Digitized by the Internet Archive in 2011 with funding from LYRASIS members and Sloan Foundation http://www.archive.org/details/potashrequiremenOOande ~VAqg\V53^ . ■ 0 ■• gjT g 'Department &f Agriculture Qfice of Experiment Statins Bulletin 334 &&&$ February, 1932 POTASH REQUIREMENTS OF THE TOBACCO CROP P. J. ANDERSON, T. R. SWANBACK AND O. E. STREET (Hxmttntuvtt Agriatiturai Uixpmmtttt Butmn N?m Huum 43 Bulletin 334 February, 1932 po,3>3Y POTASH REQUIREMENTS OF THE TOBACCO CROP P. J. ANDERSON, T. R. SWANBACK AND O. E. STREET (Unnmctxtnt Agrirultural iExpertmntt Station •Dfow Hauf n CONNECTICUT AGRICULTURAL EXPERIMENT STATION BOARD OF CONTROL His Excellency, Governor Wilbur L. Cross, ex-officio, President Elijah Rogers, Vice-President Southington George A. Hopson, Secretary Mount Carmel William L. Slate, Director and Treasurer New Haven Joseph W. Alsop Avon Edward C. Schneider Middletown Francis F. Lincoln Cheshire S. McLean Buckingham Watertown STAFF Administration. Analytical Chemistry. Biochemistry. Botany. Entomology. Forestry. Plant Breeding. Soils. Tobacco Substation at Windsor. 'Assistant Chemists. William L. Slate, B.Sc, Director and Treasurer. Miss L. M. Brautlecht, Bookkeeper and Librarian. Miss Dorothy Amrine, B.Litt., Editor. G. E. Graham, In Charge of Buildings and Grounds. E. M. Bailey, Ph.D., Chemist in Charge. C. E. Shepard Owen L. Nolan Harry J. Fisher, Ph.D. W. T. Mathis David C. Walden, B.S. J Frank C. Sheldon, Laboratory Assistant. V. L. Churchill, Sampling Agent. Mrs. A. B. Vosburgh, Secretary. H. B. Vickery, Ph.D., Biochemist in Charge. Lafayette B. Mendel, Ph.D., (Yale University) Research Associate. George W. Pucher, Ph.D., Assistant Biochemist. G. P. Clinton, Sc.D., Botanist in Charge. E. M. Stoddard, B.S., Pomologist. Miss Florence A. McCormick, Ph.D., Pathologist. A. A. Dunlap, Ph.D., Assistant Mycologist. A. D. McDonnell, General Assistant. Mrs. W. W. Kelsey, Secretary. W. E. Britton, Ph.D., D.Sc, Entomologist in Charge, State Entomologist. B. H. Walden, B.Agr. 1 M. P. Zappe, B.S. Philip Garman, Ph.D. ^Assistant Entomologists. Roger B. Friend, Ph.D. Neely Turner, M.A. J John T. Ashworth, Deputy in Charge of Gipsy Moth Control. R. C. Botsford, Deputy in Charge of Mosquito Elimination. J. P. Johnson, B.S., Deputy in Charge of Asiatic and Japanese Beetle Quarantines. Mrs. Gladys Brooke, B.A., Secretary. Walter O. Filley, Forester in Charge. 11. W. Hicock, M.F., Assistant Forester. J. E. Riley, Jr., M.F., In Charge of Blister Rust Control. Miss Pauline A. Merchant, Secretary. Donald F. Jones, Sc.D., Geneticist in Charge. W. Ralph Singleton, Sc.D., Assistant Geneticist. Lawrence C. Curtis, B.S., Assistant. Mrs. Catherine R. Miller, M.A., Secretary. M. F. Morgan, M.S., Agronomist in Charge. H. G. M. Jacobson, M.S., Assistant Agronomist. Herbert A. Lunt, Ph.D., Assistant in Forest Soils. Dwight B. Downs, General Assistant. Paul J. Anderson, Ph.D., Pathologist in Charge. T. R. Swanback, M.S., Agronomist. O. E. Street, M.S., Plant Physiologist. Miss Dorothy Lenard, Secretary. CONTENTS The Functions of Potassium in Plant Nutrition 137 Resistance to disease 139 Symptoms of Potash Deficiency in the Green Tobacco Plant .... 140 Percentage of Potash in Cured Leaves 142 Effect of quantity of fertilizer potash 142 Effect of other bases 143 Effect of season 147 Native Potassium in the Soil 147 Methods of Increasing the Availability of Native Potash 149 Leaching of Potash from the Soil 152 Potassium in the Plant 157 Compounds of potassium in the plant 159 Role of potash salts in absorption of water by cured leaves 161 Rate of Intake by the Plant 162 Role of Potash in Combustion of the Cigar 164 How Much Potash Should Be Used Annually in the Fertilizer . . 173 Quantitative series of 1926 174 Quantitative series of 1927 178 Influence of the quantity on the fire-holding capacity 181 Effect of the quantity on the amount of potash, calcium and mag- nesium in the leaf 182 Discussion of results of field tests 184 Comparison of Potash-Containing Fertilizer Materials 185 Fertilizer materials containing potash 185 Field tests of potash carriers 190 Series I. Comparison of sulfate, carbonate and nitrate of potash. Old series of 1925 190 Series II. Comparison of sulfate, carbonate and nitrate of potash. New series of 1927 193 Series III. Comparison of sulfate of potash-magnesia with high grade sulfate of potash 200 Series IV. Tobacco stems compared with mineral carriers of potash 204 Series V. Comparison of cottonhull ashes with other materials . 207 Summary 211 Literature Cited 214 POTASH REQUIREMENTS OF THE TOBACCO CROP P. J. Anderson, T. R. Swanback, and O. E. Street Tobacco as grown in New England takes from the soil more pounds per acre of potash than any other plant nutrient. Further- more, no other important crop in this region, with the possible exception of alfalfa, removes annually so large an amount. Table 1 shows how Connecticut tobacco compares in this respect with some other common crops. Not only is potash essential to the growth and health of the plant but it also has a particular function in tobacco, that of promoting the burn of the cigar, in which role it is more important than any other element. Field experiments comparing different amounts and sources of potash in the fertilizer were begun soon after the Tobacco Substa- tion was established in 1921. These have been enlarged and con- tinued each year. Laboratory and greenhouse studies have been carried on to supplement the field work. Progress reports have been included in the Annual Reports of the Tobacco Substation, but no complete statement has been published. The purpose of this Bulletin is to bring together and discuss for the general reader, as well as the scientist, all of these investiga- tions in the light of our present knowledge. For this reason there is included pertinent material from other sources, and an attempt has been made to present as complete a discussion as possible of the relation of this important element, potassium1, to cigar leaf tobacco. FUNCTIONS OF POTASSIUM IN PLANT NUTRITION Potassium is absolutely essential to plant growth and cannot be replaced entirely by any other element. Although exact knowledge of all its functions is lacking, most plant physiologists agree that the specific and all-important role of potassium in plants is its action as an activating agent (catalist) in the synthesis of carbo- hydrates (starch, sugar and cellulose). Without potassium there would be no photosynthesis, and green plants could not exist in the absence of the simple carbon-containing foods (products of photo- synthesis), from which all the organs of the plant largely are 1Both terms, potash and potassium, will be used in this Bulletin, depending on the context. In discussing fertilizers, the term potash, the oxide of potassium (KO), is commonly used, whereas the term potassium, the element (K), is more often used by plant physiologists. To convert pounds or percentage of potassium to potash, multiply by 1.2046. To convert figures for potash to potassium, multiply by .8301. 138 Connecticut Experiment Station Bulletin 334 elaborated. There is also considerable evidence that potassium has the same function in the synthesis of proteins. Cell division, or mitosis, does not occur in the absence of potassium, and in such a case, no cambium or other embryonic tissue can function, where- upon growth ceases, obviously because new protoplasm is lacking. Potassium, however, is not a constituent of protoplasm, cell walls, Table 1. Potash Removed Annually by Various Crops1 Crop Yield per acre Lbs. potash (K20) removed per acre Alfalfa hay 8 tons 230 Tobacco leaves " stalks 1800 lbs. 1200 lbs. (dry weight) 108 47 Total 155 Clover hay 4 tons 144 Potatoes 300 bu. 108 Timothy hay 3 tons 85 Corn grain " stover 100 bu. 3 tons 23 62 Total 85 Oats grain " straw 100 bu. 2]/2 tons 19 62 Total 81 Wheat grain " straw 50 bu. 2y2 tons 16 54 Total 70 Apples (fruit) wood growth Total 600 bu. 68 6 74 or any essential solids in the plant. It is present only in solution in the cell sap, from which it may, however, infiltrate or even occur as a physiological precipitate within the plant tissue (55)." 1 These figures, with the exception of those for tobacco, are taken from Hopkins' Soil Fertility and Permanent Agriculture, page 154, and are for maximum crops, much above the average. The figure for tobacco (1800 pounds) is above the average, but by no means a maximum. The figure for percentage of potash in stalks is taken from Station Bulletin 180, page 10. Hopkins' figure for 8 tons of alfalfa hay to the acre is entirely too high for Connecticut yields. 2Figures in parentheses refer to "Literature Cited" on p. 214 of this bulletin. When two numbers separated by a colon are used, the second designates the page of the publication cited. Functions of Potassium in Plant Nutrition 139 In addition to its specific function as an activating agent, potas- sium has certain general functions, that is, it accomplishes, or helps to accomplish, certain purposes that may also be accomplished by other elements. For example, potassium serves as a carrier in the absorption of nitrates and other anions through the root hairs and in their translocation throughout the plant. An adequate supply of potassium makes the tobacco plant more resistant to drought. We have frequently observed that in hot dry weather the tobacco on the low-potash fertilizer plots is the first to wilt (5 : 153, and 6:207). Resistance to Disease The statement is sometimes made that potash makes plants more resistant to disease. Thus Hall (37) says : "There is abundant experimental evidence to show that potash makes the plant more resistant to the attack of fungoid diseases." This conclusion was supported by his observations on beet leaf spot (Uromyces betae), wheat rust, and grass diseases on the fertilizer experimental fields at Rothamsted. Boening (17), after his investigations on tobacco wildfire in Germany, stated that resistance to wildfire is increased in the same degree in which the potash application is augmented and the nitrogen supply diminished. Moss and others (60) write: "Under some conditions the use of potash seems to control partially several of the leaf-spot diseases, including wildfire and blackfire, especially when used at a liberal rate. When the weather conditions favor the development of leaf- spot diseases the physiological breakdown herein described resulting from potash deficiency probably allows the organisms causing certain leaf -spots to gain entrance into the plant tissue, and these hasten the breakdown of the leaf tissue. At any rate, it is known that potash in some way aids in maintaining the general vigor of the plant. On those plots which were fertilized with a mixture carrying heavy rates of ammonia with little or no potash the various leaf-spot troubles have been more prevalent, causing serious damage ; but with more potash added to the fertilizer there has been much less damage from leaf-spot." Tobacco plants deprived of a sufficient ration of potash exhibit certain abnormal symptoms (as described in a later paragraph) and to this extent they may be spoken of as diseased ; or possibly lesions so produced may offer infection courts for disease organ- isms. Nevertheless it has not been adequately demonstrated that plants that have enough potassium to carry on their normal func- tions may be made more resistant to a specific disease organism through absorption of additional potassium. That an abundant supply of potash is not a protection against the wildfire disease, 140 Connecticut Experiment Station Bulletin 334 is demonstrated by severe epidemics of this disease in the Con- necticut Valley, where the percentage of potash in the leaf is prob- ably higher than that of any other tobacco in the world. Some important roles that potassium plays in "casing" and in combustion of cigar leaf tobacco will be discussed in subsequent sections of this Bulletin. Figure 16. Normal plant (right) and plant showing potash starvation symptoms (left) on middle leaves. Note recurved tips and margins and hobbly leaves on latter. SYMPTOMS OF POTASH DEFICIENCY IN THE GREEN TOBACCO PLANT Tobacco plants that are not supplied with a sufficient amount of potassium for normal development exhibit certain symptoms that an experienced observer is able to recognize. These symptoms are characteristic of potash hunger, and readily distinguishable from those produced by a deficiency of any one of the other nutrient elements. Potash Deficiency in Green Tobacco Plant 141 In the earliest stages the potassium-starved leaves are mottled with yellow near the margins and tips, resembling somewhat the early stages of ripening. Soon the surface of the leaf becomes rough or puckered, "hobbly." Meanwhile the centers of the mottled areas have died and the margins and tips of the leaves are speckled with numerous small white spots. As the conditions grow worse, the margins of the leaves turn downward (Figure 17) giving them a rim-bound appearance. In severe cases the dead portions may coalesce and fall out or break and make the leaf appear ragged. On large leaves in the field, when potassium deficiency is not great, Figure 17. Effect of potash deficiency. Large plant on right had all nu- trients supplied. Small plant had all nutrients except potash. Note small size and rim-bound leaves with recurved tips. Plants of same age. we have found the only symptoms to be a yellowing and sharp downward recurving of the leaf tips. The condition is illustrated in Figure 16. Unlike magnesia hunger, the symptoms of potash hunger do not always appear first on the lower leaves. As shown in Figure 16, the lower leaves may be quite normal and the worst symptoms occur on the middle leaves. In very severe cases the plants are dwarfed (Figure 17) but we have not seen one severe enough to produce dwarfing in the fields of the Connecticut Valley. Stunting of growth is apparently not uncommon in tobacco districts farther south (60). 