878
INDUSTRIAL AND ENGINEERING CHEMISTRY
The vision of the founders of American Potash & Chemical Corporation has been translated into reality. The management of the company has wisely and courageously utilized the money entrusted to it to develop this business. Its plant managers, chemists, engineers, and office workers, and its plant labor have each contributed to the building and operating of its plant. The product has been sold by its sales force. A freight rate structure which makes possible delivery to markets in competition with other producers has been negotiated by its traffic department. Cooperation has effected the cycle necessary for the development of a successful business.
VOL. 30, NO. 8
BiblioaraDhv Gale, H . S.,U. S. Geol. Survey, Bull. 580-L (1912). Manning, P. T.V., Chem. & M e t . Eng., 36, 268-72 (1929). , 520-4 (1929). Robertson, G. R . , IND. ENQ.C H E M . 21, Ropp, Alfred de, Jr., Chem. & M e t . Eng., 19,425 (1918). , 839-44 (1918). Ropp, Alfred d;, Jr., J . IND.ENG.C H E M . 10, (6) Teeple, J. E., Industrial Development of Searles Lake Brine,” A. C. S. MononraDh 49. N e w York. Chemical Catalon Co.. 1929. (7) Teeple, J. E . , J.%D. EXQ.CHEM.,13, 249 (1921); 787, 9 0 4 (1922); 19,318 (1927). (8) Turrentine, J. W., “ P o t a s h , ” pp. 74-82, N e w York, John Wiley & Sons, 1926. (1) (2) (3) (4) (5)
14,
RECEIVED June 3, 1938.
POTASH IN T H E FERTILIZER INDUSTRY P.S. LODGE The National Fertilizer Association, Washington, D. C.
P
OTASSIUM is one of about fourteen chemical elements that have been shown to be essential to the growth of plants. Plants may obtain hydrogen, oxygen, carbon, and to some extent nitrogen, from air and water. The other necessary plant foods must be furnished by the soil. Some of them are needed only in minute quantities and are usually present in agricultural soils in sufficient amounts to support normal plant growth. Nitrogen, phosphorus, and potassium are the three elements most often contained in soils in insufficient quantities to produce optimum crops; consequently they are the elements usually added in commercial fertilizers. Although no one of these fourteen elements can be said to be more essential to plant growth than the others, the continued growing and removal of crops tend to remove some of them from soils faster than others. Potassium is notably one of the elements so removed and is found as one of the principal constituents in the ash of all plants. Credit for the discovery of the role of potassium in plant nutrition is given to Justus von Liebig ( 1 ) often called the father of agricultural chemistry; in 1840he said: “Since growing plants assimilated potassium this element must necessarily be resupplied t o the soil.” He is also generally credited (6) as the originator in 1840 of the process of acidulating phosphatic material in order to make its phosphorus available to plants. Escher (18), however, suggested the idea in 1835. Later Lawes (11), applying this process to phosphate rock, produced superphosphate, the most important single fertilizer material in America, quantitative!y considered. Liebig had analyzed the ash of many different species of plants and had noticed that certain elements, of which potassium was one, were always present to a greater or lesser degree. He evolved and announced the theory that such elements were those mineral elements essential to plant growth. His own and contemporary experiments of Lawes and Gilbert (6) and the slightly later work of Ville (200)demonstrated the correctness of the theory. It has become customary to speak of the potassium content of fertilizers and fertilizer materials in terms of potassium oxide and to use the word “potash” to represent this compound in all the forms in which the element potassium is used in agriculture.‘ 1 In this paper the chemists’ designations “potassium chloride,” “potassium sulfate,” and “potass~umoxide” have been used in preference to “muriate of potash,” “sulfate of potash,” and “KzO,” respectively, whlch are more familiar in the fertllizer industry where It is maintained that the terms used convey a Bomewhat different meaning.
