils are a member of the coarse-loamy, mixed, acid, isohyperthermic family of Plinthic Trop- aquepts. The moderately well-drained Manowa soils occupy summits and upper convex slopes of upland hills in east- ern Sierra Leone. These soils have an umbric epipedon and very gravelly subsoils. On the basis of their illuvial/ eluvial clay ratio of 1.2 (Appendix C), Manowa soils are believed to have argillic horizons, as this ratio is simi- lar to those of Makeni and Njala soils for which thin sec- tions demonstrated the presence of argillic B horizons. Therefore, the Manowa soils are classified as a member of the clayey-skeletal, oxidic, isohyperthermic family of Orthoxic Palehumults. The B22t horizon has the proper- ties of an oxic horizon. If later thin-section study shows that the B horizon is not argillic, Manowa soils would be classified in the Typic Umbriorthox subgroup. The Masheka soils belong to the well-drained older tributary terraces. They are similar to Bosor soils but differ in the thickness of the gravel-free layer, which is SECTION 4:12:3 73 more than 48 inches (122 cm) thick in Masheka and overlies a gravelly subsoil. The soils have an umbric epipedon and an argillic or cainbic horizon. If they have an argillic horizon, they would be classified as a member of the fine-loamy over loamy-skeletal, mixed, iso- hyperthermic family of Orthoxic Palehumults. If further study indicates that the B horizon is not argillic, Masheka soils would be classified in the Udoxic Dystropept sub- group. The Masuba soils, which are moderately well drained, occur on the lower part of recent tributary terraces. These soils are sandy clay loam throughout the profile. They usually have an umbric horizon, but the dark A horizon of profile P9 is thin and, therefore, is an ochric epipedon. A cambic horizon present in the subsoil has some of the properties of an oxic horizon, but the amount of water-dispersible clay is too high to qualify as an oxic horizon (Appendix C). Masuba soils are a member of the fine-loamy, mixed, isohyperthermic family of "Plin- thic" Udoxic Dystropepts. The Moa soils, which occur on the alluvial floodplain along the larger streams in the upper Moa Basin in east- ern Sierra Leone, are moderately well to well drained. They have an ochric epipedon and, in the lower B hori- zon, an oxic horizon. Moa soils are classified as a member of the clayey, kaolinitic, isohyperthermic family of Tro- peptic Haplorthox. If further study indicates that these soils contain more than 3 percent of weatherable min- erals in the fraction between 20 and 200 microns, they would be classified in the Fluventic Udoxic Dystropept subgroup. The imperfectly to poorly drained Mokoli soils occur in drainageways on the alluvial floodplain of the Taia River. They contain more than 6-percent mica in the fraction between 20 and 200 microns (Appendix B) , but in other properties their B horizons have characteris- tics of an oxic horizon (Appendix C). According to the current definition (69), this amount of mica excludes them from the oxic horizon, so they are classed as having a cambic horizon with udoxic properties. These soils have an ochric epipedon and evidence of stratification. Mokoli soils are a member of the very fine clayey, kao- linitic, isohyperthermic family of Fluventic Udoxic Dys- tropepts. Chromas of mottles in the upper 39 inches (1 m) of profile N14 are not gray enough (Appendix B) to be designated aquic, but the soil is saturated to the surface annually for about two months (Fig. 30). Mokonde soils are moderately well drained and occur on upper terraces and colluvial footslopes. They have a gravel-free surface layer 10 to 24 inches (25 to 61 cm) thick, overlying a gravelly subsoil. Mokonde soils occur adjacent to Njala soils but differ from them in having a thicker gravel-free layer. The gravel-free materials are of colluvial origin and are the erosion products of fine earth brought up by the termites. Mokonde soils have an ochric epipedon and many plinthite mottles in the subsoil. Mo- konde soils have been classified as a member of the coarse-loamy over loamy-skeletal, mixed, isohyperthennic family of Plinthic Paleudults because it is believed that they have an argillic horizon ; however, thin-section data are not available to determine the extent of clay skins. If the latter are of minor extent, these soils would be classified as "Plinthic" Udoxic Dystropepts. The Momenga soils occur on steep slopes of the up- lands. The upper part of the profile is usually gravelly over an almost gravel-free lower subsoil, with soft bed- rock pieces (saprolite) often within 48 inches (122 cm). The moderate depth of profile over bedrock is caused by active geologic erosion. The diagnostic horizons are an ochric epipedon and a cainbic horizon. Cation-exchange capacity is more than 24 me/100 g of clay in all horizons (Appendix C). Base saturation is distinctly less than 50 percent in all horizons. Exchangeable aluminum is al- ways high in the subsoil, typically ranging from 6 to 12 me/100 g of the fine-earth fraction (< 2.0 mm). Mo- menga soils (profiles N123, N86, and N44) are classified as a member of the clayey-skeletal, oxidic, isohyper- thermic family of "Plinthic" Dystropepts, which reflects their relatively youthful stage of soil development. The subgroup prefix "plinthic" indicates that soft plinthite occurs within 50 inches (127 cm) of the soil surface. The Njala soils, which make up the bulk of the upland soils in the Njala area, consist of a thick surface layer of gravelly colluvial and residual material. Main compo- nents are kaolinitic clay and sesquioxides in the form of indurated to soft plinthite glaebules and mottles. The colluvial layer consists of about 50-percent hard and dense glaebules with smooth surfaces in a clayey matrix. It is most likely that rounding of the glaebules is caused by transportation, most of which has taken place over only short distances (80) . Underlying the gravelly collu- vium is a layer of residual iron glaebules in a clayey matrix. These glaebules are relatively soft and porous and have irregular forms. Their amount decreases with depth. Soft plinthite is often present in the form of red mottles. They result from the mobilization, displace- ment, and accumulation of iron in horizons that are satu- rated with water at some season. Because of alternating wet and dry conditions, the plinthite mottles may irrever- sibly harden into iron glaebules. Under current climatic conditions, these criteria are met even in the moderately well- and well-drained upland soils. When iron segrega- tion has been sufficient to permit irreversible hardening on exposure to wetting and drying, the mottles are con- sidered plinthite (69). The two Njala profiles that have been analyzed, N109 and N108, are different in some properties even though they are close together geographically (Appendix B) . On the basis of the ratio of illuvial clay to eluvial clay (Appendix C) and on the basis of clay skins observed in thin sections, both profiles have an argillic horizon. The clay skins appear to be relict rather than being formed currently, and they are weak enough that they were not described in the field. The clay activity is very 74 BUUETIN NO. 748 low. In fact, the B22l horizon of Njala profile N109 has the properties of an oxic horizon, and the soil would be classified as an Oxisol if it did not have an argillic hori- zon. Njala soils usually have an ochric epipedon, as does N108, but the A, horizon of a few profiles, such as N109. is thick enough and dark enough to qualify as an umbric epipedon. Njala profile N 109 is a member of the clayey-skeletal, oxidic, isohyperthermic family of Or- thoxic Palehumults. Njala profile N108 is classified as a member of the clayey-skeletal, oxidic, isohyperthermic family of Plinthic Paleudults, although the upper B hori- zon is slightly low in clay content to qualify for this particle-size class. The Nyawama soils are moderately well drained and occur primarily on the nearly level terrace of the Taia River. They developed in fine-loamy or clayey material that is gravel-free. Nyawama soils usually have an umbric epipedon, although the dark-colored At horizon of Nya- wama profile N15 is thin (5 inches, or 13 cm) so that it has an ochric epipedon (Appendix B). Profile N100 is fine-loamy, whereas profiles N71 and N15 are in the clayey particle-size class. On the basis of illuvial/eluvial clay ratios of 1.3 or 1.4 in their profiles, these soils have an argillic horizon (Appendix C), but thin-section data are not available to indicate the extent of clay skins. These soils also have the properties of an oxic horizon in their lower subsoils, and they would be classified as Oxi- sols (see subgroup names in Table 9) if later work shows that they do not have argillic horizons, which seems un- likely. Although these three Nyawama profiles are similar in most characteristics, they have different classifications, because of differences in thickness of the dark surface horizon (N15 is the thinnest) and differences in clay content in the B horizon (N100 contains the least clay) : N100 = Fine-loamy, mixed, isohyperthermic family of "Plinthic" Orthoxic Palehumults N71 = Clayey, kaolinitic, isohyperthermic family of "Plinthic" Orthoxic Palehumults N15 = Clayey, kaolinitic, isohyperthermic family of Plinthic "Orthoxic" Paleudults The Panlap soils are imperfectly to poorly drained and occur on gentle concave slopes near streams or on the edges of inland swamps. They have developed in nearly gravel-free, coarse-loamy material that is more than 48 inches (122 cm) thick over a gravelly layer or residual material (often saprolite). From the upland toward the valley bottom, the layer of detrital hardened plinthite glaebules (if present) gradually decreases in thickness and finally disappears in the poorly drained swamps be- cause of intense leaching of iron; only white kaolinitic clay, mixed with quartz sand and gravel, is left. Panlap soils usually have an umbric epipedon, with or without a cambic horizon. They have been classified as a member of the coarse-loamy, mixed, acid, isohyperthermic family of Aerie Plinthic Tropaquepts. The prefix aerie indicates a subhorizon at depths of less than 30 inches (75 cm) with chromas of more than 2. Pelewahun soils occupy poorly drained drainageways and swamps of the colluvial footslopes and tributary stream terraces. They have a gravel-free layer 24 to 48 inches (61 to 122 cm) thick, overlying a gravelly sub- soil. These soils are flooded for several months during the rainy season. Pelewahun soils often have an umbric epi- pedon, but in some areas it is ochric. They have a dis- tinct argillic horizon on the basis of clay accumulation in the B horizon (Appendix C) and on the basis of clay skins observed in the field (Appendix B) and in thin sections (44) . Pelewahun profile N47 is a member of the fine-loamy over clayey-skeletal, mixed, isohyperthermic family of Typic Plinthaquults. In the FAO/UNESCO classification, it is a Plinthic Acrisol (instead of a Nitosol, which is often equivalent to Ultisols) because it has a plinthic horizon and an abrupt textural change between the B2 and overlying horizons. Pelewahun profile N106 contains less clay and is a member of the fine-loamy over loamy-skeletal, mixed, isohyperthermic family of Plinthic Paleaquults. Most Pelewahun soils have less than 50-per- cent red plinthite mottles in all subhorizons above a depth of 50 inches (125 cm) and so are similar to N106 in this property, rather than N47. The Pendembu soils arc imperfectly drained and oc- cur on footslopes and upper tributary terraces in eastern Sierra Leone. They have an ochric epipedon and an argillic horizon. The latter is indicated by clay skins de- scribed in the field (Appendix B) and by the illuvial/ eluvial clay ratio of 1.3 in the profile (Appendix C). Pendembu soils are a member of the fine-loamy, mixed, isohyperthermic family of Typic Paleudults. Pujehun soils are well drained and occur on natural levees adjacent to the Taia River. They are stratified and have an ochric epipedon. They contain more than 6- percent mica in the fraction between 20 and 200 microns (Appendix B) ; but in other properties, their lower sub- soils have characteristics of oxic horizons (Appendix C). According to the current definition (69), this amount of mica excludes them from the oxic horizon, so they are classed as having a cambic horizon with udoxic proper- ties. Pujehun soils are a member of the fine-loamy, mixed, isohyperthermic family of Fluventic Udoxic Dys- tropepts. The Rokupr soils are very poorly drained, occurring in tidal swamps and up adjacent stream estuaries. They are very high in sulfur content, 1 to 11.5 percent. The two profiles that have been studied are similar in most properties, except that profile R2 is in the natural, re- duced condition, whereas profile Rl has been drained and oxidized enough that it has a sulfuric horizon. Both profiles have an ochric epipedon and are members of a fine-clayey, kaolinitic, acid, isohyperthermic family. Rokupr profile R2 is classified in the Typic Sulfaquent subgroup; profile Rl is in the Typic Sulfaquept sub- group. The well-drained, sandy Sahaina soils occur on beach ridges near the Atlantic coast. They are so high in sand content (mostly quartz) that no diagnostic horizon has SECTION 4:12:3 75 developed except in the surface. Some organic matter has accumulated, and the A horizon (0 to 20 inches, or 0 to 51 cm) is borderline between an umbric and an ochric epipedon. The colors qualify for an umbric hori- zon, but the AIJ, horizon contains less than 0.6-percent organic carbon (Appendix B) . Sahama soils are classified as a meinber of the sandy, siliceous, isohyperthermic fam- ily of Typic Quartzipsamments. Sahama profile T149 (Appendix B) is interesting in that the Em horizon has a significant accumulation of organic carbon and the highest cation-exchange capacity in the profile, which suggests that it is developing toward a Spodic Quartzi- psamment but does not yet qualify as a member of this subgroup. The well-drained Segbwema soils occur extensively on steep hills in eastern Sierra Leone. They have an ochric epipedon and the properties of an oxic horizon, except that the cation-exchange capacity of the clay fraction is slightly high (Appendix C) and the amount of weather- able minerals may be slightly high (Appendix B). Seg- bwema soils are classified as a member of the fine-loamy, mixed, isohyperthermic family of Tropeptic Haplorthox. Should further study indicate that Segbwema soils do not have an oxic horizon, they would be a member of the Udoxic Dystropept subgroup. The Taiama soils are poorly drained. They occur pri- marily in drainageways of the middle terraces of the Taia River and in the downstream portions of its tributaries. They usually have an umbric epipedon (Appendix B). Taiama soils are classified as a member of the fine-loamy, mixed, isohyperthermic family of Plinthic Umbric Pale- aquults because they have an argillic horizon, based on the illuvial/eluvial clay ratio (Appendix C) and the observation of clay skins in thin sections. The clay activ- ity is very low, and the lower subsoil has most of the properties of an oxic horizon. The Taso soils are moderately well to well drained and occur on natural levees adjacent to the Sewa River. They have an umbric epipedon and a thick oxic horizon (Appendix C). They are high in clay and silt but low- in sand content. Taso soils are a member of the clayey, kaolinitic, isohyperthermic family of Plinthic "Tropeptic" Umbriorthox. The Makundu soils along the Mabole River in central Sierra Leone are a member of this same family, and these two series have many similar char- acteristics. The Timbo soils are well drained and occur on mod- erately steep to steep slopes of the uplands. They have developed in 24 to 48 inches (61 to 122 cm) of gravelly colluvium and residual material. Timbo soils differ from Makeni soils in having partly or wholly decomposed bed- rock fragments, which always occur within 48 inches (122 cm) of the soil surface. The shallowness of these fragments suggests that erosion removed a considerable part of the overlying soil layers. The gravelly colluvial layer varies from about 12 to 20 inches (30 to 51 cm) thick; the gravels are very hard, dense, and nodular. In the residual layer, decomposed rock fragments occur that are very hard and porous in the upper part but soft to hard and porous deeper in the profile. Enrichment with iron probably caused the development of hardened de- composed rock fragments in which the rock structure is clearly visible. Some weatherable minerals may still be present, such as micas and probably some feldspars. Timbo soils usually have an umbric epipedon (Ap- pendix B) and an oxic horizon (Appendix C). Within the latter, however, less than 5 percent by volume should be showing rock structure (69) — a restriction that often imposes problems in the recognition of an oxic horizon in Timbo soils. However, the other properties agreed so closely with the oxic horizon concept that it seemed de- sirable to waive the above-mentioned restriction. Timbo soils have been classified as a member of the fine-loamy skeletal, mixed, isohyperthermic family of Typic Um- briorthox. If the rock structure is taken into account, the subgroup name would be Udoxic Dystropept. The Tubum soils are part of the moderately well- to well-drained recent tributary terraces and the colluvial footslopes. They have much in common with Bosor soils, but the gravel-free depositional layer is of a more recent age. The gravel-free layer is 24 to 48 inches (61 to 122 cm) thick, overlying a gravelly subsoil. Tubum soils have an umbric epipedon and a cambic horizon in the gravelly subsoil (Appendix B). The more recent age of Tubum soils compared with Bosor soils is reflected by the chemi- cal properties of the subsurface horizon : Tubum soils have more water-dispersible clay, more extractable bases plus aluminum, and a higher cation-exchange capacity per 100 grams of clay (Appendix C). Tubum soils are a member of the fine-loamy over loamy-skeletal, mixed, isohyperthermic family of Udoxic Dystropepts. The Vaahun soils occur on steep granitic hills in eastern Sierra Leone and usually have profiles less than 36 inches (91 cm) thick. They are moderately well to well drained. These soils have an ochric epipedon and a cambic horizon (Appendix B) . Although the illuvial/elu- vial clay ratio is 1.9 to 2.0 in the Vaahun profile that was analyzed (Appendix C), it is doubtful that an argillic horizon could form on the unstable, steep slope on which this profile occurs. The increase in clay content with depth is probably caused by colluviation rather than by illuviation. Vaahun soils are classified as a member of the clayey, kaolinitic, isohyperthermic family of Typic Dystropepts. 5. Adaptation and Management of Soils Soil series, the lowest category in the natural classifica- tion, are homogeneous with respect to many properties and can therefore be grouped for a wide variety of prac- tical purposes, such as suitability for general agricultural use and management, production of a specific crop or combination of crops, or nonagricultural uses. Only agri- cultural uses are considered in this report. In Section 5, the soil series are grouped according to their suitability for general agricultural use and their major management problems. Primary focus is on crops that require aerated soils. However, each soil is also evaluated for swamp rice, an important crop on water- saturated, poorly aerated soils. Principles of soil fertility and management of selected crops are also discussed. 5:1. IMPORTANT FACTORS . IN SOIL GROUPING A number of soil properties influence the productivity of crops. Those that may limit plant growth in varying degrees are often designated as "limiting factors." These factors include slope (erosion hazard), texture, presence and characteristics of unfavorable layers such as gravel or rock, available moisture-holding capacity, waterlog- ging, level of available nutrients, and pH. One of the most important limiting factors is the mois- ture-holding capacity of soils, especially moisture that is held available for plant growth. On soils with high avail- able moisture-holding capacity, two crops can be grown annually without irrigation — one from May through August, another from September through December. (This second crop is not practical on gravelly upland soils with low moisture-holding capacity). Growing this second crop on the better soils during the declining rains (September through December) provides an excellent opportunity to produce grain crops economically and harvest them under more favorable conditions than dur- ing the rainy season. A third crop can be grown during the later part (January through April) of the dry season if cheap irrigation water is available. The available mois- ture-holding capacities of selected soil profiles to a depth of 60 inches (153 cm) are listed in Table 10. These values are calculated from bulk density, gravel content, and 1/3 atmosphere and 15 atmospheres moisture values for the various profiles in Appendix B. Available moisture-holding capacity is greatest in soils or horizons that contain much silt. The high value for the Momenga profile N123 is due to the high silt content of its C horizon (see Appendix B). The Gbehan, Taso, Pujehun, Gbesebu, and Mokoli soils on the alluvial floodplains contain much silt (Sections 4:7 and 4:8:4) and have high available moisture-holding capacities. In contrast, the gravelly upland soils such as Makeni, Man- owa, and Timbo or sandy soils such as Sahama and Gbamani have very low available moisture-holding ca- pacities and, therefore, are droughty throughout the long dry season. On the basis of the data in Table 10, the available moisture-holding capacities are grouped as follows : Inches of avail- able moisture- holding capacity Designation per inch of soil Available moisture- holding capacity to 60 inches (1,524 mm) (inches) (mm) .01-.03 0-2 0-51 .03-.06 2-4 51-102 .06-. 11 4-7 102-178 .11-. 18 7-11 178-279 .18-.25 11-15 279-381 Very low Low Medium High Very high 5& CAPABILITY GROUPING OF SOILS To Assist in the proper use and management of soils in Sierra Leone, they have been placed in capability groups that are similar to those in a system used in the United States of America (46) . This is a practical group- ing based on limitations of the soils, the risk of damage when they are used, and the way they respond to treat- ment. The soils are grouped according to degree and kind of permanent limitation but without consideration of major and expensive land-forming that would change the slope, depth, or other characteristics of the soils. AH of the soils are grouped at two levels: capability class and subclass. One subclass, Iw, is further divided into two units, Iw- 1 and Iw-2 ( see Table 1 1 , pages 79 and 80 ) . Capability classes, the broadest grouping, aje desig- nated by Roman numerals I through VIII. As the nu- merals increase, they indicate progressively greater limita- tions and narrower choice*! for practical use. The classes are defined as follows: Class I. Soils with few limitations on their use. Class II. Soils with some limitations that reduce the choice of plants or require moderate con- servation practices. Class III. Soils with severe limitations that reduce the choice of plants, or require special conservation practices, or both. 76 SECTION 5:3 77 Class IV. Soils with very severe limitations that re- strict the choice of plants, or require very careful management, or both. Class V. Soils subject to little or no erosion but with other limitations, usually impractical to remove, that restrict their use largely to pasture, woodland, or wildlife food and cover. Table 10. Grouping of selected soils according to avail- able moisture-holding capacity to a depth of 60 inches (153 cm) Soil series Profile number Available moisture- holding capacity inches mm Class VI. Soils with severe limitations that make lU Malceni P2 1.4 36 them generally unsuited to cultivation and Sahamo T149 1 6 41 restrict their use largely to forestry, tree Gbomani T165 1.6" 42* crops such as oil palm and rubber, pasture, Manowo. ... Kpuabul 1.8" 47" or wildlife food and cover. Tmbo P19 '•' 49 Class VII. Soils with very severe limitations that L«w make them unsuited to cultivation and re- Bosor. P60 54 strict their use largely to forestry, grazing, Masheka. P49 ..,.., Pendembu Kpuabu 2 2.4" 61" or Wildlife. Baoma 144801A 2.6 66 Class VIII. Soils and landforms (such as Rock Land) Tubum P13 2.6 67 with limitations that preclude their use Mabassia, shallow . P71 2.8' , • , i , Njala N109 3.0* 76' tor commercial plant production and re- Mokonde N42 34 87 strict their use to wildlife, watershed pro- Kparva 145042 3.8 97 tection, recreation, or esthetic purposes. Medium Capability subclasses are soil groups within one class. Mabassio, deep P108 4.0 102 They are designated by adding one or two small letters Masubo.. P9 4.0 102 °, ui i TTT c Panlap PI 4.0 1 02 -e, w, s, or h — to the class numeral: IIIws, for ex- Mankone P8 4.7" 119« ample. The letter e shows that the main limitation is MOO Kpuabu 3 4.7s 1 20" risk of erosion unless close-growing plant cover is main- Makundu P104 5.7 145 tained; w shows that excess water on or in the soil inter- Segbwema 145005 5.8" 148" r -.t i i i^- • • j- i Nyawama N100 6.3 159 feres with plant growth or cultivation; s indicates gravel Toiamo N101 65 165 or hard rock in the soil, which is unfavorable for root Kania . N70 6.8 174 extension and plant growth; and h indicates restricted available moisture-holding capacity in the soil. ., „ , ., ., . i. Mokoli N14 7.2 184 Almost all of the soils in Sierra Leone are acid and Gbesebu N125 76 194 relatively low in available plant nutrients, but most of Pujehun N80 7.7 195 these deficiencies can be corrected economically on soils Toso. . . T183 9.6" 244" that are suitable for agriculture. Therefore, fertility Gbehan.. T187 10.6» 269" ,• i • i_ • -, • , ' Pelewahun ... N47 10.8 274 status is not included directly in this soil grouping, but vnoo •« j -,,,, ' ^ > ° .. mom en go IN I z J 1^.4 JI4 relative fertility of each soil is listed in Table 1 1. Fertility Status as related to texture and Organic carbon content " Based on estimated values for some part of the soil profile. is discussed in Sections 4:5 through 4:10 and Appendix season and vegetables during the dry season. Perennial The nomenclature and description of the capability crops grow near tne villages; most of them, except coffee groups do not accurately reflect the suitability of various and cocoaj are consumed by the family. In this tradi- soils for swamp rice, which grows well on water-satu- tional system, capital inputs are low: the most important rated, poorly aerated soils. Therefore, each soil is given a ;nputs are clearing the land and burning the brush, special rating for this important crop (see Table 11). vvnich are done by hand labor. Seed is of low quality, usually having been raised by the farmer and saved from 5:3. SOIL MANAGEMENT SUGGESTIONS the harvest of the year before. Farm operations such as When considering the relative suitability of the vari- weeding and harvesting are all done by hand with family ous soils and crops, attention has to be given to the type labor (Fig. 45). Technical know-how is limited. Conse- of land utilization that is envisaged. The present land- quently, crop yields are low. Further, as a result of the use system on the upland is a shifting cultivation or bush- overcropping of farmland, which is, in turn, the result fallow system, in which a particular tract of land is of increasing population, yields are expected to decline, farmed for only two years, after which the farmer moves It is very desirable to develop a new type of land on to another piece of land. Selected swamps are farmed utilization in which the shifting cultivation system is fully more regularly, producing swamp rice during the rainy replaced by a system of planned and coordinated perma- 78 BULLETIN NO. 748 Figure 45. Upland rice with interspersed maize being grown by traditional shifting cultivation practices. nent allocation of land. A less drastic new kind of land utilization could be an intermediate type in which per- manent cultivation is expanded in some areas, thus re- lieving the pressure on the remaining farm land. The fallow period in these areas could then be lengthened, which would improve the possibility for natural regenera- tion under the bush-fallow system. The permanent cul- tivation should be carried out on the better soils, with the use of modern management practices, fertilizers, etc. Considering the farmers' present level of technical know- how, the intermediate type of land utilization mentioned above is probably best, for it would allow them to make a gradual shift to a higher degree of technical know-how. The soil management suggestions described in the rest of this section are aimed at the intermediate type of land utilization. This system is characterized by permanent cultivation on the better soils and by the traditional shift- ing cultivation system, tree crops, or forestry on the less productive soils. Under regular cultivation, farm prac- tices must improve markedly to include good cropping systems, proper use of fertilizers, better crop varieties, and, where practicable, irrigation on the best soils during the dry season. The soils within one capability or management group in Table 1 1 are enough alike that they are suited to the same crops or native plants, require similar management, and have similar productivity and other responses to management. Following are descriptions of each capa- bility or management group listed in Table 1 1 and sug- gestions for the use and management of the soils in each group. Management Group Ih: Nyawama, Makundu, and Moa. These soils are moderately well to well drained and aerated, but Makundu and Moa may be flooded for a few days during the rainy season. They have medium available moisture-holding capacity but suffer from drought during the later part of the dry season. These soils are permeable, occur on nearly level areas, and are not subject to erosion. They have good physical proper- ties and can be cultivated easily. However, they are strongly acid and only fair in available plant nutrients, so that proper fertilization is necessary to obtain profit- able crop yields. These soils can be used intensively for a wide variety of both annual and perennial crops: rice, maize, groundnuts, pineapple, coffee, oil palm, citrus, etc. The soils can be used throughout the year if irrigation water can be obtained economically from the major streams near which the soils occur. Peasant farmers should be encouraged to use these soils more intensively than they now do under the bush-fallow system. Rice, for example, can be grown during the rainy season (May through August) , and maize during the season of declin- ing rains (September through December). If irrigation water is provided, a third crop can be grown during the last part of the dry season (January through April). Management Group Iw-1: Taso, Gbesebu, and Puje- hun. These three soils are similar to those in Manage- ment Group Ih in many characteristics but have higher available moisture-holding capacities and may be sub- ject to flooding for a few more days during the wet season. Accordingly, crops sensitive to brief flooding should be avoided in areas that are subject to this hazard. In other respects, however, Iw-1 soils should be managed the same as those in Group Ih. The Iw-1 soils, which oc- cur primarily in moderately large areas near major streams, offer excellent possibilities for modern com- mercial farming with efficient capital and labor inputs. They are among the most productive soils in their area of occurrence. Management Group Iw-2: Mokoli and Kania. These two soils have many characteristics in common with the soils in Management Groups Ih and Iw-1. The major differences are in natural drainage and the soil moisture regime. Kania is imperfectly drained, and Mokoli is im- perfectly to poorly drained. Under natural conditions they are waterlogged at the surface for approximately two to three months during the rainy season. They may even be submerged for several weeks. During the dry season, however, these soils may be deficient in moisture for plant growth for one to three months. If these soils are properly drained and fertilized, their suitability is similar to those in Management Groups Ih and Iw-1, and they can be used for a wide variety of crops. Inten- sive use of these soils would require a modern farming system. Without supplementary drainage, the soils in Management Group Iw-2 can be used for swamp rice during the main rainy season and for crops such as maize and vegetables during the declining rains (Septem- ber through December) . On areas near a good source of irrigation water such as the Taia River, another crop can be grown under irrigation during the last part of the dry season (January through April). SECTION 5:3 79 ia "•' *i « J! li «* 1 s ° CL O D O i C o |H 2 » 2 a 8 £ * 3 E S Si i ™ J a— ^ t "c ^ 8 £• c o o» •D C g N '" S E 1 "• O .t: - •= Q « ° 5 „ 0 "i X '6 "" O n * *-* oj i T> U 8 ? S-o 0> 1^ Recommended u»e innual and perennial crops such as rice, m :assava, pineapple, coffee, oil palm, ar i irrigation recommended. j= .0 o ility similar to group lw-1, above, if soils id. Without supplementary drainage, swi jring the rainy season with bunding and ' i and vegetables during the dry seasoi rigation. D rice during the rainy season, with bundil 1, and vegetables during the dry season, ry drainage a variety of crops can be grc I!