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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 THE 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
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INDUSTRIAL AND ENGINEERING CHEMISTRY
883
higher than that reported by other i n v e s t i g a t o r s may be a t least partially accounted for by the fact that surface runoff was prevented, causing a high percentage of the rainfall (about BO per cent) to appear as drainage. In contrast, Hendrick and Welch (S) of Scotland reported an annual loss of potash of about 10 pounds p e r a c r e . Commenting on the results he obtained f r o m l y s i m e t e r experiments in which a wide variety of soils were used, Fraps (1) stated that only small quantities of potash appeared in the percolates from most of the soils, even after heavy applications of potash were made. It may therefore be concluded, on the basis of much experimental data, that the loss of potash by leaching under most farming Conditions is not in excess of 10 to 15 pounds per awe per year. When the land is occupied by a perennial crop such as alfalfa, the loss is undoubtedly very low. Only in the case of sandy soils that are heavily fertilized with potash is there much danger of serious loss of potash by leaching.
with the exchange material facilitates rapid absorption and removal of this potassium carbonate by the plant. This, in turn, makes it possible for the exchange reaction brought about by the carbonic acid to continue a t a maximum rate. Potassium is thus held in the exchange form tenaciously enough to prevent serious loss by leaching but not so tenaciously as to be unavailable to plants.
Ready Availability of Exchangeable Potassium
Fixation of Potassium in Nonexchangeable
As a coating on the surfaces of soil particles, in varying amounts depending upon the soil, is found material which has base exchange properties. Physically this material is colloidal; chemically it may be either organic, in which case it appears to be derived from lignin, or inorganic, in which case it is a secondary aluminum silicate derived from the weathering of certain primary silicate minerals. The aluminum may be partially or wholly replaced by iron. The base exchange properties of this material are analogous to those of certain natural zeolites and also the artificial ones commonly used in water softening. Monovalent and divalent bases and the replaceable hydrogen of acids enter into exchange reactions with this material. Since the replaceable hydrogen of acids readily takes the part of a base in these reactions, the phenomenon might better be called “cation exchange” than “base exchange.” When potash salts dissolve in the soil solution, the potassium immediately tends to come to equilibrium with the other exchangeable cations; because of its relatively high replacing power, a considerable portion is soon taken up by the exchange material. The fact that the potassium which is added to soils in the form of soluble salts usually suffers only slight loss by leaching is good evidence of the strong replacing power of potassium in the exchange material. Although potassium is held as an exchangeable base quite tenaciously, it is still readily available to plants. The root hairs of plants come into contact with considerable amounts of this exchange material, and the region or area of contact is a very intimate one. It is in a sense a partially closed system so that the carbonic acid which is excreted in this system by the root hairs does not easily escape and thus tends to form a saturated or supersaturated solution. The hydrogen in this carbonic acid then effects an exchange with potassium in the exchange material so that potassium carbonate is brought into solution. Closeness of contact of the root hairs
EFFECT OF F E R T I L I Z E R CONTAININGPOTASHON BARLEYGROWNON WAUXESHA SILTLOAM Peat and muck soils usually respond to potash early in their cropping. Many mineral soilrt also respond after 25 to 50 yeare of cropping. This picture is an example. Yields per acre: right, no fertilizer 25.7 bushels. left, 225 ounds’ 0-20-10 fe;tiliaer, 50.4 tushels. phosphate alone, 225 pounds’ 0-20-0 fertilizer 40.5 bushels. Soil testa showed 10 pounds of phosphorus and 100 pounds of potassium per acre, indicating a decided lack since at least 75 and 200 ounds: respectively, are nee8ed.
Form In 1934, PI’. J. Volk (6) reported on investigations pertaining to fixation of potassium in soils in difficultly available or nonexchangeable form, and he reviewed the literature pertaining to this subject. He found that, when a mixture of soil and water containing a soluble potassium salt is evaporated to dryness a t room temperature, some of the potassium is fixed in difficultly available form. Alternate wetting and drying of these mixtures a t 70” C. causes a large portion of the potassium to be fixed in this form by certain soils. If the soils containing the soluble potassium salt are allowed to stand in a moist condition, fixation is, a t most, very slow. The colloid fraction of the soil fixed much more potassium than the other separates. His data indicate that the potassium is not just mechanically held but enters into a chemical reaction with the colloid. Previous leaching of the soil with 1 N hydrochloric acid reduced the fixation; leaching with 1 N sodium carbonate increased the fixation. Synthetic mixtures consisting of alumina gel, silica gel, calcium hydroxide, and sand did not fix potassium. Chemical, mineralogical, and x-ray studies were made of the Hagerstown silt loam from two plats of the Pennsylvania Station field; one plat had not received potash as fertilizer and the other had received 3158 pounds of potash. The conclusion was reached that muscovite had been formed in the latter, which accounted for the fixation of the potash. A reaction between the colloidal silicates of the soil and the potassium added, forming muscovite as the end product, was believed to have taken place. Later G. W. Volk ( 5 ) repeated some of the work of N. 3. Volk and corroborated the previous results. The fixing capacity of a number of minerals and materials was tested, and, of these, bentonite fixed by far the most potash. I n order to gain additional information on the minerals in soils which might be responsible for fixation of potash in nonexchangeable +formand of conditions which influence this fixa-
INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOL. 30, NO. 8
TABLE I. POTASH FIXATION BY VARIOUS MIMERALS~ Mineral
Treatment
Bentonite (natural, powdered)
10 mg. Kz0 added as KC1 t o 1-gram sample; wet and dried a t 80' C. 20 times Exchange satd. with K ; wet and dried a t 80' C. 20 times Exchange satd. with K; dried a t 110' C. for 75 hr. Exchange satd. with K; wet and dried a t SOo C. 20 times Exchange satd. with K ; dried a t 145' C. f o r 10 hr. Exchange satd. with K ; dried a t 145' C. for 48 hr. Ex_o$ange satd. with K ; dried a t 300' C. for
Bentonite (natural, powdered) Bentonite (natural, powdered) Bentonite (fine.