142 Connecticut Experiment Station Bulletin 334 PERCENTAGE OF POTASH IN CURED TOBACCO LEAVES Numerous analyses of cured tobacco from all tobacco growing sections of the world have been published. The potash percentages from a number of these are assembled in Table 2, which shows that the percentage of potash in the leaf varies widely, from 2.2 per cent to 8.5 per cent of the dry weight of the leaf. Samples from the same locality may differ considerably in this respect. The percentage of potash in the tobacco leaf is not constant, but depends on (1) the amount of potash furnished in the ferti- lizer or naturally in the soil, (2) the relation of other elements, particularly the bases, and (3) the season. Whether there is a difference in the capacity of different tobacco varieties to absorb potash has not been demonstrated. H )5 7 ^^ .y - It 73 K G / - 11 "^ ^0>'''' *< 4-' ft* 10 % t: Jr /''' ^ f 3 <0 <5* < ,°' Qs % j/ \V - 7 ! /• - r ^ 1 ^3 ^ °Q - / _^^ t 1 */ ,-"' i 1 1 i i - 3 1 1 6 70 100 130 160 130 21 0 F0MD5 °ff OTA 5H <° the JCtfE . Figure 18. Graph showing correlation between quantity of fertilizer potash and the percentage of potash found in the leaves and the fire-holding capacity. Effect of Quantity of Fertilizer Potash In order to see how the percentage of potash in the leaf is dependent on the amount of potash applied to the soil, two series of greenhouse pot experiments were made in which increasing quantities of potash were applied. In the first series, the soil used was a good tobacco soil to which no fertilizer had been applied for Potash in Cured Tobacco Leaves 143 five years, but which had been under continuous tobacco culture. In the second series, sand from a local pit was used. Analyses of the cured leaves, given in Table 3, show that each increase of fertilizer potash gave a corresponding increase in the quantity of potash found in the leaf. This is graphically illustrated in Figure 18. Otryganjew (65), growing tobacco plants in poor sandy soil in pots, was able to raise the potash content from .45 per cent to 7.22 per cent by increasing the quantity of potash applied to the soil. Table 21 shows how an increase in the quantity applied in the fertilizer under field conditions will increase the percentage of the leaf. Pot experiments by Morgan (57) show that the percentage of potash can be reduced to as low as 1 per cent, but when the content falls to about 2 per cent the plants are abnormal. The 6 to 8 per cent commonly found in Connecticut tobacco is greatly in excess of the physiological needs of the plant, the surplus being due to "luxury consumption." That the percentage of potash found in plants is primarily dependent on the quantity of potash applied to the soil in the fertilizer and may be raised or lowered very readily over a wide range has been demonstrated for a large number of plants (12). Effect of Other Bases The percentage of potassium in the plant is markedly affected by the percentage of the other mineral bases, particularly calcium and magnesium. The sum of these three dominant bases tends to be constant, that is, when one is increased, the sum of the others decreases in percentage somewhat proportionately. Schloesing (71), more than 70 years ago, called attention to the fact that in cured tobacco, the percentage of potash shows an inverse relation- ship to the percentage of calcium and magnesium. Ames and Boltz (1), working with Ohio tobacco, state that "the tobacco from limed plots contains less potassium." Graham and Carr (35) found the same effect. Anderson and Swanback (5: 197) found a reduced percentage of potash in the tobacco from all limed plots as compared with adjacent unlimed plots. This was explained as due to the repressive effect of magnesia, which had been absorbed from the limed soil in larger amounts. Morgan (57: 906) showed that calcium has the same repressive effect on potassium as has magnesium. In order to study the extent of such potash repression, field plots at Windsor which had not grown tobacco in recent years were treated with increasing quantities of hydrated magnesian lime (57 per cent CaO and 29 per cent MgO). The tobacco grown on them in 1930 was analyzed for the three bases. The results, pre- 144 Connecticut Experiment Station Bulletin 334 £ O W X U w Q < £ CO o W P5 W l"H K P C/l < M On cm -M c > X V OCv1C0 t-^odt>!odt>IrN.'o6odco"^co Tt 00 O ■* VO co uo CO O 10 CM >-< CO O cm vd co co cm co co JJ - T3 pq rt S> ^ H ^ ^ C\) °° .^CMCOCocococo^r ^ •■ — ' — ^ Ph03- I 3 S~ 5 CM . ^ PQ rt . ro W 3 iS co ^.MW g rv jj G u.c/3 W ^ be o" u < O bo- G C - o - u H< >, ■24 CD c rt PQ o CO G T3 -r ^ rt n! 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GO •<* On -T CO CM u £> = Q N pq W = ii "> » O o o t^ r^ r^ »-l i— c NO NO NO ON ON CO CO CO « C. 3 -Q 1-. i* a> o 3 O rt rt j£ H I- rt JLj i5 I- tn w > ^ Ph cn m N N M r>« On no no CO CO CO CO CO CO . bo rt as 3 >> n IS -p "i *—; w ■J-t i-i i-i. X M pq co £ .2 £ B rt a > •° rt o-s -B £ u .a * rt v E E g H rt S ^ ^2 ■^ U»-. >1 O to C b. c E Si E y o Si ij in IB E — «rt « ^ . S n 8 O O^ +J OT3 g°s B - .3 c U-5 u tr,° u rt t*> ca a .. .ti i-ja ^ art a o o E ^ E 2^ — CO o « rt© > 11 , 3 ^ r^ bo 1U CO rtX- B i-'rtcH "S° B ° ■»i ^ O co. 2 rt o u£ ^E g rt v « 'fi£ O^B- cu ui-* S IT ~- cu o b rt cu , bo •ti co ^? a s E-o CO V ^> "J c3f_i'S to^1. - a £ o o rt c ; _ ^0.B 5'? S b- 5^: j; M ca 146 Connecticut Experiment Station Bulletin 334 sented in Table 4, show that the magnesia was increased at the expense of both potash and calcium. Such reciprocal repression among the three bases is not con- fined to tobacco. Gaither (31) and Maclntire (48) found that application of lime to wheat land reduced the percentage of potas- sium, as it increased the calcium, in the wheat. Others have observed the same effect on corn (45), alfalfa (28, 72), orange trees (69), grapevines (44), peas, (70) and other plants (56). This interrelation of bases, which thus appears to be general in plants, may be explained as due to the substitution of one cation for another in the absorption of mineral compounds from the soil. Maclntire and his associates (50, 51, 52) have shown by lysimeter experiments how the addition of calcium or magnesium, in the form of liming materials, to the soil depresses the potassium content of the leached water. When calcium ions are in great Table 3. Relation of. Quantity of Potash Applied to Soil to the Percentage Found in the Leaf. Pot Experiments Pounds K 0 applied Percentage KO in leaf when grown per acre Soil Sand 0 1.48 1.16 70 3.49 1.65 100 374 1.97 130 5.47 2.26 160 5.75 2.90 190 6.54 3.45 220 6.78 5.36 excess over potassium ions in the soil solution, and cations are required as "carriers" for a certain amount of nutrient anions, such as nitrates, it is natural to suppose that more calcium than potassium ions would be used, that is, the ratio of the absorbed cations would tend toward that which exists in the soil solution. Under field conditions such as we have in this state, a substitution of calcium or magnesium for potassium would not interfere with the normal development of the plant because potassium is absorbed in great excess of the plant's physiological needs. In field experi- ments on the Station farm, it has not been possible to produce acute symptoms of potash starvation except by heavy liming of some plots where all mineral potash fertilizers have been omitted for several years, a condition that would never occur on a tobacco farm. Native Potassium, in the Soil 147 Effect of the Season The potash content of the leaf is higher during seasons of heavy rainfall than during seasons of light rainfall. Analyses showing this relationship in Connecticut tobacco have been pub- lished by the writers (6: 228) and for Pennsylvania tobacco by Haley, Nasset and Olson (36). A reasonable explanation of the increased potash during a wet year is this : The most abundant base with which the soil colloids (or acidoids) are combined is calcium. When the soil is treated with a potash salt, the potassium ions displace the calcium ions in the colloidal complex. The calcium ions, thus brought into true solution in the soil water, will be readily absorbed by the tobacco roots during a dry year. During a wet year, however, the calcium salts will be leached out of the soil water and the plant will be forced to get more of its supply of cations from potash ions of the colloidal complex. Bartholomew and Jannsen (12:55), working with a number of crops, noted such seasonal variation in the per- centage of potash but made no attempt to explain it. Table 4. Effect of Magnesian Lime on Percentage of Calcium, Magnesium and Potassium in Tobacco. (Air Dry Basis on Unfermented Leaves) Pounds magnesia applied Percentage found in the cured leaves per acre K?0 | CaO MgO None 4.83 6.75 1.32 100 3.98 6.22 2.47 200 3.12 5.63 3.13 400 3.09 5.26 3.83 600 2.40 4.95 4.59 NATIVE POTASSIUM IN THE SOIL The major (mineral) part of soil has been formed and is still being formed through disintegration or decomposition of the underlying rocks. Some of the minerals composing the original rock, and hence now present in the soil in various stages of disin- tegration, contain potassium in a highly insoluble form. The most common of these minerals are the feldspars (orthoclase and microcline, KAlSiaOs) and mica (muscovite and biotite, K, Mg, Fe, H, Al-silicates). During the process of disintegration of the parent rock by physical processes into smaller particles, there is also a slow chemical breakdown of the complex potassium-con- taining compounds into simpler compounds that are soluble and thus available for absorption into the root hairs. Carbon dioxide 148 Connecticut Experiment Station Bulletin 334 in the soil solution plays an important role in this process as may be illustrated by the following chemical equation : 2KAlSi308 + C02 + 2H20 = H4Al2Si209 + K2C03 + 4 SiO: orthoclase hydrated soluble silicate potassium carbonate silica When in the process of physical disintegration, the mineral particles have become so small that they approach, but do not actually attain, a molecular size, they assume under ordinary soil conditions a jelly-like consistency which is characteristic of some colloids. The present conception of a soil colloid is that it consists of a relatively insoluble nucleus (acidoid) which functions as a large anion and is able to hold in a replaceable condition the cations, calcium, potassium, magnesium, and others. Although calcium is the most abundant cation in the soil colloidal complex, the latter also contains considerable potassium which is in a state easily made available for plant nutrition. Thus we may distinguish three different states in which potash is present in soil, (1) insoluble minerals, (2) colloidal combinations, and (3) water soluble compounds. Only an extremely small part of the potassium remains in a water soluble form because of the soil's well-known capacity for absorb- ing potash. This may be demonstrated by adding to some soil a water solution of any of the common potash fertilizer materials such as sulfate, carbonate, or nitrate of potash. After the soil is saturated, it may be thoroughly leached by addition of excess of water. If the water that leaches through the soil is analyzed, it will be found to contain only very small amounts of potassium because most of it has been absorbed. The process of absorption consists of an exchange of bases between the potassium salt and the colloid, as may be expressed by the following equation in which X repre- sents the colloidal acidoid : K2S04 + Ca X Ca S04 + K2X potassium acidoid with calcium acidoid with sulfate calcium base sulfate potassium base Although the potassium thus attached to the colloid is insoluble in water, it is nevertheless relatively available to the plant, probably being again brought into solution through the action of carbonic or other acids. Neutral salts may also displace it. It is spoken of as "replaceable" potash and its amount in a soil probably most nearly represents the capacity of that soil to supply the potash needs of any crop grown on it. Connecticut soils, according to analyses by Morgan (57: 884), contain 25,000 to 50,000 pounds of total potash to the acre in the tillable surface, or, enough to grow maximum crops for 100 years Increasing Availability of Native Potash 149 or more if it were available. Tests show, however, that on many soils less than 200 pounds of this amount are in an exchangeable condition, hence the necessity of annual applications of potash fertilizers. From the above statements it is apparent that the soil potash is not stationary, but is in a constant state of change. The mineral potash is gradually changing into more soluble compounds and some of the soluble compounds are leached away into the lower layers or even into drainage water. Certain of the insoluble min- erals are transformed to a colloidal condition and the colloids absorb the soluble compounds or at times liberate the potassium ions. It is even possible that some of the soil potash is being reverted into insoluble minerals (12). This dynamic condition of the soil potash is the main reason why it is not possible by any chemical analysis yet devised to determine the capacity of a given soil to furnish potash for crop production. The plant appears to be able to extract from the soil water, soluble potash, replaceable potash, and even some of the so-called insoluble mineral potash (29, 8). Efforts to duplicate this capacity of the plant by chemical treatment of the soil in the laboratory have not yet been successful, but a determination of the replaceable potash (as by leaching with ammonium chloride) of a series of soils will give an indication of the relative capacity of these soils to supply potash to the plant. METHODS OF INCREASING THE AVAILABILITY OF NATIVE POTASH Since in Connecticut soils a great store of potash is always locked up around the roots, while the farmer must annually incur the expense of supplying his crop with commercial potash ferti- lizers in order that the plants will not suffer for lack of it, it is natural that agricultural scientists long ago should have directed their efforts to discover a method of liberating the native soil potash. Application of lime was for years advocated as a means to this end, but later research, as noted previously in this Bulletin, showed that lime not only did not liberate potash but that, on the contrary, it prevented its liberation. Gypsum has been investigated in this role, but with rather con- tradictory results. Bradley in Oregon (18) concluded from his experiments that application of gypsum to the soil liberated potash. Shedd in Kentucky (73) had contradictory results, but some of the tests showed an increase in the potassium of crops grown after treatment of the soil with gypsum. Tressler (75) found that gypsum liberated potash in some soils but not in others. Briggs and Breazeale (19), on the contrary, concluded as a result of their experiments with wheat seedlings: "The availability to plants of 150 Connecticut Experiment Station Bulletin 334 potash in soils derived from orthoclase-bearing rocks is not increased by the addition of lime or gypsum. In some instances a marked depression of the solubility of the potash in the presence of gypsum was observed." Cubbon (23) concluded from labora- tory tests : "Leaching various soils with saturated calcium sulfate solutions did not result in a marked liberation of potassium." Analyses of tobacco grown on plots treated with different quan- tities of gypsum for two years at the Windsor Station lend some support to the belief that gypsum may assist in liberating potash Table 5. Effect of Gypsum Application on Chemical Composition of the Tobacco. Crop of 1930. (Air Dry Basis on Unfermented Tobacco) Annual application of gypsum, pounds per acre Percentage of compounds found in the leaf 1929 1930 K20 CaO MgO S03 None 500 1000 5000 None 250 500 2500 5.55 7.03 6.68 6.16 5.40 6.26 5.47 6.69 1.71 1.56 1.43 1.43 1.13 1.57 1.75 2.19 (Table 5). According to these results there has been more of an increase in the potash, than in calcium, by the use of gypsum. This was accompanied by a decrease in magnesia, as might have been anticipated. The increase in sulfur, indicated