Sir John Russell (16), director of the Rothamsted Experiment Station a t Harpenden, England, founded by John Lawes, assigns to potash three distinct effectson the growth of plants: (a) It facilitates either the production or the translocation of sugars and starches from the leaf, hence its value for sugarand starch-making crops; (6) it stiffens the straw of cereal crops and the grass tribe generally; and ( c ) i t enables the plant to withstand adverse conditions of soil, climate, and disease, making it more resistant to drought, rust, and other diseases. By balancing the plant food ration, potash tends to counteract rankness of growth developed by abundant nitrogen. At the Fourth International Grassland Conference at Aberystwyth last year, Eckstein (4) reported upon a series of experiments to determine the influence of potash on the protein economy and the production of organic matter in the plant. He stated: “In our experiments the production of protein was definitely increased with increasing potash applications, provided always that sufficient amounts of nitrogen and phosphates were applied. . . . Increased application of potash favors growth, always provided that the other plant nutrients are present in ‘harmonious’ relation.” The effect of sufficient potash is readily seen in many crops. Cereal grains are plump and well filled, the stalks are strong and erect; root crops, such as sugar beets, turnips, and potatoes, are solid and well filled with starches and sugars; cotton is free from rust and productive; tobacco matures evenly with smooth leaves of satisfactory texture; and fruits are well colored and of good keeping quality. Conversely, potash starvation resu!ts in fallen cereal crops with shriveled grains; the foliage of root crops dies too soon to permit maximum storage of sugars and starches in the roots, and keeping quality is impaired as well as quantity reduced; cotton plants are subject to rust and the bolls fail to mature; tobacco leaves are curled and spotted; and fruits are of inferior color, flavor, and keeping quality. Harvested crops remove vast quantities of potash from the soil. Table I gives the pounds of potash removed from the soils by some important crops. Unless potash in available form is contained in the soil in sufficient amount to furnish crops with their requirements, crop yields will be reduced. However, under some harvesting practices a considerable portion of the potash removed from the soil by the crop while growing is returned to the soil in
AUGUST, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
such crop residues as the straw of cereals and the stalks of cotton. For instance, a 30-bushel wheat crop removing 25.2 pounds of potash per acre has 18 pounds of the potash in the straw and only 7.2 pounds in the grain; a 500-pound crop of lint cotton has only 15.3 pounds of potash in the seed and lint and 44.3 pounds in the stalks and leaves. If only the grain or the lint and seed are removed and the balance of the plant is left in the field, the drain on the potash content of the soil is much reduced. TABLEI Crop
Yield per Acre
Alfalfa Clover hay Corn Cotton
4 tons 2 tons 75 bu. (plus stalks) 600 lb. lint (entire plant) 50 bu. (plus straw) 300 bu. 35 bu (grain) 25 bu: (beans) 10 tons (beets) 1000 Ib. leaves (plus stalks) 30 bu. grain (plus straw)
Oats
Potatoes ;:beans Sugar beets Tobacco Wheat
Potash Removed L b . KzO 178.4 65.2 82.8 59.6 40.8
95.0
40.0 86.0 64.0 78.0
25.2
Authority Henry ( 7 ) Henry (7) Van Slyke (19 ) Brown (8) Van Slyke (29) Worthen $1) Worthen 121) Worthen (81) Henry (7) Van Slyke (19) Van Slyke (19)
It has been estimated that harvested crops in the United States remove annually over 3,500,000 tons of potash from the soil. In addition to this loss from harvested crops, there is some loss by leaching and a continual heavy loss by erosion. Addition of potash to the soil in the form of fertilizers, manures, and liming materials returns only a fraction of that removed. Much of the potash in the soil is not in a form available to plant growth. It is locked up in insoluble compounds with calcium and silica and other elements so that it is not taken into solution by the soil moisture. Some soils even have the power to fix soluble potash salts in an insoluble form through reaction with other chemical compounds already in the soil. Disintegration of insoluble potash-containing minerals in other soils constantly adds to the available potash of those soils. These and other influences cause wide ranges in the amount of soluble potash that is economically usable in agriculture. Soils containing many thousands of pounds per acre-foot of insoluble potassium may show profitable results from the application of only 50 pounds of soluble potash per acre. In some cases it is profitable to use several hundred pounds per acre It is common practice to use as much as 200 pounds per acre on the potato fields of Aroostook County, Maine, and on tobacco in the Connecticut Valley.
