U. S. DEPARTMENT OF AGRICULTURE. BDRBAn OF SOILS— inWON WIITSET, Ciiet. 220.^ / SOIL SURVEY OF THE MIDDLE GILA VALLEY AREA, ARIZONA. D 001 108 858 0 BY E. C. ECK^IANN, In Charge, MARK BALDWIN, and E. J. CARPENTER. MACY H. LAPHAM, Inspector, Western Division. [Advance Sheets— Field Operations of tlie Bureau of Soils, 1917.] UCLA SEL/Geology Collection WASHINGTON: GOVERNMENT PRINTING OFFICE. 1920. BUREAU OF SOILS. Milton Whitney, Chief of Bureau. Albert G. Rice, Chief Clerks SOIL SUBVEY. CuBTis F. Marbut, In Charge. G. W. Baumann, Executive Assistant. COMMITTEE ON THE CORRELATION AND CLASSIFICATION OF SOILS. Curtis F. Marbut, Chairman. Hugh H. Bennett, Inspector, Southern Division. W. Edward Hearn, Inspector, Southern Division. Thomas D. Rice, Inspector, Northern Division. W. E. McLendon, Inspector, Nortliern Division. Macy H. Lapham, Inspector, Western Division. M. W. Patterson, Secretary. U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF SOILS— BIILTON WHITNEY, Chief. SOIL SURVEY OF THE MIDDLE GILA VALLEY AREA, ARIZONA. BY E. C. ECKAIANN, In Charge, MAKK BALDWIN, and E. J. CARPENTER. MACY H. LAPHAM, Inspector, Western Division. [Adyance Sheets — Field Operations of the Bureau of Soils, 1917.] WASHINGTON: GOVERNMENT PRINTING OFFICE. 1920. LETTER OF TRANSMITTAL. U. S Department or Agricitlture, Bureau of Soils, Washington, D. 6'., DeceTriher 15, 1919. Sir: I have the honor to transmit herewith the manuscript report and map covering the survey of the Middle Gila Valley Area, Arizona, and to recommend that they be published as advance sheets of Field Operations of the Bureau of Soils, 1917, as authorized by law. Respectfully, Milton Whitney, Chief of Bureau, Hon. D. F. Houston, Secretary of Agriculture, CONTENTS. Page. Soil Srm-EY of the Middle Gila Valley Akea, Arizona, By E. C. EcKMAN, In Charge, Mark Baldwin, and E. J. Carpenter 5 Description of tlie area 5 Climate 8 Agriculture 11 Soils 16 Pinal gravelly sandy loam 19 Mohave sandy loam 20 Mohave fine sandy loam 21 McClellan loam 22 McClellan clay loam 24 Gila fine sand ^ 25 Gila silty clay loam 26 Pima clay 28 Rough stony land 29 Riverwash _. 29 Irrigation 30 Drainage 31 Alkali : 32 Summary 35 ILLUSTRATIONS. PLATES. Page. Plate I. Fig. 1. — View overlooking desert soils grouped in the Mohave series. Fig. 2. — Alfalfa on Mohave sandy loam, near Casa Grande 16 II. Fig. 1. — View in Gila River bottoms near Florence. Fig. 2. — Alfalfa on Gila silty clay loam, near Florence 16 colored plate. Plate A. Alkali map. Middle Gila Valley sheet 32 FIGLTIE. I'iG. 1. Sketch map showing location of the Middle Gila Valley Area, Arizona 5 MAP. Soil map, Middle Gila Valley sheet, Arizona. 3 SOIL SURVEY OF THE MIDDLE GILA VALLEY AREA, ARIZOKA. By E. C. ECKMANN, In Charge; MARK BALDWIN and E. J. CARPENTER— Area Inspected by MACY H. LAPHAM. DESCRIPTION OF THE AREA. The Middle Gila Valley area is situated in the south-central part of Arizona, mainly in Pinal County, only 2 s(|uare miles being in Maricopa County. It lies in a region of isolated or discontinuous, barren, rocky peaks and ranges, mainly of eruptive and crystalline formations, which rise from sloping or nearly level desert plains. This part of the State is recognized physiographically as the Desert region, in contrast to the much higher lying Plateau region of sedi- mentary rocks occupying the northern and northeastern parts of the State. As the title implies, the survey includes the middle valley of the Gila River, which presents a contrast to both the upper valley, in the eastern part of the State, and the lower desert valley above the confluence of the Gila Eiver with the Colorado. The area surveyed is irregular in out- line, and roughly Y-shaped. Beginning at the mouth of the Gila River Canyon, about 6 miles northeast of Florence, it spreads out westward and southwestward as a fan- shaped area, which is soon divided into two arms by the Sacaton Mountains, which it practically surrounds on the north, east, and south. The northern arm, lying between the Sacaton i\lountains on the south and the Santan Mountains on the northeast, extends westward to Pima Butte. It includes the alhmal bottoms of the Gila River, with parts of the adjacent higher lying plains. The southern arm is confined to a tier of townships extending westward from Picocho Reservoir in town- ships 5 and 6 south to the middle of range 5 east. Small parts of the adjoining townslni)s to the south are also included. The area in- cludes the Sacaton, Casa Blanca, Agency, and Blackwater units, and parts of the Casa Grande and Florence units, of the Gila River irri- FiG. 1. — Sketch map showing location of the Middle Gila Valley area, Arizona. 6 FIELD OPERATIONS OF THE BUREAU OF SOILS, lOl*?. gation project of the Office of Indian Affairs. The Casa Grande National Monument and j^art of the Gila Eiver Indian Eeservation also are within the survey. The total extent of the area is 352 square miles, or 225,280 acres. The area is made up almost entirely of river bottoms or smooth, nearly level plains, the adjoining mountains having been practically excluded, except for several small hills or buttes. The most promi- nent of these are Twin Butte, Granite Ivnob, part of Cholla Moun- tain, and part of the eastern slope of Pima Butte. The slopes of the included hills are stony and steej). Elevations within the area range from about 1,150 to 1,525 feet above sea level. Casa Grande has an elevation of 1,396 feet; Casa Grande Ruins (Casa Grande National Monument), 1,422 feet; Florence, 1,493 feet; and S'acaton, 1,280 feet. The Gila River, which crosses the area from east to west, is the sec- ond largest stream in Arizona. The lands lying along this stream are directly drained by it, but the greater part of the area is drained directly by McClellan Wash, which reaches the Gila River within the area. Santa Cruz Wash carries the drainage from the southern part of the area, around Casa Grande, and enters the Gila River a short distance west of the area. The McClellan and Santa Cruz Washes are not everywhere well defined, and they are inadequate to drain a number of large flat areas. The Gila River has a channel varying in width from less than one-fourth mile to a mile or more. The banks of this stream are generally poorly defined and unstable. Shifting of the channels and cutting of the banks take place at each overflow, and the process is increasingly destructive as the stream- bottoms are used more extensively for agriculture. The stream has an average gradient of about 10 feet per mile through the area. The McClellan and Santa Cruz Washes are the continuation of the drainage of the Santa Cruz River, which ceases to maintain a definite channel below a point in the southern part of Pinal County, its waters spreading oa er the level plain or flowing slowly down the numerous shallow washes between Picocho Reservoir and Casa Grande. The lands along the McClellan and Santa Cruz Washes are subject to overflow from flood waters that come from the region of Tucson, southeast of the area surveyed. The McClellan Wash has a fall of about 20 feet in its course from the Picocho Reservoir to its confluence with the Gila River. The retarded drainage of the southern part of the area gives rise to many shallow lakes or playa flats, which are dry except during heavy rains. These flats are dotted with and bordered by shifting sand dunes. In 1910 the population of l^inal County was 9,045 — an increase of 16 per cent over that reported in 1900. While the area surveyed SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 7 covers only about 350 square miles in Pinal County, whose total ex- tent is 5,380 square miles, it includes by far the most thickly settled part of the county. The number of Indians in 1910 on that part of the Gila Eiver Indian Reservation in Pinal County was 2,970, or about one-third the total population of the county. About 64 per cent of the total population is white. There are a few Negroes, Chinese, and Japanese. About 46 per cent of the population consists of native white j^ersons and 18 per cent of foreign-born white per- sons. Of the foreign born, people from Mexico :k>rm by far the largest num])er, the Mexicans numbering 1,360 in 1910. The population of the cities and towms is made up chiefly of white persons. The Indian population is of the Pima tribe and confined almost entirely to the reservation. Most of the younger Indians have had some education in the schools maintained by the Government and are able to use the English language. The Mexican population speaks Spanish. Cities and towns in the Middle Gila Valley area are few and small. Florence and Casa Grande are the only incorporated places. Saca- ton, an Indian village, the location of the Indian Agency and of an experimental station maintained by the United States Department of Agriculture, lies within the area covered by the survey. Black- water, Casa Blanca, Santan, and Sweetwater are the most important of the Indian villages within the reservation. Florence, with a popu- lation of 807, is the largest town in the area and the county seat of Pinal County. Casa Grande is the principal railroad and shipping point of the area. Sacate is a station on the Arizona Eastern Rail- road, in the western part of the area. Three railroad lines touch the area, but none traverse it for any distance. The Southern Pacific Railroad cuts across the extreme southwestern part, passing through Casa Grande. The Arizona Eastern Railroad crosses the extreme western portion. Florence has access to a branch of the latter railroad which follows the north bank of the Gila River in this part of the area. The town is on the south side of the stream, and during flood periods shipping from this point is sometimes delayed and frequently hazardous. Some work has been done on public roads in this area, but large tracts are still without roads. During dry weather most of the roads are readily passable, but in the rainy season travel is frequently very difficult. There are no bridges across the Gila River at the present time and fording is often impossible. The products raised in the Middle Gila Valley area are mostly of nonperishable nature and suitable for shipment with ordinary facilities. In many places farming has not been undertaken or is not sufficiently well developed to meet the local demands for agi'icultural products, which must be brought from outside points. 