S 545 .S66 Copy 1 SOME EFFECTS OF POTASSIUM SALTS ON SOILS A THESIS PRESENTED TO THE FACULTY OF THE GRADUATE SCHOOL OF CORNELL UNIVERSITY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY BY RAYMOND STRATTON SMITH SEPTEMBER, 1918 Reprinted from Memoir 35. June, 1920, of Cornell University Agricultural Experiment Station. SOME EFFECTS OF POTASSIUM SALTS ON SOILS A THESIS I'RE.SENTtD TO THE FACULTY OF THE GRADUATE SCHOOL OF CORNELL UNIVERSITY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY ii\ RAYMOND 5TRATTON SMITH 5EPTF.MBER, 1918 Reprinted from Memoir iS, June, 1920. of Cornell University Agricultural F-Xperlment Station. ! LiBnARY Or Cw.>;>tO''-' \ ^' CONTENTS PAGK Historical review 57.1 Effect of potassium and manganese salts on plant growth 571 Potassium salts 571 Manganese salts 573 Effect of potassiimi and manganese salts on nitrifi(;ation in soils . . . 574 Potassium salts 574 Manganese salts 576 Effect of reaction of the soil on nitrification 578 Interchange of leases 579 Conclusions 580 Experimental work 581 Soils used 581 Preparation of the soils 581 Plan of the experimental work 582 Experimental methods 584 Pot cultures 584 Soil extract cult urcs 584 Nitrification 584 Soil acidity determination 585 Experimental results 585 Pot cultures 585 Soil extract cultures 587 Nitrification 590 Interchange of bases 595 Summary 599 Literature cited 602 567 SOME EFFECTS OF POTASSIUM SALTS ON SOILS SOME EFFECTS OF POTASSIUM SALTS ON SOILS R. S. Smith The factors that determine the abihty of a soil to support plant growth are known to be very complex, and any modification of this ability brought about by materials added to the soil is at least equally complex. It is now generally recognized that the secondary effects of fertilizing materials which are added to a soil may ultimately prove either beneficial or injurious when measured in terms of crop yields. The deleterious effects of ammonium sulfate have been particularly noted. The secondary effects of other fertilizer salts have l)een less thoroly studied because their action is thought to be less pronounced. However, attention has been called to various effects exerted by other materials, including the salts of potassium. The somewhat conflicting experimental data bearing on the effects of the chloride and the sulfate of potassium on the soil as a medium for plant growth led to the work reported in this paper. The method of attacking the prolilem was, first, to determine the effect of various applications of potassium chloride and potassium sulfate on the growth of wheat, both in the variously treated soils and in water extracts of the soils; and secondly, to attempt to get at the causes of the. effect of these salts on crop growth as noted in this work and as noted by other investigators. HISTORICAL REVIEW EFFECT OF POTASSIUM AND MANGANESE SALTS ON PLANT GROWTH Potassium salts The stimulative action on the growth of the higher plants exerted by the salts of potassium which are commonly used as fertilizing materials, is recognized. That this action is in part secondary seems evident from the fact that the specific effects noted vai-y with different soils and with the same soil variously treated. Ordinarily, these salts would probably not be used in sufficient quantity to prove directly harmful to plant growth; but under certain intensive systems of farming, in which heavy applications of fertilizers are made, 571 572 R. S. Smith such a result might follow. Lyon, Fippin, and Buckman (1915) make the statement that "it [potassium] may be present in large quantities in the soil and yet exert no harmful effect on the crop." Whether this statement refers to soluble salts of potassium added to the soil, or to the slowly soluble compoiuids in the soil minerals, is not stated. There is a possibility, however, that even the ordinary applications of potassium salts may result in an increased loss from tlic soil of other bases, particu- larly calcium. But little work has been done to determine at what concentration the salts of potassium become toxic to plant growth in soils. Headden (1915) found that yellow-berry in wheat is increased by the application of 150 pounds of potassium to the acre. He ascribes this condition to the excess of solul)le potassium over soluble nitrogen. This effect of a comparatively small application of a potassium salt in aggravating an abnormal condition in the wheat crop is of interest in this connection in that it indicates a significant modification of the soil as a medium for plant growth. Harris (1915), from an extensive investigation of the effect of alkali salts on the germination and growth of seedlings