-- hi •5 E~ i|j 0 ~ S b ° J> o So •£ (fc c C o *- JOS -D 0 3 C «t D 0 0 .£ Mi £ £ S p rice during the rainy season, with bundil 1. Vegetables on Panlap during the dry mentary drainage, a variety of crops can -D f| • >-J g. 1 •> D> •C J 3 tt U •C 3 i K i 1 » 1 3 i I s ) J I 1 1 1 crops such as upland rice, cassava, and grc such as coffee, oil palm, citrus, and fores 3 -o <0 Ill E o to .0 £ -o .c .b 5 o « S £ <« -fe •= o '* E 2 £ t/3 u E j i j 1 E O "> 8 2 1' 5 ll 18 c t> E 1 8 a. 8 a. 8 a. 8 § 1 E O i £ . o £ .. •- v. W 1. i. 1. a u a Q- o u. .h .b o O .b Q 0 O 81" £* 0) O D D D O O '5 '6 5 _° O O O O 0 O O O * o U € •o u_ u_ U_ CL fc c o -C M M c 1 v y 'C a. O) M 11 1 £ £ £ ill E E E li § 0 §£§ £ •££•£•£ C C C C c §0000 E E E E 0 M £ 1 g 1 i E E •» CN _ CM CN CO .- o CN Z CO CO -^ •t ^ •» •* ^ — (N z CM ••» "0 o * 3 * °>£* E E E E E E E E E IS) -2 S|'S 33 3 3 3 D 3 .2 3 M? Ills ll 1 O> CO CO if x x .? V II 111 I JJIJ I I 01 X B I 1 1 o> § .« B 1 slf O 1 li... M 2 a ^* M si Z J Q. 0 g t> D w 0 n> 4> 41 4) 4) 0) V 0) 4> — 4> D a> C QQ V .E oo lal '5. 3 £ § 0 0 § Z Z Z S S § zzz C C II 1 B § § zzz 11 ||| 1 S?"* <££ 0>CM £ ,££.£ 0 O> Is £ 1 II I £ M J jt li o o — JJ CM 0 " ? I I O 0 M M g 1 E O 0 J5 .. w 0 . ° ll E E w ^ £ £ E ^ u o a o U I" « «-o ,-» Z I * Z * • * 0 J2 • M > CN > » > X a a> 4) a> o II CO CM ££ CO CM ?« <> « S £ ^ e { f C { z -Sz z zz i i •«• CM £ CN £ CO 111 '5 -£ •26 £ £ £ ill 41 I ^ 3 ° 000 5 0 _ „ '6 VI II 1 ret l-j L-i Ij ll ll .CO Dl O) 55 O) O> O) CO Co 55 to Jo <75 1 1 1 • t 1 I vt u?-« «o *o f- CN f. CN ^j E S o •£ *O* W V •^ -t >o iJ*CM — "CN •o -o rx N." IS K K K CN •<* CN CO 00 (X 'i_ 5^3 a> i E t3 fe • D a j E T a i "5 " s> Selected ch »{ o -* o X D O Z3 S •O c « § 1 1 ! II I! 0 0 0 & Masuba Mabassia, d Mosheka E o '3 co m $ h- . D t; • agriculture. 0 J) "5 3 -Q c 4) 'oS £ 0 H cn c "5 8 4> 3 £ "0 VI O> 4) •£ J = 2 •o « S c~.P u _ » Js 0 11 -D 1 1 ^ «, a> " S .a ai *• S .-1 " S-l • o o °- "* *- 3 ^ Jl .y - 11 o S suitable foi I •a c 0 4) 4) f 4, D) •8£ *i I! Upland rice coffee, oil [ promising us si 'C T3 2- s >- ESS o S ^ i K 'u V) 4) 0 S -3 3 O P » i filj si "s £ 15- Unsuitable f grow on the c D X i B 4) I Natural tree roduction. Wl a * §O 0 o o 0 >- o o a o o o o o § "5 'f a a a o o- a a a 5 u 80 v 5 v "6 £ 'o > O 4) '5 6 ,1 a. °- u_ u_ D Sc 1 «* f f 1 Bee "£ c £ | Wl • 1 § 1 il c o 0 o O E E E I i | | U 4) C z z 10 •* "O Z «O •» ^ 10 "0 CO IO iii-t E II 1 ±- i 1 1 * 0 "o H •* — a t * * ss JB ^ "o ^ >• £- £• 1 >• c S < £•= S 1 .3 J >> I 5 £ Z > > > o 3 0 o .* — J! 4) • o M- _a> 6 1 1 1 .E | • u O "5 J 4> a "3> e X > « > £ II ° .X V o S.z ± o — D b £• g a a. a. 1 11 — c — 4) 1 6? ^ Q- 2 -§J £ 6« 6? o- llll Bedrock < 36 inch* Hard bedr at surface c a cn c "3 a c M o S c _« CJI u £ X"c o | 3 c 1 I 1 £ 10 •* 0) 4) V a D aj Z Z Z Floods dail high tide u protected a Q. 4) O u "s s Ss? « o- * I Z Z.2 Z a) a> 0 0) Z Z Few days seepage over rock k. i i CO c c CO a> 2 o o o || A> _« « £ "5 0 O o "a c 4) O >- «) 4) 3 lii .c ? g z z • £ • • -D 4) TJ -D O > O O 5 SSS 1 » j -S t J J o J in in 5 M D) ^O) i/} u3 I • to 4) •5=5 ' |?« "*i ^- CN T o- o o 0 0 o O £ I 0> -f.| -D OJ M 4) 'a o I | c TJ C --J confinu 5| a "c ° D Sr 5 ^ "o o "o Z S 5 a 1 "2, E -o « o E 10 < P I i 0 _g c D -C O 0 > Rock La 1 5 *~ JZ ~ Is _a> »£•§• o|i * | > 1 J 1 | 2| 1° 1 U -° 0> SECTION 5:3 81 Management Group IIw: Taiania and Kparva. These poorly drained soils are waterlogged at the soil surface for two to four months during the rainy season and even submerged for several weeks. Taiama may be deficient in moisture for plant growth during about two months of the dry season, but Kparva usually is not. Given ade- quate supplemental drainage, these soils would be suited for a variety of crops if modern farming methods were used. Otherwise, the soils can be used only for swamp (paddy) rice during the wet season. To limit risks of sudden, deep submergence and to maintain the proper water level, bunding is necessary. This can be done easily with earth bunds and wooden spillways. Fertilizers should be applied regularly. During the dry season, enough moisture remains to grow vegetables. Swamp soils such as Taiama can be farmed regularly and will produce much higher yields if proper water control, weed control, fertilization, and crop varieties are used. Much swampland, though not yet used, could, if fully utilized, contribute much to the rice supply in Sierra Leone. Management Group Ilh: Masuba, Masheka, and Mabassia, deep. These soils are similar to those in Man- agement Group Ih in many characteristics but have lower fertility levels, lower available moisture-holding capacities, and longer droughty periods (Table 11). They are easy to cultivate and are usually not subject to ero- sion. Management recommendations for these soils are similar to those in Group Ih, except that irrigation dur- ing the dry season is usually less feasible. These soils are being used by farmers in a bush-fallow system. Improved farming practices, including proper application of fertil- izers and better crop varieties, can produce profitable yields of both annual and perennial crops. Management Group Ilhs: Bonjema, Baoina, Tubum, Bosor, and Mabassia, shallow. These soils are primarily moderately well and well drained. They differ from the soils in Management Group Ilh in having gravelly subsoils that begin at depths of 24 to 48 inches (61 to 122 cm). This reduces the available moisture-holding capacity (low, except in Bonjema) and increases the droughty period to four months. These soils occur on moderate slopes; under clean cultivation they may be subject to slight erosion, but this is easily controlled. These soils are relatively good for the traditional bush- fallow system of peasant farming. Adapted crops in- clude annual crops such as upland rice, maize, ground- nuts, and cassava and perennial tree crops such as coffee, oil palm, and citrus. Fertilization is essential for profit- able crop yields. Management Group II wh: Panlap and Pendembu. These are imperfectly to poorly drained soils. Water- logging at the soil surface during the rainy season is about four months in Panlap and two months in Pendembu. The available moisture-holding capacity is medium in Panlap and low in Pendembu. They are deficient in moisture for plant growth during one to two months of the dry season. These soils are permeable, occur on gentle slopes, and have little danger of erosion. They are strongly acid and poor to very poor in available plant nutrients, so that proper fertilization is necessary for profitable crop yields. With adequate supplemental drainage and modern farming methods, the Panlap soils are suited for a variety of crops; otherwise, these soils can be used only for swamp (paddy) rice during the rainy season. In order to limit risks of sudden sub- mergence and to maintain the proper water level, bund- ing is necessary. This can be done easily with earth bunds and wooden spillways. During the dry season, enough moisture remains to grow vegetables. Swamp soils such as Panlap can be farmed regularly and are capable of producing much higher yields, especially of swamp rice, than they do now if proper water control, weed control, fertilization, and crop varieties are used. Pendembu soils are less subject to flooding than the Panlap soils. Management Group IIIw: Gbehan. These arc poorly drained, clayey soils with a high moisture-holding ca- pacity. They are subject to waterlogging at the surface for two to four months and submergence for about one month. Floating rice can be grown without drainage improvement. If adequate drainage and flood protection are provided, other crops such as sugar cane, vegetables, bananas, and pineapples may be grown. Soil moisture is adequate for plant growth throughout the dry season. Management Group IIIws: Pelewahun. These poorly drained soils are waterlogged at the surface approxi- mately three to four months during the rainy season. They are deficient in moisture for plant growth about two months during the dry season. The depth of the gravel-free surface layer is 24 to 48 inches (61 to 122 cm) . The available moisture-holding capacity is high. These soils are suited to a variety of crops if adequate drainage is provided; however, because of their occur- rence in small patches and in long narrow strips, they can better be used for swamp rice during the rainy sea- son and vegetables during the dry season. Fertilization and bunding for water control should be practiced. Management Group Illsh: Mokonde and Njala, nearly level. These two soils are moderately well to well drained and are rarely, if ever, waterlogged at the sur- face. They are droughty about four to five months dur- ing the dry season. Both of these soils contain unfavor- able gravel, which causes a low moisture-holding capacity and impairs the extension of plant roots. Fertilization is necessary for satisfactory crop yields. Suggested annual crops include upland rice, groundnuts, and cassava. Tree crops such as coffee, oil palm, citrus, and lumber species may also be grown. These soils are fair for use with the traditional bush-fallow system of farming, if the fallow period is reasonably long. Management Group IVw: Mankane and Keya. These soils are poorly to very poorly drained, medium to low in available moisture-holding capacity, and not droughty during the dry season. Supplementary drainage in order to use the soils for a variety of crops would not be prac- tical. These soils are suited for swamp rice during the rainy season and vegetables during the dry season. 82 BULLETIN NO. 748 Management Group IVsh: Manowa, Makeni, and Njala, sloping. These are extensive gravelly soils that occur on slopes of about 3- to 15-percent gradient. They are well to moderately well drained and are never water- logged at the soil surface. They have low to very low available moisture-holding capacities and are droughty during four to five months of the dry season. They are very acid and very low in available plant nutrients. Be- cause of the high gravel content, these soils are poorly suited for cultivated crops grown with modern agricul- tural methods. They may be used under the traditional bush-fallow system of farming, but the fallow period should be long and frequent clearing should be dis- couraged. The slopes vary from gentle on the summits of the uplands to moderately steep; thus, if the vegeta- tion cover is removed, the sloping soils are subject to erosion. Since a permanent vegetative cover is necessary to control erosion on these sloping soils, forestry is the best use for these areas, but tree crops such as oil palm and citrus can also be grown. The gently sloping sum- mits have only slight erosion problems and can be used for the shallow-rooting annual field crops such as upland rice, cassava, and groundnuts that are currently grown on these soils. Fertilization should be practiced. The pro- duction of high-quality pasture on sloping Njala soils during 1971 and 1972 in experiments at Njala Univer- sity College has been very encouraging. These experi- ments include both native and introduced pasture plants under fertilization and rotational grazing. Pasture pro- duced by these improved management practices has given large cattle gains. If enough farmers adopt these practices, the beef shortage in Sierra Leone could be overcome. Properly managed pasture on these sloping Njala soils controls erosion and provides a profitable income when marketed through cattle. Management Group Vw: Rokupr. These very poorly drained, fine-clayey soils occur in tidal mangrove swamps near the coast. They require major water-control struc- tures, carefully designed and operated, before they can be used for agriculture. The water level must be main- tained at the proper level in the soil to avoid excess drainage and oxidation and the resultant development of harmful acidity (see Section 4:6). These soils are restricted to swamp rice production because of the shal- low water table that should be maintained in them. Management Group Vies: Segbwema, Momenga, and Timbo. These well-drained, gravelly soils occur on steep slopes; unless a thick vegetative cover is maintained, they are subject to moderate to severe erosion. Segbwema con- tains less gravel than the other two soils, and in all of them the gravel content is less in the lower part of the profile. The available moisture-holding capacity is usually high in Momenga, medium in Segbwema, and very low in Timbo. Most areas of these soils are too steep and erosive for cultivated crops and should be kept under forest vegetation. Some tree crops such as oil palm and citrus may be used if care is taken to cover the soil sur- face consistently. In a few places where slopes are less steep, and erosion control is adequate, some shallow-root- ing annual field crops may be grown in the traditional bush-fallow system of farming if a long fallow period is maintained. Management Group Vlhs: Gbamani and Sahama. These very sandy soils occur on beach ridges along the Atlantic coast. They are so droughty and low in fertility that they are unsuitable for any crops but coconuts. Oil palms grow on these soils, but yields are very low. Management Group Vlles: Vaahun. Vaahun soils oc- cur on high hills on the steepest slopes on which soil will form over the granitic bedrock. The profiles are less than 36 inches (91 cm) thick and are subject to severe erosion unless a thick vegetative cover is maintained on them. These soils are unsuitable for agricultural use. They should be used for forestry. Management Group VHIsh: Rock Land. This land type includes inselbergs and other areas of outcropping hard bedrock. The bedrock is always at or near the sur- face, but a thin soil layer up to 24 inches (61 cm) thick may occur locally in small pockets. The bedrock is usually granite. Slopes are usually steep, but gentler slopes occur in a few areas. This land type is unsuited for agricultural use and has little or no value for forestry production. It should remain under the natural vegeta- tion for watershed protection, wildlife use, recreation, or esthetic purposes. 5:4. PRINCIPLES OF SOIL FERTILITY 5:4:1. WELL-DRAINED AXD AERATED SOILS All of the well- and moderately well-drained soils on uplands, colluvial footslopes, and terraces are extremely infertile, especially in nitrogen, phosphorus (50), and magnesium (53, 54, 55) . They are also low in copper and other micronutrients, except for iron and manganese. Sulfur deficiencies also may be expected on some of the upland soils. Trends in soil organic matter content are discussed in Section 4:2:1. The fertility status of the well-drained soils may, with the exception of phosphorus, be determined by standard analytical methods adapted for temperate-zone soils. The available form of the essential bases are the exchangeable cations. Classical methods for determining exchangeable bases and quick tests for available calcium, magnesium, and potassium are both quite satisfactory in Sierra Leone. Because of the high iron content of many of the well-drained soils, available phosphorus is more accu- rately determined by using the Bray P2 extractant than by using the Bray Pj (10, 11) or the sodium bicarbonate extractants used on temperate-region soils. Most Sierra Leone soils, unless recently limed, are quite acid, having pH's below 4.8. They are very low in exchangeable calcium and magnesium, and they are high in exchangeable aluminum. Most of the soils need to be limed, both to increase the pH and convert exchangeable aluminum to the less toxic aluminum oxide gels and to SECTIONS 5:4:2-5:4:3 83 supply a source of calcium and magnesium for plant nu- trition. Generally, any soil with a pH below 4.8 or an exchangeable Ca + Mg to Ca + Mg + Al ratio below 0.150 may be suspected of being aluminum-toxic to many crops (see Section 4:4). If available, dolomitic lime- stone may be used to correct both the low pi I and cal- cium and magnesium deficiencies; otherwise, magnesium sulfate is usually required with regular limestone. Slight overliming of the surface plow layer to around pH 6.0 is often beneficial because it helps correct the low cal- cium and magnesium levels found in the lower B horizons and lessens the adverse effects of exchangeable alumi- num. Excess liming, however, that would raise the pH to 7.0 or over should be avoided. The steep upland soils are susceptible to severe soil erosion, a danger accentuated by mechanical cultivation, especially plowing. Because the root stalks from the "slash and burn" system are left in the field, the erosion hazard is reduced, but these root stalks also make me- chanical operations of all kinds impossible. Drill seeding, mechanical cultivation, and combine harvesting can not be done, thus barring the improved production possible through good tillage. Methods of improving production on the strongly sloping upland soils are essentially limited to increased usage of fertili/ers and improved seed and to such improvements in seedbed preparations as are possible with more careful use of native hand tools. The full benefits of mechanical tillage can be directed toward increased production on the gently sloping soils on col- luvial footslopes and terraces, and it is on these better soils that agricultural development should be empha- sized. 5:4:2. POORLY DRAINED SOILS WITHOUT EXCESS SULFUR Along the major streams, in the bolilands and inland valleys, and along the coast are poorly drained soils highly suited to swamp (paddy) and lowland rice production. These soils differ from the tidal swamp soils, Sulfaquents and Sulfaquepts, in that they are essentially free of sulfur and they become oxidized to some extent during the dry season. During the wet season they are less intensely reduced (with an Eh seldom below —0.20 v) than the tidal swamps (usually with an Eh below — 0.30 v), and upon drying there is no, or only a very slight, drop in the soil pH. These soils are fairly high in soil organic matter and often do not respond significantly to nitrogen fertil- izer during the first year of cultivation. They are acid (pH usually below 4.8), have low levels of exchangeable calcium and magnesium, and are high in exchangeable aluminum. Except for nitrogen, recommended fertilizer usage is essentially the same as that suggested for the up- land and better-drained terrace soils. Similarly, the more acid Bray P2 extractant is necessary to determine the level of available phosphorus in these soils; as with the well-drained soils, field soil samples may be dried be- fore being subject to chemical analysis. The poorly drained, sulfur-free soils are used almost exclusively for swamp (paddy) and lowland rice produc- tion. Their proper management should include some water control, where possible, through levee and dike construction. Nitrogen fertilizer practices are important; rice prefers nitrogen in the ammonium form. Only two nitrogen forms are acceptable for rice on these soils: ammonium forms, such as ammonium sulfate or am- monium phosphates, and urea, which hydrolyzes to am- monium carbonate. The nitrogen fertilizers should be worked into the surface soil to assure the adsorption of the ammonium onto the soil colloids. The soils must then be flooded within 24 to 48 hours after application to minimize oxidation of ammonium to nitrate forms. Add- ing the ammonium nitrogen fertilizers to the flood or paddy waters is not efficient because the renewal rain- water is well aerated and permits some oxidation of am- monium to nitrates before the waters become anaerobic. 5:4:3. TIDAL SWAMP SOILS men IN SULFUR The tidal swamp soils differ from other poorly drained soils in that they are flooded daily at high tide by brack- ish seawater during the dry season. They are high in sulfur, which accumulates as sulfates from the seawater; the sulfates are then reduced to sulfides and retained in the soil (see Section 4:6). These soils also accumulate salts during the dry season, becoming saline enough that some degree of weed control is achieved. These salts must be washed out at the beginning of each wet season by natural rainwater before rice can be seeded. During the rainy season the heavy discharge of fresh runoff water prevents the inland movement of brackish seawater, even at high tide, and the soil returns to a lower salt status. These soils are waterlogged the entire year and, unlike the poorly drained soils away from the coast, normally do not pass through a period of oxidation during the dry season. The tidal swamp soils are highly reduced (74, 42, 43), usually having an Eh of —0.30 v or less throughout the year. The exchangeable base content is partially renewed from the brackish seawater during the dry season, so that even after the free salts are washed out the pH re- mains in the 5.5 to 6.0 range. These soils are quite high in exchangeable manganous manganese and ferrous iron, which tend to react with any added phosphate fertili/ers (38, 41). Lime is seldom used on these soils, although some may be relatively low in exchangeable calcium and magnesium and thus show a preferential response to regular superphosphate and basic slag (82) as compared with triple superphosphate. The tidal swamp soils are relatively high in exchangeable potassium and seldom show a crop response to potash fertilizer. Conventional methods of soil analysis and handling of field samples are unsatisfactory for tidal swamp soil sam- ples. On drying, the soil becomes partially oxidized with the resulting oxidation of sulfides to sulfates and the formation of sulfuric acid. As a result, the pH of a dried 84 BULLETIN NO. 748 sample may be 2 or 3 pH units more acid than the actual field condition. Phosphorus becomes tied up as unavail- able iron and manganese phosphates when the iron and manganese are oxidixed on drying. For measurements to be meaningful, the soil sample must be preserved wet, either under nitrogen gas or something like toluene, to prevent bacterial oxidation. Even with these precautions, it is doubtful whether measurements of pH, available phosphorus, and Eh on the wet soil have much meaning. Total analyses and exchangeable cations can be deter- mined accurately, but the basic correlations of such re- sults with rice growth have not been successful. Water control is the most important single factor in the management of the tidal swamp soils. Because these soils are flooded only at high tide, empoldering and diking can keep the water at the low-tide water levels. This is especially important during the seedling-transplant and crop-establishing period. Only ammonium and urea ni- trogen fertilizers should be used. Flooding immediately after nitrogen applications is easily accomplished. Split nitrogen applications (82) are generally better than a single application at the time of transplanting. 5:5. MANAGEMENT OF SELECTED CROPS Crop production is greatly influenced by climate. The dry season is shortest in the eastern sections of Sierra Leone, with the result that this area is best suited to plantation crops such as cocoa, coffee, bananas, and oil palm. Most citrus crops, which go through an annual dormancy period, can be grown in areas where the dry season is more intense. The amount of sunlight (Ap- pendix A) is sometimes a limiting factor in production, even during the dry season ; thus, sugar cane, for example, is considered a marginal crop in Sierra Leone because of inadequate sunlight. Most of the soils in Sierra Leone tend to be highly acid, with pH below 5 ; they are very low in exchange- able calcium and magnesium and may frequently con- tain toxic levels of exchangeable aluminum (see Section 4:4). During the first year out of bush fallow, the soils generally are not highly responsive to potassium and phosphorus because of the ash residue. However, much of the nitrogen in the bush vegetation is lost during the burning, so that where good rice stands are obtained nitrogen deficiencies may occur. The success of continu- ous cultivation on the nearly level nonerosive soils be- comes highly dependent on fertilizer use after the first year out of fallow (7,8). The principal crops grown in Sierra Leone are rice, cassava, maize, groundnuts, cocoa, oil palm, coffee, and citrus. The acreages of various crops and the percentages of farmers growing them for off-farm sale are shown in Table 12. Because most farmers grow mixed crops, the acreages shown total more than the approximate 1,000,000 acres actually being farmed annually. Recent crop introductions include vegetables, fiber crops, and pasture grasses for animal feed. Farmer interest in grow- ing these new crops is increasing. Table 12. Percent of landholders growing and selling, and total acreage in pure and mixed stands of, the more important crops grown in Sierra Leone (14) Percent Percent Total Crop growing selling acres Rice 86.3 18.1 741,000 Cassava 62.3 6.2 374,600 Okra 53.2 4.0 190,400 Maize (corn) 46.1 4.2 192,300 Pepper 41.7 6.1 68,000 Kola nuts 40.4 12.1 57,700 Jackatoe 40.4 2.5 39,100 Bananas 38.5 7.6 23,000 Groundnuts 34.2 10.5 47,400 Pumpkin 33.8 1.9 29,200 Cocoa 33.2 17.3 66,400 Benniseed 33.2 5.2 14,800 Native spinach (plasas) 32.8 2.2 28,000 Tomatoe 31.7 3.8 41,900 Guinea orn 31.6 1.0 160,500 Eggplan 31.2 2.8 1 6,900 Potatoe 30.8 1.8 23,700 Palm ke nels 26.1 20.4 37,800 Coffee 21.2 9.6 90,400 5:5:1. RICE Rice is the most important food crop grown in Sierra Leone. Traditionally, it is grown on the sloping uplands, where shifting cultivation is more easily practiced under native management systems. On the more level and pro- ductive terraces, alluvial floodplains. and swamps, the sod of the tall native grass is very difficult to destroy with conventional native hand tools; therefore, develop- ment of these areas for rice production depends to some degree upon mechanization. The management sugges- tions given assume the use of some degree of mechaniza- tion, such as the plow or cultivator, to permit more ade- quate tillage of these better soils than is possible with native hand tools. If minimum mechanization is available, rice produc- tion is ideally suited to the coastal plains, river terraces, and bolilands; it can also be grown on the upland sloping areas under bush-fallow systems. Many of the colluvial footslopes and terraces are well drained and are suitable for mixed crop culture, although pure stands are prob- ably more profitable under mechanical agriculture. The more poorly drained soils are adapted to swamp or low- land rice, but mixed cropping is seldom practiced on these areas. The distribution of pure and mixed stands is approximately as follows: Upland rice Pure stand Mixed stands Swamp rice Pure stand Mixed stands 49,200 acres 540,000 acres 142,000 acres 9,200 acres The bolilands, stream terraces, and some inland valley swamps occur in large enough tracts to be suited to large- SECTIONS 5:5:2-5:5:3 85 Table 13. Response of rice (kg/ha) to N, P, K, and lime fertilization at various locations, 1965-1967 Table 1 4. Soil test calibration for rice Location Treatments''1 NPKLb -P -K -L None Rokupr (tidal swamp). . . . . 7,100 5,800 6,400 6,300 3,600 Rokupr (upland) . 6,400 6,200 6,400 5,900 3,100 Kontobe 4,800 3,500 4,200 4,100 1,900 Njala (lower nursery) . 4,600 3,900 4,200 Sama 4,200 3,900 3,800 3,700 2,100 Kenema (farm field) .... . 3,500 3,800 3,500 3,500 Kontobe . 3,800 2,500 3,700 2,600 1,800 Njalu (upland) 3,400 3,100 3,000 2,700 2,100 Average 4,725 4,088 4,400 4,114 2,433 11 All rates relatively high and adequate. 11 NPKL — nitrogen, phosphorus, potassium, lime, and magnesium sulfate. scale, mechanized rice production. Swamp, floating, and lowland rice yields are usually higher than upland rice yields (79, 81], especially under shifting cultivation. Practically all upland rice, and probably as much as 60 percent of the lowland rice, is broadcast-seeded directly on the soil. Approximately 40 percent of the swamp rice, including much of that grown in tidal swamps, is estab- lished by seedling transplants. Floating rice is usually broadcast-seeded. Practically all rice is hand harvested. Minimum mechanization of rice production, therefore, need involve only plowing and preparing the better soils for rice seeding. Rice responds especially well to nitrogen and phos- phorus fertilization. Potash responses are often small dur- ing the first year after fallow but become increasingly important with continued cultivation. Numerous studies (78, 20, 82) have documented responses of rice to fer- tilizers. The data in Table 13 support similar studies and were used to establish the soil test calibrations and fer- tilizer recommendations for phosphorus and potassium (Table 14). Limestone and magnesium sulfate are also required for good rice yields (78, 82). Dolomitic limestone is highly desirable when available. Most soils are very deficient in available or exchangeable calcium and magnesium and high in exchangeable aluminum (31). Adding limestone and magnesium sulfate corrects the calcium and mag- nesium deficiencies and decreases the probability of aluminum toxicity. Aluminum toxicity for rice should be suspected whenever the exchangeable Ca + Mg to Ca + Mg + Al ratio approaches 0.100 (see Section 4:4). For rice, soils need not be limed to a pH above 5.6 to 5.8 for good yields. Because of their high calcium contents, phosphate fertilizers such as regular superphosphate (20- percent P2O,-,) and basic slag are generally superior to triple superphosphate (45-percent P2Or,) for rice on low pH soils (82). Only ammonium and urea (29) nitrogen fertilizers should be used on swamp and lowland rice. Any nitrogen fertilizer is suitable for rice on the well- drained soils. Percent sufficiency Phosphorus" Potassium'1 Soil test values (ppm) Pert. req. (kg P/ha) Soil test values (ppm) Pert. req. (kg K/ha) 50 3 25 12 6 3 0 20 40 60 80 100 180 90 45 25 0 75 . 6 87 93 9 12 15 96 " According to Bray P: soil test (10, H). '' According to Bray soil test (10). 5:5:2. MAIZK Maize production in Sierra Leone is steadily increasing and, as the livestock industry develops, the demand for maize will increase further. With proper management and fertilizer use, maize can be grown on any of the more productive soils that are adequately drained. Maize cannot be grown on inadequately drained soils nor does it generally do well in a mixed cropping system. It can- not withstand shading, such as occurs when the rice in a mixed culture system grows faster or becomes taller than the maize. Maize is usually grown either during the early (seeded in May) or late (seeded in September) part of the rainy season (9, 21). If irrigation water is available, the seeding can be delayed to October, or the crop can be grown entirely during the dry season (January to April). Fertilizer and soil fertility requirements for maize are high. Soil phosphorus should be around 10 to 15 ppm (Bray P2 test levels), and the potassium levels should be over 100 ppm. Good yields on suitable soils and with pure stands will require 100 to 120 kg/ha of nitrogen, preferably applied in two or three split applications dur- ing the growing season. The pH should be around 6.0 and magnesium sulfate should be added. If available, dolomitic limestone may be used instead of lime and magnesium sulfate. Maize is somewhat sensitive to aluminum toxicity. If maize plants contain more than 500 ppm of aluminum or if the exchangeable Ca + Mg to Ca + Mg + Al ratio in the soil drops below 0.150, aluminum toxicity should be suspected (see Section 4:4) . Insufficient research has been conducted in Sierra Leone to properly correlate and calibrate soil tests with maize response to fertilizer use, but the fertilizer recommenda- tions given in Table 15 are thought to be reasonable in- terpretations, based upon crop requirements and known characteristics of the soils suggested for maize production. 