< 0.1 p )
Nontronite (< 1.0 p ) Bentonite (natural, powdered) Bentonite (natural, powdered)
I
Pyrophyllite Halloysite Kaolinite Muscovite a
iir,
10 mg. K20 added as KCl to 1 gram of mineral; wet and dried a t 80' C. 20 times
Original Exchange Cauacitu M. E..
t
Kz0 Fixed M . E. P . p . m.
Exchange Capacity after KzO Fixation M . E.
Reduction in Exchange Capaciky sfter K.0 Fixation M . E.
124
14.8
6,990
110 5
14.6
124
33.9
15,967
91 0
33.0
124
27.0
12,690
96 0
28.0
131.7
49.4
23,218
80 0
51.7
115
31.5
14,850
81 0
34.0
124
30.8
14,476
...
Not detd.
124 4.3
30.3 None None None 0.8
14,241 None None None 370
24:1
...
Not detd. Not detd. Not detd. detd. Not detd.
Id this and subsequent tables, milliequivalents (M. E.) are expressed on the basis of 100 grams of material.
tion, further experiments were conducted by the writers with a number of minerals as indicated in Table I. It is apparent that, of the minerals tested, only those contained in bentonite have high fixing power. Muscovite has a slight fixing power, but this is not of great significance so far as the main question is concerned. The data in Table I give some indication that fixation in nonexchangeable form is related to exchange capacity. It has been suggested that, when the exchange material is saturated with potassium and the material is then dried, which is supposed to bring the layers or plates of the crystal lattice together, the presence of the potassium offers such strong attraction as to prevent reexpansion of the crystal lattice and thus reentrance of water and opening up of the crystal lattice ; the potassium thus becomes trapped in nonexchangeable form. If the exchange material of soils, which is believed to be similar or identical to that in bentonite, causes this fixation in nonexchangeable form after repeated wetting and drying, then the amount of fixation by soils should run somewhat parallel to the exchange capacities of soils. In order to test out the possibility just mentioned, a number of soils listed in Table I1 were tested for their fixing power. The amount of fixation by these soils does run somewhat parallel to the exchange capacities of the soils. Also, the amount of potash fixation in milliequivalents corresponds to the decrease of exchange capacity in milliequivalents. This supports the idea that it is exchangeable potassium that becomes fixed in the exchange material when this material is dried. Why it is not possible to load the exchange completely in this way with potassium and thus destroy all of the exchange capacity is not quite clear. TABLE 11. Soil Type Miami silt loam Carrington silt loam Richfield clay
POTASH
FIXATION BY SOILS'
Original Exchange Horizon Capacity
A B A B
A B
M.E. 10.0 17.3 12.1 14.3 20.8 30.0
Redyc tion in Exchange Kz0 Fixed Capacity M.E. P.p.m. M.E. 1.5 700 1.9 4.7 2209 4.8 2.7 1255 2.7 3.4 1598 3.2 4.0 1880 3.8 5.0 2350 5.1
0 Soils were freed of organic matter, saturated with potassium, and wet and dried twenty times at 80' C.
Table I11 presents data relative to the fixation of several other common cations in nonexchangeable form by the minerals of bentonite. None of these bases were fixed to an extent anywhere near that of potassium. The eFtent of fixa-
tion represented by the data is not far beyond the limits of the experimental error involved. It thus appears that this type of fixation is largely peculiar to potassium. Since the potassium ion is larger than these other cations which were tested, one might expect it to become trapped or fixed more easily in nonexchangeable form. The exact nature of the mechanism involved in this fixation remains to be determined.
TABLE 111. FIXATION OF DIFFERENT CATIONSBY POWDERED
BENTONITE@
Cation
Ca Mg Na
Original Exchange Capacity M . E. 124 124 124
Final Exchange Capacity M . E. 123.5 118.2 117.5
Amount Cation Fixed M . E. 0.6 5.8 6.5
a After saturation with respective cations, the material was dried a t 110O C. for 10 hours.