in three different soils, reports the concentrations of potassium chloride and potassium sulfate at which these salts become harmful to wheat seedlings. He found that heavier applications of these salts were required to cause injury to the seedlings than would ever be applied, even in the most intensive systems of farming. McCool (1913) determined the effect of the chlorides of ammonium, magnesium, potassium, and calcium on the germination of pea seeds in soil. The salts were harmful in the order given. Potassium chloride caused slight injury when used at the rate of about 7456 pounds in 2,000,000 pounds of soil. The character of the soil is not stated by the writer. Voelcker (1909), in conducting pot experiments with wheat at the Woburn experiment station, in which the chloride, the sulfate, the car- bonate, and the nitrate of potassium were used in such amounts as to supply the soil in each case with 0.0075 per cent of the metal potassium — which is equivalent to 166 pounds of the chloride, 312 pounds of the sulfate, 248 pounds of the carbonate, and 369 pounds of the nitrate, per 2,000,000 pounds of soil — noted injury with the carbonate. It is difficult Some Effects of Potassium Salts on Soils 573 to understand how such small apphcations of any of these salts could cause injury to wheat. Much work has been done on the toxicity of bases in solution cultures with various crop plants. This phase of the study is typified by the investigations of McCool (1913) on a large number of bases, including potassium. This type of investigation, however, has little direct sig- nificance in soil studies, because the conclusions drawn cannot be applied with a soil medium due to side reactions which are involved when so complex a medium is employed. McCool found that the chlorides of barium, manganese, ammonium, magnesium, sodium, potassium, and calcium were toxic to pea seedlings in the order named. It is of interest to note that manganese stands near the head of the list. The degree of toxicity of all the salts is much less in soil than in nutrient solution. As has been noted, McCool found that potassium chloride caused slight injury to the germination of pea seeds in soil when applied at the rate of about 7456 pounds to 2,000,000 pounds of soil, and Harris reports much higher concentrations than this as l)eing necessary to produce a toxic condition except in the case of coarse sand. It thus appears that injury to plant growth has been found to result from the use of potassium salts in large quantities; that applications at the ordinary rate have been found to cause injury in but one case; and that small applications may possibly accentuate pathological conditions in the growing plant. No reports of experiments on the growth of seedlings in soil extract made from soils to which only potash salts had been added, have been found in the literature. Abbott, Conner, and Smalley (1913) report some soil-extract-culture experiments with corn, using soil high in solul^le aluminium salts. This work is of interest in this connection in that it agrees with the con- clusions of other investigators that the water extract from unproductive field soils is toxic to the root growth of seedlings. Manganese salts Manganese, as is noted later in this paper, is one of the bases replaced by potassium in some soils, and, since it has been shown by some investi- gators to have considerable influence on plant growth, a brief review of the literature regarding its action is here given. 574 R. S. Smith As sliown by Skinnor and Sullivan (1914), manganese increases the oxiclizinjr power of plant roots. This, however, was not accompanied by increased growth when the plants were grown i-n fertile soil. Infertile soils seemed to respond to manganese when it was used in small quantities, varjang from 5 to 50 parts of manganese to 1,000,000 parts of soil. Experiments by Skinner and Reid (1916) on silty clay loam of an acid nature; at Arlington, Virginia, in which manganese sulfate was applied annually at the rate of 50 pounds to the acre previous to planting, show a decrease in the yield of wheat and cowpeas and inconsistent results with rye. When the lime requirement of the soil was just satisfied, the depression was decreased; and when an excess of lime was used, the crop yields were increased by manganese, except in the case of potatoes. The results of other workers agree in the main in showing that the salts of manganese increase the yields of field crops when used in small quanti- ties. In some instances a decrease results, and the work of Skinner and Reid seems to indicate that the reaction of the soil is an important factor. Little