5:5:3. PLANTATION CROPS Plantation crops such as oil palm (78), coffee, cocoa, and rubber are being grown on a wide variety of Sierra Leone soils. Generally, the limitation to high plantation production is not a lack of suitable soils but rather the climate. The dry season is very intense: total rainfall during December, January, and February seldom exceeds BULLETIN NO. 748 Table 1 5. Suggested rates (kg/ha) of fertilizer use for some common crops when more definite soil test data are not available11 Crop Mg lime (CaCOa) Rice 45 20 40 30 4,000 Cassava 35 15 45 30 4,000 Corn 80 20 50 30 4,000 Groundnuts 0 10 35 30 4,000 Oil palm 65 15 45 30 4,000 Soybeans 0 20 50 30 4,000 Pineapple . 80 10 60 30 4,000 Bananas 40 10 50 30 4,000 Coffee 20 10 35 30 4,000 Citrus . . 50 10 50 30 4,000 Vegetables 50l) 15 40 30 4,000 '' These suggested rates are conservative and too low for maximum crop yields. h No nitrogen should be used on beans or peas, but they should be inoculated. 4 or 5 inches (Appendix A). Therefore, without irriga- tion, crops such as oil palm, coffee, cocoa, and rubber make no significant growth for three to five months of the year, especially on upland soils, and cannot be pro- duced competitively for the world market. While the well- drained soils on colluvial footslopes and terraces are more desirable than the upland soils for plantation crops, even these probably cannot retain enough extra moisture to support profitable production without dry season irriga- tion. More plantations should be established on the well- drained, better soils where irrigation is possible. Citrus fruits (oranges, grapefruit, and tangerines) have potential for development in Sierra Leone. Since their "dormancy" can be coordinated with the dry season, they produce relatively better than coffee or cocoa. Again, the well-drained soils on colluvial footslopes and terraces are more desirable than the upland soils for citrus production, but with moderate fertilization (Table 15) citrus can produce surprisingly well on the upland soils. Copper deficiency symptoms are visible on citrus fruit in all parts of Sierra Leone, and citrus and bananas will respond to copper leaf sprays. 5:5:4. OTHER CROPS A wide variety of crops including vegetables (34) , pineapple (33), soybeans (45), cocoyam (30), sweet po- tatoes (32), ginger, and cassava are grown in Sierra Le- one, mostly on the upland soils in mixed culture with rice. Generally, these upland soils, where bush-fallow systems are being followed, are not the best soils for these crops. The upland soils are highly infertile, usually gravelly, and extremely droughty during the dry season. The deeper, well-drained soils on colluvial footslopes and terraces are more suited to these crops and, when fer- tilized (Table 15), produce quite good crop yields. None of these crops have been studied in sufficient detail to provide soil test correlations for fertilizer recommendations. LITERATURE CITED 1. Alexander, L. T., and J. G. Cady. 1962. Genesis and hardening of laterite in soils. U.S. Dept. Agr. Tech. Bui. 1282. 90 p. 2. Aubert, G. 1965. Classifications des sols. Cahien ORSTOM-Srrie Pedologie, 1965, III, No. 3 : 269-288. 3. 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Soil Science Society of America. 1970. Glossary of soil science terms. 27 p. 68. Soil Survey Staff. 1951, with 1962 sup. Soil survey manual. U.S. Dept. Agr. Handbook 18. 503 p. 69. Soil Survey Staff. 1960, with 1967 Supplement. Soil clas- sification, a comprehensive system; and Soil Taxonomy, 1970. U.S. Dept. Agr., Washington, D.C. 70. Stobbs, A. R. 1963. The soils and geography of the Boli- land Region of Sierra Leone. Government of Sierra Leone, Freetown. 45 p. and maps. 71. Stoops, G. 1967. Le profil d'alteration au Bas-Congo (Kin- shasa ). Pedologie XVII 1: 60-105. 72. Surveys and Lands Division, Sierra Leone. 1966. Atlas of Sierra Leone. Edward Stanford, Ltd. Longacre, London. 73. Tomlinson, T. E. 1957. Relationships between mangrove vegetation, soil texture, and reaction of surface soil after empoldering saline swamps in Sierra Leone. Trap. Agr., Trin. 34: 41-50. 74. Tomlinson, T. E. 1957. Changes in sulphide-containing mangrove soil on drying and their effect upon the suit- ability of the soil for the growth of rico. Empire Jour. Exp. Agr. 25: 108-118. 75. van Vuure, W., and R. Miedema. 1973. Soil survey of the Makeni area, Northern Province, Sierra Leone. Njala Uni- versity College, University of Sierra Leone. 104 p., maps. 76. van Vuure, W., R. T. Odell, and P. M. Sutton. 1973. Soil survey of the Njala area, Sierra Leone. Njala University College, University of Sierra Leone, Bui. 3. 117 p., maps. 77. Waldock, E. A., E. S. Capstick, and A. J. Browning. 1951. Soil conservation and land use in Sierra Leone. Sessional paper No. 1. 124 p. 78. Walker, W. M., and S. W. Melsted. 1971. Effect of N, P, Mg, and K, and soils upon oil palm yields in Sierra Leone. Trap. Agr., Trin. 48: 237-243. 79. West African Rice Research Station Annual Report 1964- 65. 1966. West African Rice Research Station, Rokupr, Sierra Leone. 44 p. 80. Westerveld, D. H. 1969. Morphological and mineralogical differences between two types of iron concretions in a soil of Sierra Leone, West Africa. Thesis for the Ir. (M.Sc.) degree, Agricultural University of Wageningen, The Netherlands. 25 p. 81. Will, H. 1971. Two new rice varieties for Sierra Leone. Bui. No. 1, Njala University College, University of Sierra Leone. 10 p. 82. Will, H., and R. A. D. Jones. 1970. Three and a half decades of rice research at the Rice Research Station, Rokupr, Sierra Leone. Njala University College, Univer- sity of Sierra Leone. 64 p. mimeo. 83. Wright, E. H. M., and M. N. Fawty. 1971. Physical and physico-chemical characteristics of some Sierra Leone soils. African Soils 16: 5-30. 89 APPENDIX A. CLIMATIC DATA FOR SELECTED STATIONS IN SIERRA LEONE IO S- c: ID •o ID >> C O ID 01 3 tO C 4-> C O n) -LJ CO co r^ o oo co m co \o vo so co r^. ON rH ON OI-HI— t ••• ... ... r^io^o ON oo CM in rH r~ ON rH rH i — rH co ooooo r~- co m co^vX5 tHi— ico \DrH\o • • • a\m^o -a--j-r~- O-J-CM O>-^ i^-mcN cr«o>co >d- ^ T— t vO mrHM> vOC^CN ... ... ... O100O CNtjN^OC^CN r^-^CN vooxr^ voo~ioo -d-ooro tyi^f^ -d-inr^ !-HP~frH COi-HrH (HCNICN g 03 \OU~tiH tNC^JOO ^OOi-H Q) r^-CMOO vOr^vJ- iniAiH ^> ... +^cr,t-^o ficor^vor^iH r^ irtc^c^j f^mo com ^ rHCSiH i— IfHiH I— (r-ICS E H T-J r^i •^ S oomr^- \oooo r^om sd-r^-cs i-H-d-r^- oooOtH ... cNvor^ ^j-eNr^-^r^c^ OOOO u-|OOr~ OVI^iH rgcxltM iHCNiH (NiHtN rH r-\ i-H cN-d- -3-ror^- cncN>j • • • CM.-HO i-HC^tH OOi-HU-1 ^HO ooovo \oirtco • • • fH CM OOO OOO OOO O u-i I vO O CM CM O "O ON ,0 *H ON rH < 1-1 rH O CO OO O -* vo m W I I I 00 O -3- i-H » CJ\ CM -* VO v£> vO \O I I I vo -a- oo CM to m ON C^ ON O m I voO CMCM ON o CM OOOOO -d" ^o m CJ I I I 3 C CJ co x 4J C CO O c2 m 3 *-" co o e IH a. iJ -H C H * co i-» CM OOr^m r~vOvO rHCO OOO OOOOvOONOONCOVfvO COCO rH rH CM rH CM rH rH OvOCOrHONCMCMin CM CM rH CM CO i— 1 in ON co o o vO O in vO O CM OO in i — 1 vO r^- O CO ON l^* rH ON ON r^ CO ON O r^ ,-H ON <• vO vDOOr~ O~d-~d- vOr~ rHin CMvOrH i-H^TrH CMvOrH rHvO CM CM rH rH CM CM C oo rH oo m o rHino r-~vovo OCM ONON cMvoON^fvooocor^vo I-HCM O E co rH ON in , CM in o r— ON mONr— ^d'vo-} • • • • •• •• r- CMON mco mmrHoo E 0 rH O O 0 OrHrH OrHrH OCM O-* OrH O-*~d-OCMCM vO £ ^ ^ ^i ^\ ^ ^> •r- cd cd cd cd cd cd c E . . . . -5. s: d- >d~ vo m e ^ u oca) e 01 Pu ^ C -us OJPL,^! M tJ « ocdopcdo tu S HMPapLiSH 91 C OJ p~ vo m CO rH CO o co r- 00 O P^ O 00 CO O CM CM r» O 10 CO CO CO **^ o^ r** -* vo m C > rH rH rH -3- O vo O O OS in o -* rH O O rH O OS vO OO OS O O> 00 rH O 00 •-H OS P~ < CO P~ 00 OS P^ 00 00 P^ OO OO r- oo oo P^ 00 CJ\ P^ 00 00 vO P- 00 P*» 00 00 f""1* r** oo -» vO 1 OS CO OS O rH -* O vO 00 OS 00 vo o in as os o O O OO OS **3" OS 00 00 t"^ OS i-H OS o as p~ OS rH n VO 00 OS r» oo 00 \o !"**• oo P~ 00 00 vO P- OS P^ OO OO m P- oo \o r^* co VO 00 00 p- r-- oo M 0, CN rH rH in o p-» o o o vo o in CM rH O rH 0 OS P~ VO 00 O OS OO CM rH OS rH OS P-. ^ S3 P- 00 OS P- 00 00 P~ 00 OS P^ OO 00 P^ 00 OS P-. 00 00 VO P- 00 P^ 00 00 P^* P^ 00 8 G CN rH rH ~3- O \D o o o in os in CM O OS rH O OS 00 00 P^ rH OS 00 CM rH OO CM os in 0 m O r- oo os P^ 00 00 p^ 00 OS P*» p^ 00 P^ 00 00 P^ 00 00 vO P^ OO P** P** 00 r^ oo oo p^ p- OO OS CO to CM O 00 CO OO CO O O P~ m os co CM O P~ CM OS VO OS 00 vO rH 00 in CM o m CM 00 . CO OJ rH ""> (•"•n r^» oo P^ P- 00 P^ P-- 00 P^ P*. 00 P*» P^ 00 p~ r-. oo vo P- OO P^ I — 00 P~ P~ 00 P^- P^- 00 3 ^ 1o to > o u-i E *-n CM O OS -3- o m rH rH OS m o m CO rH OS CM O OS O OS P^ rH OS OO CM rH 00 CN O P~ ^ *"* f^ oo co P- 00 00 P"* OO OO P- 00 00 P~ 00 00 P^- 00 00 P^ P^ 00 p^ r-» oo P^> 00 00 P^ OO 00 E 1 vO S CO •* CM P*^ OO OS in CM os P^ 00 OO CN CM CM P^ 00 OS P^ CM VO r- oo oo CO CO CM P- OO OS CO CN CM p^ oo as rH rH rH P-. 00 OS CM i-H O P^ 00 OS -> vO 00 OS P- 00 00 ^o t^» o^ P- 00 00 VO P- OS vO P^ OS in P^ os vO P- 00 vO P^ OS vO P- 00 IJ O O g • a • • (3 • • C • • a • • C • • C • • G • • G • • C • • G ' a o 4-1 C to X •H a) eg G rt X •rt S CO C co X •H to C CO X •H a) to a co x •H a) co C cfl x •H 0) CO •H 0) 3 G cfl X •H 0) CO C co X •H 01 CO os in M e e e e s e e 0 B B e 0 BBS B 0 B BBS B B 0 000 B 0 0 as as •-^ co to CM 0 CM 0 m 0 in CN VO S O o CO 1 1 1 1 m co co C*-* 4-> o CM i-H C— vD OS vO o CO CO 3 rH ^ ^f CM CO vO rH O> OS o as OS os OS OS • • rH rH rH i-H rH i-t 0 0 CO CO j2 M A! o 4-1 CO n o m CO a M to £ j§ 1 3? S O H tO o S m 92 HI to o vo a\ m ON CM i— 1 ON ON m CM rH CM en CM CM en CM CM en rH VO O CM CM en CM rH rH rH rH rH rH rH r-- en Q CM CM en ro r^ o CM CM CO O vo i — i -^t1 r*"» ON CM CM CO CM CM CM rH VO CM CM CM en CM CM en in en CM rH CM en O in rH CM CM en CM CM en CM CM en CM CM rH rH CM rH O rH rH rH rH rH CM r~. en -3- P*. iH rH r- CM 00 OO 00 rH 0 0 0 £3 CM CM en CM r^ en O CM CM en CM CM CO co r- o CM CM CO CM CM rO CM CM CM iH r-*. CM -d1 \O ON CM CM CO CM CM CM CM CM en CM r- CM CM CM en CM t-» CM CM CM en O VO rH CM CM en CM VO rH CM CM en CM I-~ rH CM CM en CM vO ON CM CM CM OJ cn (0 o co co r^ CM rH rH rH rH O O ON rH rH rH CM r~ rH c/a CM CM en co vo co CM CM CM r-l ^ ,_| CO CM CM CO CM CM CM eM r— rH CM CM en CM VO O CM CM en rH VD O CM CM en CM VO CT> CM CM CM CM r^ cy\ CM CM CM CM VO 0-> CM CM CM 01 > 03 3233 03 CM VO 00 <£ CM CM CM co m r-. CM CM CM CM m co co m co CM CM CM CM CM CM CM VO 00 CM CM CM CM in oo tM CM CM rH in oo CM CM CM CM in co CM CM CM CM VO 00 CM CM CM CM CM CM c: c; 03 rH rH rH rH vovovcvo •a 03 r-> CM CM CM ro m oo CM CM CM CM \O O"i CO vO 00 CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM CM in oo CM CM CM CM vo cy> CM CM CM CM in oo CM CM CM in _c CM en en CM rH rH rH rH r^r^vo C CM r~ CM >-> CM CM en cO r*1" ON CM CM CM CM r~^ CM •<}" r*- ON CM CM CO CM CM CM en r^ CM CM CM en CM P-- CM CM CM en CM eM en CM CM en CM CM en CM CM en -Q 03 rH rH rH rH IOONOON en tr. en S CM CM en ON CO CM rH rH rH S <» o o o o O rH rH rH rH o en o> vo <, CM CM en - CM CM en rH 00 *a" CM CM en CM co *a~ CM CM en CM CM en i- CM CM CM CM rH rH rH rH CM CT» VD tu CM CM en -3- 00 CM CM CM CO o co m m r- o\ CM CM CO CM CM CM O oo in CM CM en CM CM en rH CM en CM CM en i-H CO CM CM en co r-. t-H CM CM CO O vO CM -^ F^» ON CM CM CO CM CM CM oo vo en rH CM en O vO CM CM CM en •a- en en rH CM en O VO CM CM CM en o vo en CM CM en O VO CM CM CM en CM CM CM N -< SEE C cO X •H Q) CO e e E • C • • C • C to X C CO X •H (1) nj -H (U cd see see • C • e a x •H a to e e e C co X •H a) to BBS min. mean max. C to x •iH 0) tO BBS • a • a a x •H 0) C3 B B 6 • C • C co X iH CJ tO BBS CM -a- (0 | ri en Sen CT» .. 0 CM 4J O § ,0 o m I CM -a- rH o in I rH -* C— CM 1 vO CM -a- i CTl en VO rH CM O O CM 1 1 1 1 en CM rH vo en ^r -a- CM CM O O CM 1 1 1 1 en CM rH vo en ^r -a- CM "o 0 g a 3 O C i J2 « 4J W PQ Bonthe 3 rH 4J O rH tO •IJ TH 4J 20) a: en CJ -_/ 10 IH Makeni Marampa Musaia to rH tO z p. 3 ,M O 03 (O o H 3 to to C B to to to trj T-} 3 to to C B 1 CO tQ Cd *r~) 93 _" *oooooor^vo ' • • • d 4J 00 ^. *y \^ o^ \o 00 xO O^ r**"' 4-> r-l CN rH CN rH 4J P o LO ^ ^ o LO i— ) oo o O*N o oo 10 ^ r-- o ^ m-*ON* OOOvOOvO r^CNI^CN 96 ^o 0*1 o oo vo o^* r^-. o f*"* OO ON CO ON vO .... OiH ^ONvocoNd" inooocN O v,o O^ r*** oo r^* o^ r^* ^^ **3* vOCOOOON^1 .... > CO rH iHrHrH OOOOOOOO tN 5*H rH ON ON ON ON CO OO o c^j o rR ll_ 1/5 v*3 -t-i t^ 03 R •M in C i-j tj t^oNoooNoooNoo om C^ONONOON .... H^ON to R CO tH •H ON 00 00 00 ^ « 0) ^O ^ vO O ON rX3 O tH 3 iHmoNCNin ^' co .... v*3ON 3 rR *^ *' 3 tHCNiHCNiH JO vOvOinvO O -j-i O 03 ^-> 03 C5 .R R 0 o •^i ooocN rHcNtHcNiH Q inin-^-^d- >Q (C T^S H-i ^ *"^ ^ 03 R c~< vo 0) c ?H vD •HCNOOOONiHO vM Oro -f-i vj-ONinoo*sfONvo Ss O' — i CNinrOOOCN OOCNrHrH O CO rH CN 00 .... 03 rH •1— R 03 rH CNCNCNCNrH rorororo <3> .C 03 EX, NJ to t> vS c 3 t/> •-5 0) ONin_, -cj-ONinooinoNvo 03 OIH ?H ' — ' > tj> H +J 0) (3 OOOOOOO fel • • •r- g ^ OOOOOOO X C -o •r- •H H 03 inoNinoNinoNin TO*H JN iHOrHOiHOrH 6 G E "* 0 CO CN OO - TO D. TO j^TO WC C 4J 3 rH S 4J H 3 S 4-J D 0) 0) CD TO I-J TO ^4 H ^ COITO^P C>-iCU^! -^ 4-1 TO i-> O O O P Z &> H &> Ot-i-r-iOO OTO»-iTO oafo^odH MOtMS 94 1 1 CO 4J 0 CO CO CM vor~~rH ovrHONOO vocNcN om. oo v^ oo LO ^o ^o ^H ^ oo CN r*-- O*N r^> \o oo vo to ^~ C • -0- vO ^,-1^1 ^I^H ^^H^I^ c CO rH ~3" rHC^rH OCSlvOOO Or^oo co m-j-in > j ^-4 "^ in co in _Q S ^.S ^ , c 0 « 1 0 VO rH s cooo Oio-^co o cs cNr^io ooo r^-ooor**- 03 inr-^-oo ^ooco t-Hoocoo •r— CQ r*** "^ r**1 C s s 0) ^ o 0 -P m rH O CO CO O CO CO *3" r^- EX, Q >^- csj <}• in CN rH CN CO in Q. ji, r^ ~* vo COr-^vO OO>i>VDin £> rHrHrH rHrH CNrHrHrH O CS 0 a o CO r^ CN CN OO CMsf '^ CNCN OO CN• 3 rHCNiH o»vD^*O Q) COo-3 rH CN i— ! c^««OCT»vO ^H S co 0 ^^d" CNCOvC-W CO O -i 4J CO ,fl •(-'•Hcjg -HcOC^cO cO^H -t-**HcJS -HcOcxcd CO r^- 4J 3 0) prj CU CO CO rH 3 E; s^ 4J 3 CD p"! CD CO CO rH 3 £ U Cj J-( CD ^^^ ^ V-J CO CO .M M AJ CJ ^j CU s™^ v^ j_i cfl cO .*^ M tO O co pq pq Q VJ cflcO 3 T- i O O cOOcOS-i jOtO 3 -r- > O O PL) SSS£304EH PPPQQP'H Ss^SP^E-* 95 S- (O OJ CD o T3 c fO r^r^iH t$ COvOiHiHin Q> S rH rH Q) § a CSCNO\CO CTiCO-rHOOl rS; &, • • • cj) S O S i inm<-rs; CNCM -COCN ta CNOON-^ -*oo •oorH Q) 'v^ ^ CO I-H CN rH • rH rH rH O m • • CM O> m rH • •• ••••• iO ••^ * * CM ^^ co co r**» ""^ * * ^D ^^ ON oo CM iH • *mcMoor^ i-H CM ^O P"* r**- ^o ON ON ON e m OOONrHCSvO rHCNvO CO t-l o H V ,3 CO 5 I O H 00 O> rH CM v£> 8 £ CO M •r-) O & H % a r-t CO CO SZ O H Mean monthly soil temperature at Njala University College (22) , compared with mean monthly minimum and maximum air temperatures Period 1966, at 12 inches depth 1967, at 6 inches depth 1968, at 6 inches depth 0900 hours 1500 hours 0900 hours 1500 hours 0900 hours 1500 hours Soil Air, min. Soil Air, max. Soil Air, min. Soil Air, max. Soil Air, min. Soil Air, max. ° Fahrenheit January 81 66 88 90 81 66 87 91 79 69 88 91 February 85 68 95 94 83 68 89 92 83 71 92 91 March • * • 71 95 85 70 93 96 84 71 93 94 April 82 72 88 92 86 72 94 95 85 72 93 95 May 84 73 90 92 85 72 91 91 82 71 88 89 June 81 71 86 87 78 71 85 88 81 73 86 87 July 81 73 85 86 79 71 87 84 80 73 84 86 August 79 72 83 84 81 71 88 82 79 72 84 83 September 79 71 84 85 80 72 85 85 80 73 84 89 October 81 72 86 88 79 72 83 88 81 73 86 87 November 81 70 85 88 78 73 81 88 81 72 85 87 December 79 69 85 89 80 69 83 89 81 83 87 Ann. ave. 81 71 87 89 81 71 87 89 81 72 87 89 "Centigrade January 27 19 31 32 27 19 31 33 26 21 31 33 February 29 20 35 34 28 20 32 33 28 22 33 33 March • * • 22 35 29 21 34 36 29 22 34 34 April 28 22 31 33 30 22 34 35 29 22 34 35 May 29 23 32 33 29 22 33 33 28 22 31 32 June 27 22 30 31 26 22 29 31 27 23 30 31 July 27 23 29 30 26 22 31 29 27 23 29 30 August 26 22 28 29 27 22 31 28 26 22 29 28 September 26 22 29 29 27 22 29 29 27 23 29 32 October 27 22 30 31 26 22 28 31 27 23 30 31 November 27 21 29 31 26 23 27 31 27 22 29 31 December 26 21 29 32 27 21 28 32 27 28 31 Ann. ave. 27 22 30 32 27 22 31 32 27 22 31 32 APPENDIX B. DESCRIPTIONS AND ANALYTICAL DATA FOR SELECTED SOIL PROFILES In this Appendix, descriptions and other data are given for 44 soil profiles. These profiles were analyzed in labo- ratories of the Agronomy Department, University of Illinois at Urbana-Champaign, Illinois, U.S.A., except for the bulk density measurements, which were made by the clod method at Njala University College. The soil de- scriptions were written using terminology in the Soil Sur- vey Manual (68) and Glossary (67). The colors are for the moist soil unless stated otherwise. The analytical methods used were essentially those published in "Methods of Soil Analysis," edited by C. A. Black and published in 1965 by the American Society of Agronomy, Madison, Wisconsin, U.S.A. (5) . Particle- size analyses were done by the sieve and pipette method. Organic carbon was determined by the Walkley-Black wet oxidation method. Cation-exchange capacity was determined by ammonium saturation. Exchangeable bases were removed by leaching with IN neutral am- monium acetate ; calcium and magnesium were measured by EDTA titration, and potassium and sodium by flame photometry. Exchangeable aluminum was removed by leaching with IN KC1, then measured by emission spec- troscopy. The pH was determined potentiometrically with a glass electrode in a 1:1 ratio of soil with water and also in a 1:1 ratio of soil with IN KC1. Soil test PI was determined by extraction with 0.03N NH4F in 0.025N HC1, and P2 with 0.03N NH4F in 0.1N HC1. Soil- test available K was extracted with 23-percent NaNO3 and determined by the sodium cobaltinitrite turbidometric method. Total phosphorus was determined by perchloric acid digestion. Total analyses of the total soil for calcium, iron, and potassium were by X-ray spectroscopy on ground, pressed samples, using National Bureau of Stan- dard samples as standards. 98 Location Physiography Relief Vegetation Drainage Parent material 0-5 inches 0-13 cm Lab. No. S28572 B2t 5-23 inches 13-58 cm Lab. No. S28571 23-43 inches 58-109 cm Lab. No. S28570 IIB32 43-67 inches 109-170 cm Lab. No. S28569 Diagnostic horizons Profile 144801A, Baoma sandy clay loam Description after Sivarajasingham (64) On the right-hand side of the road from Daru Junction to Moa Barracks, about 150 feet (46 m) past the Girls' School at the first bend of the road to the left. Undulating upland. Upper gentle slope. Cocoa 7 to 15 years old in very poor health, poor management, inadequate shade, open stand, and heavy weed growth; few tall trees of the former secondary forest remain. Well drained. A thick layer of locally transported material derived from laterite crust and partially weathered and fresh rock of a previous landscape. Dusky red (2. SYR 3/2); sandy clay loam; moderate fine sub- angular blocky; light and porous; soft, slightly sticky, slightly plastic; many fine and medium roots; clear, smooth boundary to horizon below. Red (10R 4/6) to dark red (10R 3/6); clay; less than 5% hardened plinthite glaebules of the kind in the layer below; moderate medium and fine subangular blocky; porous; friable, slightly sticky, and slightly plastic; common fine and medium roots; abrupt, smooth boundary to horizon below. Main gravel layer; red (10R 4/6); gravelly clay; 40% black- coated and uncoated, medium, round, black, dense hardened plinthite glaebules, and 10% coarse, dense, very hard, fresh rock pebbles; moderate fine subangular blocky; porous; fri- able, slightly sticky, slightly plastic; few fine roots; dif- fuse, smooth boundary to horizon below. Red (10R 4/6); gravelly clay; 40% hardened plinthite glae- bules as in HB.,, but finer in size; moderate fine subangular blocky; slightly porous; friable, slightly sticky, slightly plastic; no roots. Ochric epipedon, 0-5 inches (0-13 cm) . Argillic horizon, 5-67 inches (13-170 cm) probable, but not fully documented. Profile 144801 A, Baoma sandy clay loam Classification: Typic Paleudult (or Tropeptic Haplorthox) 99 Illinois Lab. No. Depth of horizon (inches) Horizon S28572 0-5 A, S28571 5-23 B2t S28570 23-43 S28569 43-67 Percent of entire sample > 2.0 nun . . Particle-size distribution of < 2 mm Very coarse sand 2.0-1.0 mm. . . . Coarse sand Medium sand Fine sand Very fine sand Total sand Total silt Total olay 1.0-.5 mm . .5-. 25 mm. . 25-. 1 mm . .1-.05 mm. 2.0-.05 mm. .05-. 002 mm < .002 mm 14.4 6.6 8.0 9.9 19.7 8.7 52.5 Water-dispersible clay < .002 mm. 13.4 34.1 6.9 17.3 4.9 5.3 6.8 14.3 8.4 39.4 13.9 46.7 0.9 50° 3.3 5.5 4.7 8.6 7.3 28.6 15.0 56.4 0.5 Bulk density 1.2 1.3 1.5 Moisture: 1/3 atmos. (%) 19.2 22.2 24.9 15 atmos. (%)..... 14.2 16.7 20.0 Avail, moist. -hold, capacity .... 0.05 0.06 0.03 Organic carbon (%) 2.43 0.81 0.53 Exchangeable cations (me/lOOg soil) : Ca 0.21 0.05 0.23 Mg 0.23 0.26 0.26 K 0.06 0.05 0.05 Na 0.02 0.03 0.07 Al 1.33 0.63 0.12 Cation-exch. capacity (me/lOOg) . . . 11.93 7.29 6.50 Base saturation (%) 4.4 5.3 9.4 pH H20 4.6 4.8 5.0 PH KC1 3.8 4.2 4.6 Soil tests: K (Ibs/A) 45 4 9 P1 (Ibs/A) 45 21 32 P2 (Ibs/A) 60 34 56 Total P (ppm) 2,070 1,970 2,770 Total CaO(%) 0.128 0.095 0.099 Total Fe203(%) 16.40 17.17 18.13 Total K20(%) 0.204 0.197 0.219 40° 4.0 5.9 5.0 8.6 6.2 29.3 15.0 55.7 0.4 1.5 25.8 21.2 0.04 0.24 0.36 0.34 0.04 0.04 0.16 5.36 14.6 5.2 5.0 10 27 49 2,760 0.099 18.96 0.203 .Volume percent of total sample estimated in the field. Inches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 100 Profile N39, Bonjema loam Described by J. C. Dijkerman on March 28, 1966 Location Physiography Relief Vegetation Drainage Parent material 0-4 inches 0-10 cm Lab. No. S28651 4-16 inches 10-41 cm Lab. No. S29739 Blt 16-25 inches 41-63 cm Lab. No. S28652 25-33 inches 63-84 cm Lab. No. S28653 II1B22 33-57 inches 84-145 cm Lab. No. S29740 57-70 inches 145-178 cm Lab. No. S28654 Diagnostic horizons On proposed new experimental farm northwest of Njala University College Campu; a few feet west of path from Bonjema to Belebu; 301 feet (92 m) north of the junction of this path with path towards Gbesebu. Colluvial footslope or upper river terrace. Lower part of a straight 2- to 3-percent slope. Secondary farm bush. Imperfectly drained. Gravel-free colluvium, over gravelly colluvium, over residual material. Dark grayish brown (10YR 4/2); loam; weak medium subangular blocky, breaking to moderate coarse to fine granular; friable; many medium and fine and few coarse roots; many pores of all sizes; gradual, smooth boundary to horizon below. Brown (10YR 5/3) with few fine distinct yellowish-red (SYR 5/8) and light brownish-gray (10YR 6/2) mottles; loam; very weak medium subangular blocky, breaking to weak coarse to fine granular; friable; common medium and fine roots; many pores of all sizes; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/4) with common fine distinct yellowish-red (SYR 5/8) and light brownish-gray (10YR 6/2) mottles; loam; very weak medium subangular blocky, breaking to weak coarse to fine granular; firm in place but friable t crush; common medium and fine roots; many pores of all sizes; abrupt, smooth boundary to horizon below. Yellowish brown to pale brown (10YR 5/4-6/3) with many prominent medium red (2. SYR 4/8) mottles, most of which are slightly hard to crush; gravelly (50% by volume) clay loam; the gravels form a stone line and consist mainly of quartz pebbles (35%) and dense, irregular, red (10YR 4/4-4/6) hardened plinthite glaebules (15%) 1/4" to 1/2" in diameter; massive to weak medium an fine angular blocky; firm; few medium and fine roots; common medium and fine pores; clear, smooth boundary to horizon below. Forty percent prominent fine, medium, and coarse light brownish-gray to pale brown (10YR 6/2-6/3) soft mottles, and 60% prominent fine, medium, and coarse red (10R 4/8) mottles, most of which are slightly hard to crush; gravelly (30% by volume) clay loam; gravels are irregular, nondense, red (10R 4/8) hardened plinthite glaebules, 1/4" to 3/4" in diameter; moderate medium to very fine angular blocky; firm; few medium and fine roots; common medium and fine pores; diffuse, smooth boundary to horizon below. Forty percent prominent fine, medium, and coarse light gray (10YR 6/1) soft mottles, and 60% prominent fine, medium, and coarse red (2. SYR 5/8, 10R 4/8) mottles, most of which are slightly hard or hard to crush; gravelly (20% by volume) clay; gravels are irregular, nondense, red (2.5YR 5/8, 10R 4/8) hardened plinthite glaebules, 1/4" to 3/4" in diameter; strong medium to very fine angular blocky; firm; few medium and fine roots; common medium and fine pores. Augering to a depth of 125 inches (318 cm) revealed light gray (10YR 6/1-7/1) and white (10YR 8/1) colors, with red (10R 4/8) and strong brown (7. SYR 5/8) mottles; small pieces of weathered siltstone occurred below 100 inches (254 cm) . Ochric epipedon, 0-16 inches (0-41 cm) . Argillic horizon, 16-70 inches (41-178 cm) probable, but not fully documented 101 Profile N39, Bonjema loam Classification: Plinthic Paleudult (or "Plinthic" Udoxic Dystropept) Illinois Lab. No. Depth of horizon (inches) Horizon S28651 S29739 0-4 4-16 Al A3 S28652 S28653 S29740 16-25 25-33 33-57 Blt IIB21 IIIB22 S28654 57-70 IIIB23 Percent of entire sample > 2.0 mm . . Particle-size distribution of < 2 mm ( Very coarse sand 2.0-1.0 mm. . . . Coarse sand 1.0-.5 mm . . . . Medium sand .5-. 25 mm. . . . Fine sand .25-.! mm .... Very fine sand . 1-.05 mm. . . . Total sand 2.0-.05 mm. . . . Total silt .05-. 002 mm ... Total clay <.002 mm ... Water-dispersible clay <.002 mm ... Moisture: 1/3 atmos. (%) <1 %): 1.5 4.3 8.1 19.3 15.1 48.3 38.7 13.0 5.4 21.5 6.6 2.36 1.07 0.29 0.22 0.04 0.84 8.43 19.2 4.6 3.8 202 18 19 167 0.153 1.50 0.426 4 0.5 6.5 8.3 19.5 16.2 51.0 32.6 16.4 11.0 17.9 6.5 0.57 0.18 0.13 0.02 0.04 1.02 3.93 9.4 4.3 3.6 43 4 4 78 • • • • • • 3 3.9 5.8 6.4 16.6 12.4 45.1 32.5 22.4 19.9 17.7 9.2 0.41 0.03 0.15 0.05 0.02 2.31 4.57 5.5 4.3 3.4 52 3 3 78 0.072 3.08 0.722 25 4.2 5.1 5.3 11.9 9.0 35.5 32.5 32.0 28.6 20.9 12.7 0.38 0.03 0.20 0.06 0.02 3.51 6.72 4.6 4.4 3.1 60 2 2 105 0.072 4.90 1.070 38 0.3 6.1 5.6 9.8 8.6 30.4 30.2 39.4 13.9 26.2 15.6 0.33 0.26 0.05 0.04 0.04 4.44 9.86 3.9 4.9 3.4 65 1 1 125 • • • • • • 32 2.4 2.9 2.7 5.5 6.0 19.5 34.0 46.5 4.6 28.6 18.1 0.24 0.03 0.27 0.07 0.02 10.00 13.15 3.0 4.8 3.3 65 0 1 125 0.069 8.52 2.250 15 atmos. (%) Exchangeable cations (me/lOOg soil) : Ca Me. K Na Al Cation-exch. capacity (me/lOOg) . . . Base saturation (%) pH H 0 pH KC1 Soil tests: K (Ibs/A) P (Ibs/A) P (Ibs/A) Total P (ppm) Total CaO(%) Total Fe 0 (%) Total K_0(%) 102 Profile N105, Bonjema fine sandy loam Described by D. H. Westerveld on December 28, 1966 Location Physiography Relief Vegetation Drainage Parent material 0-20 inches 0-51 cm Lab. No. S29094 Blt 20-32 inches 51-81 cm Lab. No. S29095 32-40 inches 81-102 cm Lab. No. S29097 IIIB22 40-50 inches 102-127 cm Lab. No. S29099 :iiB23 50-60 inches 127-153 cm Lab. No. S29101 Diagnostic horizons Oil Palm Station of Njala University College, adjacent to the south boundary road, 370 feet (113 m) northwest of Kania. Third (upper) terrace of the Taia River. Very gentle, straight slope. Secondary bush. Imperfectly drained. Gravel-free colluvium or alluvium, over colluvial material high in quartz gravel and hardened plinthite glaebules, over residual material weathered from bedrock. Dark brown (10YR 4/3) ; fine sandy loam; very weak fine and medium angular to subangular blocky, breaking into weak fine and medium granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/4) with few fine faint yellowish-red (SYR 5/8) mottles; sandy clay loam; weak fine, medium, and coarse angu- lar to subangular blocky, breaking into weak to moderate fine and medium granular; friable; many fine, medium, and coarse pores; many fine and medium roots; clear, wavy boundary to horizon below. Yellowish brown (10YR 5/4) with common fine and medium faint yellowish-red (5YR 4/8) mottles; gravelly sandy clay loam, with most of the gravel being rounded quartz pieces 1/4" to 1" in diameter (stone line) ; very weak fine and medium angular to sub- angular blocky, breaking into weak fine and medium granular; friable; many fine, medium, and coarse pores; common fine and medium roots; clear, wavy boundary to horizon below. Brown to dark brown (10YR 5/3-4/3) with common fine and medium distinct red (2. SYR 4/8) mottles, and few fine and medium faint yellowish-brown (10YR 5/8) mottles; gravelly clay loam; half of the gravel is rounded quartz, and half is red (10R 4/6), round and nodular, 1/4" to 1" in diameter, hardened plinthite glae- bules; very weak fine and medium angular to subangular blocky, breaking into fine and medium granular; many fine, medium, and coarse pores; few fine roots; gradual, smooth boundary to horizon below. Light brownish gray (10YR 6/2) with many fine, medium, and coarse prominent red (2. SYR 4/6) mottles, and few fine and medium faint yellowish-brown (10YR 5/8) mottles; gravelly clay loam, with most of the gravel being hardened plinthite glaebules similar to those in the 111622 h°rizon> very weak fine and medium angular to sub- angular blocky, breaking into weak fine and medium granular; firm; many fine, medium, and coarse pores; few fine roots. Ochric epipedon, 0-20 inches (0-51 cm). Argillic horizon, 20-60 inches (51-153 cm) probable, but not fully documented. 103 Profile N105, Bonjema fine sandy loam Classification: Plinthic Paleudult (or "Plinthic" Udoxic Dystropept) Illinois Lab. No. Depth of horizon (inches) S29094 S 0-20 2 • 29095 i 10-32 329097 32-40 S29099 \ 40-50 S 29101 50-60 Horizon Al E it : LIB21 IIIB22 IIIB23 Percent of entire sample > 2.0 mm 0 0 32.2 29.5 35.5 Particle-size distribution of < 2 mm (%) : 0.6 2.0 3.4 4.4 3.7 Coarse sand 1.0-.5 mm 4.0 5.1 4.7 5.0 5.5 Medium sand .5-. 25 mm 9.0 7.3 6.3 6.0 5.7 Fine sand .25-.! mm 30.2 24.3 19.1 17.1 14.4 Very fine sand . 1-.05 mm 18.1 15.4 12.9 11.9 11.0 Total sand 2,0 -.05 mm 61.9 54.1 46.4 44.4 40.3 Total silt .05-. 002 mm 26.0 24.9 24.4 24.0 23.0 Total olay < .002 mm 12.1 21.0 29.2 31.6 36.7 Water-dispersible clay < .002 mm 5.1 16.6 24.7 23.5 5.5 Moisture: 1/3 atmos. (%) 9.6 • • • 14.2 15.4 17.7 15 atmos. (%) 5.6 • • . 10.8 12.0 13.6 1.19 0.44 0.30 0.26 0.14 Exchangeable cations (me/lOOg soil) : Ca 0.18 0.10 0.08 0.13 0.18 Mg 0.10 0.10 0.10 0.31 0.10 K 0.01 0.02 0.01 0.02 0.03 Na 0.06 0.03 0.04 0.03 0.04 Al 1.50 1.55 1.89 2.11 3.44 Cation-exch. capacity (me/lOOg) 5.79 4.64 5.57 6.14 8.07 Base saturation (%) 6.0 5.4 4.1 8.0 4.3 PH H20 4.1 4.4 4.5 4.6 4.5 pH KC1 3.5 ... 3.4 3.4 3.3 Soil tests: K (Ibs/A) 56 39 35 43 48 P1(lbs/A) 11 3 2 2 3 P2 Ibs/A) 15 5 4 4 5 Total P (ppm) 137 110 140 ... Total CaO(%) 0.080 0.074 0.073 0.073 0.075 Total Fe203(%) 1.01 1.51 2.68 3.74 4.52 Total K20(%) 0.29 0.42 0.58 0.64 104 Location Physiography Relief Vegetation Drainage Parent material 11 0-9 inches 0-24 cm Lab. No. S29827 "12 9-18 inches 24-45 cm Lab. No. S29828 B21 18-24 inches 45-60 cm Lab. No. S29829 B22 24-43 inches 60-108 cm Lab. No. S29830 43-51 inches 108-130 cm Lab. No. S29831 Diagnostic horizons Profile P60, Bosor fine sandy loam Described by R. Miedema on April 30, 1968 Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE22--85g; along the path from Mabanta to Bosor, near augerhole 12. Flat summit of a low hill, on an old tributary terrace. Slope, 0 to 3 percent. Short bush, 2 to 4 years old, with many wild oil palms. Well drained. Gravel-free alluvium or colluvium, over weathering products of Precambrian granite and acid gneiss. Very dark grayish brown (10YR 3/2); fine sandy loam; weak fine and medium subangular blocky with many crumbs; friable; many macro- and mesopores; few medium distinct charcoal mottles; common coarse, many medium and fine roots; much ant and ter- mite activity; clear, smooth boundary to horizon below. Dark brown (10YR 3/3) ; fine sandy clay loam; weak fine and medium subangular blocky with many crumbs; friable; common macro- and many mesopores; common medium distinct charcoal mottles; many coarse, medium, and fine roots; much ant and termite activity; clear, smooth boundary to horizon below. Dark brown to brown (7. SYR 4/4); fine sandy clay loam; weak fine, medium, and coarse subangular to angular blocky; fri- able; many macro- and mesopores; few medium distinct charcoal mottles; common coarse and medium, many fine roots; much ant and termite activity; gradual, smooth boundary to horizon below. Yellowish red to strong brown (SYR 5/8-7. SYR 5/8); fine sandy clay loam; weak fine and medium subangular blocky; friable; common macro- and many mesopores; few coarse, common medium and fine roots; common ant and termite activity; abrupt, smooth boundary to horizon below. Yellowish red to strong brown (SYR 5/8-7. SYR 5/6); gravelly sandy clay loam; weak fine and medium subangular blocky; fri- able; common macro- and many mesopores; common fine roots; low ant and termite activity; 50% gravel (approximately 25% fine and medium angular quartz gravel, and 25% fine, medium, and coarse, hardened plinthite glaebules). Umbric epipedon, 0-18 inches (0-45 cm). Argillic horizon, 43-51 inches (108-130 cm) probable, but not fully documented. 105 Profile P60, Bosor fine sandy loam Classification: Orthoxic Palehumult (or Udoxic Dystropept) Illinois Lab. No. S29827 S29828 S29829 S29830 S29831 Depth of horizon (inches) 0-9 9-18 18-24 24-43 43-51 Horizon ^ A,, BOI BO< IIB 11 12 21 22 23 Percent of entire sample > 2.0 mm . . . 