by these analyses is not desirable in tobacco because it reduces fire-holding capacity, which would likely offset any advantage obtained from the increase in potash. Shedd (73) found that sulfur alone increased the availability of potash. The effect of sulfur is to increase the acidity of the soil, which is known to increase potash availability. Here again it might be anticipated that the sulfur content of the tobacco would be increased, but no analyses bearing on this point have been published. There is some experimental evidence to show that sodium salts may increase the availability of potash. Thus Hall (37), speaking of the potash plots at Rothamsted, says : "Potash increased the crop in every case except where nitrate of soda had been used ; the soda liberates so much potash from the soil that specific application of potassic manures is unnecessary." .On the contrary, de Turk (26), working with a number of potash-bearing native minerals, concluded as a result of his experi- ments : "The addition of soluble sodium salts to peat soil together with the minerals does not increase the yield of crop or the avail- ability of the mineral potassium." Increasing Availability of Native Potash 151 Experiments at the Windsor Station indicate that the use of nitrate of soda may increase the absorption of potash by the crop. In the nitrogen field tests, four plots received the standard quantity of all nutrients for five years, but differed among themselves only in the source of the nitrogen, each receiving all its nitrogen supply from a single carrier. The nitrogen carrier of each and the per- centage of potash found in the leaves grown on each plot in 1930 are shown in Table 6. The highest percentage of potash was seen Table 6. Effect of Nitrate of Soda on Absorption of Potash Carrier of nitrogen used in fertilizer Percentage of potash in leaves Nitrate of soda 6.88 Cottonseed meal 5.62 Sulfate of ammonia 6.07 Urea 6.39 to be in the tobacco where nitrate of soda was the only source of nitrogen. When used in moderate amounts, sodium itself is not absorbed to any considerable extent by the plant. In another set of experi- ments, however, where increasing quantities of nitrate of soda were used, it was found that a point was finally reached where sodium was taken up in considerable quantities and at that point it had a repressive effect on the potash. Below that point, however, the potash content of the leaf was increased by application of nitrate of soda. Barnyard manure increases the availability of native soil potash, as indicated by the work of Bartholomew (10), who suggests that the beneficial effect is due to the increased quantity of carbon- dioxide resulting from the breakdown of organic matter in manure. De Turk (26), however, did not find the potash in the native minerals rendered more available by the addition of manure or crop residues. He believes : "The so-called feeding power of the plant itself through the activities of the root system is an important factor in the utilization of relatively insoluble potassium." Turning under cover crops or green manure crops renders avail- able the usually insoluble potash minerals of the soil, according to the investigations of Hopkins and Aumer (41). Increase in the amount of organic matter in the soil increases the activity of soil microorganisms, which results in generation of more carbon- dioxide to dissolve the potash minerals. Also, as pointed out by Fraps (29), Prianischnikov (67), Headden (38), Ballentine (8), and others (24), the roots of plants are able to absorb a small percentage of the potash in the relatively insoluble mineral rocks (chemically "unavailable"). When the cover crops are turned 152 Connecticut Experiment Station Bulletin 334 under, this absorbed supply of potash is entirely available to the next crop. Cover crops also hold and prevent the leaching of soluble potash compounds when the main crop is not in the field. Organic residues may also exist in the soil in a colloidal condi- tion and may hold potash in a replaceable condition in the same manner as the mineral colloids. Thus it is apparent that cover crops have a quadruple function in the liberation and conservation of potash. Fertilizers that increase the acidity of the soil (such as sulfate of ammonia) also increase the amount of potash that is water soluble, and on the contrary, those that make the soil less acid decrease the water soluble potash (30). It should be remembered, however, that water solubility does not always mean increased absorption by the crop. Water soluble potash is easily leached as well as readily absorbed by the plant, and there are possibly some advantages in conserving it in a form that is water insoluble but at the same time available. LEACHING OF POTASH FROM THE SOIL The loss of potash from the soil by downward movement of water may vary widely. Differences in soil type, in crop removal, in rate of fertilization, and in amount of rainfall all combine to produce results from one set of conditions that are of doubtful application to any other. Low rates of loss, such as 10 pounds to the acre annually, have been reported by Collison and Walker (20) for Florida conditions, Hendrick and Welch (39) for Scotland, Gerlach (34) for Ger- many, Crawley and Cody (21) for Porto Rico, and Maclntire, Shaw and Young (50) for Tennessee. Most of these studies were made on heavy types of soil, with somewhat higher outgo on sandier soils. However, Lyon and Bizzell (46), working with a silty clay loam in New York, found an average loss of 57 pounds per acre for all treatments and crop conditions, and on a silt loam the same authors (47) reported an annual loss of more than 100 pounds on fallow soil. In contrast with earlier views, Maclntire and co-workers (50) have shown that the loss of potash may be materially decreased by the addition of liming materials, the amount of leaching being reduced as much as 21 per cent by high applications of burned lime materials. They have also shown (49) that by the application of lime materials the potash of a green manure may be fixed in the soil to the extent of one-half of the potash added. In order to study the losses of plant food elements under condi- tions typical of the Connecticut Valley tobacco district, a series of lysimeter tanks was installed at Windsor in the spring of 1929. Two series of cylinders of 20 inch diameter were used, the first Leaching of Potash from Soil 153 having 7 inches of soil (surface soil) and the second containing the normal surface soil placed over 12 inches of subsoil. The gen- eral plan of the installation is given by Morgan, Street and Jacob- son (59) and need not be repeated in detail. The series of shallow tanks, 34 in number, were filled with four different soil types on which tobacco is grown most extensively, as follows : Merrimac sand, a very light soil suitable only for shade tobacco production; Merrimac sandy loam, a typical light tobacco soil from the Station farm ; Enfield very fine sandy loam, an upland soil of light texture but very retentive of water, on which type a considerable acreage of Broadleaf is grown ; and Wethersfield loam, a reddish brown loam of rather high colloid content and typical of the heavier upland soils of glacial origin. Fertilization of these soils varied only with respect to nitrogen source, the following carriers being used to supply the equivalent of 200 pounds of nitrogen per acre annually : Nitrate of soda, sulfate of ammonia, urea, and cottonseed meal. The potash, to the amount of 200 pounds per acre, was derived equally from sulfate and carbonate. The 20-inch tanks were all filled with soil from one lot, the Merrimac sandy loam mentioned above, and the sources of nitrogen were : Nitrate of soda, nitrate of potash, nitrate of lime, sulfate of ammonia, ammophos "B", urea, calurea, cyanamid, cottonseed meal, castor pomace, linseed meal, fish, horn and hoof meal, dried blood, tankage, cow manure and no nitrogen. Potash fertilization was at the 200 pound rate, except that the nitrate of potash neces- sary to furnish the required amount of nitrogen also supplied 677 pounds of potash, and the castor pomace, through an error in analysis, supplied only 150 pounds in 1929. The leachates were collected after each rain and composite samples analyzed at the end of each 6-month period. The potash removal from the surface soil tanks for the four 6-month periods from May 26, 1929, to May 25, 1931, is shown in Table 7. Considering first the rate of loss as affected by soil type, it can be readily seen that the lighter soils permitted a greater outgo than the heavier types. In the summer of 1929, the rainfall was abnormally low, and the total amount of leaching, in terms of acre inches, was likewise low. The average loss of potash of the two lighter soils is almost exactly proportional to the loss of water, indicating a rather low base exchange capacity of the two soils. Between the Enfield and Wethersfield soils, however, no direct relation of water loss to loss of potash was found. The Enfield soil, while losing only two-thirds as much water as the Wethers- field, yet lost over three times as much potash, indicating the high absorptive power of the latter soil. The losses during the following winter were higher than the summer losses on all soils except the coarse sand, the highest being 154 Connecticut Experiment Station Bulletin 334 found on the Enfield soil. This would indicate that this soil was able to hold the potash only temporarily. In fact the total loss for the year was very nearly the same for the first three soils, while Table 7. The Leaching of Potash from the Surface Soil Lysimeter Tanks Pounds potash per acre Soil and source of nitrogen 1929-1930 Total for year 1930-1931 Total for year Total May 26- Nov. 26- Nov.25 May 25 May 26- Nov. 26- Nov.25 May 25 for 2 years Mer rimac coarse sand Nitrate of soda 28.617 21.771 50.388 38.271 24.376 62.647 113.035 Sulf. of ammonia 31.326 31.441 62.767 41.586 31.768 73.353 136.130 Urea 29.714 19.489 49.203 41.531 39.474 81.005 130.208 Cottonseed meal 33.207 29.087 62.294 41.153 51.140 92.293 155.587 Average 30.716 25.447 56.163 40.635 36.689 77.324 Merrimac sandy loam. Nitrate of soda 23.021 20.181 43.202 30.010 32.938 62.948 106.150 Sulf. of ammonia 25.115 46.018 71.133 35.495 65.053 102.093 173.226 Urea 24.098 37.046 61.144 30.739 44.559 75.294 136.438 Cottonseed meal 26.588 37.045 63.633 32.829 65.979 98.808 162.441 No nitrogen 24.952 34.631 59.583 30.054 46.458 76.512 136.095 Average 24.755 34.984 59.739 31.825 50.997 82.822 Enfield very fine sandy loam Nitrate of soda 15.712 35.906 51.617 26.242 42.650 68.892 120.509 Sulf. of ammonia 13.756 50.651 64.407 23.711 111.404 134.115 198.522 Urea 14.693 31.438 51.342 23.519 69.880 93.398 144.740 Cottonseed meal 14.978 40.747 55.725 23.888 95.978 119.866 175.591 Average 14.785 39.685 54.470 24.340 79.978 104.318 Wethersfield loam Nitrate of soda 5.821 6.178 11.999 10.103 13.291 23.393 35.392 Sulf. of ammonia 5.298 8.023 13.321 22.843 42.162 65.004 78.325 Urea 3.842 9.046 12.888- 8.799 25.309 34.108 46.996 Cottonseed meal 3.829 9.612 13.441 5.564 25.603 31.167 44.608 Average 4.697 8.215 12.912 11.827 26.591 38.418 the soil of high colloid content (Wethersfield loam) had losses of only 25 per cent on the same basis. Similar observations might be made on the results for the second year, as the trend is the same in most particulars. The outstanding difference is the mark- edly higher loss on the Enfield soil during the winter period, Leaching of Potash from Soil 155 which incidentally was featured by higher rainfall than any pre- ceding period. Again the Wethers field soil had a much lower annual loss. The effect of the different nitrogeneous fertilizers on the outgo of potash is quite definite. Referring to the cumulative total for two years it can be seen that the use of nitrate of soda has resulted Table 8. The Leaching of Potash from 20-Inch Lysimeter Tanks Pounds potash per acre Source of nitrogen 1929-1930 May 26- Nov. 26- Nov. 25 May 25 Total for year 1930-1931 Nitrate of soda 13.777 49.736 63.513 90.264 Nitrate of potash 11.172 43.157 54.329 169.020 Nitrate of lime 10.355 36.254 46.609 109.038 Sulfate of ammonia 11.242 44.643 55.885 159.994 Ammophos "B" 11.489 39.739 51.228 155.114 Urea 13.693 39.066 52.759 104.331 Calurea 11.824 44.242 56.066 96.888 Cyanamid 12.513 44.928 57.441 113.739 Cottonseed meal 13.939 37.303 51.242 122.411 Castor pomace 14.497 48.581 63.0781 128.640 Linseed meal 13.527 47.174 60.701 108.029 Dry ground fish 12.281 38.855 51.136 131.824 Hoof and horn meal 12.090 46.351 58.441 119.989 Dried blood 13.314 42.857 56.171 122.589 Tankage 11.196 38.900 50.096 123.993 Cow manure 14.622 32.757 47.379 124.519 No nitrogen 10.703 41.435 52.138 91.136 in a lower loss than that caused by any other carrier, or on the Merrimac sandy loam, less than was found with no nitrogen. With this treatment, especially on light soils, practically all the nitrates in the soil go out as nitrate of soda, and the potash outgo is lowered accordingly. Sulfate of ammonia has very materially raised the leaching of potash, the increased outgo paralleling the increase in acidity of the soil. Urea and cottonseed meal are not widely dif- ferent, although the latter material has caused greater losses in all soils except Wethersfield loam, where there is no real difference. In the 20-inch tanks, all of which had soil as nearly identical as possible, the only difference in treatment being in the source of nitrogen, somewhat similar results to those on the shallow soil tanks were found. Table 8 gives the results for the first year by 6-month periods, and total for the second year. 1 One hundred fifty pounds potash applied in 1929. 