work has been done to determine at what concentrations salts of manganese become toxic to plant growth in soils. McCool (1913), using a sandy loam soil, found that manganese chloride in solution was toxic to peas when added at the rate of 380 cubic centimeters of N/50 solution to 1000 grams of soil. This rate of application is equivalent to about 181 parts of the element manganese to 1,000,000 parts of soil. McCool found also that calcium overcame this injurious action, while Kelley (1908) reports that lime had no such effect. The conclusion seems justified that if a neutral salt when added to the soil replaces even small amounts of manganese, the presence of this replaced base may affect crop growth adversely or occasionally beneficially, depending on other factors not well understood. Other bases replaced by various fertilizer treatments are known to be toxic to plant growth, particularly iron and aluminium. But since neither of these elements was found to be present in the water extracts of the soils used in this work, no discussion of their action seems necessary. EFFECT OF POTASSIUM AND MANGANESE SAI.TS ON NITRIFICATION IN SOILS Potassium salts Potassium salts have been found to protluce specific effects on nitrifica- tion. Under certain conditions a stimulation has been noted, while under Some Effects of Potassium Salts on Soils 575 other conditions the reverse has been the case. The Hterature has been searched in an attempt to discover what effects potassium salts have on nitrification, and any specific effects that have been found to accompany certain conditions resulting from the application of potassium salts to soils. A close correlation between the nitrifying power of a soil and its crop-producing power may not exist, but the two are likely to be associated. A study of the nitrifying power of a soil should, then, furnish some indication of its crop-producing power and help to explain any departures from the normal in crop growth. Dumont and Crocbetelle (1893) report favorable effects of potassium salts on nitrification in soils rich in organic matter and limestone. They later (1894) report work with a sandy humous soil stated to be poor in lime. This soil as reported contained 17.5 per cent of humus and 0.285 per cent of limestone. Potassium carbonate and potassium sulfate, both with and without lime, were used in different amounts. Potassium carbonate was used in increasing amounts from 0.1 to 6 grams, to 100 grams of soil. Marked stimulation was found to accompany its use up to 4.5 grams, and then there was a steady decrease in the nitric nitrogen found. Potassium sulfate without lime had no consistent effect. The character of the results indicates that the differences found in the latter treatments were due to factors other than those under study. When 2.5 grams of limestone were applied in addition to the potassium sulfate, there was a constant increase in the amount of nitric nitrogen found with an increase in the amount of potassium sulfate used, the heaviest application being 5 grams to 100 grams of soil. Lyon and Bizzell (1918) report the nitrogen recovered from the lysimeter tanks at Cornell University. Apparently potassium sulfate without lime depressed nitrification. Lime counteracted this effect, but even with lime the sulfate did not cause any appreciable stimulation of the process. Greaves (1916), in laboratory experiments on the effect of potassium salts on the bacterial activities of sedimentary soils derived from limestone and quartzite, found that potassium chloride and potassium sulfate used at the rate of from 6.1 to 8602 parts per million depressed nitrification at all con(;cntrations. Potassium nitrate and potassium carbonate, used at the same rates, stimulated nitrification at the lower concentrations but became toxic at the higher, the nitrate at 48.9 parts per million and o7G 11. S. Smith the carbonate at 3910 parts per million. Greaves concluded that the extent of stimulation is governed largely by the cation, and that the toxicity of potassium salts is governed by the electro-negative ion com- bined with the potassium, since he found that the chlorides of sodium, magnesium, manganese, and iron, and the sulfates of calcium and manga- nese, increased bacterial activity, while the chlorides of potassium and calcium and the sulfates of sodium and potassium failed to cause any stimulation. Pichard (1884) found that potassium sulfate caused strong nitrification of the organic nitrogen in a soil high in organic matter, but that its influ- ence was not so marked as was that of calcium sulfate or sodium sulfate. Allen and Bonazzi (1915) studied