8 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. CLIMATE. The climate in this region is characterized by a long, warm grow- ing season; a shorter cooler season, during which frosts occur; and a scanty supply of rain, insufficient to insure crops without irriga- tion. Two so-called wet seasons occur, one in the spring and one in late summer. Except for the hot summer months the climate imyj be said to be exceptionally pleasant and favorable for the production of crops. The weather records kept at various places in and near the area are incomplete. In some instances statistics are available for only a short period of years, although Casa Grande and Maricopa have kept partial records since 1876. The data nevertheless indicate in a general way the conditions of temperature and rainfall. Phoenix is representative of a large region of which the area surveyed is a part. The mean annual precipitation at Phoenix for 8 years, from 1896 to 1903, inclusive, was 6.8 inches. The average number of days with a precipitation of 0.01 inch or more was 34 per year. The pre- cipitation for the driest year was 3.7 inches and for the wettest year 12.8 inches. At Maricopa, about 5 miles southwest of the area, on the open desert or plain, the mean annual precipitation for a period of years extending from 1876 to 1907, except 1878 and 1879, was 6.06 inches. The amount for the driest year recorded (1900) was 2.09 inches, and for the wettest year (1905), 13.51 inches. The table below, compiled from records of th^ Weather Bureau, shows the mean annual, seasonal, and monthly rainfall and temperature, the maximum and minimum temperatures, and the rainfall for the wettest and driest years. Normal monthhj, seasonal, and annnal temperature and preciiyitation at Maricopa. Temperature. Precipitation. Month. Mean. Absolute maximum. ■ Absolute minimum. Mean. Total amount for the driest vear. (1900). Total amount for the wet- test year. (1905.) 50.9 50.2 54. 4 "F. 89 88 92 "F. 19 S 23 Inches. 0.82 .59 .62 Inches. 0.00 .00 T. Inches. 0.85 1.60 2.70 Winter 51. S 92 8 2.03 T. 5.15 60.4 66.7 74.3 98 104 no 25 32 39 .52 .20 .09 .20 .40 T. 1.72 1.71 May T. Spring 67. 1 110 25 .SI .60 3.43 SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 9 Normal monthly, seasonal, and annual tempero/ture, etc. — Continued. Temperature. Precipitation. Month. Mean. Absolute maximum. Absolute minimum. Mean. Total amount for the driest year. (1900). Total amount for the wet- test year. (1905.) June T. 85.9 90.8 90.5 °F. 126 123 119 'F. 49 48 65 Inches. .08 .78 .99 Inches. .00 .24 T. Inches. T July 33 August 72 Summer 89.1 126 48 1.85 .24 1 05 September 83.3 70.3 58.1 117 110 101 46 30 22 .52 .43 .60 T. T. 1.25 41 October 00 November 3 47 Fall 70.6 117 22 1.55 1.25 3 88 Year 69.6 126 8 6.24 2.09 13 51 While precipitation may occur in any month in the year, two wet seasons are the general rule. The spring and fall months are usually warm and dry. The following table gives the best data available as to the annual precipitation at five stations : Annual precipitation at five stations, Middle Gila Valley Area. Year. Casa Grande. Casa Grande Ruins. Mari- copa. Flor- ence. Saca- ton. liKhes. Year. Casa Grande. Casa Grande Ruins. Mari- copa. Flor- ence. Saca- ton. 1876 Inches. Inches. Inches. 3.87 6.27 Inches. 9.33 5.35 13.49 12.02 5.35 12.14 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 . Inches. 5.67 3.20 3.21 5.04 6.40 4.65 7.18 19.52 9.53 5.70 Inches. Inches. 5.90 4.95 2.09 4.69 4.89 4.72 3.15 13.51 9.10 7.57 Inches. Inches. 1877 1878 1879 1880 4.16 1881 1.58 T. 2.11 9.26 2.02 5.02 7.71 3.65 3.95 10.70 3.62 8.75 4.92 5.82 6.30 6.43 4.23 1882 0.38 7.27 11.96 2.97 6.12 7.61 3.99 9.32 8.63 3.01 6.05 6.60 6.57 6.07 6.69 6.06 1883 1884 1885 . . . 1886 1887 1909 7.26 6.35 9.83 13.17 7.85 16.08 12.11 4.33 8.87 6.63 8.89 1888 1910 1911 5. .57 5.45 1889 13.25 13.8.5 8.24 9.95 9.63 1890 1891 1892 1893 1912 1913 1914 1915 9.56 7.15 9.87 8.89 5.03 9.37 10. 33 8.96 9.81 12.41 15. 32 12.66 12.12 8.22 16.75 15.28 1894 1916 10.39 Annual mean . 6.28 10. 38 6.24 10.40 1896 1897 11.01 Where blanks occur, no record is available. 155289°— 20 2, 10 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1017. The precipitation depends somewhat ii})on the h)cati()n with refer- ence to mountains and canyons. The summer rains or showers are often very local, and in the form of heavy downi)ours accomi)anied by lightning and thunder, while the winter rains are more general and fall more gently over a longer period of time. The summer rains are of little benefit to agriculture directly and they hinder har- vesting and fruit-drying operations, but they are important from the standpoint of irrigation. It will be noticed from the tables that to some extent wet cycles or years seem to be followed by extremely dry ones. During the wet cycles there is- more underground water present and the lands are farmed for the time being by irrigation with pumped water, wdiich during dry periods is scanty. The following table shows the mean annual and the absolute maxi- mum and minimum temperatures for several stations in different parts of the area : Average annual temperature and extremes of temperature at Casa Grande Ruins,^ Florence, and Sacaton. Casa GraiidP Ruins. Florence. Sacaton. Mean. Max. Min. Mean. Max. . Min. Mean. Max. Min. 1916 "F. "F. "F. "F. 70.6 69.0 71.0 68.9 'F. 113 113 112 114 115 °F. 20 24 27 11 "F. 69.9 68.9 7014 68.2 67.6 'F. 114 113 114 112 113 °F. 15 1915 114 112 114 113 110 113 ' 22 1914 1913 1912 69.9 67.2 66. S 68.4 68.5 23 8 18 19 16 21 9 17 1911 1910 1909 71.2 68.2 115 114 22 19 71.3 68.5 117 111 17 17 ' Now Casa Grande National Monument. The mean annual temperature ns recorded at Phoenix, for an 8- year period from 1896 to 1903, inclusive, was 70°. The absolute maximum for Maricopa is 126°, and this is the highest temperature on record in this area or vicinity. Temperatures ranging between 110° and 120° are recorded yearly, and the temperature frequently remains above 100° for periods of several days or several Aveeks dur- ing the summer. During the early summer the nights are cool, but the high relative humidity accompanying the extremes in tempera- ture during the rainy season of the middle and late summer makes this part of the year uncomfortable. The dry part of the year is one of ^remarkably low relative humidity, xllthough the tempera- tures during the greater part of the year are moderate, during the winter and spring low extremes of temperature for this part of the United States are recorded. For instance, absolute mininuun re- SOIL SURVF.Y OF THE MIDDLE GILA VALLEY, ARIZONA. 11 corded at the Maricopa station is 8^ F., though temperatures as low- as 25° are unusual, and even crops sensitive to cold can be success- fully grown. The prevailing wind direction is from the west. Hot, drying winds are frequent during the summer months. Snow very seldom falls, and hail is of local occurrence and unimportant. The growing season for the more hardy crops extends throughout the year, but frosts occur during December, January, and February. The average date of the last killing frost in the spring is about March 7, while that of the earliest in the fall is about November 27. The latest killing frost recorded in the spring at the Maricopa sta- tion occurred April 4, while the earliest in the fall was recorded by the same station on October 22. AGRICULTURE. Agriculture has not reached a very high state of development in the Middle Gila Valley area, although there is abundant evidence that irrigation fanning was carried on by the prehistoric races and Indians for centuries preceding settlement by the whites. The lack of game and wild food plants on the arid plains and treele&s moun- tains forced the early peoples to turn their attention to agriculture, and the river bottoms and adjoining higher lands that could easily be irrigated from the Gila River were made to produce. The Pima Indians have no traditions of the prehistoric race or races that carried on agriculture in this valley;, but the ruins of their dwellings and canals indicate that they had reached a rather high state of culture. Before the advent of the white man, in the latter part of the sixteenth century, American Indians were irrigating land and producing food crops. These Indians were not concerned mainly Avith warfare, but they were continually called upon to protect their stores of grain and their families from other tribes. The small farms along the Gila Eiver were irrigated with the silty waters of the stream by means of small ditches, which carried the flood waters a short distance to the cultivated land. Overflows either stimulated the yields or destroyed the crops, depending upon the time and manner of occurrence. The grain was harvested in the crudest fashion and thrashed with a flail or by trampling with horses. This method of harvesting and thrashing grain has changed little among the Indians, their hard-earth thrashing grounds being everywhere in evidence. The farming of desert land lying outside the river bottoms was not looked upon with much favor by the white settlers, and little of the desert slopes is cidtivated to-day. Extremely h>ng droughts and low average rainfall have forced settlers to abandon some areas formely cultivated. 12 riELD OPERATIONS OF THE BUREAU OF SOILS, 1917. Agriculture is confined very largely to that part of the Indian Reservation occupying the river bottoms, to scattered ranches in the vicinity of Casa (Irande and P'lorence, and to a few scattered farms in various other parts of the area. The construction of irrigation works by the Government for the Indians, covering lands in the river bottom, has practically assured the permanency of agriculture in that section. Farming as carried on by the settlers and squatters on the desert, until a more stable supply of water for irrigation is obtained, can hardly be considered profitable. The canal which supplies some of these farmers carries water only part of the season, or may even be dry, depending upon the rainfall. Others irrigate from wells,- which seem to furnish a considerable supply of water in wet years, but can hardly be depended upon in dry seasons. The expense of application is also too great for profitable irrigation. A comprehensive storage and irrigation system is necessary before the barren desert plains will be turned into permanently producing fields. The present type of agriculture differs little from that of past years. It consists largely in the production of cereals, alfalfa, and other hay and forage crops, and the raising of cattle and horses. Egyptian cotton is groAvn on a small acreage. Vegetables are grown, and some shipments are made from the area, but most of the produce is used locally, as the demand for truck and garden crops far ex- ceeds the supply. Small quantities of tree fruits, mainly peaches and nectarines, apples, quinces, apricots, and figs are produced. A small planting of the date palm has been made by the Department of Agriculture experiment station. Statistics of agriculture strictly applicable to the area are not available. The data given by the Federal census for Pinal County are, however, of some significance, as the survey covers the most important agricultural region in the county. The following table gives data for the three principal classes of products for the years 1899 and 1909 : Acreage and production of leadind closscs of crops and value of ^live stock, 1S99 and 1909. Product. 