156 Connecticut Experiment Station Bulletin 334 No essential differences in potash outgo due to fertilizer treat- ment are to be noted for either the first or the second 6-month period. Nitrate of potash, furnishing 677 pounds potash per acre, produced no increase in the amount of potash in the leachate, while castor pomace, which supplied only 150 pounds, as compared with the standard amount of 200 pounds, had as high a loss as any treatment. The greater outgo during the winter as compared with the summer months of the first year, was in agreement with the losses that occurred in the shallow tanks, but more definitely emphasized. It agreed, moreover, with the water loss during the same periods, the winter leaching being two and a half times as large as the summer. A rather higher level of potash leaching was found during the second lysimeter year, May 26, 1930, to May 25, 1931. This was correlated with higher rainfall, but differences due to the cumula- tive effect of the nitrogen fertilizers were also becoming more marked. The great excess of potash furnished by the annual addi- tion of nitrate of potash was no longer so firmly held by the soil, and perhaps this treatment will continue to lose potash in increasing amounts. Sulfate of ammonia and ammophos "B" (which con- tains half its nitrogen as sulfate of ammonia) have begun to extend their acidifying effect to the subsoil, similar to their imme- diate effect in the surface soil, and the losses of potash are pro- portionately high. The repressive effect of nitrate of soda is also to be noted, the loss with this treatment being the lowest of all. Among the group of organic nitrogeneous fertilizers commonly used to supply the bulk of the nitrogen for the tobacco crop, no real differences are evident. The results with the deep tanks, which show a higher average loss than the shallow tanks, would indicate that there is little if any retention of the potash brought by the soil solution into the subsoil, and that the solution becomes even more concentrated by passing through a greater depth of soil. Hence, these figures rep- resent an actual loss of potash from the field. In view of the large amount of potash removed by the tobacco crop itself, about 150 pounds to the acre for a good crop, the losses by leaching are of considerable aid in determining the quantity to apply. Crop responses (see p. 184 of this Bulletin) have shown that an annual application of about 200 pounds is necessary to produce tobacco year after year on the same field. A consideration of these data will show why this is sound. On the three sandy soils, the average annual loss for all treat- ments in surface soil tanks was 72 pounds potash to the acre. Some potash is released from the native soil compounds, as shown previously in this Bulletin, and this quantity aids in maintaining the balance between input and outgo in the zone of greatest root activity. If it were not for this reserve, an outgo of 222 pounds Potassium in the Plant 157 could not be satisfied with an input of 200 pounds and the crop would suffer. It might be of interest to note that Morgan (57) found from 24,000 to 28,000 pounds of total potash in the surface 7 inches of tobacco soils in this state. Although the losses of potash from the 20-inch tanks were higher than from the surface soils, a part of this loss was from a zone not as heavily drawn on by the tobacco root system. Nevertheless, it represents a loss from the total supply, and has considerable significance. As compared with the annual loss, the outgo during the actual growing season of tobacco is not large. The average loss for the six months from May 26 to November 25 of each year was about 27 pounds, which was nearly half of that for the winter months, and for the period up to harvest of the tobacco, was perhaps 15 pounds per acre in the surface soil. This is a small quantity as compared with the nitrogen loss that might occur in the same period. Therefore, it is not likely that later side dressing with potash materials would be necessary or beneficial. From the foregoing material, it would seem there would be no net accumulation of potash on cropped soils fertilized at the rate of 200 pounds per acre. In the case of the nitrate of potash deep soil tanks, a considerable fixation of potash must have occurred in the first year, but the losses in the second year would indicate that the soil does not have an unlimited capacity to store potash. POTASSIUM IN THE PLANT Absorbed through the roots in soluble mineral compounds, potas- sium is always present in considerable amounts in the transpiration stream of the plant. From this, it passes into the cells and infil- trates cell walls and all extra-cellular structures. McCallum (55) found it always absent from the nucleus, however. Concerning its distribution he states : "Potassium occurs in both the cytoplasm and the extra-cellular structures. In the latter it is present as a product of impregnation and infiltration and as a consequence there are few structures that are free from it. In the inter-cellular material and in inert or dead matter it is usually very abundant. " . . . . The potassium in cytoplasm occurs, in two conditions, that of physiological precipitation, and that of physiological or biochemical condensation. "The precipitation is not a physical character but may perhaps be of the nature of fixation, in an inert form, of the potassium in passive colloidal material in the cytoplasm. This precipitation is 158 Connecticut Experiment Station Bulletin 334 the process apparently, by which living active cells dispose of the excess of potassium salts which may invade them in very great excess. "In the condition of physiological or biochemical condensations, potassium salts in solution are concentrated in some particular part or parts of the cytoplasm and excluded from the remainder. This condition of condensation is a factor in the metabolic processes peculiar to cells. " . . . . That the salts can be in solution and at the same time confined strictly to parts of the cell is shown in Spirogyra in which the potassium is strictly localized in the immediate neighborhood of the chromatophor which is supposed to function in the synthesis of carbohydrates." Although McCallum speaks of them as "precipitates" and "con- densations," it should not be understood that the potassium com- pounds ever occur in an insoluble state. Kostytschew and Eliasberg (42) found all potash compounds in plants entirely soluble in cold water. From these facts it is evident that potassium is present only in an ionized condition, never in an undissociated combination with the protoplasm (as is the case with phosphorus and sulfur) or with other materials in the plant. Fonder (28) found in alfalfa that "the potassium present in the green material of the alfalfa stems and leaves existed largely in solution in the plant sap, very little of it being held intimately in the woody tissue." Bartholomew and Jannsen (12) working with tomato plants state: "Practically all of the potassium may be removed from the plant through successive washings with water." The solubility of the potash in cured tobacco leaves was deter- mined by the following test: Samples (seconds) of tobacco from three plots of the 1928 crop were ground and then each divided into two portions. The first portion was analyzed for potash by the usual method of ashing and precipitating the potash as the chloro-platinate salt. The second portion was placed on filter paper in a large funnel and leached by running cold distilled water through it until the leachate came through clear. Then the amount of potash in the leachate and in the residue was determined and calculated to the basis of percentage of the original weight of leaf. The results presented in Table 9 show that all the potash com- pounds of the tobacco leaf are water soluble. In view of this ready solubility of the potash compounds, is there a possibility of some of the potash being lost from the green leaves of the standing crop during long continued rains? The following test may partially answer this question. Entire green leaves were kept immersed (except for butts) in cold distilled water for 24 hours. Similar leaves from the same plants were analyzed and found to contain 5.272 per cent KaO. After 24 hours the immersed leaves still contained 5.067 per cent KsO and the Potassium in the Plant 159 water .210 per cent K2O (all figures calculated to percentage of total dry weight of the leaves). In other words, about 4 per cent of the total potash in the leaves had been leached out by this treatment. Such treatment, however, is more severe than would occur during rains and it is not likely that even this much potash would be lost. It is not improbable that a certain small amount of potash is lost from living leaves during severe rains but the quan- tity is too small to cause serious concern. Being so easily soluble in water, potassium is very mobile, that is. readily translocated from one part of the plant to another, wherever it is needed. Bartholomew and Jannsen (12) have Table 9. Solubility of Potash Compounds in Cured Tobacco Leaves Sample No. 1 2 3 Percentage of potash in leaf, determined after ashing 5.77 4.47 5.48 Potash found in leachate, on basis of original weight 5.73 4.45 5.46 Potash found in leaf residue 0.00 0.00 0.00 shown that when the supply of potassium is too small for the needs of a growing plant, it is translocated from the older parts to the young growing organs and re-utilized. This may continue until the old leaves are almost entirely deprived and die for lack of potassium. That such a concentration of potash in the younger leaves does not occur in tobacco that has a sufficient potash supply, is indicated by numerous analyses of tobacco grown at the Windsor Station. These analyses show more potassium in the lower than in the upper leaves. That the reverse relation may exist where the potash supply is low is indicated by results of tests reported on page 183 of this Bulletin. Compounds of Potassium in the Plant Since extensive investigations have not been published, our knowledge of the compounds in which potassium occurs in tobacco plants is meager. There are present in the sap several other bases besides potassium. There is also a considerable list of acid ions. In what order and proportion are the bases combined with the acid radicals ? The problem is rendered more complex by the ever changing composition of the sap during metabolism of the green plant. Besides the three dominant mineral bases, potassium, cal- cium and magnesium, there are much smaller quantities of sodium, iron, aluminum and manganese. Then there are organic bases (6) such as nicotine and ammonia. Besides the inorganic acid 160 Connecticut Experiment Station Bulletin 334 radicals, nitrate, chloride, sulfate, and phosphate, there are organic acids (77), malic, citric, and succinic, which Vickery and Pucher find to be in larger quantities than the mineral acids. Only exact and painstaking chemical determinations could prove what potas- sium compounds and their proportions exist in the plant, but certain combinations may be assumed on well-known chemical grounds. Since potassium is the strongest base it would have the greatest affinity for acids. It would combine first with the nitrate and chloride which have the highest base avidity among the acids. According to various analyses which have been made on tobacco grown here (4, 6) there is about 1 per cent nitrate nitrogen (calcu- lated as nitrate equal to about 4 per cent of the dry weight of the plant). The percentage, however, is extremely variable depend- ing on fertilization and weather (6 : 245). It is thus safe to assume that a certain part of the potassium will be in the form of potas- sium nitrate. Behrens (13) found potassium nitrate concentrated particularly in the epidermis and in the colorless parenchyma of the ribs; hence the explosive sparkling combustion frequently observed in the ribs. In the elaboration of proteins, the nitrate is rapidly taken away and the potassium is left to combine with other acids, or with other nitrate ions. Our tobacco contains about .5 per cent of chlorine (4: 44), which would also combine with the potassium. Since chlorine does not enter into synthesis of any of the plant substances, we may assume that there is always present in the sap a small amount of potassium chloride. The per- centage of sulfate in our tobacco (aside from that organically com- bined) is about .3 per cent (6: 212) and the percentage of total phosphate about .6 per cent. (Some part of it, however, is organi- cally combined). In the presence of the high percentage of calcium (about 5 per cent) which forms highly insoluble salts with these anions, it is not to be anticipated that much of the potassium would be combined with the small amounts of sulfate and phos- phate found. Therefore, if potassium sulfate and phosphate occur at all in the plant, they must be in very small quantities. After the cation requirements of the inorganic acids are all satisfied, there still remains a considerable proportion of the potassium which must be in combination with the organic acids. Vickery and Pucher (77: 191) found that 3.45 per cent of the dry weight of shade tobacco is organic acids, 85 per cent of which is malic, with much smaller quantities of citric, fumaric, succinic and oxalic acids. The oxalic acid is largely if not entirely combined with calcium. Malic and the other acids would be at least partly combined as potassium malate, citrate, and so forth. Potassium in the Plant 161 During the curing process, in which the sap is concentrated to about one twenty-sixth of its original volume (77), the greater part of the salts which have been in solution are crystallized out. The potash salts in cured tobacco must therefore be largely in crystal- line form. The small amount of free water that still remains in cured tobacco must hold a saturated solution of potash salts. Role of Potash Salts in Absorption of Water by Cured Leaves After tobacco is cured in the shed, the leaves are so dry and brittle that they cannot be stripped from the stalks and put into bundles in fair weather without serious breakage. The grower must wait for a "damp," that is, a period of rain or foggy weather during which the leaves absorb enough moisture to make them soft and pliable. That such water absorptive capacity is largely dependent on the potash compounds in the leaf is indicated by the fact (discussed more fully in a later section of the Bulletin) that tobacco that had an insufficient supply of potash in the fertilizer does not readily come into "case," or become soft. This role of the potash compounds was demonstrated by the following experiment : All the potash was leached from a lot of cured leaves by running water. Then, after drying, these leaves were saturated with 2 per cent solutions of several potash salts and again dried in an oven. After weighing, they were kept in a saturated atmosphere over night. The next day, they were weighed and found to. have absorbed the following percentages of moisture : Percentage of Leaf treatment water absorbed Untreated 12 Phosphate, primary 31 Oxalate 55 Sulfate 62 Malate 85 Acetate 126 Hydrate 190 It is quite possible that salts of other bases may play some part, but this experiment shows that the potash salts alone may account for all the absorption that is needed and in all probability are principally responsible for this property of cured tobacco. 