nitrification in soil samples from the plots at the Ohio experiment station. Anmionium sulfate in solution was used as the nitrifiable material at the rate of 21.2 milligrams of nitrogen per 100 grams of soil. The samples were incubated for ten days. The results with the samples from the potassium sulfate plots — which had received 80 pounds of the salt to the acre on corn, oats, and wheat of the five-years rotation — failed to show any increase in nitrification over the check ; in fact, denitrification apparently took place in some cases. Peck (1911) found that potassium sulfate used at the rate of 0.5 gram in 500 grams of sugar-cane soil decreased the bacterial activity, as measured by bacterial numbers and nitrogen fixation during one month of incubation. Renault (1910) cites experiments by Dumont which show that slow ammonification and subsequent nitrification is always accompanied by a low percentage of potash. It thus appears that potassium fertilizers, when applied at the usual rate under field conditions, commonly exert a depressing influence on nitrification. Under laboratory conditions both the chloride and the sulfate of potassium have generally been found to exert a depressing effect on nitrification, even when used in amounts as smaU as 12 pounds to 2,000,000 pounds of soil. Lime apparently counteracts the injurious effects of small applications of the sulfate and permits some stunulation of the process of nitrification. Manganese salts Salts of manganese are known to have marked influence on nitrification, and since manganese, as has already been stated, is one of the soil bases Some Effects ok Potassium Salts on Soils 577 replaced ])y potassium, it is of importance in this connection to note what its effects have been found to be. Kelley (1912), working with Hawaiian soils, found that those high in manganese had a stronger nitrifying power than those low in this element. However, the soils high in manganese were in a better physical condition, and their higher nitrifying power was attributed to this fact rather than to any difference in manganese content. Montanari (1914) found that manganese dioxide and manganese car- bonate apparently stimulated nitrification, while the sulfate exerted less stimulation or even depressed the process. Leoncini (1914) found that manganese dioxide increased nitrification when used in amounts as high as 2.2 per cent, but that heavier applications apparently had no influence. Brown and Minges (1916) determined the effect of various manganese compounds on nitrification and ammonification in Carrington clay loam. In the ammonification tests dried blood was used, and in the nitrification trials ammonium sulfate was used. Manganese chloride apparently had no effect on nitrification in amounts less than 0.5 per cent; but from that point on, increasingly heavy apphcations caused increased depression, until, with 5 per cent of the salt, nitrification was inhibited. With manganese sulfate there was decisive depression of nitrification when 0.5 per cent of the salt was used, but with increasingly heavy applications the results did not show an increasing depression. Manganese nitrate apparently depressed nitrification, the magnitude of depression inci'easing with the amount of the salt used. Manganous oxide in most cases depressed nitrification, altho definite conclusions regarding this point cannot be drawn from the data presented. Greaves (1916) found the chloride, the sulfate, and the nitrate of manganese toxic to ammonification in soil at concentrations of 68.6, 137.3, and 274.6 parts of added manganese, respectively, to 1,000,000 parts of soil. The carbonate of manganese was without effect even at the highest concentration used, 6045.6 parts per million. Olaru (1915) reports three experiments on nitrogen fixation in nutrient solutions with varying amounts of manganese. He found that stimulation of the process resulted from all the concentrations of manganese used, but that the proportion of 1 part of manganese to 200,000 parts of solution gave the greatest stinmlation. Olaru suggests that increases in 578 R. S. Smith crop yioUls which have been found to follow the use of fertilizing materials are clue, not only to the direct action of the materials on the plants, but also to their modification of the bacterial activities of the soil. There appears to be much conflict in the data cited regarding the effect of manganese compounds on nitrification. In some cases very low con- centrations of the various salts proved to be toxic, while in others relatively high concentrations were stimulative. Too little information is given regarding the nature of the soil