0 0 0 0 50.4 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 3.6 3.8 6.6 6.2 7.6 Coarse sand 1.0-.5 mm 8.6 7.5 8.4 7.0 7.1 Medium sand .5-. 25 mm 15.7 13.3 11.7 10.3 9.1 Fine sand .25-.! mm 28.8 25.3 22.6 22.0 17.6 Very fine sand . 1-.05 mm 12.9 13.1 12.7 13.4 12.4 Total sand 2.0-.05 mm 69.6 63.0 62.0 58.9 53.8 Total silt .05-. 002 mm 13.1 12.5 13.4 13.3 14.1 Total elay < .002 mm 17.3 24.5 24.6 27.8 32.1 Water-dispersible clay < .002 mm. . . . 3.8 6.6 10.2 11.0 4.8 Bulk density 1.2 1.2 1.3 1.3 1.4 Moisture: 1/3 atmos. (%) 12.1 13.6 13.2 13.8 16.2 15 atmos. (%) 8.5 10.0 9.6 10.4 12.3 Avail, moist. -hold, capacity 0.04 0.04 0.05 0.04 0.02 Organic carbon (%) 2.34 1.40 0.86 0.66 0.62 Exchangeable cations (me/lOOg soil): Ca 0.58 0.11 0.11 0.11 0.11 Mg 0.16 0.05 0.10 0.26 0.05 K , 0.12 0.01 0.01 0.02 0.03 Nab 0.13 0.03 0.03 0.04 0.05 Al 0.99 1.24 0.91 0.78 0.63 Cation-exch. capacity (me/lOOg) .... 7.29 6.14 4.50 4.07 4.85 Base saturation (%) 13.6 3.3 5.6 10.6 4.9 PH H20 4.7 4.7 4.7 4.8 4.8 pH KC1 4.1 4.1 4.1 4.1 4.1 Soil tests: K (Ibs/A) 194 74 35 39 56 P1(lbs/A) 15 4 3 3 2 Total CaO(%) 0.120 0.078 0.075 0.073 0.076 Total Fe203(%) 4.96 6.80 6.74 7.28 8.40 Total K20(%) 0.402 0.391 0.372 0.387 0.407 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. Estimated values. 106 Profile T165, Gbamani coarse sand Described by J. C. Dijkerman on May 26, 1966 Location Physiography Relief Torma Bum soil survey area, 528 feet (161 m) west of Sahun along path to Mani. On aerial photograph 61-SL3-023, pit T165 is 20.4 cm south and 11.5 cm west of the northeast corner mark. Beach ridge about 5 miles north of present coast. Convex 2-percent slope on the crest of a ridge about 1/4 mile wide and 10 feet (3 m) higher than the surrounding low area. Vegetation Drainage Parent material A21 0-16 inches 0-41 cm Lab. No. S28668 A22 16-41 inches 41-104 cm Lab. No. S28669 B2h 41-48 inches 104-122 cm Lab. No. S28670 B2ir 48-80 inches 122-203 cm Lab. No. S28671 80-120 inches 203-305 cm Lab. No. S28672 Forest with many oil palms and coconut trees. Well drained. Coarse beach sand of Bullom Series. Very dark gray to dark gray (10YR 4/1-3/1) ; coarse sand with many clean coarse quartz grains; single grain; very friable; many coarse, medium, and fine roots; many medium and fine pores; gradual, smooth boundary to horizon below. Dark gray (10YR 4/1-7. SYR 4/1); coarse sand with many clean coarse quartz grains; single grain; very friable; many medium and fine pores; few medium and fine roots; abrupt, wavy boundary to horizon below. Dark reddish brown (SYR 2/2); coarse sand; turns white on ignition; massive; firm in place but friable to crush; many medium and fine pores; few medium and fine roots; abrupt, irregular boundary to horizon below with vertical tongues as long as 15 inches extending into the B«. . Yellowish red (SYR 4/6); loamy coarse sand; turns red on ignition; massive; firm to very firm; common medium and fine pores; few medium and fine roots; gradual boundary to horizon below. Yellowish brown (10YR 5/4) with common distinct coarse strong brown (7. SYR 5/6) mottles; loamy coarse sand; single grain; very friable; no roots; many fine and medium pores. Diagnostic horizons Ochric epipedon, 0-41 inches (0-104 cm). Spodic horizon, 41-80 inches (104-203 cm). 107 Profile T165, Gbamani coarse sand Classification: "Arenic" Tropohumod Illinois Lab. No. S28668 S28669 S28670 S28671 S28672 Depth of horizon (inches) 0-16 16-41 41-48 48-80 80-120 Horizon A21 A22 B2h B2ir C Percent of entire sample > 2.0 mm 0+ 0+ 0+ 0+ 0+ Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 25.4 28.2 29.4 25.6 19.8 Coarse sand 1.0-.5 mm 49.5 45.0 29.4 35.0 26.8 Medium sand .5-. 25 mm 16.3 18.6 20.6 19.0 23.3 Fine sand .25-.! mm 5.0 3.9 9.8 7.5 12.8 Very fine sand .1-.05 mm 0.2 0.1 1.0 0.7 1.3 Total sand 2.0-.05 mm 96.4 95,8 90.2 87.8 84.0 Total silt .05-. 002 mm 2.3 2.9 4.2 3.4 4.9 Total clay < .002 mm 1.3 1.3 5.6 8.8 11.1 Water-dispersible clay < .002 mm 0.6 1.7 2.3 1.1 0.6 Bulk density * • * • • • 1.5 1.7 1.8 Moisture: 1/3 atmos. (%) 1.3 1.5 8.1 5.0 5.0 15 atmos. (%) 0.8 0.6 4.3 3.7 4.0 Avail, moist. -hold, capacity . . . • * • 0.06 0.02 0.02 Organic carbon (%) 0.28 0.12 2.27 0.46 0.18 Exchangeable cations (me/lOOg soil): Ca 0.03 0.03 0.06 0.06 0.06 Mg 0.03 0 0.06 0.06 0 K 0.03 0.01 0.03 0.02 0.03 Na 0.03 0.02 0.06 0.05 0.04 Al 3.22 4.89 1.28 0.40 0.62 Cation-exch. capacity (me/lOOg) 1.29 0.64 9.01 2.93 2.21 Base saturation (%) 9.3 9.4 2.3 6.5 5.9 PH H20 4.3 4.5 4.6 5.1 5.2 pH KC1 3.7 4.0 4.0 4.6 4.7 Soil tests: K (Ibs/A) 35 21 30 21 26 P^lbs/A) 7 9 0 26 125 P2(lbs/A) 7 14 0 39 125 Total P (ppm) 70 • • • Total CaO(%) 0.074 0.068 0.084 0.078 0.078 Total Fe203(%) 0 0 0.30 1.85 0.80 Total K20(%) 0.078 0.173 0.281 0.349 0.413 'inches of available moisture-holding capacity per inch of soil. 108 Location Physiography Relief Vegetation Drainage Parent material 0-5 inches 0-13 cm Lab. No. S28664 A_ 3g 5-11 inches 13-28 cm Lab. No. S28665 11-14 inches 28-35 cm Lab. No. S28666 B21g 14-23 inches 35-58 cm E22g 23-52 inches 58-132 cm Lab. No. S28667 Diagnostic horizons Profile T187, Gbehan silty clay Described by J. C. Dijkerman on March 4, 1966 Torma Bum soil survey area, near the former sugar cane ex- perimental plots; 1,954 feet (596 m) west of- the former sugar cane office and 2,323 feet (708 m) west of Sewa River, On aerial photograph 53-SL13-036, pit T187 is 13.3 cm west and 10.1 cm south of the northeast corner mark. Basin in the floodplain of Sewa River. Concave 1-percent slope in a basin, adjacent to the higher levee on which profile T183, Taso clay, is located. Short water-loving grasses. Poorly drained. Clayey alluvium. Black (10YR 2/1); silty clay; moderate fine to very fine granular; friable; many fine and medium pores; many fine and medium roots; clear, smooth boundary to horizon below. Dark gray (10YR 4/1); clay; strong very coarse prismatic, breaking into strong coarse to medium angular blocks; very firm; few medium and common fine pores; common fine and medium roots; clear, smooth boundary to horizon below. Light brownish gray (2.5Y 6/2) with common distinct fine and medium strong brown (7. SYR 5/8) mottles; clay; strong very coarse prismatic, breaking into strong coarse to medium angular blocks; very firm; few medium and common fine pores; common fine and medium roots; clear, smooth boundary to horizon below. Light gray (2.5Y 7/2) with common distinct medium and fine yellowish-red (SYR 5/6) and strong brown (7. SYR 5/6) mot- tles; clay; strong medium angular blocky; firm in place but friable to crush; many medium and fine pores; few medium and fine roots; gradual, smooth boundary to horizon below. Light gray (2.5Y 7/2) with many distinct yellowish-red (SYR 5/6) and strong brown (7. SYR 5/6) soft mottles; clay; moderate medium to very fine angular blocky; firm in place but friable to crush; many medium and fine pores; few medium and fine roots. Ochric epipedon, 0-11 inches (0-28 cm). Oxic horizon, 23-52 inches (58-132 cm). 109 Profile T187, Gbehan silty clay Classification: "Plinthic Tropeptic" Ochraquox Illinois Lab. No. S28664 S28665 S28666 S28667 Depth of horizon (inches) 0-5 5-11 11-14 23-52 Horizon Al A. 3g Blg B22g Percent of entire sample > 2.0 mm 0 0 0 21 Particle-size distribution of < 2 mm (%) : Total sand 2.0-.05 mm 1.8 1.1 0.5 2.5 Total silt .05-. 002 mm 43.7 29.5 36.1 33.9 Total clay < .002 mm 54.5 69.4 63.4 63.6 Water-dispersible clay < .002 mm 15.9 45.0 48.2 1.4 Bulk density 0.8 1.1 1.4 1.4 Moisture: 1/3 atmos. (%) 86.7 48.7 38.6 40.3 15 atmos. (%) 37.1 32.0 25.6 26.8 Avail, moist. -hold, capacity 0.40 0.18 0.18 0.15 Organic carbon (%) 13.48 5.83 0.84 0.33 Exchangeable cations (me/lOOg soil): Ca 0.11 0.03 0.24 1.01 Mg 0.31 0.39 0.91 2.44 K 0.35 0.10 0.05 0.06 Na 0.15 0.13 0.06 0.07 Al 4.72 6.44 3.33 3.22 Cation-exch. capacity (me/lOOg) 46.37 30.58 11.29 9.57 Base saturation (%) 2.0 2.1 11.2 37.4 PH H20 4.8 4.7 5.0 5.5 pH KC1 4.0 3.7 3.6 4.2 Soil tests: K (Ibs/A) 158 69 43 56 P^lbs/A) 111 14 9 8 P2(lbs/A) 125 25 10 11 Total P (ppm) . 1,550 740 * * • Total CaO(%) 0.124 0.104 0.101 0.120 Total Fe203(%) 1.83 2.50 3.15 5.81 Total K20(%) 0.500 1.080 1.270 1.330 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. no Location Physiography Profile N125, Gbesebu silty clay Described by H. Breteler on January 18, 1967 From the extreme southwestern corner of the Oil Palm Station of Njala University College, at the junction of the Kania boundary road and the path along the Taia River near surveyor stone No. PB-B 829, thence 322 feet (98 m) down the steep slope towards the river to pit N125 , near the river bank on a natural levee . Natural levee of the Taia River, on the present floodplain or first terrace. Relief Vegetation Drainage Parent material 0-4 inches 0-10 cm Lab. No. S29066 4-7 inches 10-18 cm Lab. No. S29067 7-19 inches 18-48 cm Lab. No. S29068 B22b 19-25 inches 48-63 cm Lab. No. S29069 B23 25-63 inches 63-160 cm Lab. No. S29070 Diagnostic horizons Nearly level, convex slope. Old secondary bush with much grass. Moderately well drained; may be flooded for several weeks during the wet season. Clayey alluvium. Dark brown (10YR 4/3); silty clay; weak very fine and fine sub- angular blocky, breaking to weak very fine granular; very fri- able; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4) ; clay; weak very fine and fine angular to subangular blocky, breaking to weak very fine granu- lar; friable; many fine, medium, and coarse pores; many fine, me- dium, and coarse roots; clear, smooth boundary to horizon below. Strong brown (7.5YR 5/6) with many fine and medium faint yellow- ish-red (5YR 5/6) mottles; clay; weak very fine and fine blocky, breaking into weak very fine granular; friable; many fine, medium, and coarse pores; common fine, medium, and coarse roots; mica flakes; clear, smooth boundary to horizon below. Strong brown to yellowish brown (7.5YR-10YR 5/6) with many fine, medium, and coarse faint yellowish-red (SYR 5/6) mottles; this is a buried A horizon with common fine, medium, and coarse charcoal mottles; clay; weak to moderate fine and medium blocky, breaking into weak to moderate very fine and fine granular; firm; many fine, medium, and coarse pores; common fine and medi- um roots; mica flakes; clear, smooth boundary to horizon below. Strong brown (7. SYR 5/6) with many fine, medium, and coarse faint yellowish-red (SYR 5/6) mottles; clay; weak to moderate fine and medium blocky, breaking into weak to moderate fine granular; firm; many fine, medium, and coarse pores; few fine and medium roots; mica flakes. Ochric epipedon, 0-7 inches (0-18 cm). Cambic horizon, 7-63 inches (18-160 cm) . Ill Profile N125, Gbesebu silty clay Classification: Fluventic Udoxic Dystropept Illinois Lab. No. S29066 S29067 S29068 S29069 S29070 Depth of horizon (inches) 0-4 4-7 7-19 19-25 25-63 Horizon Al A3 B2i B22b B23 Percent of entire sample > 2.0 mm 0 0 0 0 0 Particle-size distribution of < 2 mm (%) : Total sand 2.0-.05 mm 6.5 2.2 0.8 1.6 2.2 Coarse silt .05-. 02 mm 7.3 4.8 4.9 6.3 8.0 Fine silt .02-. 002 mm 36.8 33.3 33.1 31.5 31.2 Total silt .05-. 002 mm 44.1 38.1 38.0 37.8 39.2 Total clay < .002 mm 49.4 59.7 61.2 60.6 58.6 Water-dispersible clay < .002 mm 20.4 36.6 34.1 37.2 2.6 Bulk density 0.9 1.0 1.1 1.1 1.2 Moisture: 1/3 atmos. (%) 47.1 40.8 37.2 36.7 36.9 15 atmos. (%) 25.7 26.4 27.0 27.3 26.4 Avail, moist. -hold, capacity3 0.19 0.14 0.11 0.10 0.13 Organic carbon (%) 4.41 2.43 1.00 0.87 0.56 Exchangeable cations (me/lOOg soil) : Ca 0.18 0.13 0.08 0.10 0.15 Mg 0.22 0.18 0.15 0.33 0.44 K 0.03 0.02 0.02 0.01 0.02 Na 0.08 0.06 0.06 0.04 0.04 Al 2.44 2.00 1.78 1.94 1.78 Cation-exch. capacity (me/lOOg) 18.93 12.65 9.29 9.57 8.86 Base saturation (%) 2.7 3.1 3.3 5.0 7.3 pH H20 4.6 4.6 4.8 4.8 4.9 pH KC1 3.8 3.8 3.8 3.7 3.7 Soil tests: K (Ibs/A) 98 60 39 35 35 Pi (Ibs/A) 28 10 9 9 16 P2 (Ibs/A) 35 14 10 10 26 Total P (ppm) 950 * • • • • * ... Total CaO(%) 0.193 0.150 0.137 0.139 0.137 Total Fe20s(%) 5.84 6.20 7.53 7.08 7.10 Total K20(%) 1.37 1.31 1.35 1.34 1.35 ainches of available moisture-holding capacity per inch of soil 112 Profile Ml 3, Gbesebu silty clay Described by H. Breteler on January 5, 1967 Location On proposed new experimental farm northwest of Njala University College Campus. Pit N13 is on the path from Nyawama toward Taia River, about 48 feet (15 m) before the steep slope starts down to the river. On aerial photograph 39-SL25-083, pit N13 is 12.6 cm west and 7.9 cm south of northeast corner mark. Physiography Relief Vegetation Drainage Parent material Al 0-7 inches 0-18 cm Lab. No. S29127 B21 7-42 inches 18-107 cm Lab. No. S29128 B22 42-50 inches 107-127 cm Lab. No. S29129 Diagnostic horizons Levee of Taia River on the lowest terrace. Nearly level. Secondary bush. Moderately well drained, but it may be flooded for 1 to 2 weeks at the height of the wet season. Clayey alluvium. Dark brown (10YR 4/3); silty clay; weak to moderate fine, medium, and coarse angular to subangular blocky, breaking into weak very fine, fine, and medium granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, smooth boundary to horizon below. Strong brown (7. SYR 5/6); clay with much mica; weak to moderate fine, medium, and coarse angular to subangular blocky, breaking into weak to moderate very fine, fine, and medium granular; friable; many fine, medium, and coarse pores; common fine, medium, and coarse roots; clear, smooth boundary to horizon below. Strong brown (7. SYR 5/6) with many fine and medium faint red (2. SYR 4/6) mottles; clay with much mica; weak to moderate fine, medium, and coarse angular to subangular blocky^ breaking into weak to moderate very fine, fine, and medium granular; friable; common fine, medium, and coarse pores; common fine, medium, and coarse roots. Ochric epipedon, 0-7 inches (0-18 cm) . Cambic horizon, 7-50 inches (18-127 cm). 113 Profile N13, Gbesebu silty clay Classification: Fluventic Udoxic Dystropept Illinois Lab. No. S29127 S29128 S29129 Depth of horizon (inches) 0-7 7-42 42-50 Horizon A^ B B Percent of entire sample > 2.0 mm 0 0 0 Particle-size distribution of < 2 mm (%) : Total sand 2.0-.05 mm 10.0 6.8 22.2 Coarse silt .05-. 02 mm 10.4 11.7 11.7 Fine silt .02-. 002 mm 33.8 27.9 24.1 Total silt .05-. 002 mm 44.2 39.6 35.8 Total Glay < .002 mm 45.8 53.6 42.0 Water-dispersible clay < .002 mm 10.4 15.2 1.5 Moisture: 1/3 atmos. (%) 45.1 38.3 28.6 15 atmos. (%) 23.3 23.3 15.5 Organic carbon (%) 4.47 1.01 0.42 Exchangeable cations (me/lOOg soil) : Ca 1.18 0.10 0.15 Mg 1.25 0.18 0.31 K 0.82 0.02 0.03 Na 0.25 0.05 0.06 Al 2.11 2.11 1.44 Cation-exch. capacity (me/lOOg) 19.51 8.64 6.43 Base saturation (%) 17.9 4.1 8.6 pH H20 3.9 4.6 4.4 pH KC1 3.7 3.7 3.7 Soil tests: K (Ibs/A) 92 65 98 P (Ibs/A) 13 12 12 P2(lbs/A) 18 18 21 Total P (ppm) 830 ... Total CaO(%) 0.276 0.177 0.224 Total Fe203(%) 6.82 6.84 6.14 Total K20(%) 1-54 1.56 1.71 114 Location Physiography Relief Vegetation Drainage Parent material Al 0-12 inches 0-30 cm Lab. No. S29114 A3 12-16 inches 30-41 cm Lab. No. S29115 B21t 16-24 inches 41-61 cm Lab. No. S29116 B22t 24-39 inches 61-99 cm Lab. No. S29117 B23t 39-56 inches 99-142 cm Lab. No. S29118 Diagnostic horizons Profile N70, Kania clay loam Description by J.C. Dijkerman on January 11, 1967 On proposed new experimental farm northwest of Njala University College. Pit N70 is located along traverse one, 739 feet (225 m) east of surveyor's stone SLS 21/64 BP/33. On aerial photograph 39-SL-25-083, pit N70 is 9.8 cm west and 4.6 cm south of north- east corner mark. In shallow drainageway on middle terrace of Taia River. Very gentle concave slope, in the center of drainageway. Tall grass. Imperfectly drained. Gravel-free alluvium. Black (10YR 2/1); clay loam; weak fine and medium subangular blocky, breaking into weak very fine and fine granular; firm; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, smooth boundary to horizon below. Dark grayish brown (10YR 4/2); clay loam; very weak fine, medium, and coarse subangular blocky; firm; many fine and medium pores; common fine and medium roots; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/4) with few, medium faint strong brown (7.5YR 5/6) mottles; clay; weak fine and very fine subangular blocky, breaking into very weak fine and very fine granular; firm; many fine and medium pores; common fine and medium roots; clear, smooth boundary to horizon below. Pale brown (2.5Y-10YR 6/3) with common medium and distinct red (2. SYR 4/8) mottles; clay; weak fine and very fine subangular blocky, breaking into weak fine and very fine granular; firm; common fine and medium pores; common fine and medium roots; gradual, smooth boundary to horizon below. Light brownish gray (2.5Y-10YR 6/2) with many medium and coarse prominent red (2.5Y 4/8) and yellowish-red (SYR 4/8) mottles that are slightly hard to crush; clay; weak to moderate fine and very fine subangular blocky, breaking into weak to moderate fine and very fine granular; friable; few fine and medium pores; few fine roots. Umbric epipedon, 0-12 inches (0-30 cm). Argillic horizon, 16-56 inches (41-142 cm) probable, but not fully documented. 115 Profile N70, Kania clay loam Classification: "Plinthic" Orthoxic Palehumult (or Plinthic Aquic Umbriorthox) Illinois Lab. No. Depth of horizon (inches) Horizon S29114 S29115 S29116 S29117 S29118 0-12 12-16 16-24 24-39 39-56 A! A3 B2u B22t B23t Percent of entire sample > 2.0 mm 0 0 0 0 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm , 0.2 0.1 0.2 0.1 1.3 Coarse sand 1.0-.5 mm , 0.4 0.5 0.3 0.3 0.9 Medium sand .5-. 25 mm , 1.8 1.4 0.9 0.9 0.9 Fine sand .25-.! mm , 22.1 22.7 14.4 12.8 9.9 Very fine sand . 1-.05 mm , 18.6 19.0 14.5 13.4 12.1 Total sand 2.0-.05 mm 43.1 43.7 30.3 27.5 25.1 Coarse silt .05-. 02 mm , 5.2 4.8 4.1 3.9 5.5 Fine silt .02-. 002 mm 18.3 15.9 12.1 12.5 13.5 Total silt .05-. 002 mm , 23.5 20.7 16.2 16.4 19.0 Total olay < .002 mm , 33.4 35.6 53.5 56.1 55.9 Water-dispersible clay < .002 mm , 15.4 26.4 1.0 0.8 0.7 Bulk density 1.2 1.4 1.4 1.5 1.6 Moisture: 1/3 atmos. (%) , 26.5 21.3 25.6 27.0 27.5 15 atmos. (%) 15.2 14.0 18.5 19.4 20.6 Avail, moist. -hold capacity3 0.14 0.10 0.10 0.11 0.11 Organic carbon (%) , 2.73 0.86 0.62 0.29 0.19 Exchangeable cations (me/lOOg soil): Ca 0.08 0.10 0.10 0.08 0.08 Mg 0.02 0.03 0.10 0.10 0.10 K 0.05 0.04 0.04 0.02 0.05 Na 0.06 0.04 0.05 0.05 0.03 Al 1.33 1.50 1.72 1.78 1.94 Cation-exch. capacity (me/lOOg) 11.07 4.21 6.36 6.79 7.00 Base saturation (%) 1.9 5.0 4.6 3.7 3.7 pH H20 5.0 4.7 4.8 5.0 5.0 pH KC1 4.2 3.9 3.9 3.8 3.8 Soil tests: K (Ibs/A) 65 48 43 48 48 P! (Ibs/A) 19 5 4 4 4 P2 (Ibs/A) 22 5 4 4 3 Total P (ppm) 340 . . . . . . Total CaO (%) 0.084 0.076 0.074 0.072 0.070 Total Fe203 (%) 1.50 1.60 2.48 3.04 4.26 Total K20 (%) 0.84 0.90 0.89 0.91 0.94 ainches of available moisture-holding capacity per inch of soil. 116 Profile 145041, Keya loamy coarse sand Description after Sivarajasingham (64) Location Physiography Relief Vegetation Drainage Parent material 0-5 inches 0-13 cm A12 5-11 inches 13-28 cm Lab. No. S28548 In the second swamp from Tundula on the new road to Baoma and Segbwema . Bottomland (swamp) . Nearly level . It was in swamp rice in 1965, and during 1966 it was under grass. Many of the cut raphia palms have grown to a height of about 6 feet (2 m). Very poorly drained. Water table was 38 inches (96 cm) below the surface on April 20, 1966. Valley fill over residuum from quartz-rich granitic bedrock. Grayish brown to dark grayish brown (2.5Y 5/2-4/2); loamy coarse sand; loose; structureless; few fine roots; presumably a layer of recent deposition; abrupt, smooth boundary to horizon below. Grayish brown to dark grayish brown (2.5Y 5/2-4/2); coarse sand; loose to soft; structureless, but held together by many fine roots; abrupt, smooth boundary to horizon below. 11-13 inches 28-33 cm 13-21 inches 33-53 cm IIIC, lg 21-33 inches 53-84 cm Lab. No. S28549 Grayish brown to dark grayish .brown (2.5Y 5/2-4/2); loamy coarse sand; loose; structureless; many fine and medium roots of raphia palms; almost all the medium-sized roots are growing horizontally; abrupt, smooth boundary to horizon below. Grayish brown to dark grayish brown (2.5Y 5/2-4/2); loamy coarse sand; loose; structureless; common fine and medium roots of raphia palm with most of the roots extending downward; gradual, wavy boundary to horizon below. White (N 8/ ) with grayish-brown (2.5Y 5/2) common coarse distinct mottles, presumably because of mixing from the A^ materials; coarse sandy loam; many fine and medium raphia palm roots growing down- ward; much coarse quartz gravel in the first 3 inches; the 21- to 24- inch layer is like a stone line; diffuse, irregular boundary to horizon below. IVC0 2g 33-48 inches 84-122 cm IVC,, 3g 48-60 inches 122-153 cm Diagnostic horizon White (N 8/ ) and greenish blue; common, very coarse, distinct patches of soft disintegrated quartz-rich rock with greenish color due to a powdery greenish-black mineral like chlorite, probably derived from mica and hornblende; many fine micaceous particles and white powdery feldspar grains; loam; common medium raphia palm roots growing downward. Same as IVC2g, but sandy loam instead of loam. Ochric epipedon, 0-21 inches (0-53 cm). 117 Profile 145041, Keya loamy coarse sand Classification: Fluventic Tropaquent Illinois Lab. No. S28548 S28549 Depth of horizon (inches) 5-11 21-33 Horizon Al2 IIIClg Percent of entire sample > 2.0 mm . . . 6.6 8.7 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm . . . 7.5 13.6 Coarse sand 1.0-.5 mm . . . 31.6 24.3 Medium sand .5-. 25 mm . . . 26.5 12.6 Fine sand .25-.! mm . . . 23.6 10.5 Very fine sand . 1-.05 mm . . . 4.7 6.3 Total sand 2.0-.05 mm . . . 94.1 67.4 Total silt .05-. 002 mm . . . 3.6 14.4 Total clay < .002 mm . . . 2.3 18.2 Water-dispersible clay < .002 mm . . . 0.4 15.4 Moisture: 1/3 atmos.(%) . . . 4.4 14.7 15 atmos.(%) . . . 2.7 8.2 Organic carbon(%) . . . 1.08 0.28 Exchangeable cations (me/lOOg soil) : Ca . . . 0.14 0.36 Mg . . . 0.07 0.30 K ... 0.04 0.10 Na ... 0.05 0.06 Al . . . 0.50 0.69 Cation-exch. capacity (me/lOOg) . . . 2.36 3.43 Base saturation (%) ... 12.7 23.9 pH H20 ... 4.5 5.0 pH KC1 ... 3.9 4.0 Soil tests: K (Ibs/A) ... 4 19 P! (Ibs/A) ... 4 62 P2 (Ibs/A) ... 4 76 Total P (ppm) ... 140 * • • Total CaO(%) ... 0.103 0.139 Total Fe203(%) Total K20(%) ... 0.10 . . . 0.708 0.70 1.370 118 Location Physiography Relief Vegetation Drainage Parent material 0-9 inches 0-23 cm Lab. No. S28568 B2t 9-39 inches 23-99 cm Lab. No. S28567 B3t 39-66 inches 99-168 cm Lab. No. S28566 66-68 inches 168-173 cm inc2 68-80 inches 173-203 cm Lab. No. S28565 Remarks Diagnostic horizons Profile 145042, Kparva sandy clay loam Description after Sivarajasingham (64) After the second swamp from Tundula, on the right-hand side of the new road from Tundula to Segbwema via Baoma, 30 feet (9 m) from the edge of the swamp. Undulating upland. Lower part of a long gentle slope of 3 percent. A 7-year old, high, slightly impenetrable bush with many short trees. Poorly drained. A thick layer of gravel-free, locally transported material. Very dark gray (10YR 3/1) to very dark grayish brown (10YR 3/2); sandy clay loam; strong medium and fine subangular blocky and fine angular; friable, nonsticky, nonplastic; many fine and medium roots, which in the top 2 inches form a dense mat of hori- zontal spreading roots; clear, smooth boundary to horizon below. Brownish yellow (10YR 6/8) with common, coarse, faint yellowish- brown (10YR 5/4) to light yellowish-brown (2.5Y 6/4) mottles, with darker fillings of brown to dark brown (10YR 4/3) material in old burrow channels; sandy clay; strong medium and fine sub- angular blocky, except that the darker material is strong fine granular; porous; friable, slightly sticky, slightly plastic; common fine and medium roots; gradual, smooth boundary to hori- zon below. White (2.5Y 8/2) with common, medium, prominent strong brown (7.5YR 5/6) and few, coarse, distinct brownish-yellow (10YR 6/8) mottles; sandy clay; moderate fine subangular blocky; porous; friable, slightly sticky, slightly plastic; the strong brown mottles are firm to hard and may be regarded as plinthite glaebules; few fine roots; abrupt, smooth boundary to horizon below. Stone line; yellow (10YR 7/8) with common, coarse, distinct white (2.5Y 8/2) mottles; gravelly clay loam; 40% quartz pebbles and 10% porous, medium, hardened plinthite glaebules. White (2.5Y 8/2) with common, coarse, distinct brownish-yellow (10YR 6/6) and yellow (10YR 7/6) mottles; sandy clay loam; mod- erate medium subangular blocky; firm to friable, sticky, slightly plastic; no roots. Water trickled through the stone line when all of the water in the pit was baled out. Depth of water table on April 20, 1966, was 56 inches (142 cm) . Ochric epipedon, 0-9 inches (0-23 cm). Argillic horizon, 9-66 inches (23-168 cm) probable, but not fully documented. Profile 145042, Kparva sandy clay loam Classification: Aquic Paleudult (or Aquic Tropeptic Haplorthox) 119 Illinois Lab. No. Depth of horizon (inches) Horizon S28568 0-9 S28567 9-39 B2t S28566 39-66 S28565 68-80 IIIC2 12.7 7.5 9.9 7.8 1 7 2 3 5 Percent of entire sample > 2.0 mm 4.7 5.0 12.1 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-l.Omm 4.5 6.4 9.6 Coarse sand 1.0-.5 mm 24.0 15.2 16.7 Medium sand .5-. 25 mm 15.9 10.8 8.5 Fine sand .25-.! mm 15.7 10.4 8.2 15. Very fine sand .1-.05 mm 6.6 5.6 5.1 10. Total sand 2.0-.05 mm 66.2 48.3 47.7 50. Total silt .05-. 002 mm 12.4 13.1 14.6 24. Total olay < .002 mm 21.4 38.6 37.7 25. Water-dispersible clay < .002 mm 4.8 22.1 0.6 4.4 Bulk density 1.1 1.2 1.2 Moisture: 1/3 atmos. (%) 15.2 19.8 22.0 38.0 15 atmos. (%) 11.0 14.3 16.0 14.0 Avail, moist. -hold, capacity3 0.05 0.07 0.06 Organic carbon (%) 2.64 0.46 0.29 0.32 Exchangeable cations (me/lOOg soil): Ca 0.26 0.06 0.06 0 Mg 0.23 0.06 0.18 0.18 K 0.15 0.04 0.06 0.08 Na 0.05 0.04 0.05 0.08 Al 2.28 2.39 1.11 0.96 Cation-exch. capacity (me/lOOg) 10.43 5.07 5.29 11.07 Base saturation (%) 6.6 3.9 6.6 3.1 PH H20 4.4 4.6 5.2 5.0 PH KC1 3.7 3.8 4.0 4.2 Soil tests: K (Ibs/A) 22 3 Pi (Ibs/A) 7 3 150 P2 (Ibs/A) 9 1 3 325 Total P (ppm) 370 ... . • • Total CaO (%) 0.098 0.079 0.085 0.158 Total Fe203 (%) 1-82 2.89 4.08 7.30 Total K20 (%) 0.436 0.488 0.593 1.480 ainches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 120 Location Physiography Relief Vegetation Drainage Parent material 11 0-7 inches 0-17 cm Lab. No. S29832 12 7-25 inches 17-63 cm Lab. No. S29833 25-39 inches 63-99 cm Lab. No. S29834 IIB2 39-65 inches 99-165 cm Lab. No. S29835 Diagnostic horizons Profile P71, Mabassia sandy clay loam, shallow phase Described by R. Miedema on May 15, 1968 Topographic map of Sierra Leone, scale 1:50,000, sheet 43, co- ordinates HE26.-85 ; along the Makeni to Mankane path. Little depression in the flat summit of a low hill. Slope, 0 to 3 percent. Secondary bush, 3 to 7 years old. Well drained. Gravel-free colluvium, over gravelly colluvium, over weathering products of Precambrian granite and acid gneiss. Very dark (grayish) brown (10YR 2.5/2); sandy clay loam; weak fine and medium angular to subangular blocky; friable, slightly sticky, and slightly plastic; many macro- and mesopores; com- mon distinct medium charcoal particles; common coarse and fine, many medium roots; very few fine and medium hardened plinthite glaebules; much ant and termite activity; clear, smooth boun- dary to horizon below. Dark brown (10YR 3/3); sandy clay loam; fine and medium subangu- lar blocky; firm, slightly sticky, and slightly plastic; many macro- and mesopores; common distinct medium charcoal particles; few coarse, many medium, and common fine roots; few fine and me- dium hardened plinthite glaebules; much ant and termite activity; clear, smooth boundary to horizon below. Yellowish brown to light olive brown (10YR 5/4-2. 5Y 5/4); gravel- ly sandy clay loam; weak fine and medium angular blocky; firm, slightly sticky, and slightly plastic; common macro- and many mesopores; common medium and fine roots; 20% uncoated, fine and medium, rounded and nodular, dense, red, hardened plinthite glaebules; common ant and termite activity; clear, smooth boun- dary to horizon below. Yellow (10YR 7/8); sandy clay loam; very weak fine and medium angular blocky; friable, slightly sticky, and slightly plastic; many macro- and mesopores; common distinct medium and fine reddish-yellow (7.5YR 7/8), strong brown (7. SYR 5/8), and red (10R 4/8) mottles; few medium and fine roots; 10% uncoated, fine and medium, rounded and nodular, dense, red, hardened plinthite glaebules; common ant and termite activity. Umbric epipedon, 0-25 inches (0-63 cm). Cambic horizon, 25-65 inches (63-165 cm). 121 Profile P71, Mabassia sandy clay loam, shallow phase Classification: "Plinthic" Udoxic Dystropept Illinois Lab. No. S29832 S29833 S29834 S29835 Depth of horizon (inches) 0-7 7-25 25-39 39-65 Horizon AH A12 HE! HB2 Percent of entire sample > 2.0 mm ...... 0 0 20.1 9.3 Particle-size distribution of < 2mm (%) : Very coarse sand 2.0-1.0 mm ....... 8.8 5.6 15.0 11.8 Coarse sand 1.0-.5 mm ........ 13.5 10.0 14.5 16.8 Medium sand .5-. 25 mm ....... 23.2 23.7 23.5 23.4 Fine sand .25-.! mm ........ 17.6 18.4 15.0 14.6 Very fine sand .l-.05mm ....... 4.4 4.2 3.4 3.4 Total sand 2.0-.05 mm ....... 67.5 61.9 71.4 70.0 Total silt .05-. 002 mm ....... 9.6 7.0 5.7 5.8 Total Glay < .002 mm ....... 22.9 31.1 22.9 24.2 Water-dispersible clay < .002 mm ...... 4.9 7.7 10.4 2.5 Moisture: 1/3 atmos. (%) .......... 17.7 15.7 12.9 13.7 15 atmos. (%) .......... 11.7 12.6 9.3 9.8 Organic carbon (%) ............. 3.55 1.64 0.82 0.55 Exchangeable cations (me/lOOg soil): Ca .................... 2.26 0.26 0.21 0.11 Mg ............... 0.73 0.27 0.11 0.10 K. ' ................... 0.27 0.03 0.03 0.07 Naa' '. .............. 0.27 0.05 0.05 0.10 A1 \ ................... 0.44 1.04 0.72 0.40 Cation-exch. capacity (me/lOOg) ....... 12.27 7.99 4.57 2.14 Base saturation (%) ............. 28.8 7.6 8.8 17.8 PH H20 ................... 5.1 4.8 4.8 4.7 PH KC1 ................... 4.3 4.2 4.2 4.2 Soil tests: K (Ibs/A) ................ 260 74 52 94 Pi (Ibs/A) ................ 24 Total CaO (%) ......... 0.325 0.100 0.083 0.081 Total FeoOo (%) .............. 5.69 6.50 5.57 4.91 Total K20 |%) ............... 0.525 0.467 0.421 0.502 aEstimated values. 122 Location Physiography Relief Vegetation Drainage Parent material 11 0-6 inches 0-14 cm Lab. No. S29836 12 6-13 inches 14-33 cm Lab. No. S29837 Bl 13-26 inches 33-65 cm Lab. No. S29838 B21t 26-35 inches 65-90 cm Lab. No. S29839 B22t 35-59 inches 90-150 cm Lab. No. S29840 Profile P108, Mabassia coarse sandy loam, deep phase Described by J.M. Cawray and R. Miedema on June 20, 1968 Topographic map of Sierra Leone, scale 1:50,000, sheet 43, co- ordinates HE197-8?6; along the Makeni to Pundung path. Summit of a low hill, gently sloping. Slope 3 percent to northwest. Medium bush with many wild oil palms. Well drained. Gravel-free colluvium. Very dark gray (10YR 3/1) ; coarse sandy loam; weak fine sub- angular blocky; slightly sticky, slightly plastic; friable; many macro- and mesopores; few medium distinct charcoal par- ticles; many fine, medium, and coarse roots; much termite, worm, and ant activity; clear, smooth boundary to horizon below. Very dark grayish brown (10YR 3/2); sandy clay loam; weak fine subangular blocky; friable, slightly sticky, slightly plastic; many macro- and mesopores; few medium distinct charcoal par- ticles; many fine, medium, and coarse roots; much termite, worm, and ant activity; gradual, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4); sandy clay; weak fine and medium subangular blocky; friable, slightly sticky, slightly plastic; many macro- and mesopores; many fine, medium, and coarse roots; much termite, worm, and ant activity; clear, smooth boundary to horizon below. Strong brown (7. SYR 5/6); sandy clay; weak fine and medium subangular blocky; friable, slightly sticky, slightly plastic; many macro- and mesopores; many fine, common medium, and few coarse roots; common termite, worm, and ant activity; gradual, smooth boundary to horizon below. Reddish yellow (7. SYR 6/8); sandy clay; weak fine and medium subangular blocky; friable, slightly sticky, slightly plastic; many macro- and mesopores; many fine, common medium, and few coarse roots; common termite, worm, and ant activity. Diagnostic horizons Umbric epipedon, 0-13 inches (0-33 cm) . Argillic horizon, 26-59 inches (65-150 cm) 123 Profile P108, Mabassia coarse sandy loam, deep phase Classification: Orthoxic Palehumult Illinois Lab. No. S29836 S29837 S29838 S29839 S29840 Depth of horizon (inches) 0-6 6-13 13-26 26-35 35-59 Horizon All A12 B! B21t B22t Percent of entire sample > 2.0 mm 0 0 0 0 0 Particle-size distribution of < 2mm (%) : Very coarse sand 2.0-1.0 mm 10.9 8.3 7.6 9.0 12.4 Coarse sand 1.0-.5 mm 19.7 16.4 15.7 13.7 14.0 Medium sand .5-. 25 mm 20.1 16.2 16.0 12.6 11.2 Fine sand .25-.! mm 15.7 13.4 12.8 11.2 10.1 Very fine sand .1-.05 mm 4.4 4.3 3.8 4.5 4.0 Total sand 2.0-.05 mm 70.8 58.6 55.9 51.0 51.7 Total silt .05-. 