162 Connecticut Experiment Station Bulletin 334 RATE OF INTAKE BY THE PLANT As early as 1884, the French investigator Blot (16) reported the potash content of seedling tobacco plants and found that the whole plants of Connecticut tobacco contained 6.73 per cent potash, while the leaves of the same plants contained 8.06 per cent. Leaves of Sumatra tobacco at the same stage contained 10.54 per cent. Behrens (14) in 1892, reviewing the work of Blot (16) concludes that the percentage decreases as the plant grows in the field. The work of Davidson (25) on White Burley, Medley Pryor, and Yellow Oronoko tobacco indicates that there is some decrease in percentage of potash with increasing maturity of the plants. His analyses of seedlings showed 8.22 per cent potash, but at the time of topping, the whole plants contained an average of 3.86 per cent, and, at harvest the content was 3.40 per cent. The dimunition in percentage of potash with development of the plant has been demonstrated for a number of crops. Fonder (28) studied the potash content of alfalfa at various stages of growth, analyzing the leaves and stems separately. Table 10, adapted from his work, shows the average of analyses of plants grown on seven types of soil. Table 10. Percentage of Potash in Alfalfa at Different Stages of Growth. (Moisture Free Basis) First growth Second growth May 8 % July 2 % July 24 % Full bloom % Stems Leaves 4.96 3.37 1.90 2.06 4.88 2.73 1.77 1.23 Bartholomew and Jannsen (11) studied the potash content of various crops, with rates of fertilization ranging from no potash to 225 pounds in muriate of potash. One sample was taken in an early stage of growth, the second when the plant was in blossom. During that time, the average decreases for all rates of fertiliza- tion were as follows : Wheat, 2.36 per cent potash ; cowpeas 0.32 per cent; soybeans 0.47 per cent. In connection with a general project at this Station dealing with the rate of growth, samples of tobacco plants were taken at weekly intervals from a Havana Seed plot receiving standard fertilization (200 pounds potash to the acre) and cultural treatment. Plants as nearly representative as possible of the average growth at the time of sampling were taken in every case, the number of plants varying with the stage of growth. Table 11 shows the rate of intake in 1930. Rate of Intake by the Plant 163 The figures showing pounds of potash taken up by an acre of tobacco should not be considered an absolute index of average intake under field conditions, because in later stages the number of plants taken for a sample was necessarily small, being reduced finally to a single plant. The general trend is shown more con- cretely by their inclusion, however. Table 11. Intake of Potash by Tobacco Plants at Different Stages of Growth. (Moisture Free Basis) Part of plant Percent Grams K 0 Pounds K20 Stage of growth taken K20 per plant per acre Seedling Entire plant 8.00 0.0265 0.47 9 days after setting Leaves and stalk 5.93 0.0325 0.57 17 t « t ' tt tt 6.51 0.1102 1.94 24 i (t t ' tt it 7.61 0.6453 11.35 31 i a I ' ti ti 6.92 1.2315 21.67 39 t tt t ' it it 6.35 4.9912 107.82 461 i a ' ' tt a 5.77 6.4162 112.92 54 ' " ' ' a tt 6.68 10.2538 180.42 61 " (< u ti 5.99 10.7880 189.88 Aside from the seedling stage, the percentage of potash of the plant does not show a regular decrease with increasing maturity of the plant, at least up to the time of harvesting of the field. Analyses of overripe tobacco show a sharp decline as the leaves begin to lose color, but this is a condition that would never exist under field technique. The most marked drop in potash percentage is from the seedling stage to the time of the first field sampling. During this time the plants suffer from transplanting, and make very little growth for as long as three weeks, although there is no absolute loss of potash. The two points at which the plants contained the highest percentage of potash correspond very well with the dates at which the plants showed the highest nitrogen percentage. In terms of pounds per acre, the absorption of potash during the early growth in the field was a very small part of the total intake. The absorption at the end of three weeks was less than 6 per cent of the total for the season, and the intake at the end of four weeks, which represented half the growing period, was only 11 per cent of the total. The two weekly periods during which the total potash intake was the highest, from the 31st to the 39th day, and from the 46th to the 54th day, represent 45 and 35 per cent, respect- ively, of the total intake, and together they account for 80 per cent 1Plants budded 46th day, topped 50th day, and harvested 61st day. 164 Connecticut Experiment Station Bulletin 334 of the absorption during the season. During the same weeks, 65 per cent of the total dry weight was added and 60 per cent of the total nitrogen was taken in by the plants. Thus it can be seen that the climatic conditions which favor the most rapid growth and nitrogen assimilation also largely determine the intake of potash. t THE ROLE OF POTASH IN COMBUSTION OF THE CIGAR In the burning of a cigar, two distinct processes are readily seen, (1) the charring and (2) the ashing. During the first, the charring process, the brown leaf is changed to black charcoal in a narrow region just ahead of the advancing red incandescent zone. This region appears outwardly as a narrow black band, frequently called the "coal band," and in different cigars may vary from one thirty-second to one-fourth of an inch in width. Generally speaking, the narrower the coal band, the better the burn is considered to be. It is a well founded belief of smokers that a broad coal band is associated with unpleasant taste and aroma. The charring process is the same as the dry distillation of wood or other vegetable material, practiced in the manufacture of charcoal. The transformation of the organic compounds, cellulose, protein, and the like, to carbon, is accompanied by the evolution as gas of combustible hydrocarbons, ammonia, nicotine, aldehydes, water vapor and a whole series of other volatile compounds. During the lighting of a cigar or a leaf with a match, the volatile hydrocarbons burn in the air with a flame and are consumed, but during the ordinary smoking of a cigar, they merely pass off in the smoke. The temperature during the charring process is about 600° to 700° C. according to Sligh and Kraybill (74) and is some 200° lower than the temperature of the incandescent region. The black "char" which is left after completion of the first process consists of carbon and various mineral salts very finely and uniformly distributed within the carbon. The second, or ashing process, is the same as the burning of charcoal (with which process most tobacco growers are familiar since they are accustomed to raising the temperature of the curing sheds by burning charcoal). At the higher temperature (800° to 900° C.) which prevails in the incandescent region, the carbon which results from the charring process is oxidized (burns) and passes off into the air as carbon dioxide. If this process of oxida- tion goes to completion, there will be left only the mineral salts (the most of which are pure white) and the ash will be white. If, however, the combustion is not complete, some of the black carbon will be left in the ash. The mixture of black carbon and white mineral salts gives a gray ash and the larger the quantity of uncon- sumed carbon, the more nearly black will be the ash. With incom- plete combustion, the temperature is necessarily lower, which Potash in Combustion of Cigar 165 results in the evolution of volatile compounds which apparently differ either in composition or proportion from the volatile com- pounds produced during more complete combustion, and the result- ing aroma is less pleasant. For the production of a pleasant aroma and taste it is important that the combustion should be as complete as possible. This is the scientific basis of the common opinion that a cigar with a white ash is better. The broader the coal band, the greater the proportion of leaf which is being distilled at a low temperature with disagreeable aroma ; hence the advantage of a narrow coal band. Another important essential of a good cigar is that it shall con- tinue to burn (glow, or hold its fire), for a long time after the air is drawn through by the smoker. A good cigar should continue to burn for at least five minutes after puffing ceases and we have found many that will attain ten minutes. Almost any cigar may be made to burn by continuous puffing, but smoking in this way is unpleasant. The average smoker prefers to draw intermittently with fairly long resting periods between puffs. If, during this rest period, the combustion is dying out, the temperature is again low- ered with the volatilization of unpleasant odors as mentioned above, hence the advantage of a long fire-holding capacity. Both the completeness of combustion (measured by ash color) and the length of the burn (fire-holding capacity) are governed largely by the character, quantity and proportion of the mineral salts which the tobacco contains. The most important of these are the compounds of potash. As far as fire-holding capacity is con- cerned, this may be easily demonstrated. If a leaf of cured tobacco with good fire-holding capacity is leached for 24 hours with water and then tested, it will be found to contain no potash, as we have previously explained on page 158. When it is dried and ignited it will still have no fire-holding capacity, but will burn only with a flame, like paper. If potash is again introduced by soaking with a 1 per cent solution of potassium carbonate, citrate, or other potash salt, it will be found that the fire-holding capacity has been restored, which shows that potash is the only element needed to impart fire- holding capacity. This influence of potash salts has been confirmed by the investiga- tions of numerous scientists (4, 5, 6, 7, 9, 15, 32, 36, 43, 54, 62, 64, 66, 68, 71, 76) and, in a general way, it was found that those tobaccos with the largest content of potash have the longest fire- holding capacity. Yet it was long ago found that all compounds of potassium do not have the same capacity for promoting burn. Certain of the acid radicals have the property of neutralizing the good effect of potassium. A number of investigators have tested the effect of each of the common salts of potash on fire-holding capacity by impregnating tobacco leaves or pieces of filter paper with solutions of the dif- 166 Connecticut Experiment Station Bulletin 334 ferent salts and then, after the latter had dried, determining the length of time each would continue to burn (glow) after ignition. The results reported by different writers have not been altogether consistent. The differences are probably due mostly to the use of different methods, different concentrations or salts and possibly different types of tobacco and standards of judgment. In order to compare the effects of these same salts on our types of tobacco the tests were repeated by the writers according to the following method : Cured leaves from the low potash plots were thoroughly leached by running water over them for 18 hours. They were found to be free of potash, were thoroughly dried, and then immersed in .5, 1, 2, 4, and 8 per cent solutions of each of 11 potash salts. After thorough saturation, the leaves were completely dried again and then the fire-holding capacity was determined by ignition with an electric filament. Since it was found that the dried leaf will absorb a solution to the extent of three and one-half to four times its weight, it is apparent that when dried after impregnation, the actual percentage of the salt that the dry leaf contained was about three and one-half to four times that of the solution. Therefore the leaves treated with the 4 and 8 per cent solutions contained a concentra- tion of potash higher than would ever occur naturally in the leaf. The untreated check leaves (leached but not impregnated with a potash salt) burned like paper with a flame, but had no capacity for carrying or spreading the incandescent combustion. When they were heated at a high temperature and the carbon oxidized they gave a flaky white ash, obviously due to the high percentage of calcium and magnesium salts in the tobacco from these plots. Observations on duration and spread of the combustion circle, and the color and consistency of the ash are recorded in Table 12. From this series of tests we may draw certain conclusions : All of these salts of potassium have the property of imparting fire-holding capacity to a leaf unburnable without them, at least at certain concentrations. The degree of fire-holding capacity imparted differs greatly, with the salt used and with the concentration of any one salt. The lightest colored ash invariably coincides with the lowest concentration of the potash salt. With each increase in concentra- tion of potassium, the ash becomes progressively darker until it is coal black. This is in agreement with our previously published finding (7: 391) that the ash color depends primarily on the ratio of magnesium to the potassium. Salts or concentrations which cause fusion invariably give black ash and poor fire-holding capacity. Potash in Combustion of Cigar 167 rt to U to U to >> o .£ c rt 5 s to c o o o lO o o o o © »-i CM - o o o o u-> O O O o >-i N t 00 O »-i CM Tt oo O *-i CM •* CO o.2 U rt a to Sin „ - o it? u -G i-h to to w c » to 8|S en to M 168 Connecticut Experiment Station Bulletin 334 L> H S^ c l-l o en to J3 U X "3 U £ re re m o, v* re (« t3 til • ■ >. +J- &. h > > -o ^c l-O O O O © O r-i C\) Tf CO to Si re s = '3 re 5 .» (72 0 § to ^ pq J Ch 2 ° - o o - to O w'Z o o © © ■* N >0 »C MD u-i O © o © m O O O O m o © o © c> i-i og tj- oo O i-h > en nj ctj s ey CO 3 XI fe u* eu en 3 to & to v °0 b 00 rt M J Q >. >, oj - ni bo bo o ■>-> ^ .a be s b w J Q o n! -a 3 , &P 1 - o s u -go o O ti o o o o o o o o <-< cnj Tt od iO o o o o o i-J — "3 O-o +■» rt CJ*" m.c^i g rt O'" ° - ,„ 2'" rt-2rt.s 3 if -, . V — u E ~ eu eu — — C B V cd V a 0 j- a •d 1 E - o eel V CJ - E eU — ~ E o C = 2 a 3 CJ o >> T3 - O > 0 5 3 o - CD — o CO 3 rt - V 3 -= J3 « a S CO g L CJ - en en ° i 0 - — eu - o 3 3 1 o 1 V — eu O cu CJ M E > u o o C3 MTd s a c cu a a — h JlfSl -a £ c °. u c !■ o. : * o „ °'u £$? «•="-!- w .2 3 rt „, S.« a=": - 3=^n" g ~ Hii 5j« c3 5 g.§ gg BE ■O ■" E ™ nj — l- -O "•- cu O >,(/)" _" o cj u en ■ - ccj ■" ,i<- o 2 - , in bo J; — elSh o a CJ 3 f. ■_ j: " ee! - rt 3 O — ^ E — CJ CJ o 5 CU o o en - toes. > 170 Connecticut Experiment Station Bulletin 334 Potassium is absolutely essential to fire-holding capacity of tobacco and up to a certain point, each increase in potassium will increase the fire-holding capacity (see Figure 18). This point differs with different salts. Increases beyond this point will injure rather than improve the burn. Chloride. This material has usually been considered the most injurious to burn of all the acid radicals and has been investigated more than any other. It deserves this rank, not because its effect is more deleterious than some others at the same concentration but because of the greater avidity with which the plant absorbs it if there is a supply in the soil, that is, injurious concentrations in the leaf are more likely to occur. Our tests indicate that at the lower concentrations it is one of the less efficient salts in promoting burn but at higher concentrations it completely ruins the burn. Tobacco with a high percentage of chlorine is almost unburnable but the ill effect of a small amount of chlorine may be overcome if the percentage of potash is raised. After years of experiment, Nessler (63) formulated the rule that no tobacco would have a good burn which had less than 2.5 per cent of potash or more than .4 per cent chlorine, or, in other words, the potash content must be five or six times as large as the chlorine content. Thus he analyzed 47 samples of tobacco grown in southern Germany in 1888 which showed the following percentages of potash and chlorine and relative burn : Percentage content Potash Chlorine 6 samples burned 25 or more seconds 4.0 0.40 6 13-25 <( 3.5 .22 21 8-12 CO vo o 00 VO °£ CO T}-" T-i VO IT) u-j oo' i—i i— i g 30„ oo ■* ■* vo ca OO Ul N -H rt H oW ■* vo tj- oa i-i ca Ph" ? .S~.fi c en tn tn C +■» ni d & S ° S rl OT "3 tu 3 2 3 S 3 - cu O 05 *t; S fate of pot bonate of j rate of pot fate of pot; (double m rate of sod; (Nitrapo) Cottonhull ash Ground tobacc Cottonseed me Castor pomace Linseed meal Dry ground fis co l5 £ co 2 r-H i-H 1— I U tU *u *-■ rt.cu u t 3° * fe o « w < CM H On O '-' Ph to u "°c KB ON On t^ ^f rf NO NO CO On © u .1 co CO CO CO ^ >£ <-M o t^ u-> \r> co © ON t^ 00 ON Tt" CM On O O CO o NO CO T-H CO CO co CO -=1- co -3- CO -3- ^f ^ -/.i On no \o O 00 00 CM NO CO OO ^f -"3- NO CM CO NO CO CO (M On T3 2 ^" T co u"i •<*■ -sr n- -3- -=* 1" i - NO ON co O r^ r-x CM t^ T-H © «J ■a a j. r^ o r^ co CO ^H CM t^ t-h in CM Tl- CM ■* CO co CO co ^t- CO no r^ t-h T-H CO CO »-H co CO Tf CO 00 NO 00 CO CO co CO co co CO CO CO co NO CM t^ m t^ On T-I NO On CM 1-H O o o 00 ON NO CO -1 CO -3- co •<*■ ■*■ ^r CO co CO CO o +1 V V be c nf c s CM o o CM CM CM CM CO co CO *—l r~l I—1 i—1 T— ' O t-h Tt On © oo in t-h © CM on NO CO On 00 CO On O co t>» CM —| tt t-i CO CM co CO ^J- ■* TT lO Tj- t^ O NO © On © 00 1-H On CO !