1899. Acreage. Production. 1909. Acreage. Production. Cereals Tlay and forage liive stock sold or slaughtered. 3,196 4,633 Numher. Bushela. 79,330 Tons. 6,987 Value. $134,895 8,744 4,232 Number. 8,162 Buslicli. 132,371 Tons. 6,709 Valve. $148,905 SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 13 This table shows a very considerable increase in the acreage of cereals, but a decrease in the acreage of hay and forage crops during the decade, while the value of live stock sold and slaughtered was materially greater at the end than at the beginning of the period. It is certain that the acreage and production of the classes of crops stated have increased since the last census. The value of all crops and live-stock products in 1909 amounted to $406,228. Wheat, barley, and corn occupied practically the entire acreage de- voted to the cereals in 1909, and this was true in 1899, though the re- lations between the crops were ditferent. In 1899 the acreage in barley was slightly greater than the acreage in wheat, while in 1909 the acreage in wheat was nearly twice that in barley. AVheat in 1909 occupied 4,7()2 acres, from w hich the production was 57,894 bushels, an average yield per acre of about 12 bushels. There were 2,552 acres in barley, with a production of 58,220 bushels, or an average yield of 22.8 bushels per acre, and 1,275 acres in corn, pro- ducing 13,999 bushels, or about 11 bushels per acre. Corn does not yield well in the hot valley of the Gila River. It is grown under irri- gation. The cereals are grown mainly for home consumption, al- though wheat and barley are cash crops wdth some of the white farmers. From these returns it appears that the average yields per acre of the cereal crops are low% and this is substantiated by facts obtained during the survey. The low average yields are in some measure due to the antiquated methods still generally used by the Indians, not- withstanding the efforts of the Government to educate and train them in better farming practices. Among the hay and forage crops of 1909, grains cut green for hay occupied 2,721 acres, or more than half the total acreage in such crops. The production of grain hay amounted to 4,119 tons, or an average yield of 1| tons per acre. Alfalfa was the next important hay crop, the acreage being 776 acres, the production 1,569 tons, and the yield per acre a little more than 2 tons. Millet occupied 87 acres, other tame grasses 278 acres, wild grasses 250 acres, and coarse forage 119 acres. Millet yielded about 3 tons per acre; the coarse forage be- tween 2 and 3 tons ; and the other crops about 1 ton per acre. In this region, where stock runs on the range throughout the year, the production of hay is not likely to be considered very important, but some hay is made by most farmers. The acreage in alfalfa, which decreased greatly between 1899 and 1909, has increased since the latter year, and the area in this crop is extending annually, both on the river-bottom soils and on the desert ranches. This legume is one of the most valuable crops for the desert farms, where water for irrigation can be obtained. The land is flooded in checks and when the supply of water is sutiicient an irrigation is given after each cut- 14 FIELD OPERATIONS OF THE BUKIOAU OF SOILS, l'.)17. tin<^, of which there may be as many as seven. Alfalfa is allowed to occupy the land for many years without reseeding. Much of the land in cultivated grasses is pastured a part of the year, Avhich tends to reduce the yield of hay. The forage and hay crops are used largely to feed the work stock and dairy animals. According to the census neither cotton nor the sorghums were grown in Pinal County in 1909. Since then, mainly as the result of investigations by the Bureau of Plant Industry, long-staple Egyp- tian cotton and Egyptian corn and milo have been introduced. Long-staple Egyptian cotton is grown extensively in adjacent parts of the Salt Eiver Valley, and it bids fair to become an im- portant crop in this area when facilities for irrigation have been ex- tended. Several strains of this cotton, which seems to be particu- larly adapted to the soil and climate, have been bred to a high stand- ard at the United States experiment station at Sacaton. Small fields have been set out in the Middle Gila Valley area, both white and Indian farmers taking up culture of this crop. High prices during the last two years (1916 and 1917) have stimulated the interest in cotton. It is planted after all danger from frost is past, and is culti- vated and irrigated during the growing season. Much hand labor is necessary in thinning, chopping, cultivating, and picldng. Harvest- ing begins in, the fall and may continue until late in the winter, which usually is favorable for such work. Egyptian corn and milo are grown more extensively each year and promise to become important crops, as they are well adapted to the soil and climatic conditions and can be grown late in the summer after other crops are disposed of. It is necessary to irrigate the land before seeding. Later irrigations depend upon the season and rain- fall. These grains, which make excellent stock feed, are generally grown by the white farmers ; the Indians, who grow grain for food, prefer corn. Stock raising is the most important source of income of the Pinal County farmers. Cattle and horses are kept in the largest num- bers, but some hogs, sheep, and goats are raised. Practically all of the stock subsists on the desert range the year round, seldom being fed at any time of the year, except locally during severe drought. Some dairy cattle are fed and pastured on alfalfa the year round. Dairying is almost entirely in the hands of white farmers, and is best developed in the vicinity of the larger towns. The income from dairy products in 1909 was $10,546. Poultry raising is carried on in conjunction with general farm operations, the value of poultry raised in 1909 amounting to $15,306. The Indians seem more adept in the raising of stock than in farming. The (luality of the cattle on the reservation is being improved through the agency of the Government. SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 15 Up-to-date methods ai'e used in grain farming by the white farm- ers, but the Indian is slow to adopt modern methods and the use of machinery. Plowing for gi-ain is usually done in the fall and winter months, about the time of the first winter rains or following an irrigation, after which the crop is planted. In dry seasons the crop is irrigated a number of times, but irrigation may be entirely dispensed with in years of greater precipitation. Not much grain is produced by dry farming. Indians continue to cut their small fields of grain with the hand sickle and thrash the crop by driving- horses over it oil a hard earth floor, later separating the grain from the chaff by winnowing or throwing it into the air on a windy day. Little or no fertilizer except barnyard manure is used, and rota- tions are not practiced to any extent. The application of very silty irrigation waters, rich in organic matter, tends to maintain or in- crease the productiveness of the soils, even though the same crop be grown for a period of years. Facilities for irrigation and alkali-free soils have more to do with the present distribution of crops than the minor differences in the texture and color of the soil or the source and character of the soil material. OrcMnarily grain does best on the rather heavy, silty soils. Because of the droughty nature and low organic content of the up- land soils, the present agriculture is largely confined to the river bottoms. The farms on the heavier, low^er-lying soil types, in the river bottom, are much smaller than those on the upland soils, prob- ably owing to the fact that the Indians, occupying much of the river bottoms, hold only small parcels of irrigated land. Except in case of the Pinal gravelly sandy loam, topography has had little influence on the distribution of crops, as the surface of all the other types permits of irrigation and cultivation without great difficulty. Farm labor is supj^lied principally by the Pima Indians. Practi- cally all the Indians own small tracts of land, which they cultivate during part of the growing season, but many of them do farm labor in the vicinity. In and around Florence and C'asa Grande there are many Mexicans who perform day labor on the ranches in that sec- tion. The wages of farm labor are relatively high at the present time (1917). Mexicans are paid $1.25 to $1.50 a day and board for hand labor, while men who handle teams receive $1.50 to $1.75 a day and board. In 1910 only 1.3 per cent of the total area of Pinal County was in farms. The total number of farms was 614, and the average size 70.4 acres. Of this 43.5 per cent, or 30.6 acres, was improved. The average value per farm of all farm property was $3,757, the land making up 51.4 per cent of the total and the live stock 37.2 per cent. In 1910, 95 per cent of the farms were operated by owners, a small 16 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. number by tenants, and a very few by managers. This hio^h per- centage of farms operated by owners is due mainly to the large Indian population. The average assessed value of land in 1910 was $27.47 an acre. It is very difficult to estimate the average value of farm lands at the present time, as no sales of the Indian holdings take place, and transfers of other lands have been few in recent years. Values prob- ably range from a few dollars to $75 an acre, depending upon the means of irrigation and other local conditions. SOILS. The soils of the Middle Gila Valley area are derived from a variety of rocks, all the soils except those identified with the several small buttes and parts of the adjacent mountains having been transported and laid down by water. The predominating rocks in the mountains and buttes are granite, mica