Early American Potash Industry Potash was unknowingly used as fertilizer in this country for several hundred years. The practice of burning the timber of clearings added potash to the corn and pumpkin patches of the aborigine and colonist alike. Wood ashes, supplying potash, have been used in gardens for centuries; in fact, together with kelp and its ash, they furnished the only potash available until well after the middle of the last century when production started from the German mines. For many years the principal export commodity of the American colonies and the newly formed United States was crude potassium carbonate made by leaching wood ashes in pots. The process was old, since Aristotle describes it in detail in his writings. Beginning in Jamestown in 1608 (I?), where artisans were sent for that specific purpose, the industry spread over the Atlantic seaboard as the population grew, until in 1810 the value of potash exported reached the then respectable figure of %1,579,000(3). Development of the Leblanc alkali process and the later discovery of the German potash deposits and their develop-
879
ment supplanted this industry (I?). We find no record of the use in mixed fertilizers of wood ashes or of the crude potash made from them until after foreign potash salts had been imported for that purpose.
Discovery of German Deposits In 1546 Agricola (1) suggested that the saline waters of the German salt springs must come from underlying solid strata. As the population increased, the demand for salt outgrew the production from these springs. In 1834 it was again suggested that solid deposits lay below, and in 1839 a shaft was started to locate the beds if they existed. In 1843 the salt beds were reached a t a depth of 735 feet, but to the great disappointment of the operators, the salt was bitter, containing magnesium and potash. Further investigation developed that these “bitter salts’’ were interspersed in layers or lenses among large deposits of rock salt and had to be mined and laid aside in order to produce the salt. As the waste pile of the “bitter salts” accumulated, a deliberate effort was made to discover a use for them that would provide an outlet for their production, Liebig again entered the picture, and on a 10-acre tract of waste sand purchased by him in 1845 he demonstrated the value of potash in plant nutrition and crop production. His work was generally recognized and accepted about 1860, and the German potash industry from that date systematically set out to demonstrate to the agricultural world the benefits to be obtained from the use of potash on crops. Concurrently many shafts were sunk and many mines developed. Just when the first German potash was imported into America is not known, but it was probably in 1869 or 1870. It is recorded that 1400 tons of potassium chloride were imported for agricultural use in 1871. The first recorded use of German potash by an American agricultural experiment station was in 1872 on one of the experimental farms of the Pennsylvania State College. For nearly 45 years Germany furnished America, as well as the rest of the world, practically all of its agricultural potash.
Present American Potash Industry After the German potash salts became available, there was little incentive to stimulate domestic potash production in America until the blockade of German ports during the World War prevented importation. The scarcity of potash quickly became a matter of national concern. The production of maximum food crops was of prime necessity. The price of potassium chloride skyrocketed from about $38 to nearly $500 a ton, and little was obtainable a t any price. Federal, state, and commercial technical men devoted every effort to discover and develop sources of potash supply. Brines were pumped from the alkaline lakes of Nebraska and California, and crystallized; kelp was harvested along the Pacific Coast, charred, or aslied; distillery wastes were ashed; cement kiln dust was collected; wood ashes and cottonseed hull ashes were saved; alunite, a mineral double sulfate of potash and aluniina, was mined in Utah and roasted, and the potash extracted; green sand or glauconite deposits of New Jersey were processed, all to obtain potash. From 1090 tons in 1915, domestic production rose to 45,728 tons of potassium oxide in 1919. Peace came, the bottom dropped out of agriculture in 1920 and 1921, and production of potash in 1921 fell to only 4408 tons of potassium oxide. In the meantime, European production was resumed, and imports from Germany and from the newly acquired French deposits in Alsace again became available. Only one American producer survived these economic and competitive conditions. The recovery of potash from the brines of Searles Lake, Calif., was begun in 1916 and has continued unin-
‘
INDUSTRIAL AND ENGINEERING CHEMISTRY
880
terruptedly since that time. Almost insurmountable difficulties of location, climate, water supply, transportation, engineering, and chemical technic were encountered in the development of this process and production. They were met and solved. Discovery of potash deposits in the Permian Basin of New Mexico and Texas was announced in 1921 (1.2) and subsequently oil .well drillers discovered other deposits. Core drilling of the area resulted in the opening of two mine shafts and the production of potash salts. From a beginning of only a thousand tons of potassium oxide in 1915, the domestic potash industry has been developed until now production is approximately one-half of our consumption. 0 400 Imports
fl Dornestlc Production
I
1931
1932
1933
1934
1
1935
1936
CALENDAR YEARS
FIGURE
1.