>. On CM On CO CM W CM O CM O i-i i—i t-h t-h CM t-h CM 2 ON CM On no O u-> Tf- CM CM co ^ On CM CO f>. o m NO CM m On 0) <; on © CM O i—i t-h CM T-H O l-O -H- iO CM © co CM co CM ^J- co On CM —i to On NO © t-x CM —i CM CO co CO co CO iH- co ^r 00 CO UO lO ■**■ l-O 00 t^ CO Tf <-H U") CM -3" CO ON u-j On NO CM ON "3- u-j TT to T- NO Tf Tf lO l-O CM CO _, 1-H T-H T-. o o 1— 1 T— lO io t^ t^. oo oo On On w w M M w w w w W W v > ' — . — , < * V o .aS aj d> c u a . in in o oil 3* co l-v in p in m' p co iri u-j o r^ rr p in in o o in cm in in O Tf Tf CM. in in CS1 3 O CM so p t>. to ^st co so CM. p iri rt i-H in in Tf co co os r^ t^ co p oq in rf *3 ° CO so Tt p in ^ 00 CM P T-4 Tf iri CM Os Os -«f CM so Os t^ "i so CM t^. in ■^: "3 co CM CM lO Tt o o 00 co rt rt in in in co O CM SO Tf ">* "if — < o t^ CO O in O CM m' -*t CO © oo in -st -st CO OO O in in CM CO CM t^ CO ■"St ■** rH MD p © VO LO* so <-> in ^h in in co in in in CM O co_ co in in -^ oo CM rH in in 00 CN| os hi 3 t^ < ON CM t->. oq IT) Tt 0\ CM co p in in CO t^ p oq in tj-" co SO CM p in ^f in o i-j p in in 3 « rs. vq in -^t .-h o\ in p in -^t ■* co p p in Tf in CM p p in ■^: Os in p p in ■* — i 00 oq p iri in Os ■* in CM in in ^H O CO >-J in in o 00 "^ °. in in so CM in x co Tt cq in in so CO bi co in tN. sq in rt in >— • in in CO »-< Os "3- CO Os p H tj-' in CM ■* p CO in •^: go, CO ^H O CM o in CM ^ rv. co in iri r^ cm in in t-i rf rf p in in Os >n H p in ■^; in &2 ■* o oq p in in in in rt CM in in O co in in t~^ in CM p in in m CM in in CM C\ O O so io CO —i in CM in in CO CO in in SO O CM »-J in in in in p p in in 3 CM CO in in WW oo 06 Os Os u V 'Co li ** ■S'S •srt 0 CO 4) a o -Q u u u is co u ^ Si ^ 4) c W '*"' u u CO U Z 200 Connecticut Experiment Station Bulletin 334 Effect on soil reaction. The importance of maintaining an optimum degree of acidity in the soil has been discussed fre- quently in the reports and other publications of this Station. A soil may be too acid for best growth of tobacco, due mostly to toxic effects of manganese liberated by such a degree of acidity. On the other hand, if the soil is not acid enough, for example, if it tests higher than 6.00 pH, it soon becomes infested with the black rootrot fungus, Thielavia basicola, which reduces the yield of the crop until it becomes unprofitable. If the continuous use of any one potash carrier has the effect of making a soil too acid or not acid enough, then this would be an objection to the use of that carrier. It might be anticipated that carbonate of potash would neutralize the natural soil acids and have a tendency to make the soil alkaline. On the other hand one might expect that the sulfate would make it more acid. Regardless of what might be expected or what has been found in other soils under other crops, the only obvious way of making sure of what would happen under our conditions of culture, soil and practice was to test at various intervals and different times of the year the soil on adja- cent plots treated in every way the same except for the source of potash. This was done for six years on the 10 plots of the series of 1925. The first samples were taken before the series was started in the spring of 1925. The last were taken in 1931 after the experiment was complete. During 1929 the samples were taken at five different times during the growing season to see if there were any temporary or immediate effects of the fertilizer. The tests are recorded in Table 31. The reactions have varied from year to year and month to month in the same year, a seasonal variation due to weather conditions as fully discussed in a previous report (6: 264-268). All of the plots, however, rise or fall together; there is no definite tendency for any of the plots to become more or less acid than they were when the series was started. We are warranted in concluding, therefore, that under these conditions of soil, culture and climate, none of these three carriers or combinations of them when used in sufficient quantity to supply 200 pounds of potash to the acre will cause any significant change in the degree of acidity of the soil. Apparently any of them may be used indefinitely in continuous tobacco culture without fear of detrimental results, as far as soil reaction is concerned. Series III. Comparison of Sulfate of Potash-Magnesia with High Grade Sulfate of Potash The first possible benefit to be derived from the substitution of sulfate of potash-magnesia (double manure salts) for the more common sulfate of potash, lies in its content of magnesia, which is essential for the growth of tobacco and without which the plant Comparison of Fertiliser Materials 201 suffers from the malnutrition trouble commonly called sand-drown. Magnesia is also essential to proper combustion, and determines the color of the ash. This series of field plots was the first potash experiment under- taken at the Station and was repeated on six one-fortieth acre plots on Field I for six years, 1923-1928. The soil here is Merri- mac fine sandy loam with some fragments of red sandstone in the surface. It never leaches seriously nor does it suffer excessively in dry weather. It produces a heavier and better crop during a relatively dry year than during a wet one, and is not the type of soil that suffers excessively from sand-drown. In order to compare the effect of the two carriers of potash, two plots had all of their potash in high grade sulfate, two in double sulfate of potash-magnesia and the other two had the potash derived equally from each source. In all other respects the fertilizer mixture was the same. The composition of the original mixtures for the plots was as follows : Pounds of material applied per acre Fertilizer materials Plots K'l, KM. All potash in high grade sulfate Plots K2, K2-1. All potash in double sulfate Plots K3, K3-1. Potash equally from each. Cottonseed meal 2100 2100 2100 Castor pomace 800 800 800 Nitrate of soda 200 200 200 Precipitated bone 300 300 300 Superphosphate 200 200 200 Sulfate of potash 400 200 Double sulfate 800 400 Each formula supplied about 200 pounds nitrogen, 225 phos- phoric acid and 240 pounds potash to the acre and was used during the first two years of the experiment. Beginning with 1925, the quantity of fertilizer was reduced so that the plant food was on the basis of 160-160-200 of nitrogen, phosphoric acid and potash, respectively, and the superphosphate was eliminated. The precipi- tated bone was also eliminated in 1926 and 1928. Field observations throughout the six years of this experiment did not show any difference in growth characteristics between the different treatments, with the exception that for a short time in the very wet season of 1928, there was some sand-drown on the leaves of the Kl plots. This disappeared later in the season, and had no effect on the grading. Table 32, showing yields during six years of this experiment, indicates a slight difference, about 1 per cent, in favor of the combination. The grade index for five years (Table 202 Connecticut Experiment Station Bulletin 334 33), shows a very slightly higher average for the high grade sulfate. None of these differences seem large enough to be signi- ficant. Differences in chemical composition. To see whether any chemical changes in the composition of the leaf had been caused by the substitution of double manure salts for high grade sulfate, Table 32. Comparison of High Grade Sulfate with Double Manure Salts. Acre Yields for Six Years Source of potash Plot No. Acre yield by years Plot Ave. Average 12 repli- cations 1923 1924 1925 1926 1927 1928 High grade sulfate Double man- ure salts Half from each Kl Kl-1 K2 K2-1 K3 K3-1 2056 2056 1966 1966 2039 2039 1333 1387 1413 1413 1467 1333 2054 2061 1932 1892 2029 1929 1739 1832 1831 1833 1712 1648 1223 1223 1355 1234 1364 1382 1309 1280 1313 1318 1341 1378 1619 1640 1635 1609 1669 1618 1630 1622 1638 samples of seconds and darks for all plots (1926 crop) were analyzed. Since considerably more magnesia and sulfur are added to the soil in double manure salts, it was expected that a larger percentage of these elements would be found in the leaf. In view of the importance of potash in the burn, it seemed desirable to learn Table 33. Comparison of High Grade Sulfate with Double Manure Salts. Grade Indexes for Five Years Source of potash Plot No. Grade index by years Plot Ave. Average 12 replications 1924 1925 1926 | 1927 1928 High grade sulfate Double man- ure salts Half from each Kl Kl-1 K2 K2-1 K3 K3-1 .281 .291 .281 .273 .316 .270 .475 .475 .476 .471 .461 .483 .471 .505 .479 .500 .475 .461 .356 .457 .468 .383 .466 .357 .529 .516 .517 .481 .488 .472 .422 .449 .444 .422 .441 .409 .436 .433 .425 whether the amount of potash absorbed had been affected. Since calcium and magnesium have a somewhat repressive effect on each other it was also decided to determine the percentage of calcium. These chemical analyses are summarized in Table 34. Comparison of Fertilizer Materials 203 It is apparent that the use of double manure salts raised greatly the magnesia content of the leaves and correspondingly reduced the calcium. Both total sulfur and sulfate sulfur were increased and the percentage of potash absorbed was slightly lowered, especially in the seconds. Table 34. Summary of Chemical Analyses of Tobacco from High Grade Sulfate and Double Sulfate Plots. Crop of 1926. Averages of Duplicate Plots Source Grade of leaf Percentage in water free leaf of Potash Total Sulfate Lime Magnesia potash (K20) Sulfur (S) sulfur (S) (CaO) (MgO) High grade Darks 7.23 0.84 0.72 5.81 1.17 sulfate Seconds 8.07 0.72 0.58 6.84 1.41 Both 7.65 0.78 0.65 6.32 1.29 Double Darks 7.05 1.00 0.87 4.76 1.97 manure Seconds 7.54 0.81 0.69 5.94 2.28 salts Both 7.30 0.90 0.78 5.35 2.13 Half from Darks 6.98 0.86 0.73 5.84 1.49 each Seconds 7.33 0.70 0.59 6.88 1.64 Both 7.16 0.78 0.66 6.36 1.56 Effect on the burn. Since it is generally conceded that burn is roughly proportional to the potash which may form combina- tions with the organic acids after the mineral acids (sulfuric, hydrochloric, nitric, phosphoric) have been neutralized, it would be anticipated that the small increase in sulfate sulfur and the reduction in potash would be reflected in a corresponding reduction in fire-holding capacity. Strip burn tests on the fermented leaves from the crops of 1925, 1926, and 1927 disclosed that the average fire-holding capacity of all grades (total 480 tests from each treat- ment) for the three years was as follows: High grade sulfate Sulfate of potash-magnesia One-half from each 41.2 36.6 38.7 seconds The fire-holding capacity of each grade on all six plots was very high and the differences are probably too small to be signifi- cant. Comparing the three year averages, there appears to be a small but constant difference in favor of high grade sulfate, but it is questionable whether this difference is sufficiently large to offer serious objection to the use of double manure salts. 204 Connecticut Experiment Station Bulletin 334 Leaves from each plot were also made into cigars and smoked. The cigars from the double sulfate plots had a lighter colored ash and closer burn and were considered a little superior to the others. Fire-holding capacity of all was considered satisfactory. Conclusions from the six year experiments. The original purpose of this experiment was to find whether any advantage would accrue from the substitution of sulfate of potash-magnesia (25 per cent K2O) for high grade sulfate (48 per cent K2O) as a source of potash in the tobacco mixture. At the end of six years we believe this question was answered for this particular type of soil as nearly as it can be answered by field and laboratory tests. Two of these years were excessively wet (conducive to sand- drown), one was excessively dry, one just a little too dry, and other two about optimum in rainfall. When the records of the six years are averaged, the differences in yield and quality are found probably too small to be important. Offsetting a somewhat larger yield from the use of the combina- tion of the two carriers, there is a slight advantage in grading and fire-holding capacity from the use of high grade sulfate. From the standpoint of yield, grading, and freedom from sand-drown, it may be stated definitely that there is no advantage in using double manure salts as the single carrier of potash. On this type of soil there has been no advantage in getting any of it from this material. In more sandy, "leachy" locations, however, it is con- ceivable that the use of 100 or 200 pounds of double sulfate per acre, might result in some advantage unless there are other sources of magnesia present. For the double purpose of preventing sand- drown and improving the ash characters, magnesian lime may be used to better advantage. The disadvantages attending the use of double manure salts are (1) somewhat higher cost of the potash, (2) handling of a greater bulk of low grade material, (3) raising the sulfur content of the soil and leaf, (4) lowering the potash content, and (5) consequent reduction of fire-holding capacity as measured by the strip test. The advantages are (1) prevention of sand-drown and (2) making the ash whiter. The same advantages may be secured by using other carriers of. magnesia. Series IV. Tobacco Stems Compared with Mineral Carriers of Potash Although tobacco stems have been used more or less for many years by some growers, they have been applied in addition to other potash carriers and the potash which they contain has been dis- counted. In view of the fact that the potash in them is entirely water soluble and available for plant use during the first growing season, there would seem to be no good reason why this potash Comparison, of Fertiliser Materials 205 should not be rated in efficiency the same as the mineral carriers. In order to test this, three plots