schist, and other crystallines. Igneous rocks of low quartz content and of basic character occur on some of the buttes, and have entered into the formation of the soils to a small extent. In the western and southern parts of the area small fragments and bowlders of igneous rocks have been washed down over the desert plains by torrents. The soils may be classed in three main groups — namely, residual soils, or those derived in place through the weathering and distin- tegration of consolidated rocks; old valley-filling or desert soils, Avhich are derived from the weathering and other modification of old unconsolidated, water-laid material; and recent alluvial or stream bottom soils, consisting of comparativel}^ recent alluvial prod- ucts which have undergone no important changes by weathering or internal modification subsequent to. deposition. Another main group — namely, wind-laid soils — is represented, but is not of suffi- cient extent in this survey to warrant separate grouping, and it is included with the old valley-filling soils. The main groups of soils are divided into series in which the soils are similar in color, origin, mode of formation, subsoil condi- tions, and other essential features except texture. The series are divided into types, the latter being determined by the proportions of sand, silt, and clay present in any particular case. The soil type is the unit of mapping. Following this system of classification, five series of soils, each represented by one or more types, are recognized in this survey. In addition, two miscellaneous, nonagricultural soils are shown on the map — viz. Rough stony land and Riverwash. Residual soils. — The residual soils in the Middle (rila Valley area are of little importance. They are represented only by Rough stony Report of Bureau of Soils, U. S. Dept. of Agriculture, 1917. Plate I. 4||e;«-*2 Fig. I. — View Overlooking Desert Soils Grouped in the Mohave Series. The surface is smooth and gently slopmg. The vegetation is typical of the soils of this series. Fig. 2. — Alfalfa on Mohave Sandy Loam, Near Casa Grande. The crop has been cut recently. The horizontal ridges are irrigation checks. Report of Bureau of Soils, U. S. Dept. of Agriculture, 1917. Plate II. Fig. I. — View in Gila River Bottoms Near Florence. This shows the smooth, level topography of the Gila silty clay loam. The field in the foreground is in grain stubble. Fig. 2. — Alfalfa on the Gila Silty Clay Loam, Near Florence. SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 17 land and are confined to the small rocky buttes and mountain slopes. Old vaUey-flUng soils. — The soils of the old valley-filling province occupy about 75 per cent of the area. They are derived from weathered and otherwise modified, relatively old, water-laid, un- consolidated deposits, which oricrinally had their source in a variety of formations in which granites and related rocks seem to have predominated. The color of the surface soils ranges from brown to reddish brown or red. Oxidation is well advanced and the soils are characteristically low in organic matter. An abundant supply of lime is present. Heavier, more compact subsoils occur in places, and frequently a greatly compacted, or in some cases cemented, layer lies within a few inches of the surface. These soils cover practically the whole of the area except the valley of the Gila River. The sur- face is smooth and comparatively flat or gently sloping. The soils have a moderate elevation, and in places are eroded. Drainage is good over most of this area. Three series of soils are recognized — the Pinal, Mohave, and McClellan. The soils of the Pinal series are pale red or grayish red to light reddish brown in color, and predominantly gravelly or stony. Ce- mented, calcareous, gravelly hardpan or "caliche" layers are prom- inently developed. The surface is gently rolling and dissected and drainage is good. The Pinal series is inextensive in this area and unimportant agriculturally. Only one type, the Pinal gravelly sandy loam, occurs in the survey. The soils of the Mohave series have a range in color from light reddish brown to dull red or dull reddish brown. They are usually underlain by grayish or pinkish-gray very compact subsoils, fre- quently containing irregular, partially cemented seams or layers, with an approach to a dense, cemented " caliche " or hardpan. The soils are low in organic matter and high in lime. They generally kave a smooth and gently sloping surface (see PI. I, fig. 1), which is little affected by erosion. Surface drainage is usually well estab- lished, but the subdrainage is restricted and some areas are affected by alkali salts. Two types of this series are mapped, the Mohave sandy loam and fine sandy loam. The McClellan soils are browner than those of the two series just described. The surface soils are low in organic matter, high in lime, and underlain by a very compact, grayish, calcareous subsoil, which retards the movement of moisture and limits root development. The clay-loam member of the series is usually very low, flat, and poorly drained, while the loam has a gently sloping surface and much better drainage. Part of the series is affected by the accumulation of alkali salts. 155289°— 20 3 18 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. Recent -alluvial soils. — The recent-alluvial soils of this area, while not the most extensive, are the most important agriculturally. They have been made to produce crops since prehistoric times. They are confined to the Gila River bottoms and consist of recent sedimentary materials laid down by this stream. As distinguished from the old valley-filling soils, they are naturally friable and lack a compacted and cemented or altered subsoil. They are much higher in organic matter than the old valley-filling types. The soil profile represents the various coarser or finer strata laid down by the stream under different conditions of velocity, volume, and load of suspended ma- terial. The surface is generally level and smooth, and the soils are in places poorly drained and affected with alkali salts. They are also subject to overflows. Two series are included under this soil province — the Gila and the Pima. The Gila series consists of brown soils, ranging from rather light grayish brown to rather dark brown in color, frequently with a slight reddish or chocolate tint. The subsoils are generally similar in color and texture, but they may consist of variably textured, alter- nating strata. They are free from any consistent compact or hard- panlike layers. There is a rather high percentage of organic mat- ter in the surface soil, and both surface soil and subsoil are calcareous. In many places the content of mica is large. The surface of the Gila soils is usually smooth and level or v^ry gently sloping, and drainage is only fairly good. Alkali salts are sometimes present in excessive quantities. The soils are subject to periodic overflow and have a high water table. The Pima soils are dark brown or dark grayish brown, with, in many places, a slight reddish or rich chocolate brown tint. The sub- soils are of similar or of lighter and more grayish color, particularly where highly calcareous. Both surface soil and subsoil are cal- careous, effervescing freely with dilute acid. The subsoil is similar in texture to the surface soil or consists of variably textured strata without cementation or alteration in place through weathering. The surface is generally smooth and level. The soils are subject to overflow, and at times are poorly drained. In some places the Pima soils contain alkali salts, but the affected areas are easily reclaimed by drainage and flooding. In the following pages of this report the various soils of the Mid- dle Gila Valley area are described in detail, and their relation to agriculture discussed. The distribution of the soils is shown on the map accompanying this report, and the table below gives the actual and relative extent of each : SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 19 Areas of different soils. Sdl. Acres. Per cent. Soil. Acres. Percent. Mf^lnllan Jnam 60,096 1 14,208 6,464 5,056 4,608 1,728 6.3 Shallow phase 5,568 30.6 3 264 Pima clay 2.9 Siltypfea.se Gila fine sand 2.2 Mohave sandy loam 40,384 37, 824 17.8 16.8 13.4 7.2 Pinal gravelly sandy loam . Rough stony land 2.0 0.8 Total Mohave f;no sandy loam . . l.i- 836 225,280 PINAL. GRAVELLY SANDY LOAM. The Pinal gravelly sandy loam is a grayish-red to light reddish broAvn calcareous sandy loam, carrying a large quantity of rounded and subangular gravel, as well as bowlders and stones. The stony surface material usually extends to a depth of 6 to 10 inches, where a gray, calcareous hardpan or " caliche " is encountered. The soil is of rather loose, friable structure, owing to the large content of coarse material. It is high in lime but low in organic matter. The hard- pan is a firmly cemented, gravelly layer or series of layers, varying in thickness from 12 to 36 inches or more. The subsoil consists of a grayish or grayish-brown, calcareous, compacted mass of gravel and bowlders in a matrix of material finer than that in the surface soil. It extends in many places to a depth of 6 feet or more, but locally is underlain at varying depths by compact, heavy and more silty mate- rial, free from gravel. A deep, gravelly substratum underlies the type. This also is calcareous. The Pinal gravelly sandy loam occurs in areas of varying size, the largest lying west of Florence along the Blackwater and Florence Road. For several miles this area, occupying a more or less eroded terrace, forms the southern boundary of the Gila Valley. Areas of similar characteristics skirt the valley north of the river, but only a small part is included in this survey. Three small areas are mapped east of Casa Blanca and one southeast of Casa Grande. The latter is of particularly stony character. The surface of the type is somewhat undulating and eroded and not well adapted to irrigation. The gravelly, stony nature of the soil and the nearness of the " caliche " to the surface render the type difficult to handle. The surface run-off is rapid and the soil is not retentive of moisture. The Pinal gravelly sand}' loam is at present used solely for pasture. It supports only a sparse growth of grasses or creosote bush, and its pasturage value is low. 20 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. MOHAVE SANDY LOAir. The Mohave sandy loam consists of a pale-red to reddish-brown, friable, calcareous, light-textured sandy loam, about 1*2 or 14 inches deep, underlain