PRODUCTlON, IMPORTS, AND E X P O R T S O F P O T A S H
It is a fine tribute to American chemical engineering practice that three such large-scale enterprises could be so successfully developed during times of economic depression, It is believed that, if necessity arose, present operators in a comparatively short time would be able to supply all of our needs.
Potash Raw Materials Potash raw materials are roughly divided into two classesthose consisting largely of chloride salts and those relatively free from chlorine. For many years a large proportion of the potash salts imported into this country from Germany was the low-grade salts as mined. Kainit was the lowest grade, originally a.sulfate salt of potassium and magnesium analyzing 12.4 per cent potassium oxide. As the original deposits of sulfate kainit were worked out a 14 per cent potassium oxide content material with a chloride radical was substituted. Such low-grade salts were in favor with the mixed fertilizer manufacturer because they permitted him to make the lowgrade mixtures then in demand without the necessity of adding too much filler. I n the early 1900’s mixed fertilizers containing only 1 per cent potash were standard, and a 2 per cent mixture was approaching a high grade. As the uneconomic features of low-grade mixtures came to be recognized by the farmers through the educational efforts of the potash producers, fertilizer manufacturers, and official agricultural workers, the demand for higher grade mixed goods brought corresponding outlets for higher analysis potash salts. The kainit now being imported (a chloride) contains 20 per cent potassium oxide. The next most popular low-grade chloride salt imported was “manure salts,” formerly analyzing 20 per cent potassium oxide but now carrying 30 per cent. Muriate of potash or potassium chloride, containing 50 per cent potassium oxide, for many years supplied the demand for high-grade mixtures. As American production developed, the processes of refining yielded a product containing 60 per cent or more of potassium oxide. Freight savings and general competition have caused European producers to refine their potassium chloride still further so as to be able to furnish the 60 per cent grade.
VOL. 30, NO. 8
The quality of certain crops is adversely affected by a too generous supply of chlorides in the soil solution. Tobacco is a notable example. If too much chlorine is present in the soil, it is taken up by the plant and deposited in the leaf. The melting point of potassium chloride and chlorides generally is relatively low. When a cigar made from tobacco so grown is smoked, the ash of the tobacco fuses or melts, impairing the burning quality of the tobacco even to the point of putting out the cigar. Therefore it is desirable to furnish potash to the tobacco crop in a form that will not produce a fusible ash. Potash as the sulfate has been imported for years for this purpose. It comes in two forms, potassium sulfate analyzing 50 per cent potassium oxide, and potassium-magnesium sulfate (formerly called “double manure salts”), a double salt containing 30 per cent potassium oxide. The question of chlorine in tobacco fertilizers is one of balance. I n most instances more pounds of tobacco per acre will be produced if considerable chlorine is present, whereas the burning quality will be so impaired that the selling price will be materially reduced. After many years of research and experimentation, the Tobacco Research Committee, composed of leading state and government tobacco agronomists, recommends that tobacco fertilizers should contain 2 per cent of chlorine. I n their opinion, this amount seems best to give the plant enough chlorine for satisfactory growth without too much adverse effect on burning quality. Other potash salts low in chlorine that are used for this type of fertilizer mixture are the carbonates and nitrates. The cost per pound of potassium oxide is usually somewhat higher in these forms. The following table shows the quantity and percentage of the various potash materials used in fertilizers in 1936 (IS) : Material Kainit Manure salts Potassium chloride Potassium sulfate Potassium-magnesium sulfate Nitrates and carbonates Total
Short Tons
KzO
11,761 12,263 317,572 29,791 3,673 6,835 381,895
Per Cent 3.1 3.2 83.1 7.8 1.0 1.8
100.0