on Field I, located between the plots described above in Series II, were treated with a fertilizer mixture in which there was no other source of potash except the stems (plus that which was necessarily in the cottonseed meal). This series was continued for five years coordinately with the plots of Series II described above. During the first three years, long stems were applied at about the same time that the other fertilizer was spread, and then harrowed into the soil. During 1930 and 1931, sterilized ground stems were substituted and mixed directly with the other ingredients before spreading. Since the analysis of the stems differed somewhat from year to year it was necessary to change the formula slightly, but it was always adjusted to furnish 200 pounds of nitrogen and 200 pounds of potash. This also furnished phosphoric acid and magnesia, so that it was unnec- essary to add special carriers. The formula for 1930 was as follows : Ground tobacco stems 2650 lbs. Cottonseed meal 1529 lbs. Nitrate of soda 260 lbs. The same ingredients were used during the other years, but in a little different proportions for the reason explained above. In the field, the growth of tobacco appeared each year to be just as good as on any other plots and sometimes it seemed a little more luxuriant. The yields and grade indexes of the tobacco on these Table 35. Yield and Grading of Tobacco from Stems Plots Compared with That on Plots Where Other Sources of Potash Were Used Plot No. Yield of leaf Grade index potash 1927 1928 | 1930 1931 Aver- age 1927 1928 1930 1931 Aver- age K14 1222 129211958 1853 .376 .498 .492 .463 Stems K14-1 1186 1369 1948 1972 1633 .372 .486 .461 .474 .452 K14-2 1390 1378 2025 1996 .435 .475 .444 .442 Sulfate Average of 1273 1397 1910 1793 1593 .382 .437 .455 .453 .432 Carbonate all in this 1261 1333 1884 1813 1573 .408 .470 .471 .456 .451 Nitrate series 1279 1380' 1941 1835 1609 .371 .438 .464 .451 .431 three plots for four years are presented in Table 35 along with averages of all the plots treated with mineral carriers of potash in the same series. The yields have been consistently higher on the stems plot than on any of the others. The differences in grading are not large, but none of the other sources of potash has given better grading 206 Connecticut Experiment Station Bulletin 334 than stems. We may conclude from these experiments, therefore, that stems used alone will furnish all the potash needed and that their crop producing capacity is not exceeded by any of the mineral carriers. The cost of potash in stems is considerably higher than in mineral carriers, but the extra cost is at least partially offset by the value of the nitrogen, phosphorus, magnesia, and possibly other useful elements they contain. They also add organic matter to the soil. Whether these advantages are of sufficient weight to warrant the extra cost must be decided by the grower himself. Chemical analyses of tobacco from the stems plots. It has been mentioned previously that growers have been accustomed to discount the value of potash in stems. Therefore, they think it nec- essary to add other potash carriers. In these stems plots, the same amount of potash to the acre was added as in adjacent plots where other carriers were used. In order to see how much potash the crop actually absorbs from stems, as compared with other potash carriers, samples of ferment- ed crops of 1928 and 1930 were analyzed. Results of the analyses, (Table 36) show that the crop takes at least as much potash from stems as it does from mineral sources. Table 36. Percentage of Potash in Tobacco from Stems Plots Compared with Tobacco Where Other Sources of Potash Were Used Pint No. Percentage potash in leaf (air dry basis) Source of 1928 1930 Two potash Darks Sec- onds Aver- age Darks Sec- onds Aver- age aver- age K14 7.42 9.72 6.30 6.16 Stems K14-1 K14-2 7.79 9.14 8.52 5.72 5.85 6.22 5.91 6.03 7.28 Cottonhull | ashes K15-2 K15-1 K15-3 1 5.04 4.28 4.57 4.07 5.19 5.44 4.77 Sulfate K9-2 6.01 6.06 carbonate I K9-3 6.32 5.72 5.96 6.96 and nitrate! K9-4 K9-5 7.30 8.64 7.97 5.37 6.26 Effect on burning quality. Tobacco of four grades of each of the stems plots for the years 1928 and 1930 was tested by the usual strip test — 20 for each grade of each plot. This was compared with three plots where all mineral potash was used and, in 1930, Comparison of Fertilizer Materials 207 with four plots where cottonhull ashes were used for potash. All of these were in the same series and otherwise treated alike. The results, recorded in Tables 29 and 37, show that the burn on the stems plots was as good as any of the others. Cigars were also made from each and tested, but no significant differences were observed in burn, taste or aroma. Table 37. Stems and Cottonhull Ashes Compared with Potash from Sulfate, Carbonate and Nitrate of Potash. Strip Burn Tests of 1930 Crop Plot No. Duration of burn by grades Average potash Darks Mediums Lights Seconds Plot Treatment K14 42 46 47 55 47 Stems K14-1 43 — 58 56 52 50.0 K14-2 45 54 50 57 51 Sulfate, "I K9-2 47 39 50 44 45 carbonate, l K9-3 45 51 50 46 48 49.3 and nitrate K9-4 48 56 59 56 55 K15-1 39 28 26 31 Cottonhull K15-3 46 16 14 16 31 33.0 ashes K15-2 45 29 37 29 35 K1S-4 35 — 41 32 36 Series V. Comparison of Cottonhull Ashes with Other Materials Thirty to forty years ago, ash made by the burning of cotton- seed hulls in the South was a commonly used source of potash for tobacco in New England. These ashes contained a variable percentage (15 to 35 per cent) of potash in the form of carbonate, carbonates of calcium and magnesium, and some phosphoric acid, as well as small amounts of other elements, some of which may be important in plant growth. Later, the use of cottonhull ashes was discontinued, but within the last six years this material has again appeared on the market and has been used with success by many growers. • Chemical analyses of 14 samples taken at random from those submitted to the Station by growers in 1930 are given in Table 38. The percentage of chlorine, which varies in these samples from .43 to 2.33 per cent, is probably not sufficient to affect seriously the burn of the tobacco. 208 Connecticut Experiment Station Bulletin 334 Table 38. Chemical Analyses of Samples of Cottonhull Ashes Sold for Tobacco in 1930 No. of Percentage Water sample K,o 2 5 CaO MgO Cl Boron (B203) 3601 31.67 2.15 10.67 4.35 2.33 0.029 3667 23.35 2.90 12.52 4.38 1.34 0.024 3668 24.60 2.80 11.41 5.17 1.45 0.022 3669 24.79 2.78 11.47 4.99 1.47 0.035 3693 22.95 3.07 10.38 5.05 1.39 0.022 3694 23.64 2.86 10.15 4.48 1.59 0.024 3753 25.27 3.71 8.33 3.93 0.94 0.021 3786 29.97 2.72 8.50 3.97 1.97 0.029 3818 29.07 2.65 9.16 3.93 2.15 0.036 3826 23.03 2.33 15.35 5.64 0.87 0.008 3827 33.57 1.88 12.62 3.94 1.84 0.011 3949 20.97 3.18 19.94 8.14 0.43 O.'Oll 3990 38.17 2.80 14.10 4.93 1.76 0.003 4026 25.31 5.00 12.73 5.35 0.83 0.009 Average 26.88 2.92 11.95 4.87 1,45 0.020 App. 9.00-10.00 In order to compare cottonhull ashes with other sources of pot- ash, five plots were added in 1929 to those described above in Series II on Field I. The formula used was as follows : Cottonseed meal, 1765 lbs. Castor pomace, 741 lbs. Nitrate of soda, 260 lbs. Cottonhull ashes, 590 lbs. Total ( Nitrogen Nutrients Phosphoric acid per acre Potash Magnesia 120 52.9 35.3 12.4 40 14.8 7.4 5.9 40 17.7 157.3 30.4 200 85.4 200 48.7 This supplied the same quantity of the nutrient elements as was applied to the adjacent plots. The tobacco was destroyed by hail in 1929 and no results were computed. The experiment was repeated in 1930 and 1931 on the same plots. Because of lack of sufficient land, four of the plots were end plots and although two to six rows of tobacco were discarded on each extreme end before harvesting, there is still the possibility that the poor showing made by these plots may have been partly due to their unfavorable location. K15-1 was the only interior plot. The yield and grade indexes compared with the average for the other carriers are presented in Table 39. If the averages of the five cottonhull ash plots are compared with the averages for the other Comparison of Fertiliser Materials 209 potash carriers, the comparison is very unfavorable, both in yield and grading, to the cottonhull ashes plots. If, however, we assume that the end plots were not comparable and consider only the K15-1 plot, which was as favorably located as the others, we find it has an average yield of 1855, about the same as for the other sources of potash, and an index of .434, which is somewhat lower than any of the others. Table 39. Cottonhull Ash Plots; Yield and Grade Indexes Compared with Plots Where Other Sources of Potash Were Used Potash carrier Plot No. Yield Grade index 1930 1931 | Average 1930 1931 Average K15 1798 1661 .400 .385 K15-1 1809 1901 .456 .411 Cottonhull ash K15-2 1803 1775 1710 .466 .430 .400 K15-3 1562 1709 .327 .396 K15-4 1494 1589 .368 .360 Sulfate All plots 1910 1793 1852 .455 .453 .454 Carbonate of this 1884 1813 1849 .471 .456 .464 Nitrate series 1941 1835 1888 .464 .451 .458 Stems 1977 1940 1959 .466 .460 .463 A formula advocated and successfully used by many growers is one composed only of cottonseed meal and cottonhull ashes. In order to see whether this would produce better yield or quality, two plots in the center of the field were treated in 1931 with such a formula, as follows : Cottonseed meal Cottonhull ashes 3000 lbs. 441 lbs. This formula supplied 200 pounds nitrogen, 200 pounds potash, 103 pounds phosphoric acid, and 43 pounds magnesia, and was therefore considered a well balanced formula, comparable to the others on the same field. These plots were well located with refer- ence to the others and on land that had previously produced as much and as good tobacco as the others. The results for 1931, the first year of the experiment, are summarized in Table 40. Here, under the most favorable conditions, the average yield and grade index of these plots are both below those of any of the other sources of potash. 210 Connecticut Experiment Station Bulletin 334 The results do not indicate that cottonhull ashes are a more favorable source of potash than the other carriers. Since the form in which the potash occurs here is mostly carbonate of potash, it is probable that more favorable results that might be expected would come from the other elements in the ash. In view of our results with magnesia (7: 391), it seems likely that the quantity of this element in cottonhull ashes would have a favorable effect on the burn. The tobacco from the cottonhull ashes plots of 1930, were tested by the strip test and showed a shorter duration of burn than that from the other plots. It is quite possible that this may be due to decreased percentage of potassium (as shown in Table 36) and increased content of magnesium, which might be expected in tobacco from the cottonhull ashes plots. As we have previously written (7:391), this does not necessarily indicate an inferior burn when tested on the cigar. Table 40. Special Cottonhull Ash and Cottonseed Meal Plots. Yield and Grade Indexes for 1931 Potash source Plot No. Yield Grade index Plot Average Plot Average (Cottonhull ash ) Cottonseed meal Sulfate Carbonate Nitrate Stems K16 K16-1 Average oi all plots in Series II. 1762 1800 1781 1793 1813 1835 1940 .450 .444 .447 .453 .456 .451 .460 Through the courtesy of one of the large cigar manufacturing corporations, the writers compared the smoking quality of cigars from tobacco raised on a cottonhull ash formula with an equal number of others from tobacco raised on the same 12 fields, in various parts of the Connecticut Valley, but with other sources of potash (standard commercial fertilizer mixtures). Neither the writers nor the experts from the manufacturing company could detect any consistently favorable influence on the burn, taste or aroma of the cottonhull ash cigars as compared with the others. Final conclusions as to the relative value of cottonhull ashes and other potash carriers must await the continuation of these experi- ments through a longer series of years. Nothing in the results at present indicates that this material is in any way superior to the others. Summary 211 SUMMARY 1. Tobacco as compared with other crops is a heavy feeder on potash, removing annually from the soil about 150 pounds. 2. Potash functions in all plants as a catalyst in the synthesis of carbohydrates and probably proteins and in the absorption and translocation of nutrient materials. Also it makes the plants more resistant to drought and possibly to certain types of diseases. In tobacco, it has the added functions of (1) making the cured leaves soft and suitable for handling and (2) promoting the incan- descent type of combustion required for cigars. 3. Tobacco plants that have not enough potash for their physi- ological needs show characteristic starvation symptoms, the most prominent of which are yellow mottling, dead specks, "hobbly" surface, and downward incurving of margins and tips. 4. The amount of potash in the leaf is not a fixed percentage, but differs widely, depending on (1) the quantity in the soil, (2) relation of other bases in the soil, and (3) weather conditions. This percentage varies directly with the potash applied in the fertilizer, and inversely with the proportion of calcium and mag- nesium. The quantity of potash is generally higher in wet seasons than in dry. 5. The tobacco soils of Connecticut have a large supply of native potash in minerals derived from the parent rocks. This potash is not readily available to the crop. A very small percentage becomes available each year, but it is far from sufficient to meet the requirements of the tobacco crop; therefore, annual applications of potassic fertilizers are necessary. 6. Certain agricultural practices may accelerate the liberation of the native potash, but none of them alone or in combination can be relied on to furnish sufficient potash for crop needs. Ma- terials that may have some accelerating effect are gypsum, nitrate of soda, sulfur, manure, and fertilizers that increase acidity of the soil. Turning under cover crops is also beneficial in this respect. 7. Considerable quantities of potash (40-130 pounds) are lost from tobacco soils annually in the drainage water. Only a small part of this loss occurs while the tobacco is in the field. The loss in lysimeter tanks containing only the surface 7 inches of soil, varied with soil type, being lowest on a soil of high colloid content (12-38 pounds) and higher on sandier soils (72 pounds). Among nitrogeneous fertilizers, sulfate of ammonia greatly increased the outgo, while nitrate of soda had the opposite effect. A distinct correlation between water loss and leaching of potash was noted on the sandier soils. 212 Connecticut Experiment Station Bulletin 334 No differences due to treatment were reflected in the potash loss for the first year from the 20-inch tanks. During the second year the effects of sulfate of ammonia and nitrate of soda noted above became more evident, while the effect of a huge excess of potash in nitrate of potash also began to be apparent. Where organic fertilizers were used, there were no significant differences in outgo. 