by a calcareous, light reddish brown or pinkish-gray compact sandy loam or loam. The surface soil is open in structure, and, containing little organic matter, has little power to retain moisture. Considerable quantities of coarse sand and fine gravel and grit are normally present. Coarse angular gravel occurs in the soil where it adjoins the Pinal gravelly sandy loam or other stony types. The subsoil, while calcareous and compact, is not advanced in cementation to the stage of a true hardpan. In most places a water- bearing stratum of rounded gravel underlies the t3^pe at a depth of 25 to 35 feet or more, and it is from this stratum that water for irri- gation is usually obtained. Small areas of a sandy variation are included in this type, and it may include some areas having the texture of a sand. In the sandier areas the soil is usually deeper and more open in structure, and the subsoil carries some fine angular gravel. The Mohave sandy loam is an extensive and important soil. It is mapped in all parts of the area, but the largest bodies occur in the eastern and southern parts. Many of the soil areas are elongated and roughly parallel. They may extend along drainage courses, or bound large flat areas. Some are small, isolated areas of sandier material, which have been modified by wind action and may locally have a veneer of wind-laid material. The soil boundaries in most cases are definite and in many cases sharp. The surface of the type is generally smooth and well suited to irri- gation and agriculture, but some of the smaller, sandv areas are marked by small hillocks and are difficult to handle. Leveling is necessary to j^repare much of the type for irrigation. This soil usually lies slightly higher than the surrounding or adja- cent types, and drainage is toward the latter. It is well drained and is seldom affected by alkali, which occurs only along marginal areas. The greater part of this type still supports the native vegetation of creosote bush and varieties of cacti or other desert plants. Small areas are irrigated and farmed, alfalfa being the principal crop. (PI. I, fig. 2.) Where sufficient water is available the yields are good, but all crops require irrigation. Some grain is produced, but the yields are often poor. Kafir, milo, and truck crops are grown locally, and their acreage is being extended. A small acreage is devoted to peaches, apricots, and figs. Egyptian cotton is not grown on the type in this area, but it is produced on similar or identical soils outside the survey. The seed farm of the Indian Agency near Sacaton is located on this type of soil. SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 21 The value of raw land of the Mohave sandy loam ranges between $12 and $75 an acre, depending upon the location and water supply. The addition of organic matter to this soil would improve its physical condition. Where manures and green crops have been plowed under, or where the silty irrigation waters of the Oila River, rich in organic matter, have inundated the surface, tlie improvement is noticeable. MOHAVE FINE SANDY LOAM. The surface soil of the Mohave fine sandy loam is a pronounced reddish-brown or pale- red to grayish-red, rather coarse and gritty, calcareous fine sandy loam, 6 to 10 inches deep. The subsoil is a very compact, light-red or brownish-red or grayish-red calcareous fine sandy loam, or loam in which occur lenses or layers of partly cemented material. Under irrigation the hard layers soften some- what, but even the uncemented subsoil is so compact that the move- ment of moisture and the penetration of plant roots are hindered. The same condition decreases the water-holding capacity of the soil. A gravelly substratum underlies the type at considerable depth. This type is very uniform over large areas, but in places the soil has been modified by winds, the surface soil in such places being deeper and more open and friable than typical. The surface of the greater part of the type is smooth and favorable to cultivation and irrigation. The larger areas have sufficient slope to insure good drainage, and as a result of the structure of the subsoil most of the precipitation is lost as run-oiF. Some lower lying areas of the type are affected by accumulations of alkali. The narrow ridges of this type, which border flats occupied by heavier soils need leveling before they can be cultivated. The Mohave fine sandy loam is an extensive soil. Most of it occurs in large bodies north of Casa Grande and along McClellan Wash. Smaller areas are mapped to the southeast of Casa Grande, northwest of Santan, and north and northwest of Tw^in Butte. One small area occurs west of Blackwater and another west of Casa Blanca. The native vegetation consists of a growth of desert sage, creosote bush, and several varieties of cacti. In areas where alkali salts have ac- cumulated "seep weed" is a common plant. Little of the type is under cultivation. Several farms are pro- ducing alfalfa, but no data as to yields are obtainable. The non- saccharine sorghums, cotton, and truck crops can be produced where the soil is free from alkali and where subsurface conditions are fa- vorable. Peaches, apricots, and figs are produced locally. The type is low in organic matter and responds to applications of manure or to the incorporation of green manures. Much of it is very droughty, owing to the shallow soil and compact structure of the subsoil. 22 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. The results of mechanical analyses of samples of the soil and sub- soil of Mohave fine sandy loam are shown in the following table : Mechanical anaUjses of Mohave fine saoidij loam. Number. Description. Fine gravel. Coarse • sand. Medium sand. Fine sand. Very flue sand. Silt. Clay. 510411 Soil Per cent. 2.5 Per cent. 9.4 7.1 Per cent. 5.1 4.2 Per cent. 34.1 28.0 Per cent. 30.0 22.0 Per cent. 16.7 17.3 Per cent. 2.4 510412 Subsoil 2.0 19.4 M CLELLAN LOAM. The surface soil of the McClellan loam typically consists of a brown, gritty, light-textured loam, 10 to 20 inches in depth. It has usually a slight reddish or purplish tint. The surface soil is more compact and retains moisture better than the Mohave fine sandy loam and sandy loam, but it lacks organic matter and has a tendency to bake upon drying. Some fine gravel is generally present on the sur- face and coarser material occurs along the small washes or drainage ways. The soil conttiins much lime. The subsoil is a compact, highly calcareous, gritty loam, of light grayish brown or pinkish-gi'a}' color. In places it is weakly cemented and occasionally the deeper subsoil is a very compact, reddish, or red- dish-brown loam or clay loam, not well adapted to root development. Where it has been subjected to a high water table, the subsoil is often grayish or grayish brown. The type is underlain by a deep gravelly substratum. The McClellaa loam in this survey is subject to some variations in texture, color, and depth. In several places south of Casa Blanca small areas have a pronounced reddish brown color and others occu- pjang slopes have a somewhat deeper surface soil than typical. Small areas of lighter or slightly heavier texture are also included. Much of the type in the western part of the survey contains alkali in injurious quantities. The McClellan loam is one of the most extensive types in the area. It occurs in all sections except the Gila River flood plain, in both large and small bodies. The type represents part of an extensive plain, in which drainage ways are poorly developed. It is generally level or gently sloping, and is easily handled, such surface irregidarities as exist being of little hindrance to irrigation or cultivation. Parts of the type are well drained, but in general surface drainage is not well established, and the subdrainage is retarded by the impervious or compact sub- soil. The poorly drained areas contain more or less alkali. SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 23 The type is used largely for pasture because of the lack of water for irrigation. A desert growth of Atriplex or desert sage, mesquite, creosote bush, cacti, and seep weed forms the principal vegetation. "Where the soil is free from alkali and can be irrigated, alfalfa, non- saccharine or grain sorghums, and other grains are produced. Al- falfa and the sorghums give good returns, but the yields of other crops are only fair. Garden truck, melons, peaches, apricots, and figs are grown locally. Egyptian cotton is produced on this type outside the area. The content of organic matter in this soil is low. oxidation of humus being rapid. Liberal applications of manure or the turn- ing under of gi-een crops is necessary for best results. The selling value of land of this type varies greatly, depending upon the location and the facilities for irrigation. McClellmi loam, shallow pJiase. — The shallow phase of the Mc- Clellan loam differs from the typical soil chiefly in the depth of the surface soil. The soil section consists of (1) a layer of brown loam or fine sandy loam, 3 to 6 inches deep, and (2) a layer of compact, reddish-brown or brown loam weakly or intermittently cemented and approaching a hardpan in general characteristics. Both soil and sub- soil are calcareous. The principal areas of this phase are mapped along McClellan Wash and southwest of Casa Blanca. It supports in general a stunted vegetation of sage, seep weed, and dwarf cactus. A few barren spots occur. The soil is level and poorly drained. It is over- flowed frequently from the McClellan Wash, and occasionally re- ceives seepage from the higher lying types. The unfavorable struc- lure of the soil, the liability to overflow, and the accumulations of alkali render the land of little value except for pasture, and none of it is cultivated at present. McClellan loam^ sUty phase. — The silty phase differs from the typical McClellan loam in having a larger content of silt in the upper foot or two. and in having larger proportions of organic matter. The soil consists of a dark-brown silty loam 5 to 24 inches deep, and the subsoil of material like that of the typical soil, but somewhat more porous. The excess of silt is due to the deposition of material carried by irrigation or overflow waters. The soil is darker than the typical McClellan loam. Parts of the phase are spotted with alkali. This soil is not very extensive. The principal areas are situated several miles east and southeast of Casa Grande, and southeast of the Casa Grande National Monument. Those east and southeast of Casa Grande are elongated and form shallow