Analytical Methods In connection with the use of potash in fertilizers, the analytical determination of potassium in fertilizer materials and mixed fertilizers of various kinds became of considerable importance. According to Kraybill and Thornton (Q), the Association of Official Agricultural Chemists adopted the first official method for the determination of potash in fertilizers in 1884. Three years later, the Lindo-Gladding method was adopted and with slight modifications remained the official method until 1935. As early as 1900 it was recognized that this method gave results lower than theoretical on many fertilizer mixtures, particularly on those containing superphosphate and potash salts without addition of nitrogen carriers. As a rule the discrepancy became greater as the percentage content of potash in the mixture increased. The financial loss to the fertilizer industry was considerable, and this figure continued to increase as the average content of potash in mixed fertilizers became greater year after year. Chemists of the fertilizer industry were constantly a t work seeking a more accurate method, because it was necessary to add in certain mixtures a full extra 0.5 per cent of potash above the overrun customarily figured on nitrogen and phosphoric acid in order to ensure that the state control official would find the potash content of the mixture equal to that guaranteed. The Association of Official Agricultural Chemists continued their collaborative work on the subject, and
AUGUST, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
tried many proposed modifications of the official method and many other methods, without finding a satisfactory solution to the problem. I n 1935 Ross and his associates (16)reported that the insoluble residues remaining after the determination of potash by the official method contained potash in determinable quantities. In 1935 Kraybill and Thornton (IO)reported to the A. 0.A. C. a study of residues from fertilizer mixtures which had been extracted by the then official method. The results proved that all the potash had not been removed from the residues by the official method, and also Neubauer pot tests showed that the potash remaining in the extracted residues was available to plants.
I
t
Price of K ~ O i.1 \D. Unit M u r i a t e of Potash
881
oxide, and a quotation of 60 cents per unit for potash means that a ton of 50 per cent muriate of potash is being quoted a t $30. The price of potash rose during the World War from 75 cents to $10 a unit; it dropped in 1922, as import movement began to fill the demand, to 67 cents per unit and remained fairly constant till 1934 when the effect of new American and foreign production was reflected by a drop in the unit price to 48 cents. I n 1935 a price war developed during a competitive struggle between foreign producers for certain portions of the world market, and the average unit price dropped in this country to 41 cents, with some large contracts at lower figures. Stabilization in the world market has increased the price gradually to a present level of 53 cents a unit. Potassium sulfate, a product manufactured by a chemical process, has always commanded a higher price per unit than the natural or refined chlorides. These prices are all based on potassium chloride for Atlantic port deliveries for both foreign and domestic production as they are in direct competition in consuming markets. The rapidly increasing American production was an important factor in this general reduction of price in this country.
Potash Consumption in Fertilizer
.---I WI ’.-,.------I----..I
1880
FIGURE 2.
I
I
1890
1900
I
I
I
1910
1920
1930
1
1940
POTASH CONTENTOF COMPLETE MIXEDFERTILIZERS
(1880
TO
1937)
Kraybill (8) in his report to the A. 0. A. C. as associate referee on potash for 1935 reported collaborative results on a proposed modification of the official method which essentially consisted of boiling the sample in a solution of ammonium oxalate and ammonia for the extraction. Results by this method on most samples were found to be much more nearly in agreement with the theoretical amount of potash present than did results by the official method; the results ran from 0.27 to 0.57 per cent potassium oxide higher by the modified method. As a result, the modification was adopted as a change in the official method. Additional study over the next year confirmed the previous results, and the modified method was adopted as the official method in 1936. The change has been of financial importance to the fertilizer industry because of the fact that there was no difference in the results obtained when the two methods were applied to the potash salts themselves, so that the manufacturer of mixed fertilizers was forced to absorb the cost of the analytical loss in connection with fertilizer mixtures.