002 mm 9.3 9.5 8.8 10.0 10.0 Total clay < .002 mm 19.9 31.9 35.3 39.0 38.3 Water-dispersible clay < .002 mm 5.0 17.0 11.5 0.9 0.3 Bulk density 1.1 1.2 1.2 1.3 1.4 Moisture: 1/3 atmos. (%) 14.2 16.9 17.8 18.4 19.6 15 atmos. (%) 9.0 12.1 13.3 13.8 14.0 Avail, moist. -hold, capacity3 0.06 0.06 0.05 0.06 0.08 Organic carbon (%) 2.14 1.71 1.25 0.90 0.51 Exchangeable cations (me/lOOg soil): Ca 1.37 0.53 0.38 0.16 0.32 Mg 0.47 0.21 0 0.10 0.31 K 0.34 0.06 0.02 0.02 0.03 Nab 0.34 0.10 0.04 0.04 0.05 Al 0.49 0.98 1.04 0.70 0.21 Cation-exch. capacity (me/lOOg) 7.71 7.92 7.85 5.71 4.07 Base saturation (%) 32.7 11.4 5.6 5.6 17.4 pH H20 5.0 4.7 4.7 4.8 5.2 pH KC1 4.2 4.2 4.1 4.1 4.6 Soil tests: K (Ibs/A) 377 86 43 30 39 P! (Ibs/A) 16 7 7 6 4 Total CaO (%) 0.187 0.116 0.098 0.087 0.092 Total Fe203 (%) 6.64 10.12 11.47 12.00 11.56 Total K20 (%) 0.564 0.528 0.480 0.516 0.528 ^Inches of available moisture-holding capacity per inch of soil. ^Estimated values. 124 Profile P2, Makeni very gravelly sandy clay loam Described by W. van Vuure and R. Miedema on March 8, 1968 Location Physiography Relief Vegetation Drainage Parent material 0-10 inches 0-25 cm Lab. No. S29804 B21t 10-20 inches 25-50 cm Lab. No. S29805 B22t 20-67 inches 50-170 cm Lab. No. S29806 Diagnostic horizons Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE 27^-865; on traverse A, near augerhole 4. Dissected erosion surface, sloping. Slopes 14 percent to SSW and 10 percent to SE. Secondary bush, 4 to 10 years old. Well drained. Gravelly to very gravelly weathering products of Pre- cambrian granite and acid gneiss. Dark brown (10YR 3/3) ; very gravelly sandy clay loam; structure and consistence not observable because of gravel content; common macro- and many mesopores; few fine distinct charcoal mottles; common coarse, many medium and fine roots; common ant and termite activity; 74% uncoated, fine and medium, rounded, dense, red and yellow, hardened plinthite glaebules ; clear, smooth boundary to horizon below. Yellowish red (SYR 4/8); very gravelly clay; very weak, very fine angular blocky; consistence is not observable because of high gravel content; common macro- and meso- pores; common coarse, many medium and fine roots; low biological activity; 77% uncoated, fine and medium, rounded and nodular, dense, red and yellow, hardened plinthite glaebules; gradual, smooth boundary to horizon below. Yellowish red (SYR 5/8); very gravelly clay; very weak, very fine angular blocky; firm, slightly sticky and plastic; common macro- and mesopores; few medium, com- mon fine roots; 80% yellow-coated, medium and coarse, nodular and angular, dense, red, hardened plinthite glaebules, and a few very fine quartz gravels. Umbric epipedon, 0-10 inches (0-25 cm). Argillic horizon, 10-67 inches (25-170 cm). Profile P2, Makeni very gravelly sandy clay loam Classification: Typic Paleudult 125 Illinois Lab. No. Depth of horizon (inches) Horizon S29804 0-10 S29805 10-20 B21t S29806 20-67 B22t Percent of entire sample > 2.0 mm 74.1 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 6.8 Coarse sand 1.0-.5mm 5.7 Medium sand .5-. 25 mm 12.1 Fine sand .25-.! mm 20.7 Very fine sand .1-.05 mm 7.4 Total sand 2.0-.05 mm 52.7 Total silt .05-. 002 mm 14.2 Total clay < .002 mm 33.1 Water-dispersible clay < .002 mm 6.9 Bulk density 1.3 Moisture: 1/3 atmos. (%) 27.5 15 atmos. (%) 15.9 Avail, moist. -hold, capacity3 0.04 Organic carbon (%) 4.19 Exchangeable cations (me/lOOg soil): Ca 2.63 Mg 2.10 K 0.25 Na 0.10 Al 0.27 Cation-exch. capacity (me/lOOg) 14.14 Base saturation (%) 35.9 pH H20 5.2 pH KC1 4.4 Soil tests: K (Ibs/A) 194 P! (Ibs/A) 14 Total CaO(%) 0.397 Total Fe203(%) 9.97 Total K20(%) 0.375 76.7 7.8 3.2 5.1 9.3 5.2 30.6 13.2 56.2 18.6 1.4 28.4 21.7 0.02 1.87 0.21 0.84 0.04 0.09 1.05 8.14 14. 4. 4.2 65 3 0.087 15.57 0.282 81.1 4.7 3.1 4.5 7.3 4.9 24.5 23.7 51.8 1.7 1.5 30.4 23.7 0.02 1.13 0.68 0.79 0.03 0.06 0.16 5.28 29.5 5.2 4.6 30 1 0.105 16.60 0.268 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 126 Profile P104, Makundu clay Described by J. M. Cawray and R. Miedema on June 18, 1968 Location Physiography Relief Vegetation Drainage Parent material 0-8 inches 0-20 cm Lab. No. S29841 12 8-16 inches 20-41 cm Lab. No. S29842 AB 16-21 inches 41-53 cm Lab. No. S29843 Bl 21-28 inches 53-71 cm Lab. No. S29844 B21 28-43 inches 71-108 cm Lab. No. S29845 B22 43-74 inches 108-188 cm Lab. No. S29846 Diagnostic horizons Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE12^-912; 300 feet (91 m) from Mabole River, on the road from Makundu to the river. Nearly level river terrace. Concave, very gentle 1-percent slope to the south. Dense secondary bush, with many wild oil palms. Moderately well to well drained. Alluvium from the Mabole River. Very dark gray (10YR 3/1); clay; weak fine angular and subangular blocky; friable, slightly sticky, and slightly plastic; many macro- and mesopores; few medium distinct charcoal mottles; many coarse, medium, and fine roots; much ant, termite, and worm activity; clear, smooth boundary to horizon below. Very dark grayish brown to dark brown (10YR 3/2.5); clay; weak fine angular and subangular blocky; friable, slightly sticky, and slightly plastic; many macro- and mesopores; few medium dis- tinct charcoal mottles; many coarse, medium, and fine roots; much ant, termite, and worm activity; clear, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4); silty clay; weak fine angular and subangular blocky; friable, sticky, and plastic; many macro- and mesopores; few medium distinct charcoal mottles; many coarse, medium, and fine roots; much ant, termite, and worm activity; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/6); clay; moderate fine and medium angular and subangular blocky; firm, sticky, and plastic; many macro- and mesopores; few medium distinct charcoal mottles; few fine faint yellowish-red (SYR 4/6) mottles; common coarse, many medium and fine roots; much ant, termite, and worm activity; gradual, smooth boundary to horizon below. Brownish yellow (10YR 6/6); clay; moderate fine and medium angular and subangular blocky; firm, sticky, and plastic; common macro- and mesopores; common medium distinct yellowish-red (SYR 4/8) mottles; few medium, common fine roots; much ant, termite, and worm activity; gradual, wavy boundary to horizon below. Brownish yellow (10YR 6/6); clay; moderate angular and subangular blocky; firm, sticky, and plastic; common macro- and mesopores; many medium prominent yellowish-red (SYR 5/6) mottles; common fine roots; common ant, termite, and worm activity. Umbric epipedon, 0-16 inches (0-41 cm). Oxic horizon, 21-74 inches (53-188 cm). 127 Profile PI 04, Makundu clay Classification: Plinthic "Tropeptic" Umbriorthox Illinois Lab. No. Depth of horizon (inches) Horizon S29841 S29842 0-8 8-16 11 12 S29843 S29844 16-21 21-28 AB B, S29845 S29846 28-43 43-74 B 21 B 22 Percent of entire sample > 2.0 mm. . Particle-size distribution of < 2 mm Very coarse sand 2.0-1.0 mm. . . . Coarse sand 1.0-.5 mm . . . . Medium sand .5-. 25 mm. . . . Fine sand .25-.! mm .... 0 1 2 5 .8 .7 .2 .4 0 1 1 6 .4 .0 .7 .6 Very fine sand .1-.05 mm. . . . 5 .9 7 .9 Total sand 2.0-.05 mm. ... 16 .0 17 .6 8. 1 5 .4 4 .7 4.3 Total silt .05-. 002 mm ... 37 .1 35 .6 42. 1 34 .8 34 .0 35.3 Total clay < .002 mm ... 46 .9 46 .8 49. 8 59 .8 61 .3 60.4 Water-dispersible clay < .002 mm . . 12 .7 9 .0 27. 9 1 .3 0 .5 1.0 Bulk density 0 .8 0 .9 1. 0 1 .1 1 .2 1.3 Moisture" 1/3 atmos. (%) 43 .0 39 .7 36. 4 32 .4 32 .5 33.3 29 .1 28 .9 27. 1 25 .8 25 .8 25.2 Avail, moist. -hold, capacity .... 0 .11 0 .10 0. 09 0 .07 0 .08 0.11 Organic carbon (%) 5 .06 3 .62 2. 57 1 .40 0 .78 0.40 Exch. cations (me/lOOg soil): Ca 3.20 0.42 0.21 0.21 0.21 0.21 Me , 1.16 0.42 0.21 0.11 0.26 0.11 K 0.53 0.19 0.08 0.05 0.05 0.07 Lb. ::::::::::::::. 0.53 0.20 0.11 0.08 0.08 0.10 Al 0.41 1.35 1.94 1.69 0.81 1.04 Cation-exch. capacity (me/lOOg). . . 23.62 22.9 19.69 6.2 15.77 3.9 9.70 4.6 8.85 6.8 3.79 12.9 oH H 0 . 5.3 5.0 4.7 4.9 5.2 5.4 oH KC1 4.5 4.3 4.2 4.1 4.2 4.2 Soil tests: K (Ibs/A) 369 166 P^lbs/A) 18 12 Total CaO(%) 0.290 0.130 Total Fe203(%) 10.39 Total K20(%) 10.94 1.324 1.288 86 5 56 3 0.110 0.097 11.10 11.46 56 3 65 8 0.087 0.082 11.79 10.84 1.435 1.382 1.172 1.192 1Inches of available moisture-holding capacity per inch of soil. Estimated values. 128 Profile P8, Mankane sandy loam Described by W. van Vuure and J. M. Cawray on March 20, 1968 Location Physiography Relief Vegetation Drainage Parent material 0-6 inches 0-15 cm Lab. No. S29807 Bs 6-21 inches 15-54 cm Lab. No. S29808 g 21-25 inches 54-64 cm Lab. No. S29809 Diagnostic horizons Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE27»-87,; on traverse E, approximately 16 feet (5 m) from Mayankan stream bed. Valley bottom swamp. Concave, very gentle 1-percent slope to southeast. Grasses, rice, few raphia palms, and few wild oil palms. Very poorly drained. Gravel-free alluvium over kaolinitic residuum from quartz- rich granitic bedrock (Precambrian) . Dark gray (10YR 4/1) ; sandy loamj weak fine and medium subangular blocky; slightly sticky and plastic; many macro- and mesopores; many fine distinct root- rust mottles; many fine and few medium roots; clear, smooth boundary to horizon below. Gray to light gray (10YR 6/1) ; sandy loam; weak fine and medium angular blocky; slightly sticky and plastic; many macro- and mesopores ; many prominent fine and medium yellowish-red (SYR 5/8) plinthite mottles; few fine, common medium roots; gradual, smooth boundary to horizon below. Light brownish gray (10YR 6/2); loamy coarse sand; very weak fine and medium angular blocky; nonsticky, slightly plastic; many macro- and mesopores; many prominent fine and medium yellowish-red (5YR 5/8) , and yellowish-red to red (2. SYR 5/8-5YR 5/8) plinthite mottles; very few fine roots. Ochric epipedon, 0-6 inches (0-15 cm). Cambic horizon, 6-21 inches (15-54 cm). 129 Profile P8, Mankane sandy loam Classification: Plinthic Tropaquept Illinois Lab. No. Depth of horizon (inches) Horizon S29807 0-6 S29808 6-21 B8 S29809 21-25 Cg Percent of entire sample > 2.0 mm 1.0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 2.1 Coarse sand 1.0-.5 mm 8.9 Medium sand .5-. 25 mm 20.4 Fine sand .25-.! mm 28.8 Very fine sand . 1-.05 mm 11.0 Total sand 2.0-.05 mm 71.2 Total silt .05-. 002 mm 16.1 Total alay < .002 mm 12.7 Water-dispersible clay < .002 mm 4.3 Bulk density 1.0 Moisture: 1/3 atmos.(%) 16.5 15 atmos.(%) 7.2 Avail, moist. -hold, capacity3 0.09 Organic carbon(%) 1.79 Exchangeable cations (me/lOOg soil) : Ca 0.21 Mg 0.42 K 0.03 Na 0.10 Al 0.77 Cation-exch. capacity (me/lOOg) 4.21 Base saturation (%) 18.1 pH H20 4.6 pH KC1 4.2 Soil tests: K (Ibs/A) 65 P! (Ibs/A) 9 Total CaO(%) 0.108 Total Fe203(%) 2.24 Total K20 (%) 2.023 1.5 4.1 13.0 ,5 ,7 ,3 23, 24, 8. 73.6 13.4 13.0 12.3 1.3 12.2 6.2 0.08 0.55 0.16 0.26 0.02 0.08 0.40 2.43 21.4 4.9 4.1 48 3 0.094 2.12 2.080 0.8 4.9 16.5 27.5 24.9 6.7 80.5 9.1 10.4 10.4 1.4 9.3 4.7 0.06 0.43 0.16 0.21 0.01 0.07 0.33 1.79 25.1 4.9 4.1 43 10 0.088 0.54 1.402 ^Inches of available moisture-holding capacity per inch of soil. 130 Location Physiography Relief Vegetation Drainage Parent material Al 0-10 inches 0-25 cm Lab. No. S 28558 10-21 inches 25-53 cm Lab. No. S28557 B21 21-35 inches 53-89 cm B22t 35-70 inches 89-178 cm Lab. No. S28556 Remarks Diagnostic horizons Profile Kpuabu 1, Manowa sandy clay loam Description after Sivarajasingham (64) Kpuabu Cocoa Experiment Station; about 450 feet (137 m) from the Kenema-Joru road on the road to the Station Office, and about 150 feet (46 m) on the right-hand side from the Station Office road. Accordant, flat-topped hill of the dissected lateritic upland. Upper, convex 5-percent slope. Cocoa plantation under many tall trees of original secondary vegetation; good grass cover. Moderately well drained. A thin layer of gravel-free material over a thick, very gravel- ly layer of locally transported material. Very dark grayish brown (10YR 3/2); sandy clay loam; moderate medium and fine subangular blocky; porous; friable, slightly sticky, slightly plastic; common fine, few medium, and very few coarse roots; clear, smooth boundary to horizon below. Dark brown (10YR 3/3); very gravelly sandy clay; 70% yellow- coated, nodular, coarse and medium, dense, red and yellow, hard- ened plinthite glaebules; weak fine subangular blocky aggregates with no strong interface; friable, sticky, slightly plastic; few fine and very few medium roots; gradual, smooth boundary to horizon below. Dark yellowish brown to yellowish brown (10YR 4/4-5/6); very gravelly sandy clay; 60% yellow-coated and uncoated, round, fine, dense, red and black, hardened plinthite glaebules; weak fine subangular blocky aggregates with no strong interface; fri- able, sticky, slightly plastic; very few fine and medium roots; gradual, smooth boundary to horizon below. Strong brown (7. SYR 5/8); very gravelly clay; 75% yellow-coated, nodular, coarse, dense, red and yellow, hardened plinthite glaebules; weak fine subangular blocky aggregates with no strong interface; porous; friable, sticky, slightly plastic; very few fine and medium roots. This soil is very gravelly and droughty and would be expected to be unsuitable for cocoa. The cocoa planted in 1959 appears as stunted trees of very poor health, with many vacant patches because of low survival rate of the planted seedlings. Manage- ment is very good, but shade appears to be excessive. Umbric epipedon, 0-21 inches (0-53 cm). Argillic horizon, 21-70 inches (53-178 cm) probable, but not fully documented. 131 Profile Kpuabu 1, Manowa sandy clay loam Classification: Orthoxic Palehumult (or Typic Umbriorthox) Illinois Lab. No. S28558 S28557 S28556 Depth of horizon (inches) 0-10 10-21 35-70 Horizon A. A aVolume percent of total sample estimated in the field. Inches of available moisture amount of > 2.0 mm material. o Percent of entire sample > 2.0 mm ...... 0 70 75 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm ........ 3.3 3.4 3.3 Coarse sand 1.0-.5 mm ......... 9.0 7.1 9.2 Medium sand .5-. 25 mm ........ 12.1 9.8 7.7 Fine sand .25-.! mm ......... 22.8 19.6 11.5 Very fine sand .1-.05 mm ........ 10.2 9.5 7.7 Total sand 2.0-.05 mm ........ 57.4 49.2 38.9 Total silt .05-. 002 mm ........ 11.8 12.4 13.3 Total clay < .002 mm ........ 30.8 38.4 47.8 Water-dispersible clay < .002 mm ....... 2.9 3.9 0.6 Bulk density .................... 1.4 1.5 Moisture: 1/3 atmos. (%) .......... 18.8 17.1 22.0 15 atmos. (%) . ........ 12.6 13.3 17.6 Avail, moist. -hold, capacity ........... 0.02 0.02 Organic carbon (%) .............. 2.69 1.90 0.71 Exchangeable cations (me/lOOg soil) : Ca ..................... 0.01 0.07 0 Mg ..................... 0.10 0.08 0.08 K ..................... 0.10 0.07 0.06 Na ..................... 0.04 0.05 0.04 Al ..................... 3.06 2.50 0.67 Cation-exch. capacity (me/lOOg) ....... 11.79 9.29 6.00 Base saturation (%) ............. 2.1 2.9 3.0 PH H20 .................... 4.3 4.5 4.8 PH KC1 .................... 3.8 3.9 4.2 Soil tests: K (Ibs/A) ................. 9 3 1 ................. 5 0 P2(lbs/A) ................. 8 4 2 Total P (ppm) ................ 390 370 Total CaO(%) ................. 0.076 0.074 0.069 Total Fe203(%) ................ 8.10 8.99 11.19 Total K20(%) ................. 0.169 0.180 0.215 Inches of available moisture-holding capacity per inch of soil, adjusted for the 132 Profile P49, Masheka sandy loam Described by J. M. Cawray, A. A. Thomas, and R. Miedema on April 9, 1968 Location Physiography Relief Vegetation Drainage Parent material 11 0-16 inches 0-40 cm Lab. No. S29823 12 16-26 inches 40-65 cm Lab. No. S29824 B21 26-38 inches 65-96 cm Lab. No. S29825 B22 38-54 inches 96-137 cm 54-68 inches 137-173 cm Lab. No. S29826 Diagnostic horizons Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE25R-86q. Gently sloping, old tributary terrace. Slope 4 percent east toward swamp. Upland farm of pigeon peas, with nearby vegetation of tall elephant grass and many wild oil palms . Well drained. Gravel-free colluvium or alluvium or a mixture of both, over weathering products of Precambrian granite and acid gneiss. Very dark brown (10YR 2/2); sandy loam; weak fine and medium subangular blocky; slightly hard, friable, slightly sticky, and slightly plastic; few fine distinct charcoal particles; many fine, medium, and coarse roots; much termite and ant activity, few worm holes; gradual, smooth boundary to horizon below. Very dark grayish brown (10YR 3/2); sandy clay loam; weak medium subangular blocky; slightly hard, friable, slightly sticky, slightly plastic; many macro- and mesopores ; many fine, common medium and coarse roots; much termite and ant activity, common worm holes; clear, smooth boundary to horizon below. Brown to dark brown (10YR 4/3); sandy clay loam; weak medium and coarse angular blocky; slightly hard, friable, slightly sticky, and slightly plastic; many macro- and mesopores; few medium prominent charcoal particles; many fine, common medium and coarse roots; much termite and ant activity, and common worm activity; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/6) ; sandy clay loam; weak medium and coarse angular blocky; slightly hard, friable, slightly sticky, and plastic; common macro- and mesopores; few fine faint yellowish-red (SYR 4/8) mottles; common fine and medium, few coarse roots; common termite, ant, and worm activity; clear, smooth boundary to horizon below. Yellow (2.5Y 7/6); gravelly sandy clay loam; weak medium and coarse angular blocky; friable, slightly sticky, and plastic; common macro- and mesopores; many medium prominent yellowish- red (5YR 4/6) mottles; common fine, few medium roots; common termite, ant, and worm activity; 39% fine, uncoated, red, hardened plinthite glaebules, and a few quartz gravels. Umbric epipedon, 0-26 inches (0-65 cm) . Argillic horizon, 54-68 inches (137-173 cm) probable, but not fully documented. Profile P49, Masheka sandy loam Classification: Orthoxic Palehumult (or Udoxic Dystropept) 133 Illinois Lab. No. Depth of horizon (inches) Horizon S29823 0-16 S29824 16-26 A12 S29825 26-38 B21 S29826 54-68 Percent of entire sample > 2.0 mm 0 0 0 39.0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 5.8 4.7 7.1 9.4 Coarse sand 1.0-.5 mm 15.8 11.9 15.4 13.4 Medium sand .5-. 25 mm 29.7 25.3 23.5 19.4 Fine sand .25-.! mm 18.3 18.8 15.4 12.9 Very fine sand .l-.05mm 4.3 5.3 4.6 4.3 Total sand 2.0-.05 mm 73.9 66.0 66.0 59.4 Total silt .05-. 002 mm 9.7 9.0 9.6 12.2 Total alay < .002 mm 16.4 25.0 24.4 28.4 Water-dispersible clay < .002 mm 3.7 7.4 13.4 1.6 Bulk density 1.1 1.2 1.3 Moisture: 1/3 atmos. (%) 14.5 12.2 12.0 13.4 15 atmos. (%) 9.0 9.2 10.0 10.8 Avail, moist. -hold, capacity 0.06 0.04 0.03 ... Organic carbon (%) 2.96 1.17 0.70 0.47 Exchangeable cations (me/lOOg soil) : Ca 1.89 0.26 0.11 0.05 Mg 0.47 0.21 0.15 0.16 K 0.11 0.03 0.02 0.03 Nab 0.12 0.06 0.05 0.05 Al 0.33 1.28 1.04 0.75 Cation-exch. capacity (me/lOOg) 8.79 5.86 4.07 3.99 Base saturation (%) 29.5 9.6 8.1 7.3 PH H20 5.4 4.5 4.5 5.0 PH KC1 4.6 4.1 4.0 4.1 Soil tests: K (Ibs/A) 125 56 48 52 P1(lbs/A) 17 6 5 Total CaO(%) 0.305 0.095 0.094 0.078 Total Fe203(%) 3.23 3.98 3.55 4.64 Total K20(%) 1-092 1.076 1.041 1.157 ^Inches of available moisture-holding capacity per inch of soil. Estimated values. 134 Profile P9, Masuba sandy clay loam Described by R. Miedema and A. A. Thomas on March 20, 1968 Location Physiography Relief Vegetation Drainage Parent material 0-7 inches 0-19 cm Lab. No. S29810 Bl 7-22 inches 19-57 cm Lab. No. S29811 B2 22-67 inches 57-170 cm Lab. No. S29812 Diagnostic horizons Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE27R-872; on traverse E, 525 feet (160 m) from profile P8. Lower part of stream terrace near valley edge. Slope 0 to 3 percent. Farm with cassava, Kandi trees and weeds, and many wild oil palms. Moderately well drained. Gravel-free, transported alluvial/colluvial material. Very dark grayish brown (10YR 3/2) ; sandy clay loam; weak fine to medium angular blocky; very hard; common macro- and many mesopores ; few distinct fine charcoal mottles; many coarse, medium, and fine roots; many large and medium ant holes; clear, smooth boundary to horizon below. Pale brown (10YR 6/3) ; sandy clay loam; weak fine to medium angular blocky; very hard; many macro- and mesopores; few distinct fine charcoal mottles; common fine distinct reddish-yellow to strong brown (7.5YR 5.5/8) to red (2. SYR 5/8) mottles; common coarse, many medium and fine roots; less than 10% uncoated, nodular, coarse, porous, red, hardened plinthite glaebules, with few quartz grains; many large and medium ant holes; gradual, smooth boundary to horizon below. Very pale brown (10YR 6.5/3); sandy clay loam; weak fine angular blocky; firm; many macro- and mesopores; many distinct fine and medium yellowish-red (SYR 5/8) and reddish-yellow (7. SYR 6/8) mottles; common distinct fine and medium charcoal mottles; few coarse, common medium, and many fine roots; less than 10% gravel, similar to B-^ horizon, and one quartz stone; common worm holes with dark coatings. Ochric epipedon, 0-7 inches (0-19 cm). Cambic horizon, 7-67 inches (19-170 cm). 135 Profile P9, Masuba sandy clay loam Classification: "Plinthic" Udoxic Dystropept Illinois Lab. No. Depth of horizon (inches) Horizon S29810 0-7 S29811 7-22 Bi S29812 22-67 B2 Percent of entire sample > 2.0 mm 0.9 Particle-size distribution of < 2 mm (%) : . . . Very coarse sand 2.0-1.0 mm 3.7 Coarse sand 1.0-.5 mm 19.1 Medium sand .5-. 25 mm 20.9 Fine sand .25-.! mm 14.1 Very fine sand . 1-.05 mm 6.2 Total sand 2.0-.05 mm 64.0 Total silt .05-. 002 mm 12.6 Total clay < .002 mm 23.4 Water-dispersible clay < .002 mm 14.5 Bulk density 1.1 Moisture: 1/3 atmos.(%) 15.8 15 atmos.(%) '. . . . 10.1 Avail, moist. -hold. capacitya 0.06 Organic carbon (%) 1.25 Exchangeable cations (me/lOOg soil) : Ca 0.47 Mg 0.37 K 0.03 Na 0.08 Al 0.99 Cation-exch. capacity (me/lOOg) 5.71 Base saturation (%) 16.6 pH H20 4.7 pH KC1 4.1 Soil tests: K (Ibs/A) 60 P! (Ibs/A) 8 Total CaO(%) 0.133 Total Fe203(%) 2-67 Total K20(%) 1-361 1.8 4.8 18.1 18.2 12.5 6.0 59.6 13.6 26.8 14.5 1.3 15.1 10.1 0.06 0.62 0.16 0.16 0.02 0.08 1.09 3.79 11.1 4.6 4.0 65 3 0.078 3.13 1.277 2.0 5.7 20.9 17.6 10.9 5.3 60.4 13.9 25.7 2.5 1.3 15.7 10.3 0.07 0.51 0.21 0.16 0.01 0.08 1.05 3.14 14.6 4.8 4.0 43 3 0.078 3.18 1.200 ainches of available moisture-holding capacity per inch of soil. 136 Location Physiography Relief Vegetation Drainage Parent material 0-6 inches 0-15 cm Lab. No. S28555 B21 6-21 inches 15-53 cm Lab. No. S28554 B22 21-31 inches 53-79 cm B3 31-59 inches 79-150 cm Lab. No. S28553 lg 59-71 inches 150-180 cm Diagnostic horizons Profile Kpuabu 3, Moa clay Description after Sivarajasingham (64) Kpuabu Cocoa Experiment Station; near the path from the nursery buildings to the wooden bridge over the stream. Bottomland (river terrace) . Middle of a narrow, level terrace adjoining a stream whose bed has incised about 10 feet (3 m) below the terrace surface. A thick stand of cocoa planted in 1960, with dense foliage form- ing a close canopy under adequate shade of many tall trees of the original secondary forest. Moderately good. The land may be flooded two or three times a year for durations of one or two weeks . Flood water drains rapidly from the surface layers, but even during the height of the dry season the water table is encountered within 6 or 7 feet (2 m) below the surface. A thick layer of clayey river alluvium. Very dark grayish brown (10YR 3/2); clay; strong fine subangu- lar blocky and fine granular; porous; friable, slightly sticky, slightly plastic; termites and earthworms present; many fine and medium roots; clear, smooth boundary to horizon below. Strong brown to dark brown and brown (7.5YR 5/6-4/4); clay; strong fine subangular blocky; porous; friable, sticky, slightly plastic; common fine and medium roots; gradual, smooth boundary to horizon below. Strong brown (7. SYR 5/6-5/8) with few, fine, distinct yellowish- red (SYR 4/8) to red (2. SYR 4/8) mottles; clay; strong medium and fine subangular blocky; porous; friable, sticky, slightly plastic; common fine and medium roots; gradual, smooth boundary to horizon below. Brownish yellow (10YR 6/8) with few, medium distinct strong brown (7. SYR 5/8) and red (2. SYR 4/8) mottles; yellow (2.5Y 7/6) mottles are more numerous with increasing depth; clay; strong medium subangular blocky; porous; friable, sticky, slightly plastic; few fine and medium roots; gradual, smooth boundary to horizon below. Mottled white (N 8/ ), yellow (2.5Y 7/6), yellowish brown (10YR 5/8), and strong brown (7. SYR 5/6) in a variegated pattern; sandy clay; wet; massive clods; the strong brown mottles are firm to hard and may be considered as incipient plinthite glaebules. Ochric epipedon, 0-6 inches (0-15 cm). Oxic horizon, 21-59 inches (53-150 cm) probable, but not fully documented . 137 Profile Kpuabu 3, Moa clay Classification: Tropeptic Haplorthox (or Fluventic Udoxic Dystropept) Illinois Lab. No. Depth of horizon (inches) Horizon S28555 0-6 S28554 6-21 B21 S28553 31-59 B3 Percent of entire sample >2.0mm 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 2.3 Coarse sand 1.0-.5 mm 5.1 Medium sand .5-. 25 mm 7.0 Fine sand .25-.! mm 14.8 Very fine sand . 1-.05 mm 7.9 Total sand 2.0-.05 mm 37.2 Total silt .05-. 002 mm 22.2 Total clay < .002 mm 40.6 Water-dispersible clay < .002 mm 14.4 Bulk density 0.7 Moisture: 1/3 atmos.(%) 27.8 15 atmos.(%) 18.4 Avail, moist. -hold, capacity3 0.07 Organic carbon (%) 2.98 Exchangeable cations (me/lOOg soil) : Ca 0.61 Mg 0.23 K 0.14 Na 0.05 Al 2.78 Cation-exch. capacity (me/lOOg) 13.79 Base saturation (%) 7.5 PH H20 4-5 pH KC1 3-8 Soil tests: K (Ibs/A) P! (Ibs/A) P2 (Ibs/A) 7 Total P (ppm) 44° Total CaO(%) °-146 Total Fe203(%) 7.38 Total K20(%) °-570 2.3 1.7 5.0 5.1 11.7 7.7 31, 20 48 9.4 0.8 26.6 19.3 0.06 0.91 0.06 0.08 0.09 0.08 1.78 7.94 3.9 4.6 3.8 8 1 2 320 0.097 8.35 0.557 5.3 2.6 5.3 5.3 11.4 6.8 31.3 19.8 48.9 0.3 1.3 27.6 20.4 0.09 0.41 0.06 0.21 0.07 0.05 1.17 6.50 6.0 5.1 4.0 10 1 7 0.078 8.98 0.519 ainches of available moisture-holding capacity per inch of soil. 138 Profile N14, Mokoli silty clay Described by J. C. Dijkerman on April 1, 1966 Location Physiography Relief Vegetation Drainage Parent material Al 0-6 inches 0-15 cm Lab. No. S29123 6-15 inches 15-38 cm Lab. No. S29124 B21 15-27 inches 38-68 cm Lab. No. S29125 B22 27-60 inches 68-153 cm Lab. No. S29126 Diagnostic horizons On the proposed new experimental farm northwest of the Njala University College Campus, pit N14 is located 422 feet (129 m) east of the Taia River and 53 feet (16 m) south of the path from Nyawama to Rover. On aerial photograph 39-SL25-083, pit N14 is 12.4 cm west and 7.4 cm south of northeast corner mark. Drainageway in lower terrace of Taia River. Very gentle concave, in middle of drainageway. Water- loving bushes and low grasses. Poorly drained; waterlogged for three months. Clayey alluvium. Very dark grayish brown (10YR 3/2); silty clay; moder- ate fine and medium subangular blocky, breaking into moderate medium granular; friable; common fine and medium pores; common fine and medium roots; clear, smooth boundary to horizon below. Yellowish brown to dark brown (10YR 5/4-4/3) with common fine faint soft reddish-brown (SYR 4/4) mottles; clay; strong medium to very fine subangular blocky; friable; common fine and medium pores; common fine and medium roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/4) with common medium distinct yellowish-red (5YR 5/6) mottles; clay, with much mica; strong medium to fine blocky; friable? common fine and medium pores; few fine and medium roots; diffuse, smooth boundary to horizon below. Light yellowish brown (10YR 6/4) with many medium distinct yellowish-red and reddish-brown (SYR 5/6 and 2. SYR 4/4) mottles; clay, with much mica; strong med- ium to fine blocky; friable; common fine and medium pores; few fine and medium roots. Ochric epipedon, 0-15 inches (0-38 cm). Cambic horizon, 15-60 inches (38-153 cm). 139 Profile N14, Mokoli silty clay Classification: Fluventic Udoxic Dystropept Illinois Lab. No. S29123 S29124 S29125 S29126 Depth of horizon (inches) 0-6 6-15 15-27 27-60 Horizon Al A3 B2i B22 Percent of entire sample > 2.0 mm , . . 0 0 0 0 Particle-size distribution of < 2 mm (%) : Total sand 2.0-.05 mm . . 2.8 1.7 1.9 5.3 Coarse silt .05-. 02 mm . . 2.4 5.6 4.0 8.0 Fine silt .02-. 002 mm . . 37.6 26.1 31.4 30.3 Total silt .05-. 002 mm . . 40.0 31.7 35.4 38.3 Total clay < .002 mm . . 57.2 66.6 62.7 56.4 Water-dispersible clay < .002 mm . . 32.2 50.4 2.2 1.0 Bulk density . . 1.3 1.3 1.3 1.4 Moisture: 1/3 atmos.(%) . . 44.4 34.5 35.2 34.7 15 atmos. (%) . . 28.2 27.2 27.6 25.9 Avail, moist. -hold, capacity3 . . 0.21 0.09 0.10 0.12 Organic carbon (%) . . 5.54 1.50 0.65 0.55 Exchangeable cations (me/lOOg soil) : Ca . . 0.31 0.10 0.08 0.13 Mg . . 0.33 0.08 0.25 0.46 K . . 0.12 0.01 0.01 0.02 Na . . 0.10 0.04 0.04 0.05 Al . . 2.89 2.61 2.05 1.61 Cation-exch. capacity (me/lOOg) . . 22.58 11.57 9.07 8.43 Base saturation (%) . . 3.8 2.0 4.2 7.8 pH H20 . . 4.5 4.6 4.8 5.0 pH KC1 , , 3.7 3.6 3.7 3.7 Soil tests: K (Ibs/A) . .116 48 35 56 P! (Ibs/A) . . 35 5 8 9 P2 (Ibs/A) . . 45 7 15 17 Total P (ppm) . .820 • • • Total CaO(%) . . 0.152 0.117 0.113 0.141 Total Fe203(%) Total K20(%) . . 4.57 . . 1.14 5.98 1.13 7.52 1.18 7.73 1.23 alnches of available moisture-holding capacity per inch of soil 140 Location Physiography Relief Vegetation Drainage Parent material 0-5 inches 0-13 cm Lab. No. S28648 5-15 inches 13-38 cm Lab. No. S29732 15-30 inches 38-76 cm Lab. No. S 28649 IIIB22 30-39 inches 76-99 cm Lab. No. S29734 IIIB23 39-60 inches 99-153 cm Lab. No. S28650 IIIB24 60-67 inches 153-170 cm Lab. No. S29736 Diagnostic horizons Profile N42, Mokonde fine sandy loam Described by J. C. Dijkerman on March 23, 1966 On proposed new experimental farm northwest of Njala University College Campus; a few feet east of path from Bonjema to Belebu, 2,550 feet (777 m) north of junction of this path with path toward Gbesebu. Colluvial footslope or upper river terrace. Upper part of a straight 2- to 3-percent slope. Secondary farm bush. Moderately well drained. Gravel-free colluvium, over gravelly colluvium, over residual material. Very dark gray (10YR 3/1) ; fine sandy loam; weak fine and medium subangular blocky, breaking to weak medium to fine granular; friable; common medium and fine, and few coarse roots; many pores of all sizes; gradual, smooth boundary to horizon below. Dark grayish brown (10YR 4/2) to dark brown (10YR 4/3); fine sandy loam with a few clean quartz grains; weak fine and medium subangular blocky, breaking to weak fine and medium granular; friable; common fine and medium, and few coarse roots; common fine and medium pores; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/4); very gravelly (60% by volume) sandy clay loam; gravels are mainly irregular to round, 1/4" to 1/2" in diameter, dense, red- dish-black to dusky red (10R 2/1-3/2) hardened plinthite glaebules ; common quartz pebbles; massive to fine and very fine weak granular; firm in place but friable to crush; common medium and fine roots; common medium and fine pores; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/4-5/6) with many prominent medium and coarse red (10R 4/4-2. SYR 4/6) and yellowish-red (SYR 4/6) mottles, most of which are hard to crush (gravel) ; gravelly (40%) sandy clay loam; gravels are irregu- lar, 1/4" to 3/4" in diameter, nondense, hardened plinthite glaebules with colors described under mottles; massive to very weak medium and fine angu- lar blocky; firm and hard in place; friable to crush except for hardened mot- tles; common medium and fine roots; common pores of all sizes; gradual, smooth boundary to horizon below. Light yellowish brown (2.5Y 6/4) to brownish yellow (10YR 6/6) with many prominent medium and coarse red (10R 4/4-2. SYR 4/6) and yellowish-red (SYR 4/6) mottles, most of which are hard to crush (gravel); gravelly (40%) sandy clay loam; gravels as in IIIB-- horizon; massive; very firm and very hard; common medium and fine roots; common pores of all sizes; gradual, smooth boundary to horizon below. Light brownish gray (2.5Y 6/2-6/3) with many prominent medium and coarse red (10R 4/4-2. SYR 4/6) and yellowish-red (SYR 4/6) mottles, most of which are hard to crush (gravel) ; gravelly (30%) clay loam; gravels as in IIIB22 hori- zon; massive to weak medium and fine angular blocky; firm and hard; few medium and fine roots; common pores of all sizes. Ochrlc epipedon, 0-15 inches (0-38 cm). Argillic horizon, 15-67 inches (38-170 cm) probable, but not fully docu- mented. 141 Profile N42, Mokonde fine sandy loam Classification: Plinthic Paleudult (or "Plinthic" Udoxic Dystropept) Illinois Lab. No. Depth of horizon (inches) Horizon S28648 S29732 S28649 S29734 S28650 S29736 0-5 5-15 15-30 30-39 39-60 60-67 IIB 21 IIIB22 IIIB23 Percent of entire sample > 2.0 mm. . . . 1 5 55 55 53 40 Particle-size distribution of < 2 mm (%) : . . 