used in the various experiments to permit any attempt to account for the discrepancies. EFFECT OF REACTION OF THE SOIL ON NITRIFICATION The reaction of the soil is generally considered to be an important factor in determining its capacity to support a vigorous nitrifying flora. Brown (1911:55) apparently takes an extreme position when he says: " The effect of lime on nitrification and the necessity for the presence of lime in the soil for the process to occur, have long been a matter of common knowledge." The literature bearing on this problem is voluminous and no attempt is made here to summarize it. The stimulating action of lime on nitrifi- cation is generally conceded, but apparently the process may go on in soils very deficient in lime. Fred and Graul (1916) state that " it seems that under laboratory conditions, the beneficial effect of calcium carbonate on plant growth must be accounted for by some processes other than the direct effect on nitrification." Temple (1914) and White (1914) report vigorous nitrifica- tion in strongly acid soils. In the work herein reported, the heaviest treatments with the chloride and the sulfate of potassium caused a slight increase in the lime require- ment of the soils, but in no case was the increase more than 300 pounds of calcium carbonate to 2,000,000 povmds of soil. This small difference in reaction is not considered significant so far as nitrification is concerned, particularly in view of the fact that nitrification has been shown to proceed in strongly acid soils. The increasing depression in nitrification which will be shown to have accompanied increasingly heavy applications of the potassium salts must be accounted for on some basis other than increased acidity. Some Effects of Potassium Salts on Soils 579 interchange of bases As stated by Sullivan (1907), the fact that water is purified by filtration thru sand was known in the time of Aristotle. That common salt can be removed from water by filtering the water thru sand or soil has likewise been known for many years. Hilgard (1911 : 267) states that the latter is a clearly physical effect. When neutral salt solutions are filtered thru soil, the filtrate may be either acid or alkaline, depending on whether the cation or the anion of the salt has been removed the more strongly. This phenomenon has been attributed to selective ion adsorption. Truog (1916) and Sullivan (1907) think that it is better accounted for by an exchange of bases, in which iho base of the soluble salt interchanges in part with the iron or the aluminium of the soil. The salts of the latter metals hydrolyze strongly in dilute solution and give an acid value. The fact that soils enter into a chemical exchange with salt solutions was recognized at an early date by Thompson (1850), who found that an ammonium sulfate solution filtered thru soil gave up its ammonium in exchange for calcium. Way (1850, 1852, 1854), in a number of experi- ments, extended the observations of Thompson and found that the nitrates, the chlorides, and the sulfates of ammonium, potassium, sodium, and magnesium, when filtered thru soil, exchanged their bases for calcium from the soil. Way concluded that the active constituent of the soil entering into this interchange was a hydrated alumino-silicate of the clay fraction. It is now thought that any silicate is capable of entering into these reactions, according to Sullivan (1907). Peters (1860) found that the absorption of the cation of a salt in neutral solution was of about the same magnitude regardless of the form of com- bination. Thus, he found that potassium was absorbed in about equal amount from equivalent solutions of ils. Four wheat plants were grown in each flask by using a paraf- fin (h1 paper cover thru which four holes were punched to receive the rootlets. The plants were allowed to grow for four weeks. They were then removed, photographs were taken of the roots, and the dry weights were determined. Nitrification In th(> nitrification trials, tumblers were used for containers and 100 grains of soil was placed in each tumbler. Three nitrifiable materials — ammonium sulfate, ammonium hydroxide, and dried l)lood — were used. •Official and provisinnal methods of analysis, Association of Official Agricultural Chemists. U. S. Bur. Chum., Bui. 107. 