The importance of fertilizer consumption to the potash industry is evidenced by the fact that more than 95 per cent of all potash used in the United States is utilized as plant food ( I S ) . Beginning in 1871, when 1400 tons of potassium chloride were imported from Germany, consumption increased slowly until about 1900. During that year 71,817 tons of potassium oxide were imported. A rapid increase in consumption occurred over the next 10 years, reaching 274,434 tons of potassium oxide in 1910. On account of reduction in general fertilizer use because of agricultural depression, consumption dropped somewhat up to 1914, when the blockade of German ports stopped all imports for several years. Only 11,446 tons were used in 1916 (all that was obtainable). Because of increased domestic production, three times as much was used in 1917 and slightly more in 1918. Resumption of imports brought consumption in 1920 to nearly 240,000 tons, but the agricultural recession of 1921 reduced consumption to 68,444 tons. Consumption generally increased until 1930 when the effects of the depression caused a 45 per cent drop by 1932. Recovery in agriculture has increased our potash use to an all-time high in 1937 of 410,000 tons of potassium oxide. Table I1 shows the number of short tons of potash destined for use in agriculture in the United States for the past ten years and the source of supply (14). 1
TABLEI1
Potash Prices Control laws in forty-seven of our states require that fertilizers and fertilizer materials shall be offered for sale on the basis of a guaranteed plant food content of nitrogen, phosphoric acid, or potash, or a combination of two or more of them. The grade of a fertilizer is generally indicated by numbers representing the guaranteed content of these three plant foods in the above order. A 5-8-7 fertilizer is one guaranteed to contain not less than 5 per cent of nitrogen, 8 per cent of available phosphoric acid, and 7 per cent of available potash. Prices of the different mixtures vary as their plant food content varies. Prices of raw materials are usually quoted in terms of units. In fertilizer parlance a unit is 1 per cent per ton, or 20 pounds. A unit of potash is 20 pounds of potassium
Year 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 a
b
Domestic Production 43,510 59,910 61,590 61,270 63,880 61,990 143,378 144,342 192,793 247,340 270,O0Oa
Imports 224,973 297,000 325,000 359,044 214,909 109,604 214,021 169,865 243,571 204,603 352,300b
Exports 7,751 4,877 10,000 10,224 19,476 1,221 16,852 16,793 45,590 62,384 62,384
Apparent Supply 260,732 352,033 376,590 410,090 259,313 170,373 340,547 297,414 390,774 389,559 559,9166
Sales. Unusually large imports September-December, 1937.
The story of potash in both Europe and America is one of industrial romance. The deliberate German program of search and research for a market to dispose of the by-product
882
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 30, NO. 8
capital has developed the deposits found in the Southwest until we can now see our complete independence as to potash, should any emergency arise in the future, and our economic independence now.
a00
aoo $0
Literature Cited
$2 zoo
10 0
1870
‘eo
‘M
‘so
‘so
-00
‘OB
‘IO
’IS
‘20
POTASH CONSUMPTION FIGURE 3. ESTIXATED
‘a5
-ao
‘SS
IN T H E UNITED
STATES(1870 TO 1937)
“bitter-salts” potash, and its success, due to Liebig’s discovery, is one of the outstanding examples of combined scientific and commercial research on record. The educational program in America (or perhaps “sales propaganda”) of the foreign potash producers has been of incalculable assistance to agriculture in proving to our farmers the value of potash in connection with other plant foods in the production of crops. When war demonstrated to the Government and the people how completely dependent on other nations we were in our potash requirements, every effort was made to protect ourselves. Private capital continued to operate the one project economically capable of competing with foreign production after importation was resumed. Private capital and government appropriations provided for core drillings and other types of search and research for potash sources. Private