8. In the plant, potassium exists only in soluble ionizable com- pounds, never in organic combination with the protoplasm or other essential parts. All potash may be removed from the cured leaves by leaching with cold water. It is the hygroscopicity of these potash compounds that makes cured tobacco come into "case" during damp weather. 9. A study of the rate of potash absorption in the field showed that, exclusive of the seedling stage, no consistent trend toward increase or decrease in percentage in the plant occurred during the growing season. When the percentage of potash in the plant was high, nitrogen also was found to be high for the same period, thus indicating a parallel absorption. Maximum potash absorption, in terms of pounds per acre, occurred during the fifth and seventh weeks of field growth, the same periods that showed the greatest increases in dry weight and total nitrogen. 10. Fire-holding capacity of cured leaves is dependent on the potash salts contained. The different salts of potassium are not equally suitable for imparting fire-holding capacity. In the order of their excellence, those tested rank as follows : carbonate, malate, citrate, oxalate, acetate, nitrate, hydrate, sulfate, secondary phos- phate, chloride and primary phosphate. In general, the organic salts were most effective. The inorganic salts impart at most only a small degree of fire-holding capacity. 11. Increase in the amount of potash in the leaf makes the ash darker in color. 12. The annual application of potash should be about 200 pounds per acre to produce the best results under such conditions as those on the fields of the Tobacco Substation. 13. Reduction in the fertilizer potash affects the quality more than the quantity of the crop. Only at our lowest rate (40 pounds per acre) was there a reduction in yield, and this was not apparent the first year. In quality, however, the leaves with insufficient potash were quite inferior, being harsh, dry, short, and non-elastic. 14. Chemical analyses of the leaves show that with every de- crease of fertilizer potash there is a corresponding reduction in the percentage of potash in the leaf, and at the same time an in- crease in the calcium and magnesium. Summary 213 15. Each decrease in potash is also accompanied by a reduction in the fire-holding capacity as measured by the strip test. In the same degree, the ash becomes whiter. 16. Six carriers of potash — sulfate, carbonate, nitrate, sulfate of potash-magnesia, stems and cottonhull ashes — were compared on field plots through a series of years. As far as yield of leaf and percentages of grades are concerned, the differences have been very small. Somewhat the best results have been obtained with stems. 17. Potash in all these carriers is fully available. Potash in stems should be rated at its full value in preparing the fertilizer formula. 18. Chemical analyses do not show a greater quantity of potash absorbed by the plant from one carrier than from another, except materials containing repressive amounts of magnesium. 19. Fire-holding capacity of leaves grown on these different carriers, as determined by the strip test, is about the same, except for cottonhull ashes, which is somewhat lower. Cigars made from leaves grown with the use of each of these carriers all have a satis- factory burn. 20. None of these carriers produces any significant change in soil reaction when used in sufficient amount to supply 200 pounds of potash to the acre. 21. In short, each of these six carriers appears to be satisfac- tory for use in a tobacco mixture. It is suggested, however, that the grower furnish the potash in two or more carriers, rather than one. 214 Connecticut Experiment Station Bulletin 334 LITERATURE CITED 1. Ames, J. W., and G. E. Boltz. Influence of fertilizers on composition and quality of tobacco. Ohio Agr. Expt. Sta., Bui. 285 : 173-221. 1915. 2. Anderson, P. J., and others. Report of the tobacco station at Windsor for 1925. Conn. Agr. Expt. Sta., Tob. Subst. Bui. 6 : 1-93. 1926. 3. Anderson, P. J., and N. T. Nelson. Report of the tobacco station at Windsor for 1926. Conn. Agr. Expt. Sta., Tob. Subst. Bui. 8: 1-58. 1927. 4. Anderson, P. J., N. T. Nelson and T. R. Swanback. Report of the tobacco station at Windsor for 1927. Conn. Agr. Expt. Sta., Tob. Subst. Bui. 10 : 1-82. 1928. 5. Anderson, P. J., and T. R. Swanback. Report of the tobacco substa- tion at Windsor for 1928. Conn. Agr. Expt. Sta., Bui. 299 : 145-203. 1929. 6. Anderson, P. J., T. R. Swanback, O. E. Street and others. Tobacco substation at Windsor, report for 1929. Conn. Agr. Expt. Sta., Bui. 311 : 207-273. 1930. 7. Anderson, P. J., T. R. Swanback, O. E. Street, and others. Tobacco substation at Windsor, report for 1930. Conn. Agr. Expt. Sta., Bui. 326 : 357-450. 1931. 8. Ballenttne, W. Experiments with feldspar as a source of potash. Maine Agr. Expt. Sta., Ann. Rpt. for 1889 : 135-144. 1890. 9. Barth, Max. Untersuchungen von im Elsass gezogenen Tabaken und einige Beziehungen zwischen der Qualitat des Tabaks und seiner Zusammensetzung. Landw. Vers. Sta., 39 : 81-104. 1891. 10. Bartholomew, R. P. The availability of potassium to plants, as affected by barnyard manure. Jour. Amer. Soc. Agron., 20 : 55-81. 1928. 11. Bartholomew, R. P., and G. Jannsen. Luxury consumption of potas- sium by plants and its significance. Jour. Amer. Soc. Agron., 21 : 751-765. 1929. 12. Bartholomew, R. P., and G. Jannsen. The rate of absorption of potassium by plants and its possible effect upon the amount of potas- sium remaining in soils from applications of potassium fertilizers. Ark. Agr. Expt. Sta., Bui. 265 : 1-70. 1931. 13. Behrens, J. Weitere Beitrage zur Kenntniss der Tabakpflanze. V. Der anatomische Bau und die Bestandteile des Tabakblattes in ihrer Bezie- hung zur Brennbarkeit. Landw. Vers. Sta., 43 : 271-301. 1894. 14. Behrens, J. Weitere Beitrage zur Kenntniss der Tabakpflanze. Landw. Vers. Sta., 41 : 191-206. 1892. 15. Bemmelen, J. M. van. Liber die Zusammensetzung der Asche der Tabak- blatter in Beziehung zu ihrer guten oder schlechten Qualitat insbeson- dere zu ihrer Brennbarkeit. Landw. Vers. Sta., 37 : 405-436. 1890. 16. Blot. Determination des epoques ou le tabac vert contient le maximum de potasse aux acides organiques et le minimum de nicotine. Memorial des Manufactures de l'etat. T abacs I. Livr : I. Paris. 1884. 17. Boening, K. Die Wildfeuerkrankheit des Tabaks. Flugbl. 55. Bayer Landesanstalt f. Pflanzenbau u. Pflanzenschutz. Munich. 1929. 18. Bradley, C. E. The soils of Oregon. Oreg. Agr. Expt. Sta., Bui. 112. 1912. Literature Cited 215 19. Briggs, L. J., and J. F. Breazeale. Availability of potash in certain orthoclase-bearing rocks as affected by lime and gypsum. Jour. Agr. Res., 8 : 21-28. 1917. 20. Collison, S. E., and S. S. Walker. Loss of fertilizers by leaching. Fla. Agr. Expt. Sta., Bui. 132: 1-20. 1916. 21. Crawley, J. T., and W. B. Cody. The application of fertilizers to the soil and losses by leaching. Porto Rico Bd. Agr. Expt. Sta., Bui. 8 : 17-23. 1915. Abstract in E. S. R. 33 : 122. 22. Cserhati, A. Versuche iiber die Brennbarkeit des Tabaks. Jour. Landw., 43 : 379-458. 1895. 23. Cubbon, M. H. Calcium sulfate as a soil amendment. N. Y. (Cornell) Agr. Expt. Sta., Mem. 97: 1-51. 1926. 24. Cushman, A. S. The use of phosphatic rocks as fertilizers. U. S. D. A. Bur. PI. Indus., Bui. 104: 1-31. 1907. 25. Davidson, R. J. Analyses of parts of tobacco plants at different stages of growth. Va. Agr. Expt. Sta., Bui. 50 (new ser.) : 25-52. 1895. 26. DeTurk, E. Potassium-bearing minerals as a source of potassium for plant growth. Soil Sci., 8: 269-301. 1919. 27. Fesca, M. (In collaboration with H. Imai.) Ueber Kultur, Behandlung und Zusammensetzung Japanischer Tabake. Landw. Jahrb., 17 : 329-372. 1888. (Berlin) 28. Fonder, John F. Variations in potassium content of alfalfa due to stage of growth and soil type and the relationship of potassium and calcium in plants grown upon different soil types. Jour. Amer. Soc. Agron., 21 : 732-750. 1929. 29. Fraps, G. S. Relation of the water-soluble potash, the replaceable, and acid-soluble potash to the potash removed by crops in pot experiments. Tex. Agr. Expt. Sta., Bui. 391 : 1-18. 1929. 30. Fudge, J. F. The influence of various nitrogenous fertilizers on the availability of phosphate and potassium. Ala. Agr. Expt. Sta., Bui. 227: 1-47. 1928. 31. Gaither, E. W. The effect of lime upon the solubility of the soil con- stituents. Jour. Indus, and Engin. Chem., 2: 315. 1910. 32. Garner, W. W. The relation of the composition of the leaf to the burning qualities of tobacco. U. S. Dept. Agr. Bur. Plant Indus., Bui. 105 : 27. 1907. 33. Garner, W. W., and D. E. Brown. Fertilizer experiments with tobacco. Md. Agr. Expt. Sta., Bui. 225 : 157-183. 1919. 34. Gerlach, M. The action of kainit and high-percentage potash salts. Fuhling's Landw. Ztg., 50: 377-388, 409-416. 1901. Abs. in E. S. R. 13 : 539. 35. Graham, DeV., and R. H. Carr. Chemical factors determining the quality of tobacco. Jour. Amer. Chem. Soc, 4&: 695-702. 1924. 36. Haley, D. E., E. S. Nasset, and Otto Olson. A study of certain con- stituents of the leaf and their relation to the burning qualities of tobacco. Plant Physiol., 3 : 185-197. 1928. 37. Hall, A. D. Fertilizers and manures. 3d ed. John Murray, London. 1929. 216 Connecticut Experiment Station Bulletin 334 38. Headden, Wm. P. The carbon dioxide in the soil atmosphere and its action on the feldspar particles in the soil. Colo. Agr. Expt. Sta., Bui. 319. 1927. 39. Hendrick, J., and H. D. Welch. The substances removed by the drain- age from a Scottish soil. Proc. and Papers 1st Internatl. Cong, of Soil Sci., 2 : 358-366. 1927. 40. Hopkins, Cyril G. Soil fertility and permanent agriculture. Ginn and Co. 1910. 41. Hopkins Cyril G., and J. P. Aumer. Potassium from the soil. 111. Agr. Expt. Sta., Bui. 182. 1915. 42. Kostytschew, S., and P. Eliasberg. Ueber die Form des Kaliumverbin- dungen in lebenden Pflanzengeweben. Zeitsch. f. Phys. Chemie 111 : 228-235. 1920. 43. Kraybill, H. R. Effect of some alkali salts upon fire-holding capacity of tobacco. Bot. Gaz., 64 : 42-56. 1917. 44. Lagatu, H., and L. Maume. Antagonisme du calcaire, a l'egard de l'absorption de la potasse par la vigne. Com. Cong. Internatl. du vin et du pin maritime. Bordeaux. 1928. 45. Lipman, J. G., A. W. Blair, and A. L. Prince. The effect of lime and fertilizers on the potash content of soils and crops. Internatl. Rev. Sci. and Pract. Agr., 4 : 546-553. 1926. 46. Lyon, T. L., and J. A. Bizzell. Lysimeter experiments. New York (Cornell) Agr. Expt. Sta., Memoir 12. 1918. 47. Lyon, T. L., and J. A. Bizzell. Lysimeter experiments. New York (Cornell) Agr. Expt. Sta., Memoir 41. 1921. 48. MacIntire, W. H. The influence of fertilizers upon the composition of wheat. Penn. State Col. Ann. Rpt. 1910-11: 190. 1911. 49. MacIntire, W. H., and K. B. Sanders. The fixation of the potash of a green manure by liming materials. Soil Sci., 29: 109-117. 1930. 50. MacIntire, W. H., W. M. Shaw, and J. B. Young. A five-year lysi- meter study of the supposed liberation of soil potassium by calcic and magnesic additions. Soil Sci., 16 : 217-223. 1923. 51. MacIntire, W. H., W. M. Shaw, and K. B. Sanders. The influence of liming on the availability of soil potash. Jour. Amer. Soc. Agron., 19 : 483-504. 1927. 52. MacIntire, W. H., W. M. Shaw, and J. B. Young. The repressive effect of lime and magnesia upon soil and subsoil potash. Jour. Agr. Sci., 20 : 499-509. 1930. 53. Mathewson, E. H. The burning quality of tobacco with suggestions for its improvement in the flue-cured types of eastern North Carolina. Bur. Plant Indus. Circ. issued Nov. 19, 1910. 54. Mayer, Adolf Eduard. tiber die Verbrennlichkeit des Tabaks. Landw. Vers. Sta., 38: 127-139. 1891. 55. McCallum, A. B. On the distribution of potassium in animal and vegetable cells. Jour. Physiol., 32: 95-128. 1905. (British) 56. McCool, M. M., and M. D. Weldon. The effect of soil type and fertiliz- ation on the composition of the expressed sap of plants. Jour. Amer. Soc. Agron., 20: 778-792. 1928. 57. Morgan, M. F. The soils of Connecticut. Conn. Agr. Expt. Sta., Bui. 320. 1930. Literature Cited 217 58. Morgan, M. F., P. J. Anderson, and Henry Dorsey. Soil reaction and liming as factors in tobacco production in Connecticut. Conn. Agr. Expt. Sta., Bui. 306 : 773-806. 1929. 59. Morgan, M. F., O. E. Street, and H. G. M. Jacobson. Fertilizer losses through leaching as measured by lysimeter experiments. Conn. Agr. Expt. Sta., Bui. 326: 432-441. 1931. 60. Moss, E. G., J. E. McMurtrey, W. M. Lunn, and J. M. Carr. Ferti- lizer tests with flue-cured tobacco. U. S. Dept. of Agr., Tech. Bui. 12. 1927. 61. Nelson, N. T., and P. J. Anderson. Fertilizer experiments with tobacco. Conn. Agr. Expt. Sta., Tob. Sta. Bui. 5 : 1-34. 1925. 62. Nessler, J. Der Tabak seine Bestandtheile und seine Behandlungen. Mannheim. 1867. 63. Nessler, J. tlber die Wirkung des Bodens und der Diingung auf die Verbrennlichkeit des Tabaks. Biedermann's Zentbl., 18 : 488-494. 1889. (Abs.) 64. Nessler, J. tiber den Bau und die Behandlung des Tabaks. Landw. Vers. Sta., 40 : 395-438. 1892. 65. Otryganjew, A. W. Experiments with different forms and quantities of nitrogen and potassium fertilizers. Krasnodar (Russia) Tob. Expt. Sta., Bui. 28 : 60-62. 1926. 66. Patterson, H. J. The effects of different fertilizing elements on the composition and combustibility of tobacco. Agr. Sci., 8 : 329-352. 1894. (Reprint.) 67. Prianischnikov, D. Vegetationsversuche mit verschiedenen kalihaltigen Mineralien. Land. Vers. Sta., 77 : 399. 1912. 68. Quajat, E. Untersuchung iiber die Verbrennlichkeit einiger Tabaks- sorten. Biedermann's Zentbl., 9: 345-347. 1880. (Abs.) 69. Reed, H. S., and A. R. C. Haas. Studies on the effects of sodium, potas- sium and calcium on young orange trees. Calif. Agr. Expt. Sta., Tech. Paper 11 : 1-23. 1923. 70. Sayre, C. B., J. J. Willaman, and Z. I. Kertesz. Factors affecting the quality of commercial canning peas. N. Y. (Geneva) Agr. Expt. Sta., Tech. Bui. 176: 1-75. 1931. 71. Schloesing, Th. "Ober die Verbrennlichkeit des Tabaks. Jour. Prakt. Chem., 81 : 143-150. 1860. 72. Sewell, M. C, and W. L. Latshaw. The effect of lime, superphosphate and potash on reaction of soil and growth and composition of alfalfa. Jour. Amer. Soc. Agron., 23: 799-814. 1931. 73. Shedd, O. M. Influence of sulfur and gypsum on the solubility of potas- sium in soils and on the quantity of this element removed by certain plants. Soil Sci., 22 : 335-354. 1926. 74. Sligh, T. S. Jr., and Henry R. Kraybill. Temperature of a burning cigar. Bui. Amer. Inst. Mining & Metall. Engin. 1919: 2241-2246. 75. Tressler, D. K. The solubility of soil potash in various salt solutions. Soil Sci., 6 : 237-257. 1918. 76. Vedroedi, Viktor. Eine Studie fiber die Verbrennlichkeit des Tabaks. Landw. Vers. Sta., 45 : 295-310. 1895. 77. Vickery, H. B., and G. W. Pucher. A preliminary study of the non- volatile organic acids of tobacco leaves. Conn. Agr. Expt. Sta., Bui. 323 : 155-202. 1931. University of Connecticut Libraries 3y1b3UZ88bbb&0