1912. Some Effects of Potassium Salts on Soils 585 The ammonium sulfate and the ammonium hydroxide were appHed in dikite sohition, and the dried blood was well mixed with the soil on a piece of oilcloth. The cultures were incubated at room temperature and were brought to weight every six days with distilled water. Excessive evapora- tion was prevented by covering the tumblers with a layer of cotton placed between pieces of cheesecloth. The period of incubation, percentage of moisture maintained, and nitrifiable material used, are shown with each table in which the results are given. Nitrates were determined by the phenoldisulphonic-acid jnethod as described by Schreiner and Failyer (190G). Soil acidity determination The lime requirement of the soils was determined by a modified Veitch method (White, 1914). EXPERIMENTAL RESULTS Pot cultures The crop on the Hagerstown and Dekalb soils was attacked by sparrows on the afternoon of the day before it had been intended to harvest the pots, and as a result only the yield of straw is given. In the case of the Volusia soil, the probable error of the average for the quadruplicate pots is so high as to render most of the possible comparisons of questiona])le value. The probable errors were computed by means of Peter's formula as given by Mellor (1909), -( + v) R = ± 0.8453 - , n v^i-1 in which - (+ v) denotes the sum of the deviations of each observation from the mean, disregarding their sign, and n denotes the number of observations made. The results of the pot experiments are given in tables 3 and 4. Potassium sulfate increased the yield of straw over the check in both the Hagerstown and the D(4vall) soil. In the Plagerstown soil there was a continued increase in yield with an increase in the rate of application after 500 pounds was reached. In the case of the Dekalb soil the data are not conclusive, except that, as witli the Hagerstown soil, there is no evidence of a toxic condition with any of the treatments. 586 R. S. Smith TABLE 3. Yield of Wheat Straw in Pot Cultures with Hagerstown and Dekalb Silt Loams (Lime requirement of soils just satisfied) Pot Pounds of K.SO, to 2,60(),0()() pounds of soil Yield of straw in grams Duplicates Average Pounds of KCl to 2,000,000 pounds of soil Yield of straw in grams Duplicates Average 1 2 3 4 5 6 1 2 3 4 5 6 200 500 1,000 2,000 3,000 200 500 1,000 2,000 3,000 Hagerstown silt loam 4.36 4.25 5.56 5.26 5.02 5.15 6.70 4.85 6.50 5.65 6.69 16.16 Dekalb silt loam /1. 85 1.87 1.82' 1.92 1.85 1.8S 1.59 1.71 2.08 l.SS 2.01 2.10 4.31 5.41 5.09 5.77 S.08 6.43 86 87 86 65 98 2 06 200 500 1,000 2,000 3,000 200 500 1,000 2,000 3,000 4.12\ 4.18 ■ 4.45 4.37 4.87 4.07 3.91 3.95 3.86 4.02 3.11 3.41 4.15 4.41 4.47 3.93 3.94 3.26 1.95 1.91 1.79 1.94 1.68 1.68 Potassium chloride apparently became toxic at the lOOO-poiind treat- ment with the Hagerstown soil and at the 200()-pound treatment with the Dekalb soil. The data, however, are not conclusive, and warrant only tentative conclusions regardino; the rate of application necessary to bring aI)out a toxic condition in these soils. Some Effects of Potassium Salts on Soils 587 TABLE 4. Yield of Wheat Straw and Grain in Pot Cultures with Volusia Silt Loam Series Pounds of KCl to 2,000,000 pounds of soil Straw (average of quadruplicates, in grams) Grain (average of quadruplicates, in grams) I No lime; lime requirement 3393 pounds CaCOa to 2,000,000 pounds of soil 200 500 1,000 2,000 6.3±0.41 6.5±0.45 6.6 ±0.40 6.7±0.14 8.6±0.44 3 03 ±0.10 3. 14 ±0.18 3.17±0.13 3.22±0.13 3.85 ±0.19 II Lime requirement just satisfied 200 500 1,000 2,000 8.8 ±0.85 7.2±0.37 6.6 ±0.23 7.4±0 13 7.9 ±0.13 4 09 ±0.62 3:46 ±0.30 2 79 ±0.13 3 12 ±0.12 3.59 ±0.05 III 4000 pounds CaCO,, to 2,000,000 pounds of soil in excess of lime requirement 200 500 1,000 2.000 12.1 ±0.76 13.4 ±0.53 10.7 ±0.22 15.5 ±2.45 11.9 ±0 33 6.06 ±0.68 5. 13 ±0.66 2.80 ±0.44 5.18 ±0.64 4.14 ±0.12 Soil extract cultures Both the root and the top growth of the wheat seedhngs were very uniform in the duphcate water extract cuhures. The dry weights, how- ever, while uniform between duphcates, did not give a good measure of the comparative root growth betweeii cultures, and consequently are not reported. The presence of some toxic substance or substances in certain of the cultures is indicated in figures 161 to 163. The sensitiveness of the roots of seedlings to toxic substances has been adequately demonstrated by Schreiner and his associates in the United States Bureau of Soils, and by Breazeale and LeClerc, of the Laboratory of Plant Physiology of the United States Department of Agriculture. In the extract from the Hagerstown soil (fig. 161) the chloride is seen to have stimulated root growth thruout the series, the greatest degree of stimulation resulting from the 500-pound treatment. In the sulfate series there is seen a progressive stimulation of root growth up to the 588 R. S. Smith Fig. 161. root growth of wheat seedlings in water extracts from hagerstown silt loam which had