5. 4 1. 0 15. 7 1 .6 19. 7 1.3 Coarse sand 1.0-.5 mm . . . . . . 8. 6 10. 6 9. 1 13 .7 8. 1 13.9 Medium sand .5-. 25 mm. . . . . . 10. 5 10. 8 7. 0 8 .5 4. 7 7.9 Fine sand .25-.! mm .... . . 25. 0 21. 7 15. 4 13 .0 8. 3 10.7 Very fine sand .1-.05 mm. . . . . . 15. 9 14. 8 11. 2 10 .1 7. 1 8.8 Total sand 2.0-.05 mm ... . . 65. 4 58. 9 58. 4 46 .9 47. 9 42.6 Total silt .05-. 002 mm ... . . 22. 7 21. 9 17. 8 18 .9 19. 8 22.3 Total clay < .002 mm . . . . . 11. 9 19. 2 23. 8 34 .2 32. 3 35.1 Water-dispersible clay < .002 mm . . . . 9. 2 12. 5 23. 6 27 .8 10. 1 1.7 . . 1. 4 1. 4 1. 5 1 .7 1. 8 1.8 Moisture: 1/3 atmos. (%) . . 15. 4 15. 3 14. 8 21 .3 17. 0 22.5 15 atmos. (%) . . 7. 1 7. 5 10. 0 13 .2 12. 4 14.5 . . 0. 12 0. 10 0. 03 0 .06 0. 04 0.08 Organic carbon (%) , , 1. 70 0. 83 0. 49 0 .48 0. 28 0.21 Exchangeable cations (me/lOOg soil) : Ca . . 0. 46 0. 08 0. 03 0 .20 0. 04 0.13 Mg . . 0. 27 0. 10 0. 07 0 .03 0. 13 0.13 K . . 0. 10 0. 04 0. 06 0 .05 0. 06 0.04 Na . . 0. 04 0. 06 0. 03 0 .08 0. 03 0.04 Al . . 2. 00 0. 95 1. 89 1 .77 2. 50 4.22 . . 7. 29 4. 79 4. 36 6 .57 6. 14 10.07 Base saturation (%) . . 11. 9 5. 8 4. 4 5 .5 4. 2 3.4 pH H20 . . 4. 5 4. 4 4. 7 4 .6 4. 9 4.9 pH KC1 3. 6 3. 7 3. 7 3 .6 3. 5 3.4 Soil tests: K (Ibs/A) . . 102 65 65 65 69 55 P,(lbs/A) . . 12 6 3 1 1 1 P2(lbs/A) . . 12 6 3 1 1 1 Total P (ppm) 144 78 100 148 142 182 Total CaO(%) . . 0. 109 , , . 0. 069 4 . . 0. 067 . . . Total Fe203(%) , . 1. 60 •• • 3. 81 * '* 13 Total K20(%) , . 0. 375 * t i • 0. 662 • • * 0. 933 t • • alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 142 Profile N123, Momenga gravelly clay Described by H. Breteler on January 18, 1967 Location Extreme southwestern corner of the Oil Palm Station of Njala University College. From the junction of the Kania boundary road and the path along the river near surveyor stone No. PB-B 829, 111 feet (34 m) down the steep slope towards the Taia River. Pit N123 is on the lower part of the steep slope. Physiography Escarpment of higher erosion surface towards the river. Relief Lower part of very steep (54-percent) slope. Vegetation Drainage Parent material Old secondary bush. Well drained. Colluvial material high in hardened plinthite glaebules, over residual material from weathering siltstone. 0-3 inches 0-8 cm Lab. No. S29058 Dark yellowish brown (10YR 4/4); gravelly (50% by volume) clay; gravels are mainly round, 1/4" to 1/2" in diameter, hardened plinthite glaebules with out- side colors of dark brown (7.5YR 2/3) and inside colors of dark red to red (10R 3/6-4/8); very weak fine and medium angular to subangular blocky, breaking to weak very fine granular; friable; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. 3-9 inches 8-23 cm Lab. No. S29060 Strong brown (7.5YR 5/6); gravelly (50%) clay; gravels are mainly round and nod- ular hardened plinthite glaebules similar to those in the A^ horizon; weak very fine and fine angular to subangular blocky, breaking into weak to moderate very fine and fine granular; friable; common fine, medium, and coarse roots; many fine, medium, and coarse pores; gradual, smooth boundary to horizon below. B2 9-33 inches 23-84 cm Lab. No. S29062 Yellowish red (SYR 5/6) with common fine, medium, and coarse, slightly hard, dis- tinct dark red to red (10R 3/6-4/8) mottles, and few fine, medium, and coarse, distinct white (N 8/ ) rock mottles (saprolite); gravelly (25%) clay; gravels are mainly angular, round and nodular, hardened plinthite glaebules, 1/3" to 3" in diameter, with outside colors of dark red to black and inside colors of dark red to red (10R 3/6-4/8); some quartz gravels; weak to moderate fine, medium, and coarse angular to subangular blocky, breaking into weak to moderate very fine and fine granular; friable; common fine, medium, and coarse roots; many fine, medium, and coarse pores; gradual, smooth boundary to horizon below. 33-40 inches 84-102 cm Lab. No. S29064 Reddish yellow (7.5YR 6/7) with many fine, medium, and coarse, slightly hard and soft, distinct dark red (10R 3/6) mottles, and common fine, medium, and coarse, distinct white (N 8/ ) rock mottles (saprolite); gravelly clay with a few hard- ened plinthite glaebules similar to those in the 82 horizon; weak to moderate fine and medium angular blocky, breaking into weak to moderate very fine and fine granular; friable; common fine, medium, and coarse pores; few fine and me- dium roots; gradual, smooth boundary to horizon below. IIC 40-62 inches 102-157 cm Lab. No. S29065 White (N 8/ ) with few fine, medium, and coarse, distinct dark red to red (10R 3/6-4/8) mottles, and many fine, medium, and coarse yellow (10YR 8/6-7/6) mot- tles; silty clay; very weak fine angular blocky, breaking into weak to moderate very fine and fine granular; firm; common fine and medium pores; few fine roots. This horizon is a transition zone to the unweathered bedrock (soft siltstone); more than 50% of this horizon consists of soft white (N 8/ ) weathering bedrock (saprolite) . Diagnostic horizons Ochric epipedon, 0-9 inches (0-23 cm). Gamble horizon, 9-40 inches (23-102 cm). 143 Profile N123, Momenga gravelly clay Classification: "Plinthic" Dystropept Illinois Lab. No. S29058 S29060 S29062 S29064 S29065 Depth of horizon (inches) 0-3 3-9 9-33 33-40 40-62 Horizon Al A3 B2 IIB3 IIC Percent of entire sample > 2.0 mm. . . . 34.6 37.2 30.8 34.6 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 5.9 4.5 4.3 2.5 0.1 Coarse sand 1.0-.5 mm 4.4 3.2 3.1 2.0 0.1 Medium sand .5-. 2 5 mm 4.2 3.0 2.6 1.7 0.2 Fine sand .25-.! mm 6.9 5.2 4.2 2.5 0.3 Very fine sand . 1-.05 mm 4.8 4.7 4.2 3.0 1.6 Total sand 2.0-.05 mm 26.2 20.6 18.4 11.7 2.3 Coarse silt .05-. 02 mm 3.4 3.6 3.0 2.6 3.8 Fine silt .02-. 002 mm 25.8 22.0 24.2 33.5 52.6 Total silt .05-. 002 mm 29.2 25.6 27.2 36.1 56.4 Total clay < .002 mm 44.6 53.8 54.4 52.2 40.6 Water-dispersible clay < .002 mm. . . . 25.6 38.6 38.0 39.5 28.6 Bulk density 1.4 1.6 1.5 1.5 1.5 Moisture: 1/3 atmos. (%) 33.5 29.8 30.2 33.6 37.7 15 atmos. (%) 21.2 21.0 21.1 20.5 10.5 Avail, moist. -hold, capacity3 0.11 0.09 0.10 0.13 0.41 Organic carbon (%) 3.94 1.32 0.54 0.31 0.06 Exchangeable cations (me/lOOg soil) : Ca 0.84 0.20 0.10 0.05 0.05 Mg 0.77 0.47 0.16 . . . 0.80 K 0.24 0.07 0.06 0.05 0.04 Na 0.08 0.06 0.04 0.04 0.04 Al 6.11 6.44 8.44 12.78 9.11 Cation-exch. capacity (me/lOOg) 21.08 15.29 15.65 20.36 13.00 Base saturation (%) ... 9.2 5.2 2.3 . . . 7.2 pH H20 4.1 4.2 4.4 4.6 4.2 pH KC1 3.2 3.4 3.3 3.1 3.0 Soil tests: K (Ibs/A) 182 110 65 48 35 Pi (Ibs/A) 29 6 2 3 2 P2 (Ibs/A) 32 7 2 3 2 Total P (ppm) 440 Total CaO(%) 0.168 0.077 0.070 0.067 0.062 Total Fe203(%) 5.26 5.43 5.46 5.02 2.47 Total K20(%) 1.76 1.82 2.10 2.56 3.32 alnches of available moisture-holding capacity per inch of soil, amount of > 2.0 mm material. adjusted for the 144 Location Physiography Relief Vegetation Drainage Parent material 0-6 inches 0-15 cm Lab. No. S29135 6-16 inches 15-41 cm Lab. No. S29137 Bl 16-24 inches 41-61 cm Lab. No. S29139 Profile N86, Momenga gravelly sandy clay loam Described by D.H. Westerveld on January 23, 1967 On proposed new experimental farm northwest of Njala University College Cam- pus. Pit N86 is along the north boundary traverse of the farm, about 1,000 feet (305 m) east of the Taia River. On escarpment from second terrace toward upland. Straight, steep 15-percent slope. Secondary bush. Well drained . Colluvium high in hardened plinthite glaebules and quartz gravel, over re- siduum weathered from bedrock. Very dark grayish brown (10YR 3/2) ; gravelly sandy clay loam; one-third of the gravel is rounded quartz, and two-thirds is round and nodular, 1/4" to 3" in diameter, hardened plinthite glaebules, reddish black (10R 2/1) out- side and dusky red (10R 3/2-3/4) inside; moderate to weak fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown to strong brown (10YR-7.5YR 5/6); gravelly sandy clay loam; gravel is similar to that in the A-^ horizon except that half is hardened plinthite glaebules and half is rounded quartz; weak fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Strong brown (7. SYR 5/8); gravelly clay, with gravel similar to that in the A3 horizon; weak fine, medium, and coarse granular; friable; many fine, me- dium, and coarse pores; common fine and medium roots; clear, wavy boundary to horizon below. 24-38 inches 61-96 cm Lab. No. S29141 38-50 inches 96-127 cm Lab. No. S29143 IIB3 50-63 inches 127-160 cm Lab. No. S29145 Diagnostic horizons Reddish yellow (7. SYR 6/8) with few fine and medium brownish-yellow (10YR 6/8) and red (2. SYR 4/8) mottles; gravelly clay; half of the gravel is angular quartz (part of a residual vein), and half is round and nodular, 1/4" to 1" in diameter, hardened plinthite glaebules, red (10R 4/6-4/8) outside and inside; weak to moderate fine and medium angular to subangular blocky, breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, me- dium, and coarse pores; few fine roots; gradual, smooth boundary to horizon below. Reddish yellow (7. SYR 6/8) with many fine and medium distinct red (2. SYR 4/8) mottles, and few fine and medium faint yellow (10YR 7/6) mottles; gravelly clay, with gravel similar to that in the HB2i horizon; weak to moderate fine and medium angular to subangular blocky, breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; few fine roots; gradual, smooth boundary to horizon below. Yellow (10YR 7/6) with many fine and medium distinct red (2. SYR 4/8) and com- mon fine and medium faint dark yellowish-brown (10YR 4/8) mottles, and few fine and medium faint saprolitic white (N 8/ ) mottles; gravelly clay, with gravel similar to that in the IT-^21 horizon; weak fine and medium angular to subangular blocky, breaking into weak fine, medium, and coarse granular; fri- able; many fine, medium, and coarse pores; few fine roots. Ochric epipedon, 0-16 inches (0-41 cm). Cambic horizon, 16-63 inches (41-160 cm). 145 Profile N86, Momenga gravelly sandy clay loam Classification: "Plinthic" Dystropept Illinois Lab. No. Depth of horizon (inches) S29135 0-6 S29137 6-16 S29139 16-24 S29141 24-38 S29143 38-50 S29145 50-63 Horizon Al A3 Bl IIB21 IIB22 IIB3 Percent of entire sample > 2.0 mm. . . . 42. 0 37 .1 42 .9 30 .5 34.9 37.9 Particle-size distribution of < 2 mm (%) : Very coarse sand 2 .0-1.0 mm 18. 1 26 .7 14 .5 9 .3 7.6 5.1 Coarse sand 1 .0-.5 mm 6. 6 9 .1 7 .9 5 .9 5.1 4.2 Medium sand .5-. 25 mm 4. 3 3 .7 4 .1 3 .6 3.1 2.8 Fine sand 25-. 1 mm 10. 6 6 .8 6 .4 5 .7 4.9 4.6 Very fine sand .1-.05 mm 7. 5 5 .0 4 .9 4 .8 5.0 4.8 Total sand 2 .0-.05 mm 47. 1 51 .3 37 .8 29 .3 25.7 21.5 Total silt 05-. 002 mm 27. 7 18 .3 21 .1 25 .3 27.7 30.7 Total olay < .002 mm 25. 2 30 .4 41 .1 45 .4 46.6 47.8 Water-dispersible clay < .002 mm .... 18. 9 26 .3 31 .3 15 .8 19.8 21.2 Moisture: 1/3 atmos. (%) 22. 1 19 .2 23 .9 27 .8 30.8 33.7 15 atmos. (%) 12. 9 12 .4 16 .5 18 .3 19.7 20.8 Organic carbon (%) . 2. 26 1 .04 0 .60 0 .36 0.34 0.25 Exchangeable cations (me/lOOg soil) : Ca 1. 08 0 .23 0 .28 0 .18 0.13 0.18 Mg 0. 48 0 .21 0 .23 0 .23 0.33 0.26 K 0. 11 0 .04 0 .04 0 .04 0.04 0.04 Na 0. 05 0 .04 0 .04 0 .04 0.05 0.04 Al 3. 00 3 .67 4 .22 6 .67 8.67 11.10 Cation-exch. capacity (me/lOOg) 12. 15 8 .72 10 .15 12 .50 15.22 17.08 Base saturation (%) . 14. 2 6 .0 5 .8 3 .9 3.6 3.0 pH H20 4. 3 4 .3 4 .4 4 .5 4.6 4.7 pH KC1 3. 4 3 .3 3 .3 3 .3 3.3 3.2 Soil tests: K (Ibs/A) 174 99 102 74 74 78 P! (Ibs/A) .... 8 3 2 1 1 1 P2 (Ibs/A) .... 8 4 3 1 1 1 Total P (ppm). . . . 180 ... ... Total CaO(%). . . . 0. 152 0 .078 0 .080 0 .071 0.067 0.068 Total Fe203(%). . . 3. 80 4 .42 5 .82 6 .18 6.96 6.68 Total K20(%). . . . 1. 48 1 .56 1 .93 2 .15 2.26 2.49 146 Profile N44, Momenga gravelly fine sandy loam Described by J. C. Dijkerman on March 23, 1966 Location Physiography Relief Vegetation Drainage Parent material 0-7 inches 0-18 cm Lab. No. S28645 7-15 inches 18-38 cm Lab. No. S29728 B2! 15-33 inches 38-84 cm Lab. No. S28646 33-42 inches 84-107 cm Lab. No. S29729 IIB23 42-57 inches 107-145 cm Lab. No. S28647 [IB24 57-69 inches 145-175 cm Lab. No. S29730 Diagnostic horizons On proposed new experimental farm northwest of Njala University College Cam- pus. Pit N44 is a few feet west of path from Bonjema to Belebu, about 3,700 feet (1,128 m) north of junction of this path with the path toward Gbesebu. Dissected upland erosion surface. Convex 5-percent slope, near the crest of a distinct ridge. Secondary farm bush. Well drained. Colluvial material high in hardened plinthite glaebules, over residual mate- rial weathered from bedrock. Very dark grayish brown (10YR 3/2); gravelly fine sandy loam; gravel is main- ly irregular to round, 1/4" to 1/2" in diameter, dense, reddish-black to dusky red (10R 2/1-3/2) hardened plinthite glaebules, plus some quartz grav- el; weak fine and very fine granular; friable; common medium and fine roots; common pores of all sizes; gradual, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4) ; very gravelly clay loam, with gravel similar to that in the AI horizon; weak fine and very fine granular; friable; common medium and fine roots; common pores of all sizes; clear, irregular lower boundary with tongues, 1 to 2 inches wide, going down to the middle of the horizon below. Yellowish red (SYR 5/6-4/6); very gravelly clay; gravel is mainly round to irregular, 1/4" to 3/4" in diameter, nondense, red (10R 4/4-4/6) hardened plinthite glaebules, plus some quartz gravel; weak medium to very fine sub- angular blocky; firm in place but friable to crush; common medium and fine roots; common pores of all sizes; clear, smooth boundary to horizon below. Yellowish red (SYR 4/6-5/6) with common, medium and coarse, slightly hard to hard, distinct red (10R-2.5YR 4/6) mottles, and few medium and fine, soft, distinct brownish-yellow (10YR 6/6) mottles; gravelly clay, with gravel that is nondense, irregular, hardened plinthite mottles; moderate fine and very fine angular blocky; firm in place but friable to crush; common medium and fine roots; common pores of all sizes; gradual, smooth boundary to horizon below. Mixed yellowish red (SYR 5/6) and reddish yellow (7. SYR 6/6) with many, me- dium and coarse, distinct red (2. SYR 4/6) mostly hard mottles, and common, medium and fine, distinct brownish-yellow (10YR 6/6) soft mottles; gravelly clay, with gravel similar to that in the IIB22 horizon; moderate medium to very fine angular blocky; slightly firm in place, friable to crush; common medium and fine roots; common pores of all sizes; gradual, smooth boundary to horizon below. Reddish yellow (7. SYR 7/6) to yellow (10YR 7/6), with many coarse prominent red (2. SYR 4/6) mostly hard mottles, and common, medium and fine, pale yellow (2.5Y 8/4) soft mottles; clay, with gravel similar to that in the IIB22 hor- izon; strong medium to very fine angular blocky; slightly firm in place, friable to crush; few fine roots; common pores of all sizes. Augering to a depth of 120 inches (305 cm) revealed a gradual decrease in the matrix chroma to light gray (10YR 7/1) with small pieces of weathered siltstone (the local bedrock) below 100 inches (254 cm) . Ochric epipedon, 0-15 inches (0-38 cm) . Cambic horizon, 15-69 inches (38-175 cm) . 147 Profile N44, Momenga gravelly fine sandy loam Classification: "Plinthic" Dystropept Illinois Lab. No. Depth of horizon (inches) Horizon S28645 0-7 Al S29728 7-15 A3 S28646 15-33 B21 S29729 33-42 IIB22 S28647 42-57 IIB23 S29730 57-69 IIB24 Percent of entire sample > 2.0 mm . . Particle-size distribution of < 2 mm ( Very coarse sand 2.0-1.0 mm. ... Coarse sand 1.0-.5 mm . . . . Medium sand .5-. 2 5 mm. . . . Fine sand .25-.! mm .... Very fine sand .1-.05 mm. . . . Total sand 2.0-.05 mm. . . . Total silt .05-. 002 mm ... Total clay < .002 mm ... Water-dispersible clay < .002 mm . . Moisture: 1/3 atmos. (%) 51 %): 8.1 6.9 7.5 21.4 15.6 59.5 21.3 19.2 3.1 75 1.0 7.8 5.2 15.1 14.3 43.4 22.9 33.7 13.9 63 13.4 4.1 2.2 4.0 4.4 28.1 20.1 51.8 38.8 40 0.5 7.0 4.3 6.2 6.5 24.5 21.9 53.6 25.2 32.2 35 6.3 3.1 1.8 3.7 4.9 19.8 27.1 53.1 8.6 31.2 16 0.6 7.2 4.7 6.3 7.2 26.0 27.7 46.6 3.0 33.3 15 atmos. (%) 24.0 23.0 21.2 Organic carbon (%) 3.35 1.45 0.68 0.52 0.35 0.23 Exchangeable cations (me/lOOg soil) : Ca 3.77 0.36 0.03 0.15 0.06 0.18 Me. 1.15 0.29 0.31 0.13 0.22 0.10 K 0.18 0.09 0.11 0.08 0.11 0.10 Na 0,07 0.09 0.03 0.08 0.03 0.14 Al 0.77 3.89 8.44 7.78 12.78 12.67 Cation-exch. capacity (me/lOOg) . . . 13.50 38.3 9.30 8.9 12.50 3.8 17.30 2.5 17.58 2.4 • • • pH H?0. 5.0 4.7 4.7 5.0 4.9 5.2 pH KC1 4.0 3.3 3.4 3.3 3.4 Soil tests: K (Ibs/A) 174 126 106 106 102 86 Pi (Ibs/A) . 15 4 0 1 0 1 P? (Ibs/A) . 16 6 2 1 1 1 202 138 138 135 127 127 Total CaO(%) 0.327 0.067 0.064 * • • Total Fe203(%) 4.09 8.73 11.00 Total K?0(%) 0.773 • 1.860 • • • 2.160 • • • 148 Location Physiography Relief Vegetation Drainage Parent material 0-14 inches 0-35 cm Lab. No. S29072 A3 14-21 inches 35-53 cm Lab. No. S29074 B21t 21-49 inches 53-125 cm Lab. No. S 290 76 B22t 49-62 inches 125-157 cm Lab. No. S29078 Diagnostic horizons Profile N109, Njala gravelly clay loam Described by H. Breteler on December 29, 1966 Southwestern corner of the Oil Palm Station of Njala University College. From the junction of the Kania boundary road and the village path to Pujehun, 84 feet (26 m) along the boundary line uphill towards the Taia River. Pit N109 is located between palms 1155 and 993. Dissected erosion surface; on the slope between the highest erosion surface and the upper river terrace. Lower part of convex 8-percent slope, on mapping unit 3, Njala, sloping. Oil palm plantation. Well drained. Colluvial material high in hardened plinthite glaebules. Dark brown (10YR 3/3); very gravelly (70% by volume) clay loam; gravels are mainly round and nodular, 1/4" to 1/2" in diameter, hardened plin- thite glaebules with outside colors of yellowish red (SYR 4/6) and in- side colors of yellowish red and very dusky red (SYR 4/6, 4/8, 5/8, and 10R 2/2); weak to moderate very fine and fine subangular blocky, break- ing into very weak, very fine granular; very friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. This A., horizon is thick enough and just dark enough to qualify as an umbric epipedon (see Section 4) . Most pro- files of Njala soils have thinner or lighter colored A horizons, which are ochric rather than umbric. Dark yellowish brown (10YR 4/4); very gravelly (80%) clay; gravels are mainly round and nodular, 1/4" to 3" in diameter, hardened plinthite glaebules with outside colors of yellowish red and very dusky red (SYR 5/8 and 10R 2/2) and inside colors of dark red, red, and reddish yellow (10R 3/6, 4/8, and 7. SYR 6/8); weak very fine, fine, and medium subangu- lar blocky, breaking into weak to moderate very fine, fine, and medium granular; very friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Strong brown (7. SYR 5/8); very gravelly (70%) clay; gravels are mainly round and nodular, 1/4" to 3" in diameter, hardened plinthite glaebules with outside colors of red (2. SYR 4/8-5/8) and inside colors of red and very dusky red (10R 4/6 and 2/2); very weak fine, medium, and coarse angular to subangular blocky, breaking into weak to moderate very fine and fine granular; friable; many fine, medium, and coarse pores; common fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish red (SYR 5/8); gravelly (50%) clay; gravels are mainly round and nodular, 1/4" to 1" in diameter, hardened plinthite glaebules with outside colors of yellowish red (5YR 5/8) and inside colors of red and very dusky red (10R 4/6 and 2/2); very weak fine, medium, and coarse angular to subangular blocky, breaking into weak to moderate very fine and fine granular; friable; common fine, medium, and coarse pores; common fine, medium, and coarse roots. Umbric epipedon, 0-14 inches (0-35 cm). Argillic horizon, 21-62 inches (53-157 cm). Profile N109, Njala gravelly clay loam Classification: Orthoxic Palehumult 149 Illinois Lab. No. Depth of horizon (inches) Horizon S29072 0-14 A, S29074 14-21 S29076 21-49 B21t S29078 49-62 B22t Percent of entire sample > 2.0 mm 47.2 45.2 40.4 35.6 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 5.4 7.4 7.2 7.0 Coarse sand 1.0-.5 mm 4.6 3.6 3.6 3.0 Medium sand .5-. 25 mm 7.1 3.1 2.4 2.0 Fine sand .25-.! mm 16.4 9.0 5.2 4.2 Very fine sand .1-.05 mm 9.1 9.0 5.8 5.5 Total sand 2.0-.05 mm 42.6 32.1 24.2 21.7 Coarse silt .05-. 02 mm 5.3 4.1 3.7 4.1 Fine silt .02-. 002 mm 16.4 13.2 11.6 15.5 Total silt .05-. 002 mm 21.7 17.3 15.3 19.6 Total clay < .002 mm 35.7 50.6 60.5 58.7 Water-dispersible clay < .002 mm 15.7 41.4 27.5 1.5 Bulk density ... 1.5 1.6 Moisture: 1/3 atmos. (%) 23.3 25.4 26.3 15 atmos. (%) 19.9 21.4 22.0 Avail, moist. -hold, capacity ... 0.04 0.05 Organic carbon (%) 2.78 1.31 0.68 0.46 Exchangeable cations (me/lOOg soil): Ca 0.36 0.15 0.28 0.28 Mg 0.28 0.16 0.23 0.21 K 0.06 0.02 0.04 0.03 Na 0.06 0.05 0.04 0.03 Al 3.00 2.94 1.72 1.83 Cation-exch. capacity (me/lOOg) 13.22 9.65 7.72 7.43 Base saturation (%) 5.7 3.9 7.6 7.4 pH H20 4.5 4.6 4.8 4.8 pH KC1 3.8 3.8 3.7 3.6 Soil tests: K (Ibs/A) 98 78 65 43 P1(lbs/A) 10 4 3 3 P2(lbs/A) 12 4 3 3 Total P (ppm) 274 226 229 181 Total CaO(%) 0.113 0.081 0.083 0.077 Total Fe20 (%) 5.09 5.86 6.80 6.90 Total K20(%) 0.74 0.84 ... 1.15 Inches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 150 Location Physiography Relief Vegetation Drainage Parent material 0-4 inches 0-10 cm Lab. No. S29080 Profile N108, Njala gravelly fine sandy loam Described by D.H. Westerveld on December 12, 1966 Oil Palm Station of Njala University College, adjacent to the south boundai road and 1,874 feet (571 m) northwest of Kania. Upper (third) river terrace, near the upland. Very gentle, slightly concave slope. Secondary bush. Moderately well drained. Colluvial material, high in hardened plinthite glaebules and quartz, over residual material weathered from bedrock. Very dark grayish brown (10YR 3/2); gravelly fine sandy loam; weak fine anc medium angular to subangular blocky, breaking into weak to moderate fine ai medium granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, smooth boundary to horizon below. 4-14 inches 10-35 cm Lab. No. S29082 [IBlt 14-24 inches 35-61 cm Lab. No. S29084 IB21t 24-35 inches 61-89 cm Lab. No. S29086 IIIB22 35-57 inches 89-145 cm Lab. No. S29088 Diagnostic horizons Dark yellowish brown (10YR 4/4) ; gravelly sandy clay loam; most of the el is round and angular, 1/4" to 1" in diameter, hardened plinthite glae- bules, dark reddish brown (SYR 2/2) outside and weak red (2. SYR 4/2) insidi and the rest is rounded quartz gravel; very weak fine and medium angular t( subangular blocky, breaking to weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, wavy boundary to horizon below. Yellowish brown (10YR 5/6) to reddish yellow (7. SYR 6/8) and strong brown (7. SYR 5/8) with few fine distinct light red to red (2. SYR 6/8-5/8) mottle! gravelly sandy clay loam, with gravel similar to that in the IIA3 horizon except that two-thirds is hardened plinthite glaebules and one-third is rounded quartz gravel; very weak fine, medium, and coarse angular to suban] ular blocky, breaking into weak to moderate fine, medium, and coarse granu- lar; friable; many fine, medium, and coarse pores; common fine, medium, an< coarse roots; gradual, wavy boundary to horizon below. Yellowish brown (10YR 5/8) with common medium distinct red (2. SYR 4/8) mot- tles and few fine faint brownish-yellow (10YR 6/8) and dark brown (10YR 3/1 mottles; gravelly clay loam; half of the gravel is rounded quartz, and hall is nodular and angular, 1/4" to 1" in diameter, hardened plinthite glae- bules, strong brown (7 . 5YR 5/6) outside and red (2. SYR 4/8) inside; weak fine, medium, and coarse angular to subangular blocky, breaking into weak I moderate fine, medium, and coarse granular; friable; many fine, medium, an< coarse pores; few fine and medium roots; gradual, wavy boundary to horizon below. Brownish yellow (10YR 6/6) with many medium and coarse prominent red (2.5Y1 4/8) mottles and few medium faint brownish-yellow (10YR 6/8) and yellowish- brown (10YR 5/4) mottles; gravelly clay loam, with gravel similar to that : the IIB2it horizon but mostly red (2. SYR 4/8) hardened plinthite glaebules with only a few rounded quartz gravels; very weak fine and medium angular 1 subangular blocky, breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; few fine and mediut roots. Ochric epipedon, 0-14 inches (0-35 cm). Argillic horizon, 14-57 inches (35-145 cm). 151 Profile N108, Njala gravelly fine sandy loam Classification: Plinthic Paleudult Illinois Lab. No. S29080 S29082 S29084 S29086 S29088 Depth of horizon (inches) 0-4 4-14 14-24 24-35 35-57 Horizon Al IIA3 IIBlt IIB21t IIIB22 Percent of entire sample > 2.0 mm. . . . 38.6 38.7 36.8 36.8 43.1 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 4.3 12.4 8.9 8.1 9.6 Coarse sand 1.0-.5 mm 6.0 5.2 8.2 7.4 6.9 Medium sand .5-. 25 mm 12.4 6.7 6.5 5.3 4.6 Fine sand .25-.! mm 24.6 17.8 13.8 9.9 8.8 9.6 12.0 11.0 9.6 9.7 Total sand 2.0-.05 mm 56.9 54.1 48.4 40.3 39.6 Total silt .05-. 002 mm 23.9 21.4 21.8 21.1 23.4 Total clay < .002 mm 19.2 24.5 29.8 38.6 37.0 Water-dispersible clay < .002 mm .... 3.7 8.7 25.2 2.5 Moisture: 1/3 atmos. (%) 20.2 17.9 • • • 20.3 21.5 15 atmos. (%) 8.6 8.9 . . . 13.5 14.9 Organic carbon (%) 3.05 1.22 0.71 0.54 0.33 Exchangeable cations (me/lOOg soil) : Ca 0.33 0.10 0.10 0.07 0.07 Mg 0.13 0.13 0.08 0.06 0.13 K 0.05 0.02 0.05 0.07 0.02 Na 0.06 0.04 0.04 0.03 0.03 Al 2.72 1.94 1.61 1.44 1.33 Cation-exch. capacity (me/lOOg) 10.65 6.50 5.14 6.00 6.72 Base saturation (%) 5.4 4.5 5.3 3.8 3.7 pH H20 4.0 4.4 4.6 4.4 4.5 pH KC1 3.5 3.8 3.6 3.6 Soil tests: K (Ibs/A) 126 86 90 98 60 P-L (Ibs/A) 16 6 5 4 2 P2 (Ibs/A) 16 6 5 4 2 Total P (ppm) 149 110 129 ... Total CaO(%) 0.090 0.081 0.074 0.070 0.068 Total Fe203(%) 1.89 2.47 2.97 5.56 7.98 Total K90(%) 0.53 0.63 0.76 0.94 1.08 152 Location Physiography Relief Vegetation Drainage Parent material Al 0-21 inches 0-53 cm Lab. No. S29102 21-31 inches 53-79 cm Lab. No. S29103 B21 31-42 inches 79-107 cm Lab. No. S29104 B22t 42-60 inches 107-153 cm Lab. No. S29105 Diagnostic horizons Profile N100, Nyawama sandy clay loam Described by H. Breteler on December 2, 1966 Near the office of the Oil Palm Station at Njala University College. After crossing the Taia River, the main road (planted with coconut palms) goes northwest until it turns toward the office; pit N100 is located 470 feet (143 m) southwest from this turn in the road, and 32 feet (10 m) northwest from the middle of the road between palms 70, 71, and 117. On aerial photograph 39-SL25-083, pit N100 is 8.2 cm west and 7.8 cm south of north- east corner mark. Second terrace of Taia River. Very gentle, convex slope. Oil palm plantation. Moderately well drained. Gravel-free alluvium. Very dark grayish brown (10YR 3/2); sandy clay loam; weak fine, medium, and coarse subangular blocky, breaking into weak very fine, fine, and medium granular; firm; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Dark brown (10YR 3/3); sandy clay loam; weak fine, medium, and coarse angular to subangular blocky, breaking into very weak fine and medium granular; friable; many fine, medium, and coarse pores; common fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/4) with common fine distinct yellowish- red (SYR 5/8) mottles; sandy clay loam; very weak fine, medium, and coarse angular to subangular blocky, breaking into very weak fine and medium granular; firm; many fine, medium, and coarse pores; common fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/4) with many fine and medium distinct yellowish-red (5YR 5/8) mottles; sandy clay loam; very weak fine, medium, and coarse angular to subangular blocky, breaking into weak fine, medium, and coarse granular; firm; common fine, medium, and coarse pores; common fine, medium, and coarse roots. Umbric epipedon, 0-31 inches (0-79 cm). Argillic horizon, 42-60 inches (107-153 cm) probable, but not fully documented. 153 Profile N100, Nyawama sandy clay loam Classification: "Plinthic" Orthoxic Palehumult (or Plinthic Umbriorthox) Illinois Lab. No. Depth of horizon (inches) Horizon S29102 0-21 AT S29103 21-31 S29104 31-42 B21 S29105 42-60 B22t Percent of entire sample > 2.0 mm 0 0 0 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 0.2 0.3 0.3 0.3 Coarse sand 1.0-.5 mm 0.8 0.9 1.1 1.0 Medium sand .5-. 25 mm 5.7 4.9 5.5 4.6 Fine sand .25-.! mm 37.2 33.9 31.3 30.2 Very fine sand .1-.05 mm 18.4 18.2 17.2 15.2 Total sand 2.0-.05 mm 62.3 58.2 55.4 51.3 Coarse silt .05-. 02 mm 5.0 5.0 5.4 4.9 Fine silt .02-. 002 mm 9.6 9.3 8.6 9.0 Total silt .05-. 002 mm 14.6 14.3 14.0 13.9 Total clay < .002 mm 23.1 27.5 30.6 34.8 Water-dispersible clay < .002 mm 4.2 10.8 14.2 12.0 Bulk density 1.4 1.5 1.5 1.6 Moisture: 1/3 atmos. (%) 16.1 16.6 17.6 20.1 15 atmos. (%) 9.1 10.5 11.2 12.3 Avail, moist. -hold, capacity3 0.10 0.09 0.10 0.12 Organic carbon (%) 1.26 0.60 0.41 0.28 Exchangeable cations (me/lOOg soil) : Ca 0.08 0.08 0.08 0.13 Mg 0.10 0.10 0.05 0.10 K 0.02 0.01 0.02 0.02 Na 0.05 0.05 0.04 0.04 Al 2.00 1.83 1.50 1.33 Cation-exch. capacity (me/lOOg) 6.72 4.93 4.64 4.64 Base saturation (%) 3.7 4.9 4.1 6.2 pH H20 4.3 4.3 4.3 4.3 PH KC1 3.7 3.7 3.7 3.5 Soil tests: K (Ibs/A) 69 56 52 56 P! (Ibs/A) 11 5 3 3 P2 (Ibs/A) 12 5 4 4 Total P (ppm) 200 ... ... ... Total CaO(%) 0.076 0.070 0.069 0.074 Total Fe203(%) 1.45 1.73 1.89 2.02 Total K20(%) 0.33 0.35 0.41 0.45 alnches of available moisture-holding capacity per inch of soil. 154 Profile N71 , Nyawama clay loam Described by D. H. Westerveld on January 6, 1967 Location On proposed new experimental farm northwest of Njala University College Campus. Pit N71 is on traverse 1, about 800 feet (244 m) west of the junction of this traverse with the east boundary creek. On aerial photograph 39-SL25-083, pit N71 is 9.6 cm west and 4.7 cm south of northeast corner mark. Physiography Relief Vegetation Drainage Parent material Al 0-11 inches 0-28 cm Lab. No. S29119 Bl 11-17 inches 28-43 cm Lab. No. S29120 B21t 17-26 inches 43-66 cm Lab. No. S29121 B22t 26-50 inches 66-127 cm Lab. No. S29122 Diagnostic horizons Middle terrace of Taia River. Nearly level. Secondary bush. Moderately well drained. Gravel-free alluvium. Dark brown (10YR 3/3); clay loam; weak fine and medium subangular blocky, breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4); clay; weak fine and medium angular to subangular blocky, breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/8) with few fine and medium distinct red (2.5YR 4/8) mottles; clay; weak fine, medium, and coarse angular to subangular bio cky^ breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; common fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Brownish yellow (10YR 6/8) with few fine faint reddish- yellow (7.5YR 6/8) and many fine, medium, and coarse distinct red (2. SYR 4/8) slightly hard mottles; clay; weak fine, medium, and coarse angular to subangular blocky^ breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; few fine, medium, and coarse roots. Umbric epipedon, 0-11 inches (0-28 cm). Argillic horizon, 17-50 inches (43-127 cm) probable, but not fully documented. Profile N71, Nyawama clay loam Classification: "Plinthic" Orthoxic Palehumult (or Plinthic Umbriorthox) 155 Illinois Lab. No. Depth of horizon (inches) Horizon S29119 0-11 A. S29120 11-17 B. S29121 17-26 B 21t S29122 26-50 B 22t Percent of entire sample >2.0mm 0 0 0 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 0.2 0.1 0.1 0.2 Coarse sand 1.0-.5 mm 1.1 0.8 0.8 0.8 Medium sand .5-. 25 mm 2.5 1.9 1.5 1.4 Fine sand .25-.! mm 20.6 18.0 14.2 11.8 Very fine sand .1-.05 mm 15.5 15.6 14.2 12.4 Total sand 2.0-.05 mm 39.9 36.4 30.8 26.6 Total silt .05-. 002 mm 23.0 22.9 21.9 22.5 Total clay < .002 mm 37.1 40.7 47.3 50.9 Water-dispersible clay < .002 mm 8.7 20.2 13.3 0.8 Moisture: 1/3 atmos. (%) 22.6 20.6 21.7 24.4 15 atmos. (%) 16.0 15.3 17.0 19.1 Organic carbon (%) 2.55 1.23 0.78 0.34 Exchangeable cations (me/lOOg soil): Ca 0.15 0.10 0.08 0.15 Mg 0.08 0.10 0.05 0.03 K 0.06 0.06 0.06 0.06 Na 0.03 0.07 0.05 0.05 Al 2.05 1.67 1.39 1.11 Cation-exch. capacity (me/lOOg) 10.22 6.29 5.64 5.72 Base saturation (%) 3.1 5.2 4.3 5.1 PH H 0 4.7 4.7 4.8 5.1 PH KC1 4.0 3.9 3.8 3.9 Soil tests: K (Ibs/A) 98 74 82 78 P^lbs/A) 8 P2(lbs/A) 9 3 3 3 Total P (ppm) 220 ... ... — Total CaO(%) 0.091 0.081 0.075 0.076 Total Fe203(%) 2.46 2.87 3.34 4.24 Total K20(%) 0.81 0.84 0.83 0.82 156 Profile NT 5, Described by H. Nyawama sandy clay loam Breteler on January 5, 1967 Location Physiography On proposed new experimental farm northwest of Njala University College Campus. Pit N15 is 528 feet (161 m) east of Taia River and 37 feet (11 m) south of the path from Nyawama to the river. On aerial photograph 39-SL25-083, pit N15 is 12.3 cm west and 7.3 cm south of northeast corner mark. Middle terrace of Taia River , close to the escarpment down to the lowest terrace. Relief Vegetation Drainage Parent material 0-5 inches 0-13 cm Lab. No. S29130 5-14 inches 13-35 cm Lab. No. S29131 B21t 14-33 inches 35-84 cm Lab. No. S29132 B22t 33-50 inches 84-127 cm Lab. No. S29133 Diagnostic horizons Nearly level. Bamboo and ferns. Moderately well drained. Gravel-free alluvium. Dark brown (10YR 3/3) ; sandy clay loam; weak fine and medium angular to subangular blockyj breaking into very weak very fine granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/5) with few fine faint dark brown (10YR 3/3) mottles; sandy clay loam; weak to moderate very fine, fine, and medium angular to sub- angular blocky^ breaking into weak to moderate very fine granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/8) with few fine faint red (2. SYR 5/8) mottles; clay; weak very fine, fine, and medium angular to subangular blocky, breaking into weak very fine and fine granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/8) with many fine, medium, and coarse distinct red (2. SYR 5/8) mottles; clay; weak to moderate very fine, fine, and medium angular blocky breaking into weak very fine and fine granular; friable; common fine, medium, and coarse pores; common fine, medium, and coarse roots. Ochric epipedon, 0-14 inches (0-35 cm). Argillic horizon, 14-50 inches (35-127 cm) probable, but not fully documented. 