drainage channels. The phase lies lower than the adjacent soils, and in places receives run-off from surrounding areas. The drainage is nevertheless good over most of it. 24 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1^17, The silty phase is better adapted to farming than the typical Mc- Clellan loam and practically all of it is cultivated, being devoted to alfalfa, grain, and the sorghums. m'clei.lan clay loam. The McClellan clay loam consists of a brown, rather smooth, sticky, compact clay loam, relatively high in silt from 3 to 12 inches deep. The soil is somewhat darker than the soils of the Mohave series and the red color is much less pronounced, though a reddish or purplish brown tint is noticeable in most of the ai'eas. The con- tent of organic matter also is higher than in the Mohave soils, but nevertheless the type bakes and hardens upon drying, and assumes a dense, impervious structure which retards percolation and absorp- tion of water. The subsoil is a light reddish brown or pinkish, stick}' clay loam, which becomes more compact with depth and is weakly and irregularly cemented in places, in character approaching a hardpan. Its close structure renders the percolation of water very slow and retards root development. The subsoil usually becomes lighter colored or reddish brown at a depth of 3 feet or more. In some places, where the shallow, silty surface material has been removed, the entire soil column consists of the impervious, com- pacted subsoil material. A substratum, consisting of gravel and bowlders, lies at about 25 feet below the surface. Both surface soil and subsoil, but particularly the latter, contain large amounts of lime. The McClellan cla}^ loam is a very extensive soil, occurring prin- cipally in the southern, western, and northwestern parts of the survey. Many of the areas are large " playa " flats, or smooth flat areas of puddled soil, barren of vegetation. Others occupj^ elongated, shalloM' depressions or channels which may carry the run-off or may hold water until it is ren^oved by evaporation and percolation. The elongated areas roughly parallel the principal drainage ways. Areas of this type are frequently separated from each other by ridges of lighter textured, wind-blown material, and the flats are usually bordered by such ridges. In general the areas of this soil lie near the principal drainage ways in the desert part of the area. The surface is uniformly level and flat, drainage ways being very feebly developed except in the case of the larger washes. During periods of drought these flats are dry and the soil is baked, but during the rainy season, or after heavy showers, they are occupied by shallow lakes. The surface material, consisting mainly of silt and clay, is largely the result of deposition from the turbid drainage waters. Alkali salts are usually present in greater or less concentra- tions. In the southern part of the survey only small amounts of SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 25 alkali are present, but injurioiis quantities occur in the western and northwestern parts. While much of the McClellan clay loam is without vegetation, parts of it have a growth of mesquite, sage, and dwarf cactus. The occasional presence of standing water, followed by a baked condition of the soil, renders the broad fiats occupied by this type unsuited to the native plants even where the content of alkali is low. The bar- ren areas are known locally as " slicks." The soil is used to some extent for pasture. Owing to the generally poor physical condition of the soil, the poor drainage, the alkali accumulations, and the cost of reclamation, farming has not been attempted except in a few of the more favorable situations. Grain is the principal crop grown. Where the subsoil conditions are better than typical and the soil is free from alkali, good yields are obtained under irrigation, but the selling value of the land is low. The table below gives the results of mechanical analyses of samples of the soil and subsoil of the McClellan clay loam : Meclxnnkal analyses of McClellan clay loam. Number. Description. Fine gravel. Coarse sand. Medium sand. Fine sand. Very fine Band. Silt. Clay. 510417 Soil Per cent. 0.3 2.4 Per cent. 2.0 7.1 Per cent. 1.4 3.5 Per cent. 10.8 14.5 Per cent. 18.2 17.1 Per cent. 42.8 25.6 Per cent. 24.6 51041S Subsoil 29 6 GILA FINE SAND. The Gila fine sand consists of a friable, brown fine sand, 3 to 6 feet deep, underlain by variably textured stratified sediments. The mellow, open soil is not as high in organic matter as the Gila silty clay loam, but it is moderately well supplied. It absorbs moisture easily, but does not retain it as well as the silty clay loam. The soil is micaceous and well supplied with lime. In poorly drained areas the subsoil is often slightly more compact and lighter colored than the surface soil, but it is favorable to root development except where waterlogged. In local areas adjacent to the Gila River the soil is more silty than typical, and sometimes a light fine sandy loam in texture, while along the Little Gila it contains more sand and fine sand. The subsoil is highly calcareous. Small amounts of gravel occur locally along the streams. Two small islands in the Gila River are clas.sed Avith the type, although the soil is coarser textured than typical. The channels of the Gila and Little Gila Rivers are occupied by material similar to this soil, but owing to their position they are classed with River- wash. 26 FIELD OPERATIONS OF THE BUREAU OF SOILS, lf>17. The (hla fine sand is not extensive. It occurs only in tlie Gila River bottoms from the northeastern end of the area westward to l*.inia Butte. The soil is developed in long;, narrow strips along; the channel of Gila and Little Gila Rivers. The soil is well drained in the upper 3 or 4 feet, and in places to a much greater depth, but much of it has a high water table. The texture and structure of the soil being favorable to the capilliary movement of the water, parts of the type contain large quantities of alkali, though tlie areas periodically overflowed do not contain in- jurious amounts. The surface is generally level, but not always smooth. Overflows usually leave it in a hummocky or slightly eroded condition, and con- siderable leveling is necessary to fit the land for irrigation. Wliere alkali is absent there is a growth of cottonwood and willow. In the alkali areas such plants as seep weed, mescjuite, greasewood, and pickleweed flourish. Alfalfa, cotton, nonsaccharine sorghums, grains, corn, and truck and root crops produce good yields on the well-drained parts of the type, which are free from alkali. Many kinds of tree fruits, the date palm, vegetable crops, and melons are grown at tlie experiment station at Sacaton, and it is likely that some of these crops will be more extensively grown by the farmers. Manures and fertilizers are not Avidely used. The results of mechanical analyses of samples of the soil and sul:)- soil of the Gila fine sand are given in the following table : Mechanical analyses of Gila fine sand. Number. Description. Fine gravel. Coarse sand. Medium sand. Fine sand. Very fine sand. Silt. Claj-. 510407. JL.. . Soil Per cent. 0.0 .0 Per cent. 0.8 _ 2 Per cent. 0.5 .1 Per cent. 06. 6 15.9 Per cent. 20.0 11.1 Per cent. 8.6 51.8 Per cent. 2.8 610408 17.6 GILA SILTY CLAY LOAM. The Gila silty clay loam is a smooth, close-structured, brown, silty clay loam, the color in places having a slightly reddish or choco- late-brown tint. The soil usually extends to a depth of 3 to 6 feet with little change, except that below a depth of 1 or 2 feet the color may be somewhat lighter and the structure somewhat more compact. The surface soil contains a relatively large proportion of organic matter and is distinctly micaceous. The soil and subsoil material is high in lime. In many places the materials forming this type do not appear to be of as recent deposition as those giving the Gila fine sand, but even here the .subsoil has not been cemented or altered by weathering. SOIL SUEVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 27 The type as mapped includes some variations. While the color of tlie surface soil is uniform for so extensive a type, some areas have a darker color, owing to a larger admixture of organic matter. In de- pressions the soil is both heavier and darker than the typical soil, and on some narrow ridges it is coarser and lighter. As mapped some material of silt-loam texture is included. AVhere.poor drain- age exists and alkali has accumulated the subsoil is usually lighter colored and more compact than the subsoil in other parts of the type. Harmful concentrations of soluble salts occur over a large part of the type. The substratum is similar to the subsoil to a depth of many feet. Below this are l)eds of river gravels. The Gila silty clay loam is an extensive and important soil occu- pying the greater part of the Gila River bottoms. The surface is generally level and moderately smooth, well adapted to irrigation and cultivation (see PI. II, fig. 1). The sandier ridge areas require leveling before they are farmed. Much of the type lies on a second terrace a few feet above the normal overflow of the river. On the whole it is not thoroughh^ drained, and much of it as the result of seepage has a high water table. Capillary movement of moisture is rapid and much of the type is damaged by alkali, small tracts being barren of vegetation. AYhile not often overflowed by fl(^ods in the Gila River it is subject to overflow from other sources. Mesquite. greasewood, seep weed, and a little salt grass are the characteristic plants in the vegetation. The Indians have farmed parts of the Gila silty clay loam for many years, growing wheat, barley, hay, alfalfa, corn, sorghums, and, recently, cotton. Truck and root crops are grown locally. Be- cause of its low-lying position the type is not well adapted to fruit culture. Large areas are unproductive because of the excessive ac- cumulations of alkali, but in the eastern part of the area less alkali is present, arid the white farmers here produce good crops of grain. The Indians get only fair yields on this type, considerably below those obtained by the white farmers. The uncultivated areas of the type are used as pastures. All crops are grown under irrigation, water being obtained from the Gila River and by ])umping from wells. Much of this type within the Indian reservation is under a canal system installed by the Government. Reclamation is accom- plished by checking the land and flooding it for several months or for