(1) Berliner, J. F. T., U. S. Bur. Mines, Bull. 327, 44 (1930). (2) Brown, H. B., “Cotton,” p. 192, New York, McGraw-Hill Book Co., 1927. (3) Browne, C. A., Proc. NatE. Fertilizer Assoc., 11, 95 (1935). (4) Eckstein, O.:‘Rept. 4th Intern. GrassEand Congr., 1937, 317-25. (5) Hall, A. D., Fertilizers and Manures,” p. 119, New York, E. P. Dutton & Co., 1935. (6) Ibid., pp. 12-13. (7) Henry and Morrison, “Feeds and Feeding,” pp. 660-5, Madison, Wis., Henry-Morrison Co., 1916. (8) Kraybill, H. R., J . Assoc. Oficial Agr. Chem., 18, 237-43 (1935). (9) Kraybill, H. R., .and Thornton, S. F., Ibid., 18, 261-81 (1935). (10) Ibid.. 18. 281 (1935). (115 Lawes, J. B., British Patent 9353 (1842). (12) Mansfield, G. R., and Lang, W. B., Am. Inst. Mining Met. Engrs., Tech. P u b . 212, 3 (1929). (13) Minerals Yearbook, U. S. Bur. Mines, 1937. (14) Ibid., 1928-1937. (15) Ross, W. H., J . Assoc. OficiaE Agr. Chem., 18, 327 (1935). (16) Russell, E. J., “Student’s Book on Soils and Manures,” p. 145, London, Cambridge Univ. Press, 1915, (17) Smith, H. I., chapter on “Potash,” in “Industrial MineraIs and Rocks,” pp. 571-600, New York, Am. Inst. Mining Met. Engrs., 1937. (18) Speter, Max, Superphosphate, 7, 207 (1934). (19) Van Slyke, L. L., “Fertilizers and Crop Production,” p. 113, New York, Orange Judd Pub. Co., 1932. (20) Ville, Georges, “Artificial Manures ’’ London, Longmans Green & co.. 1909 (21) Worthen, E. L., “Farm Soils-Their Management and Fertilization,’’ p. 81, New York, John Wiley & Sons. 1935. RECEITED May 7, 1938.
FATE OF SOLUBLE POTASH APPLIED
TO SOILS EMIL TRUOG A N D RANDALL J. JONES University of Wisconsin, Madison, Wie.
vv
-HEN potassium in the form of fertilizer salts, animal
manure,or crop residues is applied to soils,it usually becomes dissolved in the soil solution shortly afterwards. At this stage some may be absorbed by growing plants and, in case heavy rainfall ensues, some may be lost by leaching. Usually, however, the major portion is fixed by base exchange reactions in exchangeable form. As long as it stays in this form, it is readily available to plants, since it may be easily brought into solution again through the interaction of carbonic acid excreted in large amounts by the roots of plants. Abundant evidence exists (6) to demonstrate conclusively that under certain conditions some of the exchangeable potassium gradually passes over to a nonexchangeable and difficultly available form. The main portion of this paper will be devoted to a discussion of the factors and conditions involved in this fixation of potassium in nonexchangeable form.
Loss of Potassium by Leaching The extent to which potassium is lost by leaching has been given considerable study. Voelcker’s early analyses cited by
Hall (9)of the underdrainage waters from plats a t Rothamsted showed that the amount of potash ranges from 1.7 p. p. m. in the case of the manured plat to 5.4 in the case of plats manured annually with 300 pounds per acre of potassium sulfate. A drainage of 1,000,000 pounds per acre represents approximately 5 inches of rainfall, so that with an underdrainage of 10 inches the annual loss per acre in the case of the manured plat showing the greatest loss becomes twice 5.4, or 10.8 pounds. Dyer’s results of chemical analysis of the soils from some of these Rothamsted plats, also cited by Hall (g), show that of the potash applied during fifty years and not removed by the crops grown during the same period, about one-half was still to be found in the top 9 inches, much of it soluble in one per cent citric acid; further quantities of the applied potash, also soluble in the same citric acid, were to be found in the second and third 9-inch layers of soil. Results of lysimeter experiments by Lyon and Bizzell (4) a t Cornell, in which silt loam and silty clay loam soils were used, show an annual loss by leaching of the cropped soils of about 70 pounds of potash per acre. The fact that this is