Summary When soluble potash is added to soils, it soon dissolves in the soil solution and then moves about by diffusion and the movement of the soil water. Some of this potash may be absorbed immediately by growing plants, and a small amount may be lost by leaching, especially if heavy rainfall ensues. In most cases, however, the major portion reacts with the base exchange material of soils and through cation exchange becomes fixed as an exchangeable base. In this condition the potash is readily available tb plants, since exchange of hydrogen from the carbonic acid which is excreted in large amounts by plant roots for the potassium in the exchange material brings the potassium into solution as the carbonate so that it may be absorbed by plants. Thus, as long as the potassium remains in exchangeable form, it is readily available to plants. It has been found, however, that in many soils a portion of the exchangeable potassium passes over in time to a nonexchangeable form. Some evidence has been obtained indicating that this nonexchangeable form is muscovite or a closely allied mineral. It has also been found that alternate wetting and drying hasten the fixation in nonexchangeable form. T o explain this, it has been suggested that, when the exchange material is saturated with potassium and the material is then dried, which is supposed to bring the layers or plates of the crystal lattice together, the presence of the potassium offers such strong attraction aa to prevent reexpansion of the crystal
AUGUST, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
lattice and thus reentrance of water and opening up of the crystal lattice, causing the potassium to become trapped in nonexchangeable form. Other cations, such as sodium and calcium, which are smaller than potassium, are not fixed or trapped in this manner. From a practical standpoint the question arises: How can this fixation in nonexchangeable form be lessened or prevented? Application of potash fertilizers a t a depth of several inches instead of a t the surface so as to lessen the influence of alternate wetting and drying suggests itself as a measure worthy of attention. Localized application of fertilizer and the use of granular forms should help considerably. Introduction of organic matter, which supplies organic base exchange material, should also be helpful, since entrance of
885
potassium in the organic exchange renders the potassium safe from fixation in nonexchangeable form for the time being.
Literature Cited 171 (1914).
(1) Fraps, G . S., Texas Agr. Expt. Sta., Bull.
(2) Hall, A. D., “Fertilizers and Manures,” 3rd ed., p. 180, New York, E. P. Dutton & Go., 1928. (3) Hendrick. J., and Welch, H. D., Proc. 1st Intern. Congr. Soil Sei., 2, 358-66 (1927). (4) Lyon, T. L., and Bizrell, J. A., Cornell Univ. Agr. Expt. Sta., Memoir 194 (1936). ( 5 ) Volk, G. W., Soil Sci., 45, 263-76 (1938). (6) Volk, N. J., Ibid., 37, 267-87 (1934). RECEIVED May 16, 1935. Published with the permission of the Director of the Wisconsin Agricultural Experiment Station. This work was supported by a grant from the -4merican Potash Institute, Inc.
POTASH IN PLANT METABOLISM Deficiency Symptoms as Indicators of the Role of Potassium G. N. HOFFER American Potash Institute, Inc., Lafayette, Ind.
T
HE importance of potassium in plant growth is being reflected in the increasing number of deficiency symptoms of various crops in many of the arable soils in the country. The symptoms are appearing in widespread areas, and much publicity is being given to cotton “rust” in the South and the “edge scorch” of the leaves and root rot of corn in the Midwest. Housewives are complaining because
Researches on the role of potassium show that it is intimately related with certain organic constituents in plants. I t is essential in all cell metabolic processes. It influences the rate of respiration. It operates in the synthesis of foods and their translocation in plants. Accordingly, when deficiencies in the soil supply of available potassium occur, changes in any one or all of these vital physiological processes may result, sooner or later, in definite outward manifestations, such as foliage discolorations, necroses of various kinds, and greater susceptibility to fungous diseases. These various injuries not only reduce the yields and quality of the plant products but emphasize the important role of potassium in plant metabolism and economy.
potatoes from certain areas turn dark and soggy when cooked; tobacco growers are producing lower quality leaf; and farmers in southern Illinois are finding it difficult to maintain the productivity of their soils with lime, phosphates, and legumes. These problems are being solved by supplying potash to these crops in the field, but how potassium functions in plants to produce these beneficial effects is not fully known. Eckstein, Bruno, and Turrentine (6) published a descriptive treatise on potash deficiency symptoms of practically all of the commercially important plants. This book is invaluable as a reference on the maladjustments of crops when growing with insufficient available potassium. The discussion of the role of potassium in this paper will refer to certain pertinent researches only to feature the relation that apparently exists between potassium and some of the vital processes in plant metabolism and growth. Our knowledge of deficiency symptoms is largely dependent upon the facts gained in biochemical investigations. By making comparative studies of potassium-starved and normal plants, both in the field and in controlled nutrient cultures, important facts are being discovered which doubtless will contribute to the more profitable use of potash salts in the control of these malnutrition difficulties. Up to the present time, even though many physiological studies have been made on this element, there seems to exist little definite evidence indicating the nature of the mechanism by which potassium functions. It has a specific role in influencing the absorption of certain other mineral elements, in assimilating carbon, in translocating sugars and forming starch, in regulating the rate of respiration, in affecting the rate of transpiration, and also in influencing the action of enzymes. Many researches on these subjects show that potassium is necessary in all protoplasmic activity, but the chief difficulty is to allocate the exact function of potassium to specific steps in the whole series of these interrelated physiological processes. A disturbance in any one affects the