several seasons, depending upon the concentration of salts. Much of the type requires artificial drainage. No fertilizers are used and crop rotations are seldom followed. The price of land of this type depends largely upon its condition for farming and the location. Little of it has changed hands re- cently and the Indian lands are not sold. Prices range from as low 28 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. as $5 or $10 an acre to $100 an acre where <;ood stands of grain can be obtained. The table below gives the resnlts of mechanical analyses of samples of the soil and subsoil of the Gila silty clay loam : MccliiHik-dl an(iJii!escriptlon. Fine gravel. Coarse sand. Medium saud. Fine sand. Very fine sand. Silt. Clay. 510405 Soil Per cent. 0.1 .0 Per cent. 0.4 .2 Per cent. ().3 .1 Per cent. 3.4 6.1 Per cent. 18.2 22.3 Per cent. 53.2 48.0 Per cent. 24.3 510406 Subsoil 23.1 PIMA CLAY. The soil of the Pima clay consists of a dark-brown or dark gi-ayish brown clay, in many places relatively high in silt, 18 to 24 inches deep. It is sticky when wet and cracks when dry, but it contains much organic matter and retains moisture well. The type through- out contains a large amount of lime. The subsoil is a light grayish brown silty clay loam to clay, extending to a depth of more than C feet. It differs from the surface soil in its lighter color, and in being compact, but it has not been materially changed by leaching, cementa- tion, or weathering in place. Small areas here and there are under- lain by gravel or sand at a depth of several feet, which alloAVS the water to penetrate more rapidly, and a gravelly substratum underlies the type at various depths. The Pima clay is not extensive, but it is important in the agricul- ture of the area. The type is confined to the flood plain of the Gila Kiver, where it occurs in irregular-shaped areas or in long, narrow strips, generally roughly paralleling the stream. It is found in all parts of the valley from the eastern to the western boundary of the area. The surface is level or slightly depressed. Flood water stands on the surface until removed by percolation or evaporation. This is a slow process, and more time must elapse between overflows and culti- vation than in case of some of the other bottom soils. The type main- tains a better moisture supply during droughts than the river-bottom soils of lighter texture. Parts of the type contain alkali, but in- jurious accumulations are less common than in the Gila silty clay loam. The type is not directly overflowed by the river, the water coming from other sources. Water is easily applied in irrigation, and much of the type is under gravity canals. In most places the vegetation consists mainly of a heavy growth of mescpiite, but Avhere alkali is present such plants as greasewood, salt- bush, and salt grass grow. SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 29 Many of the Indian farmers cultivate parts of the Pima clay, buildinjj their towns and houses on the adjoinin<; terraces of Gila silty clay loam, which are generally affected by alkali. Wheat, bar- ley, alfalfa (PL II, fig. 2), corn, hay, sorghum, truck, and root crops are grown, and good yields are obtained. None of the farmers use fertilizer, and no crop rotation is followed. The type brings as high prices as any in the Gila Yalley. In the table below are given the results of mechanical analyses of samples of the soil and subsoil of the Pima clay : Mechanical analyses of Pima clay. Number. Description. Fine gravel. Coarse sand. Medium sand. Fine sand. Very fine sand. Silt. Clay. 510415 Soil Per cent. 0.1 .0 Per cent. 0.5 .1 Per cent. 0.2 .0 Per cent. 3.1 2.8 Per cent. 4.7 IS. 6 Per cent. 37.0 52.7 Per cent. 54.4 510416 25.8 BOUGH STONY LAND. Rough stony land consists of steep, rough, and stony areas that have no present agricultural value. It includes various shallow soils occupying buttes and the lower slopes of mountains. The soils are of residual origin, and derived almost entirely from granite, gneiss, mica schist, and associated rocks. There are numerous outcropping ledges, and loose stones and rock fragments of all sizes are abundant, especially around the lower slopes of the buttes and mountains. This type is of small extent, as the survey covers only the most desirable agricultural lands of the region. The most important areas lie southeast of Casa Grande, at Twin Butte, and on Cholla Moun- tain. Smaller areas are mapped on small buttes within the area, and on parts of the hill and mountain slopes. The vegetation over the greater part of the Rough stony land is sparse and of low grazing value. It consists mainly of cacti of vari- ous kinds, creosote bush, and several other unimportant plants. RIVERWASH. Riverwash consists of the material occupying the bed of the Gila River. The soil is a mixture of coarse, medium, and fine sands, together with some finer sediments, and differs chiefly from the Riverwash of the Solomonsville area, in the Upper Gila Valley, in carrying less gravel, stones, and coarse sandy material. The type is usually more silty along the edges of the stream bed, where the current is sluggish. The boundaries of the strip of Riverwash are very irregular, and in many places they are drawn rather arbitrarily. The surface of 30 FIELD OPERATIONS OF THE BUREAU OF SOILS, 1917. the type is smooth, with a very gentle gradient toward the stream. It is flood-swept during periods of high water and during tlie rainy season, and at all times the water table is high. The type is of no present agricultural importance. IRRIGATION. Irrigation is necessary in the Middle Gila Valley area because of the low rainfall and the long dry seasons. The Indians practiced irrigation before the coming of the white man, using a rude system of canals to take water from the river and distribute it over the river bottoms and near-by desert slopes. The 1910 census reports a total of 89,400 acres in Pinal County embraced in irrigation projeets, but only 25,431 acres actually irrigated, of which 13,831 acres were sup- plied with water by partnership and individual enterprises, 3,500 acres by cooperative enterprises, and 8,000 acres under the Indian Reservation project. The irrigated acreage for Pinal County is practically all Avithin the limits of the present survey. Nearly all the water for irrigation is drawn from the Gila River by gravity canals. In 1917, 9,000 acres were under irrigation on the units of the Indian Reservation within the present survey. The Gila River is a broad stream, with poorly defined banks throughout most of its course. During the rainy season gi'eat volumes of water fill the channel and overfloAv the banks, but during the dry season its sandy bed is bare. In the absence of a storage supply, irrigation from the river is impossible during parts of the year. The water of the Gila River is of good quality for irrigation, the flood Avaters containing only small amounts of soluble salts. A sample of such water taken at Florence contained 68 parts of soluble salts per 100,000, but during normal flow the water is slightly higher in salts. The river water is very high in silt, and the flood waters carry in addition much organic matter washed from mountain slopes by the torrential rains. These sediments are deposited on the soils by irrigation and overflow waters, and while some inconvenience is caused by the rapid and frequent silting up of canals, much benefit results from such deposits, especially in the case of the desert soils of light texture and Ioav organic content. The continued use of the silty irrigation water even improves the texture of the lighter soils. During the last few years many wells have been sunk for irriga- tion purposes in various parts of the river bottoms, and a few in the adjacent areas of old valley-filling soils of the desert. In most in- stances a good supply of water has been obtained, the shallower wells in the stream bottoms furnishing a more abundant su]i])ly than the wells in the desert areas. Water obtained in the desert sections generally is of good quality, usually containing less than 50 parts SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZONA. 31 of soluble salts per 100,000. The water from wells in the river bot- tom is usually higher in soluble salts, the proportion ranging from 120 to 160 parts per 100,000. In a numl)er of instances there are indications of sodium carbonate. Most of the wells in the desert section tap a strata giving moderate supply of water at depths rang- ing from 125 feet downward, the water rising in the wells to within 35 feet of the surface. The United States Indian Office has quite thoroughly investigated and developed the water supply for parts of the Indian reservation within the area. Most of the water is obtained from the Gila River and conducted to the land by a system of main ditches and laterals, wells supplementing the gravity water supply during the dry season. A series of nine wells supplying 25 second- feet extends across the Santan District, and furnishes water for a main ditch when the river supply is short. A well at Sacaton supplements the river sup- ply for the experimental farm of the Bureau of Plant Industry and that of the Indian agency. Another series of wells is used to irri- gate the United States Indian seed farm near Sacaton, no gravity water being applied. The amount of water necessary to mature crops in this region de- pends largely on the situation of the land, the nature of the soil, and the crop grown. Areas in the river bottoms require less water than those in the desert, and the heavier textured soils produce good yields with less water than the types of more open structure. Many of the bottom lands are naturally subirrigated, but this condition is likely to be accompanied by accumulations of alkali, which is brought to the surface through the capillary rise and evaporation of soil water. Surface irrigation is beneficial on the subirrigated soils, as this tends to wash the salts into the subsoil. Alfalfa requires much w ater for maximum yields, one flooding for each cutting being necessary during the dry season. Other crops such as grain and grain hay require less water, as they mature early. Cultivated crops like corn, cotton, truck, and tree fruits require water during the growing season, and this is applied by the furrow method. Most of the irrigated land lies in the Gila River bottoms and in- cludes Indian allotments as w^ell as large ranches. Only small patches are cultivated in the desert section, but farming centers are developing in the vicinity of Florence and