157 Profile N15, Nyawama sandy clay loam Classification; Plinthic "Orthoxic" Paleudult (or Plinthic Haplorthox) Illinois Lab. No. S29130 S29131 S29132 S29133 Depth of horizon (inches) 0-5 5-14 14-33 33-50 Horizon A! A3 B21t B22t Percent of entire sample > 2.0 mm 0 0 0 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 0.5 0.2 0.1 0.1 Coarse sand 1.0-.5 mm 0.5 0.2 0.2 0.4 Medium sand .5-. 25 mm 1.5 0.9 0.6 0.9 Fine sand .25-.! mm . 29.2 24.5 19.3 15.1 Very fine sand . 1-.05 mm . 21.6 22.6 21.3 18.3 Total sand 2.0-.05 mm . 53.3 48.4 41.5 34.8 Total silt .05-. 002 mm . 23.1 19.2 17.7 19.4 Total clay < .002 mm . 23.6 32.4 40.8 45.8 Water-dispersible clay < .002 mm 7.6 16.8 16.8 0.4 Moisture: 1/3 atmos. (%) . 18.0 17.0 19.3 22.4 15 atmos. (%) . 12.0 12.4 14.4 17.4 Organic carbon (%) 3.34 1.01 0.78 0.52 Exchangeable cations (me/lOOg soil) : Ca 2.33 0.43 0.28 0.15 Mg 1.12 0.34 0.26 0.21 K 0.11 0.03 0.06 0.03 Na 0.05 0.06 0.06 0.04 Al 0.49 1.17 1.28 1.22 Cation-exch. capacity (me/lOOg) . 10.29 5.50 5.14 5.64 Base saturation (%) . 35.1 15.6 12.8 7.6 pH H20 5.0 4.8 4.3 4.8 pH KC1 4.0 3.9 3.8 3.8 Soil tests: K (lbs/A) . 114 78 106 56 P! (lbs/A) . 18 8 3 4 P2 (lbs/A) . 20 9 4 5 Total P (ppm) . 180 * • • Total CaO(%) 0.301 0.131 0.117 0.089 Total Fe203(%) 2.14 2.66 3.22 5.14 Total K?0(%) 1.40 1.40 1.33 1.19 158 Location Physiography Relief Profile PI, Panlap sandy loam Described by W. van Vuure and R. Miedema on March 8, 1968 Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE27--86. ; on traverse A, near old rail line. D 4 Valley bottom, at the edge of a swamp. Concave, gentle slope of 3 percent to SSW. Vegetation Drainage Parent material 11 0-11 inches 0-28 cm Lab. No. S29800 A12 11-23 inches 28-58 cm Lab. No. S29801 AC 23-37 inches 58-93 cm Lab. No. S29802 g 37-60 inches 93-153 cm Lab. No. S29803 Diagnostic horizon Abandoned rice farm with grasses and raphia palm. Poorly drained. Gravel-free alluvium or colluvium or a mixture of both from adjacent hills. Black (10YR 2/1); sandy loam; very weak, very fine sub- angular blocky; very friable, slightly sticky, and plastic; common macro-and mesopores; few faint root-rust mottles and few medium distinct charcoal mottles; common coarse, many medium and fine roots; common ant and termite activity, and a few worm holes; clear, smooth boundary to horizon below. Very dark grayish brown to dark grayish brown (10YR 3.5/2); loamy sand; weak fine subangular blocky; friable, slightly sticky, and nonplastic; few macro- and many mesopores; common coarse, many medium, and common fine roots; very few fine quartz gravels, and very few very fine, red, hardened plinthite glaebules; common ant, termite, and worm activity; clear, smooth boundary to horizon below. Brown (10YR 5/3); loamy sand; weak fine subangular blocky; friable, slightly sticky, and nonplastic; few macro- and many mesopores; many coarse prominent yellowish-red (SYR 5/8) plinthite mottles, vertically elongated along root channels; few coarse, common medium and fine roots; few fine quartz gravels, and very few very fine, red, hardened plinthite glaebules; few ants and termites, and common worm activity; clear, smooth boundary to horizon below. Light brownish gray (10YR 6/2); coarse sandy loam; very weak fine subangular blocky; friable, slightly sticky, and nonplastic to slightly plastic; many mesopores; many coarse prominent strong brown (7. SYR 5/8), reddish-yellow (7. SYR 6/8), yellowish-red (10YR 6/7), and red (2. SYR 5/8) plinthite mottles; few faint white kaolinite mottles; common fine quartz gravel; common worm activity. Umbric epipedon, 0-11 inches (0-28 cm). 159 Profile PI, Panlap sandy loam Classification: Aerie Plinthic Tropaquept Illinois Lab. No. Depth of horizon (inches) Horizon S29800 0-11 S29801 11-23 A12 S29802 23-37 AC S29803 37-60 °g Percent of entire sample > 2.0 mm 1.5 2.6 9.2 6.0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 2.4 4.8 6.4 9.8 Coarse sand 1.0-.5 mm 12.9 15.0 17.1 19.5 Medium sand .5-. 25 mm 39.1 30.7 31.9 28.8 Fine sand .25-.! mm 19.0 24.0 20.2 16.1 Very fine sand .l-.05mm 4.6 6.7 5.3 3.8 Total sand 2.0-.05 mm 78.0 81.2 80.9 78.0 Total silt .05-. 002 mm 11.0 8.1 7.3 9.5 Total alay < .002 mm 11.0 10.7 11.8 12.5 Water-dispersible clay < .002 mm 2.3 5.7 9.4 11.8 Bulk density . 1.1 1.3 1.4 1.5 Moisture: 1/3 atmos. (%) 12.4 8.8 9.3 13.4 15 atmos. (%) 6.2 5.5 5.9 6.4 Avail, moist. -hold, capacity3 0.07 0.04 0.05 0.09 Organic carbon (%) 1.60 0.67 0.35 0.27 Exchangeable cations (me/lOOg soil) : Ca 0.58 0.58 0.47 0.38 Mg 0.47 0.47 0.48 0.44 K 0.02 0.02 0.02 0.03 Na 0.07 0.07 0.06 0.09 Al 0.85 0.65 0.37 0.31 Cation-exch. capacity (me/lOOg) 3.64 3.00 1.79 1.71 Base saturation (%) 31.3 38.0 57.5 55.0 pH H20 4.9 4.9 5.0 4.7 pH KC1 4.2 4.2 4.0 Soil tests: K (Ibs/A) 56 43 43 43 P! (Ibs/A) 16 9 4 Total CaO(%) 0.099 0.082 0.080 0.099 Total Fe203(%) 1.12 1.17 3.08 1.59 Total K20(%) 0.999 0.884 0.841 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 160 Profile N47, Pelewahun loam Described by J.C. Dijkerman on March 28, 1966 Location Physiography Relief Vegetation Drainage Parent material Al 0-11 inches 0-28 cm Lab. No. S28655 Bl 11-17 inches 28-43 cm Lab. No. S29737 B21t 17-25 inches 43-63 cm Lab. No. S28656 [IB22t 25-41 inches 63-104 cm Lab. No. S28657, matrix Lab. No. S29738, channel IB23t 41-72 inches 104-183 cm Lab. No. S28658 Diagnostic horizons On proposed new experimental farm northwest of Njala University College Cam- pus. From junction of path from Bonjema to Belebu with path to Gbesebu, 132 feet (40 m) along path towards Belebu, thence 253 feet (76 m) east along small farm path; pit N47 is 74 feet (22 m) southeast of this point. Lower portions of colluvial footslopes or in drainageways and swamps. In the bottom of a small drainageway, on a 2-percent concave slope. Sedges and water-loving shrubs. Poorly drained. Gravel-free colluvium, over gravelly colluvium, over residual material. Very dark gray to dark gray (10YR 4/1-3/1) with common fine, and few medium and coarse, distinct yellowish-red (SYR 4/8) mottles, mainly along root channels; loam; weak coarse to fine subangular blocky, breaking to moder- ate coarse to fine granular; friable; many medium and fine roots; many pores of all sizes; clear, smooth boundary to horizon below. Gray (10YR 5/1) with common fine distinct strong brown (7. SYR 5/8) mottles; sandy clay loam; weak to moderate medium and fine angular blocky; friable; common medium and fine roots; many pores of all sizes; clear, smooth boun- dary to horizon below. Light brownish gray (10YR-2.5Y 6/2) with many, medium and fine, soft, dis- tinct, strong brown (7. SYR 5/8) mottles and many coarse prominent red (10R 4/6) mottles, most of which are slightly hard to crush; clay loam; moder- ate coarse and medium angular blocky, with thin distinct light gray (10YR 6/1) clay coatings on some horizontal and vertical ped surfaces; slightly firm in place but friable to crush; common medium and fine roots; common pores of all sizes; abrupt, smooth boundary to horizon below. Sixty percent coarse hard prominent red (10R 4/6) mottles, 30% coarse, slightly hard, prominent yellowish-red (SYR 5/8) mottles, and 10% coarse, soft, prominent light gray (10YR 7/1) mottles in the form of clayey verti- cal channels about 1 cm wide; very gravelly clay loam; the gravels form a stone line and consist of equal proportions of quartz pebbles and irregu- lar, nondense, red (10R 4/6) hardened plinthite glaebules 1/4" to 3/4" in diameter; massive; very firm; no roots; few medium pores; clear, wavy boun- dary to horizon below. A few gray (10YR 6/1) gravelly clay, vertical channels, 2 to 3 inches wide, break through this massive horizon and connect %2].t with IIIB23f The channels were sampled separately under Lab. No. S29738. White (10YR 8/1) with many soft fine, medium, and coarse, distinct red (10R 4/6) and strong brown (7. SYR 5/8) mottles; clay, with common fragments of weathered bedrock (siltstone) ; strong medium to fine angular blocky, with distinct thick light gray (10YR 7/1-6/1) clay coatings on most hori- zontal and vertical ped surfaces; firm; no roots; few medium pores. Umbric epipedon, 0-11 inches (0-28 cm). Argillic horizon, 17-72 inches (43-183 cm). 161 Profile N47, Pelewahun loam Classification: Typic Plinthaquult Illinois Lab. No. Depth of horizon (inches) Horizon S28655 S29737 S28656 S29738 S28657 S28658 0-11 11-17 17-25 25-41 25-41 41-72 AI Bj B2it IIB22t IIB22t IIIB23t channel matrix Percent of entire sample > 2.0 mm. . Particle-size distribution of <2 mm (% Very coarse sand 2.0-1.0 mm . . . Coarse sand 1.0-.5 mm. . . . Medium sand .5-. 25 mm . . . Fine sand .25-.! mm. ... Very fine sand . 1-.05 mm . . . Total sand 2.0-.05 mm . . . Total silt .05-. 002 mm. . . Total alay < .002 mm. . . Water-dispersible clay < .002 mm . . <1 ): 1.4 3.4 6.5 16.2 11.4 38.9 38.1 23.0 11.5 1.5 26.0 9.7 0.24 2.39 0.17 0.16 0.15 0.03 2.89 10.21 5.0 4.3 3.5 158 23 24 195 0.085 1.53 0.684 1 0.7 11.4 14.1 17.6 9.2 53.0 22.4 24.6 23.6 1.7 16.9 8.8 0.14 0.32 0.20 0.08 0.02 0.05 3.50 7.22 4.8 4.4 3.2 48 6 6 75 * . • 5 4.6 10.8 10.2 11.8 6.3 43.7 23.8 32.5 30.6 1.8 19.2 11.4 0.13 0.19 0.05 0.26 0.05 0.03 5.44 8.29 4.7 4.4 3.2 56 3 4 98 0.070 3.09 1.170 20 0.7 8.3 4.3 4.9 2.8 21.0 28.9 50.1 46.6 30.6 19.6 ... 0.53 0.28 0.44 0.05 0.09 5.22 13.29 6.5 4.3 3.2 86 8 8 132 ... • • • ... 54 11.3 13.6 8.1 4.7 3.5 41.2 19.2 39.6 7.4 1.9 22.6 14.2 0.07 0.21 0.05 0.46 0.06 0.04 5.89 9.58 6.4 4.8 3.3 78 1 2 175 0.072 9.00 1.840 10 1.6 2.0 1.5 2.0 2.2 9.3 37.3 53.4 35.0 1.9 36.0 20.4 0.27 0.19 0.26 0.49 0.08 0.04 8.44 12.65 6.9 4.8 3.2 86 1 1 178 0.077 7.88 2.940 Moisture: 1/3 atmos. (%) 15 atmos. (%) Avail, moist. -hold, capacity^. . . . Exchangeable cations (me/lOOg soil): Me Na Al Cation-exch. capacity (me/lOOg). • • oH Kfl .... Soil tests: K fibs /A') . • PI nv»«?/A^ Po nh 2 mm material. 162 Location Physiography Relief Vegetation Drainage Parent material 0-15 inches 0-38 cm Lab. No. S29089 V 15-26 inches 38-66 cm Lab. No. S29090 B21gt 26-41 inches 66-104 cm Lab. No. S29091 IIB-. 22g 41-58 inches 104-147 cm Lab. No. S29093 Diagnostic horizons Profile NT 06, Pelewahun fine sandy loam Described by D.H. Westerveld on December 28, 1966 Oil Palm Station of Njala University College, on the south boundary road, 655 feet (200 m) northwest of Kania. On aerial photograph 39-SL25-083, pit N106 is 10 cm west and 9.5 cm south of northeast corner mark. Drainageway in the third river terrace. Very gentle concave, low area. Secondary bush. Poorly drained . Deep gravel-free colluvial material, over colluvial material high in plinthite glaebules and quartz. Dark grayish brown to very dark grayish brown (10YR 4/2-3/2) ; fine sandy loam; weak fine and medium angular to subangular blocky, breaking into weak to moderate fine and medium granu- lar; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, wavy boundary to horizon below. This horizon is darker and thicker than in typical Pelewahun. Gray (10YR 5/1-6/1) ; clay loam; weak fine and medium angular to subangular blocky, breaking into weak to mo'derate fine and medium granular; friable; many fine, medium, and coarse pores; common fine and medium roots; gradual, wavy boundary to horizon below. Gray (10YR 5/1-6/1) with common fine and medium distinct yellowish-red (SYR 5/8) and red (2. SYR 4/8) mottles; clay loam; weak fine and medium angular to subangular blocky, breaking into weak to moderate fine and medium granular; firm; many fine, medium, and coarse pores; common fine and medium roots; clear, wavy boundary to horizon below. Gray (10YR 6/1) with many fine and medium prominent red (2. SYR 4/8) mottles, and common fine and medium distinct yellow (10YR 7/8) mottles; gravelly (50% by volume) clay loam, with half of the gravels rounded quartz gravels, and half nodular, very hard laterite glaebules, 1/4" to 3" in diameter, with outside and in- side colors of red (2. SYR 4/8); very weak fine and medium angu- lar to subangular blocky, breaking into fine and medium granu- lar; firm; common fine, medium, and coarse pores; few fine roots Umbric epipedon, 0-15 inches (0-38 cm). Argillic horizon, 15-41 inches (38-104 cm). 163 Profile N106, Pelewahun fine sandy loam Classification: Plinthic Paleaquult Illinois Lab. No. S29089 S29090 S29091 S29093 Depth of horizon (inches) 0-15 15-26 26-41 41-58 Horizon Aj_ Blgt B21gt IIB22g Percent of entire sample > 2.0 mm 0 0 0 33.1 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 1.0 1.6 1.8 6.4 Coarse sand 1.0-.5 mm 2.8 4.1 3.7 5.7 Medium sand .5-. 25 mm 7.3 5.2 4.4 5.3 Fine sand .25-.! mm 26.8 19.3 13.6 13.0 Very fine sand .1-.05 mm 14.8 11.0 11.3 10.2 Total sand 2.0-.05 mm 52.7 41.2 34.8 40.6 Coarse silt .05-. 02 mm 8.6 7.4 6.3 7.1 Fine silt .02-. 002 mm 23.3 23.9 23.0 25.0 Total silt .05-. 002 mm 31.9 31.3 29.3 32.1 Total alay < .002 mm 15.4 27.5 35.9 27.3 Water-dispersible clay < .002 mm 10.2 25.1 22.0 13.6 Moisture: 1/3 atmos. (%) 11.3 13.9 16.4 15.8 15 atmos. (%) 6.2 9.9 12.3 11.5 Organic carbon (%) 1.12 0.41 0.32 0.22 Exchangeable cations (me/lOOg soil) : Ca 0.10 0.13 0.03 0.10 MK ' 0.08 0.03 0.07 0.10 K '. 0.02 0.02 0.03 0.01 Na '.'.!! 0.03 0.04 0.05 0.05 Al !'.!.. 1-72 2.00 2.66 3.17 Cation-exch. capacity (me/lOOg) 5.86 5.64 6.72 7.79 Base saturation (%) 3.9 3.9 2.7 3.3 PH H20 4.4 4.4 4.4 4.7 pH KC1 3.6 3.5 3.3 3.4 Soil tests: K (Ibs/A) 52 39 39 43 P! (lbs/A) 12 29 P2 (lbs/A) 15 31 Total P (ppm) 135 68 100 105 Total CaO(%). 0.077 0.072 0.069 0.067 Total Fe20o(%) 0.60 0.92 1.62 3.82 Total K20(%). 0.24 0.44 0.62 0.71 164 Location Physiography Relief Vegetation Drainage Parent material Profile Kpuabu 2, Pendembu fine sandy loam Description after Sivarajasingham (64) Kpuabu Cocoa Experiment Station, about halfway between the nursery buildings .and the stream. Accordant, flat-topped hill of the dissected lateritic upland. Long, gentle, concave slope of about 2 percent. Cocoa plantation under adequate shade of many tall trees of original secondary forest. Although the soil is deep and gravel-free and would have been expected to be suitable, the cocoa planted in 1959 shows many large, vacant patches. Imperfectly drained. A thick layer of gravel-free, locally transported, leached parent material. 1 0-7 inches 0-18 cm Lab. No. S28552 7-18 inches 18-46 cm Lab. No. S28551 Blt 18-37 inches 46-94 cm B2t 37-54 inches 94-137 cm Lab. No. S28550 B3t 54-72 inches 137-183 cm lg 72-80 inches 183-203 cm Diagnostic horizons Very dark gray (10YR 3/1); fine sandy loam; weak, medium, and fine, subangular blocky; friable, slightly sticky, nonplastic; very few fine pores; common fine and medium roots; clear, smooth boundary to horizon below. Dark grayish brown (2.5Y 4/2-10YR 4/2); sandy clay loam; dense clods breaking to weak fine subangular blocky aggregates with no characteristic interface; friable, slightly sticky, slightly plas- tic; very few pores and few large burrow holes; common fine and medium and few coarse roots in the first 5 inches, then decreas- ing gradually with depth; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/4) to light olive brown (2.5Y 5/4); sandy clay loam; dense clods as in A3 horizon; friable to firm, slightly sticky, slightly plastic; few pores with clay coatings along the pore walls; few fine and medium roots; gradual, smooth boundary to horizon below. Yellow (2.5Y 7/6) to brownish yellow (10YR 6/6); sandy clay loam; massive clods breaking to weak very fine subangular blocky aggre- gates with no characteristic interface; friable to firm, slightly plastic, slightly sticky; few pores with clay coatings along the pore walls; very few fine and medium roots; gradual, smooth boun- dary to horizon below. Pale yellow to yellow (2.5Y 7/6) with common medium, faint yellowish- brown (10YR 5/6) and few medium, prominent red (2. SYR 4/8) mottles; sandy clay loam; massive clods as in ~&2t horizon; firm, slightly sticky, slightly plastic; many fine pores with clay coatings; very few very fine roots; gradual, smooth boundary to horizon below. White (2.5Y 8/2) with common medium, prominent yellowish-brown (10YR 5/6) and strong brown (7. SYR 5/8) mottles; sandy clay; massive; wet; firm, sticky, slightly plastic; the strong brown mottles are firm to hard and may be considered as incipient plinthite glaebules; no roots. Ochric epipedon, 0-18 inches (0-46 cm). Argillic horizon, 18-27 inches (46-183 cm). 165 Profile Kpuabu 2, Pendembu fine sandy loam Classification: Typic Paleudult Illinois Lab. No. S28552 S28551 S28550 Depth of horizon (inches) 0-7 7-18 37-54 Horizon Aj A-j ^>2t Percent of entire sample >2.0mm 15.5 3.1 2.4 Particle-size distribution of < 2mm (%) : Very coarse sand 2.0-1.0 mm 3.4 3.6 3.6 Coarse sand 1.0-.5 mm 11.9 10.1 10.3 Medium sand .5-. 25 mm 5.3 11.6 11.9 Fine sand .25-.! mm 26.8 24.6 21.4 Very fine sand .1-.05 mm 10.8 13.2 10.5 Total sand 2.0-.05 mm 68.6 63.0 57.5 Total silt .05-. 002 mm 11.7 13.2 12.2 Total alay < .002 mm 19.7 23.8 30.3 Water-dispersible clay < . 002 mm 2.7 6.8 0.3 Bulk density 0.9 0.9 1.0 Moisture: 1/3 atmos. (%) 14.3 13.3 15.0 15 atmos. (%) 9.1 8.7 10.7 Avail, moist. -hold, capacity3 0.04 0.04 0.04 Organic carbon (%) 2.25 0.85 0.32 Exchangeable cations (me/lOOg soil): Ca 0 0.06 0.06 Mg 0.08 0.03 0.03 K 0.10 0.06 0.05 Na 0.05 0.04 0.04 Al 3.56 2.39 1.22 Cation-exch. capacity (me/lOOg) 9.44 4.79 3.50 Base saturation (%) 2.4 4.0 5.1 pH H20 4.1 4.4 4.7 PH KC1 3.6 3.8 3.9 Soil tests: K (Ibs/A) 5 p, (Ibs/A) 10 ?2 (Ibs/A) 12 4 4 Total P (ppm) 240 Total CaO (%) 0.076 0.072 0.067 Total Fe20o (%) 2.52 3.00 3.10 Total K20 t%) °'194 °'219 °'249 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 166 Profile N80, Pujehun fine sandy clay loam Described by J. C. Dijkerman on January 11, 1967 Location Physiography Relief On proposed new experimental farm northwest of Njala University College Campus. Along the surveyor path following the Taia River from Gbesebu to Nyawama, pit N80 is 591 feet (180 m) south of the Gbesebu path, at surveyor stone SLS 21/64 BP 138; it is 10. 2 cm west and 3.7 cm south of northeast corner mark on aerial photo- graph 39-SL-24-083. Lower terrace of Taia River. Very gentle convex slope, on natural levee along the Taia River. Vegetation Drainage Parent material Al 0-4 inches 0-10 cm Lab. No. S29110 4-12 inches 10-30 cm Lab. No. S29111 B21 12-31 inches 30-79 cm Lab. No. S29112 B22 31-55 inches 79-140 cm Lab. No. S29113 Diagnostic horizons Secondary bush. Well drained. Gravel-free alluvium. Very dark grayish brown to dark brown (10YR 3/2-3/3) ; fine sandy clay loam; very weak fine and very fine sub- angular blocky, breaking into weak fine and very fine granular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; clear, smooth bound- ary to horizon below. Dark yellowish brown (10YR 4/4) ; fine sandy clay loam with much mica; very weak fine and very fine subangular blocky, breaking into very weak fine and very fine gran- ular; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth bound- ary to horizon below. Yellowish red (10YR 5/6) ; fine sandy loam with much mica; very weak fine and very fine subangular blocky, breaking into very weak fine and very fine granular; friable; many fine and medium pores; common fine and medium roots; gradual, smooth boundary to horizon be- low. Strong brown (7. SYR 5/6) with common fine and medium faint yellowish-red (5YR 4/6) mottles; clay loam con- taining much mica; weak to moderate fine and very fine angular blocky to subangular blocky, breaking into fine and very fine granular; friable; many fine and medium pores; common fine and medium roots. Ochric epipedon, 0-12 inches (0-30 cm). Cambic horizon, 12-55 inches (30-140 cm). Profile N80, Pujehun fine sandy clay loam Classification: Fluventic Udoxic Dystropept 167 Illinois Lab. No. Depth of horizon (inches) Horizon S29110 0-4 Al S29111 4-12 A3 S29112 12-31 B21 S29113 31-55 B22 Percent of entire sample > 2.0 mm 0 0 0 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 0.4 0.1 0.1 0 Coarse sand 1.0-.5mm 0.2 0.1 0.1 0.1 Medium sand .5-. 25 mm 1.6 1.5 1.1 0.7 Fine sand .25-.! mm 39.6 40.3 46.1 23.8 Very fine sand .1-.05 mm 20.8 21.2 24.3 20.4 Total sand 2.0-.05 mm 62.6 63.2 71.7 45.0 Coarse silt .05-. 02 mm 3.8 3.4 2.6 5..3 Fine silt .02-. 002 mm 13.2 10.8 9.0 15.0 Total silt .05-. 002 mm 17.0 14.2 11.6 20.3 Total clay < .002 mm 20.4 22.6 16.7 34.7 Water-dispersible clay < .002 mm 3.6 10.4 10.7 0.7 Bulk density 1.2 1.4 1.4 1.5 Moisture: 1/3 atmos. (%) 20.3 17.0 12.8 26.2 15 atmos. (%) 11.3 9.5 7.3 14.6 Avail. moist. -hold, capacitya 0.11 0.10 0.08 0.17 Organic carbon (%) 2.71 0.94 0.32 0.28 Exchangeable cations (me/lOOg soil): Ca 0.10 0.10 0.10 0.08 Mg 0.08 0.05 0.05 0.12 K 0.05 0.04 0.01 0.02 Na 0.04 0.04 0.05 0.05 Al 1.61 1.02 0.61 0.95 Cation-exch. capacity (me/lOOg) 8.86 4.86 2.79 4.43 Base saturation (%) 3.0 4.7 7.5 6.1 PH H20 4.4 4.5 4.5 4.8 PH KC1 3.9 4.0 Soil tests: K (Ibs/A) 106 60 52 60 Pi (Ibs/A) 15 4 6 P2 (Ibs/A) 4 Total P (ppm) 300 Total CaO (%) 0.293 0.289 0.327 0.190 Total Fe203 (%) 2.89 3.02 2.56 4.36 Total K20 (%) 2.10 2.18 2.68 1.96 alnches of available moisture-holding capacity per inch of soil. 168 Profile Rl , Rokupr clay, oxidized phase Described by J. C. Dijkerman and D. H. Westerveld on May 5, 1967 Location Physiography Relief Vegetation Drainage Parent material Al 0-5 inches 0-13 cm Lab. No. S29747 5-22 inches 13-56 cm Lab. No. S29748 B22g 22-57 inches 56-145 cm Lab. No. S29749 Remarks Diagnostic horizons Rice Research Station, Rokupr; pit Rl is in plot 47 on side of ditch; 210 feet (64 m) east of Great Scarcies River. The area east of this ditch is empoldered (for a map of the Station see 1955 Annual Report of the West African Rice Research Station^ Rokupr, Sierra Leone). Tidal swamp. Nearly level. Land is plowed and ready for the next rice crop, original vegetation was mangrove. The Very poorly drained. The plot is empoldered and the surface has dried (oxidized) thoroughly during the dry season. When the soil description was written, brackish water was 20 inches below the surface during low tide. Alluvium. Very dark gray to very dark grayish brown (10YR 3/1-3/2) with common medium and coarse prominent yellowish-brown (10YR 5/6) and brown (7. SYR 5/6) mottles; clay; some pieces of undecomposed organic matter; ripe, cannot be molded through fingers (firm) ; many large crab holes (0.5 to 2 cm wide); sticky and plastic; clear, smooth boundary to horizon below. Very dark gray (10YR 3/1-N 3/ ) with common medium and coarse prominent yellowish— brown (10YR 5/6), strong brown (7. SYR 5/6), and yellowish-red (5YR 5/8) mottles; when dry, these mottles are pale yellow (2.5Y 8/4); clay loam; some pieces of undecomposed organic matter; half ripe, can just be molded through fingers; many large crab holes (0.5 to 2 cm wide); sticky and plastic; gradual, smooth boundary to horizon below. Very dark gray (N 3/ ); few, very fine, faint strong brown (7. SYR 5/6) mottles; silty clay; some pieces of unde- composed organic matter; half ripe, can just be molded through fingers; sticky and plastic. Very low pH and yellow mottles are typical cat clay characteristics, which develop upon oxidation. Ochric epipedon, 0-5 inches (0-13 cm). Sulfuric horizon, 5-22 inches (13-56 cm). 169 Profile Rl , Rokupr clay, oxidized phase Classification: Typic Sulfaquept Illinois Lab. No. Depth of horizon (inches) Horizon S29747 0-5 S29748 5-22 B21g S29749 22-57 B22g Percent of entire sample > 2.0 mm 0 0 Particle-size distribution of < 2 mm (%) : Total sand 2.0-.05 mm 14.9 22.4 Coarse silt .05-. 02 mm 8.0 9.8 Fine silt .02-. 002 mm 24.5 30.1 Total silt .05-. 002 mm 32.5 39.9 Total olay < .002 mm 52.6 37.7 Water-dispersible clay < .002 mm 14.8 10.5 Organic carbon (%)* 6.05 ... Exchangeable cations (me/lOOg soil)a: Ca 3.50 3.80 Mg 2.67 0.42 Al 1.44 4.33 Cation-exch. capacity (me/lOOg) 25.90 20.30 Water rethanol extract (ppm) : Ca 400 92 Mg 135 540 Mn 12 120 Fe 45 9,000 Al 16 2,450 PH H20 2.9 3.0 Soil test: Total P (ppm) 265 160 Total S(%)b 1-15 11.54 0 15.2 9.2 31.4 40. 44, .6 .2 4.8 4.40 1.97 4.77 23.30 185 1,150 120 1,950 460 4.5 205 9.06 a!.ON KC1 extract instead of conventional NltyOAc method, b Analyses fromC. Chavengsaksongkram (15). * Analyses by D.S. Amara. 170 Profile R2, Rokupr silty clay, reduced phase Described by J. C. Dijkerman and D. H. Westerveld on May 5, 1967 Location Physiography Relief Vegetation Drainage Parent material 0-3 inches 0-8 cm Lab. No. S29750 B0 2g 3-26 inches 8-66 cm Lab. No. S29751 Diagnostic horizon Rice Research Station, Rokupr. Pit R2 is in the middle of plot 54, 75 feet (23 m) east of Great Scarcies River. This area is not empoldered and does not become dry during the dry season. Tidal swamp. Nearly level. The land is plowed and ready for the next rice crop. The original vegetation was mangrove. Very poorly drained. Flooded daily at high tide. Brackish water was 5 inches below the surface during low tide when this soil description was written. Alluvium. Very dark grayish brown (10YR 3/2) with common medium and coarse, distinct, strong brown (7. SYR 5/6) mottles; silty clay; some undecomposed organic matter that is mainly roots ; half ripe , can be molded through fingers ; sticky and plastic; boundary to horizon below is clear and irregular because of plowing. Very dark gray (N 3/ ); clay; some large remnants of man- grove vegetation; half ripe, can be molded through fingers; sticky and plastic. The color of the subsoil changes from very dark grayish brown (10YR 3/2) to very dark gray (N 3/ ) by exposing water-saturated subsoil clods to the air. This change is completed in about half a minute. Ochric epipedon, 0-3 inches (0-8 cm). Profile R2, Rokupr silty clay, reduced phase Classification: Typic Sulfaquent 171 Illinois Lab. No. Depth of horizon (inches) Horizon S29750 0-3 S29751 3-26 B2g Percent of entire sample >2.0mm 0 0 Particle-size distribution of < 2 ram (%) : Total sand 2.0-.05 mm 11.5 4.0 Coarse silt .05-. 02 mm 14.7 9.8 Fine silt .02-. 002 mm 30.0 26.2 Total silt .05-. 002 mm 44.7 36.0 Total clay < .002 mm 43.8 60.0 Water-dispersible clay < .002 mm 2.4 3.0 Organic carbon (%)* 6.13 •• • Q Exchangeable cations (me/lOOg soil): Ca 3.00 4.90 Mg 3.25 3.75 Al 2.13 4.00 Cation-exch. capacity (me/lOOg) 20.00 24.60 Water :ethanol extract (ppm) : Ca 90 580 Mg 420 800 Mn 22 55 Fe 135 420 Al 24 125 pH H20 4.3 2.1 Soil test: Total P (ppm) 500 Total S (%)b 1-87 5.18 a!.ON KC1 extract instead of conventional NH.OAc method. bAnalyses from C. Chavengsaksongkram (15) . *Analyses by D.S. Amara. 172 Profile T149, Sahama sand Described by J. C. Dijkerman Location Physiography Relief Vegetation Drainage Parent material 0-6 inches 0-15 cm Lab. No. S29722 A12 6-11 inches 15-28 cm Lab. No. S29723 11-20 inches 28-51 cm Lab. No. S29724 Bl 20-31 inches 51-79 cm Lab. No. S29725 B21 31-40 inches 79-102 cm Lab. No. S29726 B22 40-55 inches 102-140 cm Lab. No. S29727 Diagnostic horizons Torma Bum soil survey area; just before entering the village of Sahama, about 1 mile north of Gbamani. On aerial photograph 61-SL3-023, pit T149 is 8.8 cm west and 16.0 cm south of northeast corner mark. Beach ridge, about 8 miles from the coast and parallel to it. The slope is very gentle, convex on a ridge about 1/8-mile wide. Secondary bush with many oil palms. Well drained. Beach sand of Bullom deposits. Very dark grayish brown (10YR 3/2); sand; single grain to very weak medium and fine granular; very friable; many coarse, medium, and fine roots; many coarse, medium, and fine pores; gradual, smooth boundary to horizon below. Very dark grayish brown to dark brown (10YR 3/2-3/3) ; sand; single grain to very weak medium and fine granular and subangular blocky; very friable; many coarse, medium, and fine roots; many coarse, medium, and fine pores; gradual, smooth boundary to horizon below. Dark brown (10YR 3/3); sand; single grain to very weak medium and fine granular and subangular blocky; very friable; common medium and fine roots; many medium and fine pores; gradual, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4); sand; single grain to very weak medium and fine granular and subangular blocky; friable; common medium and fine roots; many medium and fine pores; gradual, smooth boundary to horizon below. Brown to dark brown (7. SYR 4/4); sand; single grain to very weak medium and fine granular and subangular blocky; friable; common medium and fine roots; many medium and fine pores; gradual, smooth boundary to horizon below. Strong brown (7. SYR 5/6); loamy sand; single grain to very weak medium and fine granular and subangular blocky; friable; few medium and fine roots; common medium and fine pores. Borderline umbric-ochric epipedon; umbric colors 0-20 inches (0-51 cm) , but organic carbon content of the Ai2 horizon is below 0.6%. 173 Profile T149, Sahama sand Classification: Typic Quartzipsamment Illinois Lab. No. Depth of horizon (inches) Horizon S29722 S29723 S29724 S29725 S29726 S29727 0-6 6-11 11-20 20-31 31-40 40-55 Ai2 A3 BI B21 B22 Percent of entire sample > 2.0 mm 1 < 1 < 1 < 1 < 1 < 1 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 1. 4 1. 1 0. 8 1. 6 2. 6 0.9 Coarse sand 1.0-.5 mm 27. 8 28. 3 27. 3 36. 6 41. 5 28.1 Medium sand .5-. 25 mm 28. 0 25. 9 26. 5 27. 3 26. 0 29.0 Fine sand .25-.! mm 28. 2 27. 5 28. 5 22. 0 20. 6 26.4 Very fine sand . 1-.05 mm 7. 2 7. 4 7. 8 4. 6 4. 2 5.5 Total sand 2.0-.05 mm 92. 6 90. 2 90. 9 92. 1 94. 9 89.9 Total silt .05-. 002 mm 1. 2 1, 2 1. 8 0. 7 0. 2 0.9 Total alay < .002 mm 6. 2 8. 6 7. 3 7. 2 4. 9 9.2 Water-dispersible clay < .002 mm 2. 9 5. 2 3. 6 4. 7 1. 4 5.4 Bulk density 1. 4 1. 6 1. 7 1. 7 1. 8 1.9 Moisture: 1/3 atmos. (%) 4. 1 4. 4 5. 2 5. 1 b. 1 5.0 15 atmos. (%) 2. 8 3. 1 3. 4 3. 2 3. 8 3.6 Avail, moist. -hold, capacity3 0. 02 0. 02 0. 03 0. 03 0. 02 0.03 Organic carbon (%) 0. 90 0. 52 0. 78 0. 55 1. 66 0.29 Exchangeable cations (me/lOOg soil): Ca 0. 10 0. 15 0. 13 0. 10 0. 41 0.10 Mg 0. 10 • * , 0. 02 0. 03 0. 31 0.05 K 0. 07 0. 02 0. 06 0. 03 0. 09 0.04 Na 0. 08 0. 06 0. 03 0. 06 0. 10 0.06 Al 0. 68 0. 69 0. 83 0. 74 0. 70 0.50 Cation-exch. capacity (me/lOOg) 3. 29 2. 07 3. 22 2. 36 5. 22 2.64 Base saturation (%) 10. 6 . . . 7. b y. 3 I/. 4 9.5 pH H20 4. 9 4. 8 4. 6 4. 7 4. 3 5.1 pH KC1 4. 0 4. 2 4. 0 4. 2 3. / 4.4 Soil tests: K (Ibs/A) 106 90 98 86 166 86 Pi (Ibs/A) 18 22 11 15 41 23 P2 (Ibs/A) 18 22 11 Ib 41 27 ainches of available moisture-holding capacity per inch of soil. 174 Profile 145005, Segbwema gravelly sandy clay loam Description after Sivarajasingham (64) Location Physiography Relief Vegetation Drainage Parent material 0-13 inches 0-33 cm Lab. No. S28564 B21 13-28 inches 33-71 cm B22 28-60 inches 71-153 cm Lab. No. S28563 60-94 inches 153-239 cm Lab. No. S28562 Diagnostic horizons On a very high hill on the right-hand side of the road from Mano Junction to Segbwema Junction. The path leading to the pit starts from the village of Niahun and goes southwards. Very high hills. The pit is on the middle part of a very steep (42- percent) , straight slope of a very high hill. The land was in upland rice during 1965; in 1966 it was under a low succulent to woody herbaceous vegeta- tion with many wild oil palms. Well drained. Residual, presumably from rock of granodioritic com- position. Strong brown (7.5YR 5/6); gravelly sandy clay loam; strong fine subangular blocky and granular; medium density and porosity; friable, slightly sticky, slightly plastic; common fine and medium roots; clear, smooth boundary to horizon below. Red to weak red (10R 4/6-4/4) ; heavy sandy clay loam, slightly gritty; strong medium subangular blocky; porous; friable, slightly sticky, slightly plastic; few fine roots; gradual, smooth boundary to horizon below. Red (2.5YR 4/6) with few coarse red (10R-7.5R 4/6) mottles; clay loam with fine white specks of decomposing feldspar indicating its saprolitic nature; strong med- ium subangular blocky; porous; friable, slightly sticky, slightly plastic; few fine roots; diffuse, smooth boundary to horizon below. Red (2.5YR 4/8 and 10R 4/8) in equal amounts present as coarse faint mottles; also contains white decomposing feldspar and black decomposing hornblende; sandy clay loam; weak fine subangular blocky; porous; nonsticky, slightly plastic; few fine roots. Ochric epipedon, 0-13 inches (0-33 cm). Oxic horizon, 13-60 inches (33-153 cm) probable, but not fully documented. Profile 145005, Segbwema gravelly sandy clay loam Classification: Tropeptic Haplorthox (or Udoxic Dystropept) 175 Illinois Lab. No. Depth of horizon (inches) Horizon S28564 0-13 S28563 28-60 B22 S28562 60-94 Cl Percent of entire sample > 2.0 mm 22.8 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 13.9 Coarse sand 1.0-.5 mm 14.5 Medium sand .5-. 