Casa Grande. The de- velopment of the greater part of the agricultural area outside the stream bottoms will i^robably depend upon effective storage of the Gila River waters. DRAINAGE. The natural drainage in the Gila River bottoms, where most of the agricultural development has taken place, is poor. These lands lie 32 FIELD OPERATIONS OF THE BUREAU OF SOILS, 19V1. onl}' a little above the channel of the stream. An nndei-lyino^ stratum of gravel and sand permits of the ready movement of under- ground water, and there is generally a high water tal)le. The poor drainage of the bottoms is further accentuated by seepage from irri- gation upon adjacent terraces or uplands and by the underground flow from tributary creeks and drainage ways. The latter is of im- portance in numerous places, but is especially pronounced at the place where the McClellan Wash enters the Gila River bottoms. Drainage is also poorly developed locally in the shallow and imperfect drain- age ways of the desert. Here the gradient is low, and the run-oif and percolation much retarded. The greater surface slope and more pervious subsoils of the bottoms make the drainage more perfect than in the case of the low, flat desert areas of old valley-filling soils, with their slight slope and dense compacted subsoil. The high water table of the bottoms is often relieved by open ditches and sometimes by tile drains. Little attempt has been made to provide drainage for the broad flats of the desert, cultivation being confined to the better drained soils. ALKALI. The Middle Gila Valley area is situated in an arid region of excessive evaporation, where soluble salts are readily accumulated. More than 50 per cent of the area is more or less affected by alkali accumulation. The following table shows the results of an analysis of a composite sample of alkali crust taken in various parts of the survey : Chemical analysis of alkali crust. [Parts per 100,000.] Constituent. Quantity. Constituent. Quantity. Ions: Mg Trace. 16,673 208 8,408 16,080 424 2,792 Trace. Conventional combinations: CaS04 Trace. Na MgSOi Trace K K2S04 . 463 S0< NajSOi . 12 066 CI NaCl. 26 535 ncoa NalTCOj 584 C03 Na2C03 4 937 Ca The above re.sults show that sodium chloride, sodium sulphate, and sodium carbonate predominate in the alkali of this area. Sodium chloride, or common salt, is by far the most abundant, composing a little more than 25 per cent of the average crust. The sodium sul- phate constitutes a little over 12 per cent, while the proportion of sodium carbonate, commonly known as black alkali, is less than 5 per SOIL SURVEY OF THE MIDDLE GILA VALLEY, ARIZON^A. 33 cent. A very small proportion of sodium bicarbonate is also present. Of the principal bases which combine to form the alkali salts, sodium is the only one of importance represented in the surface crust. Potassium, magnesium, and calcium exist only in very small amounts, or traces. The alkali salts are all highly soluble and their presence in the surface soil is due principally to the evaporation of soil waters. They have for the most part been transported to the localities in wdiich they occur by subsurface and surface drainage waters carrying them in solution. The conditions of drainage in the bottom soils differ from those in the upland or desert soils. The soils of the Gila River bottoms, as has been pointed out, are affected by seepage and have a high water table ; this, with their texture and structure, which favor capillarity, has caused the large accumulations in the valley. The heavy alkali crusts formed during the dry season are partly removed in surface drainage waters or are carried downward during the rainy period. The desert or upland soils generally have impervious subsoil lay- ers, and where they are affected by alkali, little free movement of the salts in subsurface waters is possible. In many places the crusts of surface salts are very thin even during the driest season, although the areas are barren of vegetation and the total average alkali con- tent high. Many of the barren alkali flats are interrupted or bordered by slightly higher lying soils of lighter texture, which are frequently free from surface accumulations of alkali. The flats receive run-off from the adjacent soils, and the water remains until removed by evaporation or percolation. Both the suspended sediments and the salts in solution are deposited, and upon drying form a smooth, hard, surface which greatly retards the movement of the salts. Owing to these different conditions the distribution of alkali salts in the 6-foot profile varies greatly with the different soils and situa- tions. Alkali in general is more uniformly distributed through the soil profile in the recent-alluvial soils than in the old valley-filling or desert types with compacted subsoils. Where the distribution is un- equal, the zone of maximum concentration usually lies between the first and third feet in the recent-alluvial soils, while in the desert types the zone of highest salt content is usually deeper. The distribution and degree of concentration of the alkali areas are shown on the accompanying alkali map. The mapping is based upon field determinations with the electrolytic bridge method. The aver- age salt content of the 6-foot profile, based upon the content of each foot section, is determined. The results are expressed in terms of parts per 100,000. Five grades of alkali land are shown. Grade A comprises soils in which the average concentration of salt is under 34 FIELD OPEKATIONS OF THE BUREAU OF SOILS, 1917. 200 parts per 100,000 of air-dry soil; jrrade B represents soils con- tainiiiortant money crop with both white farmers and Indians. The methods in use by the white farmers are good, but the Indian is slow to adopt modern methods and machinery. The i^ossibility of irrigation and presence of alkali have had more influence on the distribution of crops than has soil character. The Pima Indians and Mexicans supply most of the farm labor. Over 95 per cent of the farms were operated by the owners. The soils of the Middle Gila Valley fall into three main groups — residual, old valley filling, and recent alluvial. The old valley-filling group is most extensive, and includes the desert or upland soils. The recent-alluvial group includes the soils at present of greatest agri- cultural value. The residual group is unimportant, including the one nonagricultural type, Eough stony land. Five series, including eight soil types, are recognized and mapped in this area, in addition to Eough stony land and Riverwasli. The old . valley-filling soils cover about 75 per cent of the area. They are derived from weathered and altered old-alluvial deposits, and are characterized by a limy, compacted or cemented subsoil or hardpan. The surface is smooth or undulating. Three soil series are recognized under this group, the Pinal, Mohave, and McClellan. The Pinal gravell}^ sandy loam has a cemented, gravelly hardpan. The Mohave series consists of light-textured, red or reddish-brown soils, with a compact subsoil approaching a hardpan. Two types, in which some alkali occurs, are included in this series. The McClel- lan series is darker and browner in color than the Mohave. Two types are included, the heavier of which has a level surface and con- tains alkali. The recent-alluvial soils, confined to the bottoms and low terraces of the Gila River, are classified with the Gila and Pima series. These SOIL SURVEY OF CHE MIDDLE GILA VALLEY, ARIZONA. o7 tj^pes liHve more friable subsoils, contain more organic matter, and are more poorly drained than those of the old valley-filling group. The Gila soils are brown and underlain by a permeable subsoil; the soils of the Pima series have similar characteristics except color, Avhich is darker. Alkali is present in places in both these series. The soils are overflowed and have a high water table. Irrigation is necessary to insure crops in this region. In 1910 there were 25,431 acres under irrigation. Practically all the water for irrigation is obtained by gravity from the Gila Kiver. This is generally of good quality. Water is also obtained from wells. This may be somewhat higher in soluble salts than the river water. Stor- age of the waters of the Gila River is necessary to the permanent development of the desert lands. More than 50 per cent of the lands in this area contain more or less alkali. Sodium chloride, sodium sulphate, and sodium carbonate predominate in the alkali crust. Sodium chloride is by far the most abundant. The chief alkali areas occur at the lower levels, in the western and southwestern parts of the survey. The largest alkali - free areas occur northeast and east and to the west of McClellan Wash, Alkali-free areas also occur along the Southern Pacific Rail- road and on the mountain and foothill slopes. o 5DJL MAP 5^ r- 'wa_- i=t:is~ ^^ sarj; [Public Resolution — ^No. 9.] JOINT RESOLUTION Amending public resolution numbered eight, Fifty-sixth Congress, second session, approved February twenty-third, nineteen hundred and one, " providing for the printing annually of the report on field operations of the Division of Soils, Department of Agriculture." Resolved hy the Senate and House of Representatives of the United States of America in Congress assembled, That public resolution numbered eight, Fifty- sixth Congress, second session, approved February twenty-third, nineteen hun- dred and one, be amended by striking out all after the resolving clause and in- serting in lieu thereof the following: That there shall be printed ten thousand five hundred copies of the report on field operations of the Division of Soils, Department of Agriculture, of which one thousand five hundred copies shall be for the use of the Senate, three thou- sand copies for the use of the House of Representatives, and six thousand copies for the use of the Department of Agriculture : Provided, That in addition to the number of copies above provided for there shall be printed, as soon as the manuscript can be prepared, with the necessary maps and illustrations to accom- pany it, a report on each area surveyed, in the form of advance sheets, bound in paper covers, of which five hundred copies shall be for the use of each Sena- tor from the State, two thousand copies for the use of each Representative for the congressional district or districts in which the survey is made, and one thousand copies for the use of the Department of Agriculture. Approved, March 14, 1904. [On July 1, 1901, the Division of Soils was reorganized as the Bureau of Soils.] MOHAVE APACHE Areas surveyed in Arizona.