25 mm 9.4 Fine sand .25-.! mm 11.5 Very fine sand . 1-.05 mm 7.0 Total sand 2.0-.05 mm 55.9 Total silt .05-. 002 mm 17.3 Total clay < .002 mm 26.8 Water-dispersible clay < .002 mm 11.4 Bulk density 1.1 Moisture: 1/3 atmos. (%) 20.0 15 atmos. (%) 13.8 Avail, moist. -hold, capacity3 0.05 Organic carbon (%) 2.01 Exchangeable cations (me/lOOg soil) : Ca 0.96 Mg 0.44 K 0.35 Na 0.06 Al 0.93 Cation-exch. capacity (me/lOOg) 10.65 Base saturation (%) 17.0 pH H20 4.7 pH KC1 3.8 Soil tests: K (Ibs/A) 62 P! (Ibs/A) 4 P2 (Ibs/A) Total P (ppm) 240 Total CaO(%) 0.205 Total Fe203(%) 5.50 Total K20(%) 1-270 11.4 10.1 8.6 5.6 8.8 8.4 41.1 25.1 34.0 0.2 1.2 28.0 16.6 0.12 0.24 0.05 0.13 0.03 0.04 1.28 6.86 3.6 5.2 4.0 10 0 0 0.066 7.78 0.501 8.5 16.2 12.6 5.8 8.5 8.6 51.1 25.5 23.7 0.2 1.4 23.0 14.3 0.11 0.10 0.05 0.10 0.08 0.07 1.11 6.00 5.0 5.5 4.0 14 0 0 0.067 4.85 1.890 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. 176 Location Physiography Relief Vegetation Drainage Parent material Al 0-13 inches 0-33 cm Lab. No. S29106 3g 13-31 inches 33-79 cm Lab. No. S29107 B21gt 31-42 inches 79-107 cm Lab. No. S29108 B22gt 42-63 inches 107-160 cm Lab. No. S29109 Diagnostic horizons Profile N101, Taiama clay loam Described by T.N. Lamboi on December 21, 1966 At Njala University College, near the office of the Oil Palm Station, pit N101 is 227 feet (69 m) southwest and 26 feet (8 m) northwest of junction of road 6 and road 1. On aerial photograph 39-SL25-083, pit N101 is 8.3 cm west and 8.1 cm south of northeast corner mark. Drainageway on middle terrace of Taia River. Gentle concave slope; bottom of drainageway. Oil palm plantation. Poorly drained . Gravel-free alluvium. Very dark grayish brown (10YR 3/2); clay loam; very weak to weak fine, medium, and coarse angular to subangular blocky, breaking into weak to moderate fine, medium, and coarse granu- lar; friable; many fine, medium, and coarse pores; many fine, medium, and coarse roots; gradual, smooth boundary to horizon below. Dark gray (10YR 4/1) with a few fine, faint light gray (N 7/ ) mottles; sandy clay loam; very weak fine, medium, and coarse angular to subangular blocky, breaking into weak to moderate fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; many fine and medium roots and common coarse roots; abrupt, smooth boundary to horizon below. Gray to light gray (10YR 6/1-7/1) with many medium and coarse distinct red (2. SYR 4/8) mottles, common medium and coarse dis- tinct yellowish-brown (10YR 5/6-5/8) mottles, and few fine and medium distinct dark gray (10YR 4/1)' mottles; sandy clay loam; very weak fine, medium, and coarse angular to subangular blocky, breaking into weak fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; common fine and medium roots and few coarse roots; diffuse, irregular boundary to horizon below. Gray (10YR 6/1) with many fine, medium, and coarse prominent red (2. SYR 4/8) mottles, and common fine, medium, and coarse dis- tinct yellowish-brown (10YR 5/8) mottles; sandy clay; very weak fine, medium, and coarse angular to subangular blocky, breaking into very weak fine, medium, and coarse granular; friable; many fine, medium, and coarse pores; few fine, medium, and coarse roots. Umbric epipedon, 0-13 inches (0-33 cm). Argillic horizon, 31-63 inches (79-160 cm). 177 Profile N101, Taiama clay loam Classification: Plinthic Umbric Paleaquult Illinois Lab. No. S29106 S29107 S29108 S29109 Depth of horizon (inches) 0-13 13-31 31-42 42-63 Horizon AI A3g B21gt B22gt Percent of entire sample > 2.0 mm 0 0 0 0 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 0.3 0.6 0.7 0.6 Coarse sand 1.0-.5 mm 0.6 1.5 2.0 1.8 Medium sand .5-. 25 mm 2.5 6.3 6.4 6.6 Fine sand .25-.! mm 17.2 36.6 32.9 26.9 Very fine sand .1-.05 mm 10.7 17.2 14.2 13.1 Total sand 2.0-.05 mm 31.3 62.2 56.2 49.0 Coarse silt .05-. 02 mm 6.5 5.3 4.3 4.0 Fine silt .02-. 002 mm 27.0 11.0 8.8 9.6 Total silt .05-. 002 mm 33.5 16.3 13.1 13.6 Total clay < .002 mm 35.2 21.5 30.7 37.4 Water -dispersible clay < .002 mm 10.3 14.1 2.2 0.6 Bulk density 1.2 1.6 1.7 1.7 Moisture: 1/3 atmos. (%) 21.8 15.6 15.5 19.0 15 atmos. (%) 12.0 8.9 10.0 12.4 Avail, moist. -hold, capacity3 0.12 0.11 0.09 0.11 Organic carbon (%) 3.24 0.46 0.13 0.06 Exchangeable cations (me/lOOg soil) : Ca 0.20 0.15 0.08 0.10 Mg ! ! 0.13 ... 0.12 0.10 K 0.02 0.01 0.02 0.02 Na 0.06 0.03 0.03 0.03 Al . . . 3.56 1.94 2.28 2.89 Cation-exch. capacity (me/lOOg) 14.15 5.14 5.00 6.36 Base saturation (%) 2.9 ... 5.0 3.9 pH H20 4.4 4.2 4.4 4.7 PH KC1 3.6 3.4 3.2 3.3 Soil tests: K (Ibs/A) 86 30 39 52 P! (Ibs/A) 29 12 4 P2 (Ibs/A) 32 4 4 Total P (ppm) 300 Total CaO(Z) 0.088 0.069 0.070 0.069 Total Fe203(%) 1.52 0.74 1.14 1.62 Total K20(%) 0.54 0.37 0.62 0.77 alnches of available moisture-holding capacity per inch of soil. 178 Profile T183, Taso clay Described by J. C. Dijkerman on March 4, 1966 Location Torma Bum soil survey area, near the former sugar cane experimental plots; 528 feet (161 m) west of the former sugar cane office, and 898 feet (274 m) west of Sewa River. On aerial photograph 53-SL13-036, pit T183 is 12 cm west and 10 cm south of the northeast corner mark. Physiography Relief Vegetation Drainage Parent material 0-6 inches 0-15 cm Lab. No. S28660 6-12 inches 15-30 cm Lab. No. S28661 B21 12-22 inches 30-56 cm Lab. No. S28662 22-35 inches 56-89 cm B23 35-50 inches 89-127 cm Lab. No. S28663 Diagnostic horizons Sewa River natural levee. Convex 1-percent slope. Predominantly tall elephant grass. Moderately well drained. Clayey alluvium. Black (10YR 2/1); clay; moderate very fine to coarse granular; friable; many fine and medium pores; many fine and medium roots; clear, smooth boundary to horizon below. Very dark grayish brown (10YR 3/2) ; clay; moderate coarse prismatic breaking into moderate medium to coarse angular blocks; firm; few medium and common fine pores; many fine and medium roots; clear, wavy boundary to horizon below. Yellowish brown (10YR 5/6) with common faint and distinct fine and medium strong brown (7. SYR 5/8) and yellowish- red (SYR 4/6) mottles; silty clay; moderate fine to very fine angular blocky; friable; many fine and medium pores; many fine and common medium roots; gradual, smooth boundary to horizon below. Yellowish brown to light brown (10YR 6/4-2. 5Y 6/4) with common to many distinct fine and medium strong brown (7. SYR 5/8) and yellowish-red (SYR 4/6) mottles; silty clay; moderate fine to very fine angular blocky; friable; many fine and medium pores; common fine and medium roots; gradual, smooth boundary to horizon below. Pale yellow (2.5Y 7/4) with many distinct fine and medium strong brown (7. SYR 5/8) and yellowish-red (SYR 4/6) mottles; silty clay; moderate very fine to fine angular blocky; friable; many fine and medium pores; few fine and medium roots. Umbric epipedon, 0-12 inches (0-30 cm). Oxic horizon, 12-50 inches (30-127 cm). Profile T183, Taso clay Classification: Plinthic "Tropeptic" Umbriorthox 179 Illinois Lab. No. Depth of horizon (inches) Horizon S28660 0-6 A, S28661 6-12 S28662 12-22 B21 S28663 35-50 B23 Percent of entire sample > 2.0 nun. ... <1 <1 0+ 0+ Particle-size distribution of < 2 mm (%) : Total sand 2.0-.05 mm 3.4 2.7 3.1 6.7 Total silt .05-. 002 mm 38.0 ... 43.2 46.5 Total elay < .002 mm 58.6 ... 53.7 47.7 Water-dispersible clay < .002 mm .... 16.8 32.0 0.5 0.3 Bulk density 0.8 1.0 1.3 1.3 Moisture: 1/3 atmos. (%) 49.7 41.8 34.9 33.8 15 atmos. (%) 31.4 28.8 22.9 20.7 Avail, moist. -hold, capacity3 0.15 0.13 0.16 0.17 Organic carbon (%) 8.39 3.98 0.47 0.26 Exchangeable cations (me/lOOg soil): Ca 0.80 0.03 0.03 0.06 Mg . ! . 1.02 0.20 0.20 0.24 K 0.44 0.15 0.06 0.09 Na 0.07 0.04 0.04 0.04 Al .!!.... A. 39 3.89 1.56 1.61 Cation-exch. capacity (me/lOOg) 34.65 21.94 7.43 6.79 Base saturation (%) 6.7 1.9 4.4 6.3 PH H20 4.8 4.8 5.3 5.4 PH KC1 3.8 3.9 4.0 4.0 Soil tests: K (Ibs/A) 280 146 86 P^lbs/A) 125+ 10 P2(lbs/A) 125+ 13 6 14 Total P(ppm) 1,460 680 590 680 Total CaO(%) 0.196 0.132 0.114 0.143 Total Fe203(%) 6.85 7.50 5.70 7.H Total K20(%) 1-550 1.520 1.740 2.200 alnches of available moisture-holding capacity per inch of soil. 180 Location Profile PI 9, Timbo gravelly sandy clay loam Described by J. M. Cawray, A, A. Thomas, and R, Miedema on March 27, 1968 Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates Physiography Relief Vegetation Drainage Parent material 0-12 inches 0-30 cm Lab. No. S29818 12 12-19 inches 30-49 cm Lab. No. S29819 AB 19-28 inches 49-70 cm Lab. No. S 29 820 B21 28-43 inches 70-110 cm Lab. No. S29821 B22 43-70 inches 110-179 cm Lab. No. S29822 Diagnostic horizons HE26 -85 ; near Timbo along the motor road from Makeni to Panlap. Dissected erosion surface. Slope 6 percent to south. Cassava and short weeds and grasses. Well drained. Gravelly weathering products of Precambrian granite and acid gneiss. Very dark grayish brown (10YR 3/2) ; gravelly sandy clay loam; weak fine Subangular blocky; slightly hard, friable, slightly sticky, and slightly plastic; many macro- and mesopores; few fine distinct char- coal particles; common coarse and medium roots; 44% fine and medium, uncoated nodular, red, hardened plinthite glaebules, and a few decom- posed rock fragments; clear, smooth boundary to horizon below. Dark brown (10YR 3/3) ; very gravelly sandy clay loam; weak fine sub- angular blocky; slightly hard, friable, slightly plastic; many macro- and mesopores; few fine distinct charcoal particles; common coarse, medium, and fine roots; 50% medium and fine, uncoated nodular, very hard, porous, yellow and red, decomposed rock fragments; clear, wavy boundary to horizon below. Yellowish red (5YR 4/6) ; gravelly sandy clay loam; weak fine subangu- lar blocky; friable, slightly sticky, and slightly plastic; many macro- and mesopores; few coarse, medium, and fine roots; 47% un- coated, very hard, porous, red and yellow, decomposed rock fragments; few feldspars and micas, especially in the decomposing rock pieces; gradual, wavy boundary to horizon below. Yellowish red (5YR 4/8); gravelly sandy clay loam; weak medium angu- lar and subangular blocky; friable, slightly sticky, and slightly plastic; many macro- and mesopores; few coarse, medium, and fine roots; 44% coarse, medium, and fine, uncoated, soft to hard, porous, red and yellow, decomposed rock fragments; few micas and feldspars; diffuse, smooth boundary to horizon below. Yellowish red (5YR 5/8) ; gravelly sandy clay loam; weak medium angu- lar blocky; sticky and plastic; common macro- and mesopores; few coarse, medium, and fine roots; 20% coarse and medium, uncoated, soft to hard, porous, red and yellow, decomposed rock fragments, with feldspars and micas. Umbric epipedon, 0-19 inches (0-49 cm) . Oxic horizon, 28-70 inches (70-179 cm) somewhat questionable because of the presence of primary minerals and evidence of rock structure. Cambic horizon, 19-70 inches (49-179 cm) if there is no oxic horizon between 28 and 70 inches. Profile P19, Timbo gravelly sandy clay loam Classification: Typic Umbriorthox (or Udoxic Dystropept) 181 Illinois Lab. No. Depth of horizon (inches) Horizon S29818 S29819 S29820 S29821 S29822 0-12 12-19 19-28 28-43 43-70 11 12 AB H 21 22 Percent of entire sample > 2.0 mm . . 44 .4 50. 6 46 .6 43. 7 28. 7 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm . . 14 .4 13. 2 17 .7 19. 2 18. 6 Coarse sand 1.0-.5 mm . • 8 .3 8. 9 10 .1 8. 3 7. 2 Medium sand .5-. 25 mm . . 15 .2 12. 9 10 .9 9. 4 7. 7 Fine sand .25-.! mm . . 23 .5 17. 3 12 .9 12. 6 11. 4 Very fine sand . 1-.05 mm . . 6 .8 6. 9 6 .0 6. 2 6. 8 Total sand 2.0-.05 mm . . 68 .2 59. 2 57 .6 55. 7 51. 7 Total silt .05-. 002 mm . . 11 .7 12. 6 11 .7 13. 6 14. 6 Total olay < .002 mm . . 20 .1 28. 2 30 .7 30. 7 33. 7 Water-dispersible clay < .002 mm . , 3 .1 6. 2 9 .6 1. 1 0. 6 Bulk density . . 1 .2 1. 2 1 .2 1. 2 1. 3 Moisture: 1/3 atmos. (%) . . 15 .9 17. 2 17 .3 16. 4 17. 2 15 atmos. (%) . . 9 .8 11. 2 12 .4 12. 8 13. 1 Avail, moist. -hold, capacity . . 0 .04 0. 03 0 .03 0. 02 0. 04 Organic carbon (%) 2 .34 1. 87 1 .05 0. 70 0. 51 Exchangeable cations (me/lOOg soil) : Ca . . 0 .47 0. 21 0 .16 0. 21 0. 38 Mg . . 0 .27 0. 21 0 .21 0. 11 0. 15 K , . . 0 .15 0. 09 0 .09 0. 06 0. 13 Nab . . 0 .15 0. 12 0 .12 0. 10 0. 15 Al . . 0 .82 1. 09 0 .43 0. 31 0. 24 Cation-exch. capacity (me/lOOg) . . 7 .64 6. 36 4 .57 3. 79 3. 79 Base saturation (%) . . 13 .6 9. 9 12 .7 12. 7 21. 4 pH H20 . . 4 .6 4. 8 4 .8 4. 8 4. 9 pH KC1 4 .2 4. 2 4 .2 4. 4 4. 6 Soil tests: K (Ibs/A) . . 166 125 106 102 118 P^lbs/A) 28 8 4 3 2 Total CaO(%) . . 0 .122 0. 094 0 .083 0. 081 0. 086 Total Fe203(%) , . 10 .36 11. 45 13 .50 14. 44 14. 86 Total K20(%) . . 0 .492 0. 525 0 .488 0. 433 0. 485 alnches of available moisture-holding capacity per inch of soil, adjusted for the .amount of > 2.0 mm material. D Estimated values. 182 Profile P13, Tubum sandy loam Described by J. M. Cawray, A. A. Thomas, and R. Mledema on March 23, 1968 Location Physiography Relief Vegetation Drainage Parent material "11 0-4 inches 0-11 cm Lab. No. S29813 12 4-13 inches 11-34 cm Lab. No. S29814 Bl 13-25 inches 34-64 cm Lab. No. S29815 B21 25-33 inches 64-85 cm Lab. No. S29816 IIB22 33-54 inches 85-138 cm Lab. No. S29817 Diagnostic horizons Topographic map of Sierra Leone, scale 1:50,000, sheet 43, coordinates HE27--87,.; on traverse E, 1,500 feet (457 m) from pit P7. Gently sloping terrace. Slope 7 percent to NNW. Tall elephant grass, medium trees, and many wild oil palms. Well drained. Alluvium or colluvium or a mixture of both, over weathering products of Precambrian granite and acid gneiss. Very dark brown (10YR 2/2); sandy loam; weak fine to med- ium subangular blocky; hard, friable, slightly sticky, and slightly plastic; many macro- and mesopores ; few medium distinct charcoal particles; common coarse and medium, many fine roots; clear, smooth boundary to horizon below. Dark brown (10YR 3/3) ; sandy loam; weak coarse angular blocky; slightly hard, friable, slightly sticky, and slightly plastic; many macro- and mesopores; few medium distinct charcoal particles; few coarse, common medium, and many fine roots; clear, irregular boundary to horizon below. Dark yellowish brown (10YR 3/4) ; sandy clay loam; weak medium and coarse angular blocky; hard, firm, sticky, and plastic; many macro- and mesopores; few medium distinct charcoal particles; common coarse, medium, and fine roots; gradual, smooth boundary to horizon below. Dark yellowish brown (10YR 4/4) ; sandy clay loam; weak medium subangular blocky; hard, firm, sticky, and plastic; many macro- and mesopores; few medium distinct charcoal particles; common medium and many fine roots; abrupt, wavy boundary to horizon below. Yellowish brown (10YR 5/6); very gravelly sandy clay loam; weak fine subangular blocky; hard, firm, slightly sticky, and slightly plastic; many macro- and mesopores; few medium distinct charcoal particles; many fine roots; about 30 percent coarse quartz gravel and 40 percent medium black- coated and uncoated, nodular, dense, black to yellow, hardened plinthite glaebules. Umbric epipedon, 0-13 inches (0-34 cm). Cambic horizon, 13-54 inches (34-138 cm). 183 Profile PI 3, Tubum sandy loam Classification: Udoxic Dystropept Illinois Lab. No. S29813 S29814 S29815 S29816 ^— ^— — — ^^— S29817 Depth of horizon (inches) 0-4 4-13 13-25 25-33 33-54 Horizon All A12 Bl B21 IIB?? Percent of entire sample > 2.0 mm 0.8 0.7 1.0 1.7 77.2 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 2.5 3.0 3.2 4.1 8.7 Coarse sand 1.0-.5 mm . 14.5 16.2 15.4 14.4 18.5 Medium sand .5-. 25 mm . 27.6 26.4 22.5 21.1 19.7 Fine sand .25-.! mm . 24.3 21.6 18.9 18.6 14.7 Very fine sand . 1-.05 mm 9.0 8.1 7.8 8.3 6.8 Total sand 2.0-.05 mm . 77.9 75.3 67.8 66.5 68.4 Total silt .05-. 002 mm . 10.3 6.7 11.6 11.3 10.6 Total clay < .002 mm . 11.8 18.0 20.6 22.2 21.0 Water-dispersible clay < .002 mm 3.6 5.6 8.7 9.8 12.7 Bulk density 1.1 1.2 1.3 1.4 1.5 Moisture: 1/3 atmos. (%) . 12.9 13.2 13.9 13.8 13.3 15 atmos. (%) 6.5 8.1 8.9 8.7 8.8 Avail, moist. -hold, capacity3 0.07 0.06 0.06 0.07 0.02 Organic carbon (%) 2.65 1.64 1.09 0.74 0.55 Exchangeable cations (me/lOOg soil) : Ca 0.74 0.16 0.16 0.05 0.21 Mg 0.47 0.37 0.37 0.21 0.11 K 0.15 0.04 0.08 0.06 0.06 Na 0.14 0.09 0.12b 0.10b 0.10b Al 0.67 1.12 1.30 1.29 0.98 Cation-exch. capacity (me/lOOg) 6.78 5.71 5.36 4.79 3.85 Base saturation (%) . 22.1 11.6 13.6 8.8 12.5 pH H20 4.9 4.7 4.7 4.6 4.7 pH KC1 4.2 4.2 4.2 4.1 4.2 Soil tests: K (Ibs/A) . 190 86 65 52 65 P! (Ibs/A) . 21 8 5 4 4 Total CaO(%) 0.154 0.086 0.082 0.080 0.077 Total Fe203(%) 2.04 2.73 3.24 3.36 3.28 Total K20(%) 1.427 1.434 1.475 1.494 1.431 alnches of available moisture-holding capacity per inch of soil, adjusted for the amount of > 2.0 mm material. ^Estimated value. 184 Profile 145010, Vaahun gravelly sandy clay loam Description after Sivaraj asingham (64) Location Physiography Relief Vegetation Drainage Parent material 0-6 inches 0-15 cm Lab. No. S28561 Bl 6-20 inches 15-51 cm Lab. No. S28560 B2 20-28 inches 51-71 cm Lab. No. S28559 28-40 inches 71-102 cm On a very high hill on the left side of the road from Mano Junction to Segbwema Junction after the village of Niahun. The foot path to the hill starts from the road at a point opposite the village school. Very high hills. The pit is on the upper part of a very steep (38-percent) slope of a very high hill. The area was in upland rice during 1965; in 1966 it was under low, succulent herbaceous bush. Moderately well drained. Residual from quartz-rich granite. Very dark gray (10YR 3/1) ; gravelly sandy clay loam, slightly gritty; few fine, very hard, fresh rock gravel and charcoal particles; strong fine granular and fine subangular blocky; friable, nonsticky, slightly plastic; common fine and medium roots; clear, smooth boundary to horizon below. Yellowish brown (10YR 5/6) with large fillings in old burrow holes of dark brown (10YR 3/3) material, presumably derived from A-^; gravelly clay; strong fine subangular blocky; friable, slightly sticky, slightly plastic; common fine and medium roots; gradual, smooth boundary to horizon below. Yellowish brown (10YR 5/6) with many medium, faint dark yellowish-brown (10YR 4/4) mottles; gravelly clay; strong fine subangular blocky; friable, slightly sticky, slightly plastic; few hard, decom- posing and fresh rock gravel; soil material probably derived from rock weathered in place with a little local movement; common fine and medium roots; abrupt, irregular to wavy boundary to horizon below. Soft, decomposing, coarse-grained, quartz-rich, gneissic granite containing feldspar, biotite, and coarse horn- blende grains. Diagnostic horizons Ochric epipedon, 0-6 inches (0-15 cm). Cambic horizon, 6-28 inches (15-71 cm) 185 Profile 145010, Vaahun gravelly sandy clay loam Classification: Typic Dystropept Illinois Lab. No. S28561 S28560 S28559 Depth of horizon (inches) 0-6 6-20 20-28 Horizon A B B2 Percent of entire sample > 2.0 mm 26.9 30.1 33.4 Particle-size distribution of < 2 mm (%) : Very coarse sand 2.0-1.0 mm 20.5 11.5 8.2 Coarse sand 1.0-.5 mm 15.0 8.8 Medium sand .5-. 25 mm 7.0 4.1 4.4 Fine sand .25-.! mm 8.3 5.3 5.8 Very fine sand .1-.05 mm 5.6 3.6 4.8 Total sand 2.0-.05 mm 56.4 32.1 31.7 Total silt .05-. 002 mm 14.5 11.1 13.2 Total clay < .002 mm 29.1 56.8 55.1 Water-dispersible clay < .002 mm 6.5 24.0 15.3 Moisture: 1/3 atmos. (%) 19.4 26.1 28.1 15 atmos. (%) 14.7 20.5 21.1 Organic carbon (%) 3.80 1.10 0.90 Exchangeable cations (me/lOOg soil) : Ca 5.18 1.17 1.05 Mg 1.51 0.60 0.52 K 0.55 0.06 0.07 Na 0.06 0.07 0.08 Al! 0.31 2.33 1.83 Cation-exch. capacity (me/lOOg) 18.79 15.01 16.95 Base saturation (%) 38.9 12.7 10.1 PH H20 5.3 4.8 PH KCL 4.4 3.8 3.9 Soil tests: K (Ibs/A) P (Ibs/A) 4 P2 (Ibs/A) 9 Total P (ppm) 310 200 Total CaO(%). 1-190 0.566 0.743 Total Fe203(%) 5.80 7.05 7.50 Total K20(%) 0.716 0.510 0.250 186 187 APPENDIX C. AMOUNT AND CHARACTERIZATION OF THE CLAY FRACTION IN SELECTED SOILS IN SIERRA LEONE Information given in the left-hand portion of Table I in Appendix C indicates the activity of the clay and the ease with which it disperses in water. This information is especially useful in classifying the soil series into higher categories according to Soil Taxonomy (69) , as discussed in Section 4:12. Estimates of amounts of different kinds of clay miner- als were made primarily on X-ray diffractograms of glycolated, Mg-saturated, and K-saturated orientated clays on glass slides, using Cu Ka radiation at 35 kv and 15 ma (See also Table 3, pages 20 and 21 ). Other helpful analyses for estimating the kinds and amounts of clay minerals included the following : — Cation-exchange capacity of the clay fraction by saturating the clay with IN neutral ammonium acetate and removing excess salts on ceramic plates prior to distillation. — Thermal gravimetric analyses (TGA) by weighing clay samples in an oven at hundred-degree intervals from 100° to 600° C. — -Differential thermal analyses (DTA) of a few key clay samples to check especially for kaolinite and gibbsite. The composition of the clay fraction (< 0.002 mm) was determined primarily by measuring the areas under peaks of diffractograms of Mg-saturated samples (peak heights, in counts per second, were also compared). For illite, these were checked against total K2O analyses of the clay fraction, where available. It is generally recog- nized (47) that kaolinite content tends to be overesti- mated from diffractograms because of the high intensity of their diffraction patterns. Therefore, the Mg-saturated area estimates for kaolinite content were reduced, usually 10 to 20 percent, on the basis of regressions between the content of kaolinite estimates from Mg-saturated area diffractograms versus weight loss from heat at 350° to 550° C. When the percent kaolinite estimates were re- duced accordingly, estimates for the other clay materials were correspondingly increased to total 100 percent. In general, the reductions in kaolinite estimates for clay samples that contained interstratified materials were less than for samples that did not contain interstratified material. The following clay minerals occurred in the soil sam- ples studied: kaolinite, gibbsite, quartz, goethite, chlorite, illite, and an assemblage of interstratified minerals with 2d spacings of 10, 12, 14, and 24 A (right-hand portion of Table I) . According to Lucas (47) , 10 A illite interstrati- fied with 14 A chlorite gives a 24 A mineral ( 10-14C) that is stable and unaffected by glycerol or heat treatment. We have found that potassium treatment likewise does not affect this mineral. Illite interstratified with 14 A vennic- ulite gives a mineral (10-14V) that is unaffected by gly- cerol treatment but that decreases to 10 A on heating to 550° C (47) ; we have further found that potassium treat- ment also collapses this mineral to 10 A. Diffractograms show that the interaction of 10 A illite with a 14 A min- eral — chlorite or vermiculite or both — is common in Sierra Leone soils and gives a sequence of 10, 12, 14, and 24 A spacings. However, the proportion of 10 A versus 14 A material available influences the resultant assemblage of pure clays with these spacings and the interstratified combinations. For example, if all 10 A material reacts with excess 14 A material, no pure 10 A material (illite) will remain, but 24 A, 14 A, and second-order 12 A lines occur. Likewise, if all of the 14 A material is interstrati- fied, no pure chlorite (14 A) will be evident. Vermiculite as a constituent of interstratification is common, but it is found only in trace amounts as an individual mineral. Gibbsite is present in many of the soils; however, a limited number of DTA analyses showed lower amounts than the X-ray diffraction analyses. The problem of evaluating small percentages of gibbsite, primarily on the 4.8 A diffraction line, is confounded by the 5.0 A line of illite and a 4.7 A line of chlorite. Therefore, when illite and chlorite are present in considerable amounts, the gibbsite values listed are probably maximum values. Lucas (47) identified sepolite in Triassic clays, pri- marily on a sharp 12 A line. It must be pointed out, however, that many of the soil clays, particularly in the Rokel River Series in Area G* in Sierra Leone, exhibit a 12 A peak along with lines from kaolinite, illite, and chlorite that could mask the several diagnostic lines of sepolite. Therefore, sepolite could not definitely be ruled out as a constituent of these soils. Because interlayering is so pronounced, the 12 A line seems to be more a second-order spacing of a 24 A line rather than the mineral sepolite. The amount of amorphous material in the clay frac- tion was not considered in this study. No alkali or re- ductant-base extractions or electron micrographs were made that would help evaluate the presence of amor- phous minerals, which may occur in significant amounts. The clay fraction (< 0.002 mm) of selected samples was analyzed for total potassium, iron, aluminum, and titanium by X-ray spectroscopy (Table II). The K2O content (x 10) was especially helpful in estimating the amount of illite in the clay fraction. The clay was pre- pared by fusing 0.1 g of hydrogen-saturated clay with 0.1 g of La2O3 and 0.8 g Li2B4O7 in graphite crucibles, followed by grinding and pressing. 188 Table I. Amount and characterization of the clay fraction (< 0.002 mm) in selected soils in Sierra Leone Me. extr. Composition of the clay fraction bases + Me. 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III I I I I 111 CX. 1 I 1 1 1 1 « .5 i 111 i i i i ii 111 i i i i a. i i i 3 . 73 e * i-H CM ft D. O C «J -H a, a. g 5 tq 01 ^ J3 ^ 5 " 3 § (0 'rl "O *3 ^ s c c r3 3 ** Z ^ *" -^ 1 "S ^ O g —i 3 CM *4 r*i "MCO 8>n (03 3 "H B 3 WPM *t* 3 C 3 pH 2O 3x> 2 ^ -T ^ J3 " ^: o xi o Otp BOO • O *Q M 1-1 o - i « u~i oo in C3 O -T >. in C3 Section 4:1. agnostic properties io of clay in the er-dispersible claj io of conventional isor is Z conventic er Lucas (47). C,\ j, 192 Table II. Total analyses of the clay fraction « 0.002 mm) in selected soils in Sierra Leone Soil Soil series and province profile number (Fig. 8) Depth, inches Horizon Total analyses of clay, % Loss on ignition, % K20 Fe203 A1203 Ti02 B* Sandy beach ridges 80-120 C 0.54 6.6 32.6 1.00 13.8 Gbamani, T165 D* Alluvial floodplain grasslands Taso, T183 0-6 6-12 12-22 35-50 Al A3 B21 B23 0.58 0.47 7.3 7.7 8.4 7.9 33.8 35.6 0.84 0.80 13.5 13.1 Gbehan, T187 0-5 5-11 11-14 23-52 Al A3g Big B22g 0.44 0.52 1.9 2.5 2.8 4.6 31.3 38.4 0.76 0.87 12.6 15.2 G* Rokel River Series, Njala area 0-7 15-33 42-57 Al B21 IIB23 1.97 2.22 8.2 8.5 10.6 28.1 32.4 1.07 1.29 11.1 10.5 Momenga , N44 Mokonde, N42 0-5 39-60 Al IIIB23 1.47 1.76 7.3 11.7 31.4 34.0 1.00 1.11 10.8 11.7 Bonjema, N39 0-4 25-33 57-70 Al IIB21 IIIB23 1.68 2.69 6.3 8.9 8.7 26.4 29.9 1.1 1.3 10.5 10.0 Pelewahun, N47 matrix 0-11 17-25 25-41 41-72 Al B21t IIB22t IIIB23t 1.60 2.22 4.2 4.8 8.1 5.3 29.6 29.9 1.29 1.20 10.5 10.2 L* Granite and acid qniess in the upper Moa Basin, Kenema area 7.0 6.7 6.6 35.1 40.4 0.66 0.60 13.6 14.2 Vaahun, 145010 0-6 6-20 20-28 Al Bl B2 0.42 0.36 Segbwema, 145005 0-13 28-60 60-94 Al B22 Cl 0.41 0.38 8.3 9.5 7.4 35.5 36.6 0.58 0.53 13.2 13.1 Manowa , Kpuabu 1 0-10 10-21 35-70 Al A3 B22t 0.45 0.42 13.9 13.4 14.7 33.1 39.7 2.03 1.70 14.9 15.2 Baoma, 144801A 0-5 5-23 43-67 Al B2t IIB32 0.28 0.28 15.3 17.9 20.3 24.4 34.6 1.06 1.37 13.8 14.4 Keya, 145041 5-11 21-33 A12 IHClg 0.74 0.44 1.3 1.4 20.9 37.7 0.25 0.73 12.8 14.6 Pendembu, Kpuabu 2 0-7 7-18 37-54 Al A3 B2t 0.57 0.48 7.2 7.7 6.6 34.6 36.2 1.35 1.31 13.4 14.6 Kparva, 145042 0-9 9-39 39-66 68-80 Al B2t B3t IIIC2 0.56 0.52 5.1 5.8 4.2 5.4 35.6 37.9 0.99 1.06 13.3 15.2 Moa , Kpuabu 3 0-6 6-21 31-59 Al B21 B3 10.8 10.7 9.7 193 APPENDIX D. ESTABLISHED SOIL SERIES IN SIERRA LEONE, SOIL PROVINCE IN WHICH THEY OCCUR, DIAGNOSTIC: HORI/ONS, THICKNESS OF GRAVEL-FREE LAYER, AND INDEX FOR SOILS DESCRIBED IX THIS PUBLICATION Thickness Index: page on which is Soil series^/ Soil of gravel- Management province Diagnostic horizons (69) free top Dis- Classi- recommen- (Fig. 8) Epipedon Subsurface layer (in.) cussion fication dations Data Babaibunda I* Ochric Oxic or argillic >48 Bali D* Umbric Oxic >48 Baoma L* Ochric Argillic (or oxic) 10-48 59 69 81 98 Batieraa G* Ochric Argillic 10-24 Batkanu I* Ochric Argillic (or oxic) 0-10 Belebu G* Ochric Argillic 0-10 Belia I* Ochric Cambic 0-10 Bora I* Ochric Cambic >48 Bonganema G* Ochric Argillic (or cambic) >48 Bon j ema G* Ochric Argillic (or cambic) 24-48 39 69 81 100, 102 Bosor J* Umbric Argillic (or cambic) 24-48 51 69 81 104 Diabama I* Ochric Cambic 10-24 Dowjo L* Umbric Cambic >48 Fanima L* Umbric Oxic 0-10 Gbamani B* Ochric Spodic >48 29 69 82 106 Gbehan B* Ochric Oxic >48 32 69 81 108 Gbesebu G* Ochric Cambic >48 45 69 78 110, 112 Giema L* Umbric Oxic 0-10 Gullied Land^/ G* Ochric Cambic >48 Hahun B* Umbric >48 Kania G* Umbric Argillic (or oxic) >48 43 71 78 114 Keya L* Ochric >48 62 71 81 116 Kontobe I* Ochric Cambic (or argillic) >48 Koyema D* Ochric Oxic >48 Kparva L* Ochric Argillic (or oxic) >48 62 72 81 118 Mabang I* Ochric Argillic >48 Mabanta J* None or 0-24 ochric Mabassia J* Umbric Cambic or argillic 10-48 51 72 81 120, 122 Mabole I* Ochric Oxic or argillic >48 Madina I* Ochric Oxic (or argillic) >48 Magbunga I* Ochric Cambic >48 Makeni J* Umbric Argillic 0-10 49 72 82 124 Makoima I* Ochric Oxic >48 Makoli I* Ochric Argillic or oxic 10-24 Makonte I* Ochric Oxic or argillic >48 Makundu J* Umbric Oxic >48 56 72 78 126 Malansa I* Ochric Oxic or argillic >48 Malinka I* Ochric Argillic or cambic 0-10 Malop I* Ochric Petroferric contact 10-24 Mamalia I* Ochric Argillic or oxic, 10-24 petroferric contact Mamu D* Ochric >48 Mandu L* Ochric Cambic (or oxic) 24-48 Mani D* Ochric >48 Mankahun I* Ochric Argillic or cambic 24-48 Mankane J* Ochric Cambic >48 55 72 81 128 Manowa L* Umbric Argillic (or oxic) 0-10 59 72 82 130 Mara I* Ochric Argillic 24-48 Maroki. I* Ochric >48 Masebra I* Ochric Oxic or argillic, 24-48 petroferric contact Masheka J* Umbric Argillic (or cambic) >48 53 72 81 132 Massimo I* Ochric Cambic (or argillic) >48 (Footnotes given at end of table. ) 194 Soil series^/ Soil provinc (Fin. 8 a Diagnostic horizons (69) Thickness of gravel- free top layer (in.) Index: page on which is Dis- cussion Management Classi- recommen- fication dations Data ) Epipedon Subsurface Masuba J* Ochric Cambic >48 54 73 81 134 Masuri I* Ochric Argillic or cambic 24-48 Matamba I* Ochric Argillic or oxic >48 Mateboi I* Ochric Cambic >48 Matutu I* Ochric Argillic or oxic, 10-24 petroferric contact Mayanki I* Ochric Argillic or oxic 0-10 Moa L* Ochric Oxic (or cambic) >48- 64 73 78 136 Mogbondo G* Ochric Cambic 24-48 (or umbric) Mokoli G* Ochric Cambic >48 46 73 78 138 Mokonde G* Ochric Argillic (or cambic) 10-24 36 73 81 140 Momenga G* Ochric Cambic 0-10 33 73 82 142, 144, 146 Mosungo G* Ochric Variable Moyambaworo G* Ochric Argillic >48 Naba D* Umbric Oxic >48 Ngelehun L* Ochric Oxic >48 Njala G* Ochric Argillic 0-10 36 73 81, 148, or umbric 82 150 Nyawama G* Umbric Argillic (or oxic) >48 42 74 78 152, or ochric 154, 156 Panderu L* Ochric Oxic (or argillic) 24-48 Panlap J* Umbric >48 55 74 81 158 Pelewahun G* Umbric Argillic 24-48 41 74 81 160, or ochric 162 Pendembu L* Ochric Argillic 36-54 62 74 81 164 Pujehun G* Ochric Cambic >48 44 74 78 166 Rochin I* Ochric Cambic >48 Rock Land£/ G*,J*, None or 0-24 47, 82 L* ochric 58 Rokel I* Ochric Oxic (or argillic) >48 Rokupr C* None or Sulfuric or none >48 30 74 82 168, ochric 170 Romankne I* Ochric Cambic (or argillic) >48 Rosinth J* Ochric Argillic 10-24 Bahama B* Ochric or >48 29 74 82 172 umbric Sangama D* Umbric Cambic >48 Segbwema L* Ochric Oxic (or cambic) >48 59 75 82 174 Sell I* Umbric Oxic or cambic >48 Senehun D* Ochric >48 Sewa D* Umbric Cambic >48 Tabai I* Ochric Cambic >48 Taiama G* Umbric Argillic >48 43 75 81 176 Talia D* Umbric Oxic >48 Taso D* Umbric Oxic >48 32 75 78 178 Timbo J* Umbric Oxic (or cambic) 0-10 47 75 82 180 Tisso L* Umbric Oxic (or argillic) 24-48 Torma Bum D* Ochric Cambic >48 or umbric Tub urn J* Umbric Cambic 24-48 52 75 81 182 Vaahun L* Ochric Cambic 0-10 58 75 82 184 Walma L* Ochric Oxic 10-24 War! I* Ochric Petroferric contact 0-10 Yumbuma L* Ochric Oxic >48 ^f ± ri& L-& C-Ul/L-\ £/Land type. UNIVERSITY OF ILLINOIS-URBAN*