received varymg amounts of the chloride and the sulfate of potassium Fig. 102. root growth (jf wheat seedlings in water extracts from dekalb silt loam WHICH HAD received VARYING AMOUNTS OF THE CHLORIDE AND THE SULFATE OF POTAS- ' SIUM Some Effects of Potassium Salts on Soils 589 2000-pound treatment, and a marked toxicity with the 3000-pound treat- ment. These latter results agree in the main with the yield of straw in the pot cultm-es except in the case of the heaviest sulfate treatment. In this case the extract cultures showed strong toxicity, while no such condition was present in the pot cultures. In the extract from the Dekalb soil (fig. 162) no distinct toxicity was shown in any of the cultures when compared to the checks. The checks, however, were apparently toxic. With the chloride the 200-pound treat- ^PL jpa^ ipi ^^^S^^^^Em^^^S jraH! mi ^.^ffl_4Un--JrPi- JEEBSL Ml ' r Fig. 163. root growth of wheat seedlings in water extracts from volusia silt loam WHICH HAD received VARYING AMOUNTS OF POTASSIUM CHLORIDE, BOTH WITH AND WITH- . OUT LIME ment caused the greatest stimulation of root growth, while with the sulfate there was little difference between the degree of stimulation in the 200- and the 500-pound treatments. These results are not reflected in the yields from the pot cultures. The yields from the pots were very small and the final weights are probably not a good index of the relative vigor of growth. In the Volusia extract cultures (fig. 163) the important point l)rought out is the neutralization of the toxic condition by the calcium carbonate. 590 R. S. Smith A distinctly toxic condition was evident in the no-lime scries with the heavier chloride treatments. This condition was less pronounced in the series receiving enough lime to just meet the lime requirement of the soil, and almost entirely disappeared when 4000 pounds of lime to 2,000,000 pounds of soil in excess of the lime requirement of the soil was used. Nitrification As a measure of the activity of the nitrifying organisms in the variously treated soils, determinations were made of the nitrates accumulated over long periods of time and of the nitrification of added materials. The accumulation of nitrates in the three soils used is shown in tables 5, 6, and 7, respectively. The figures represent the milligrams of nitrate nitrogen in 100 grams of soil as determined when the pots were set up and at stated intervals thereafter. The difference between the initial nitrate content and that after a given interval represents the actual TABLE 5. Accumulation op Nitrates in Hagerstown Silt Loam as Determined AT Intervals after the Experiment Was Set U^p (Moisture content, 24 per cent) Pounds of potassium salt to 2,000,000 pounds of soil Rlilligrams of nitrogen as nitrates in 100 grams of soil At time of setting up experi- ment After 33 days After 61 days After 86 days (KCl) 1.90 2.12 1.66 1.50 Trace 1.41 2.50 1.86 1.80 1.94 2.09 2.04 3.33 3.07 2.91 2.82 3.02 3.26 3.10 200 2.86 500 3.05 1,000 2.94 2,000 2.82 3,000 2.83 0. (K.SO4) 1.53 1.96 1.68 1.69 2.15 1.46 2.06 2.53 2.83 2.61 2.53 2.54 3.88 3.22 3.65 3.89 3.81 3.97 3.87 200 3.60 500 1,000 3.35 4.06 2,000 4.40 3,000 4.48 Some Effects of Potassium Salts on Soils 591 accumulation, or, in some cases, loss. In the case of the Volusia soil, nitrate accumulation was determined but once, after a seven-months period. TABLE 6. Accumulation op Nitrates in Dekalb Silt Loam as Determined at Intervals after the Experiment Was Set Up (Moistu re content, 24 per cent) Pounds of potassium salt to 2,000,000 pounds of soil Milligrams of nitrogen as nitrates in 100 grams of soil At time of setting up experi- ment After 33 days After 61 days After 86 days 0. (KCl) Trace Trace Trace Trace Trace Trace 0.65 0.40 0.49 0.68 0.36 Trace 1.14 0.92 1.04- 0.91 0,60 0.49 1 69 200 1 36 500 1 56 1,000 2,000 1.44 1 27 3,000 69 (K0SO4) Trace Trace Trace Trace Trace Trace 0.71 0.70 0.67 0.89 0.81 0.63 1.44 1.31 1.65 1.86 2.13 1.87 1 25 200 500 1.97 2.27 1,000 2.71 2,000 2.16 3,000. ... 2.08 It will be noted that in every case the potassium chloride decreased the accumulation of nitrates, and that the depression increased regularly with an inci'ease in the amount of chloride applied except for one or two minor exceptions. In the Volusia soil the degree of depression with the heavy chloride treatments was less in the lime series than in the no-lime series, indicating the tendency of the lime to overcome the harm- ful effects of the potassium chloride. Potassium sulfate seems to have exerted a stimulating effect on nitrate accumulation. In the Dekalb soil the greatest degree of stimulation occurs with the 1000-pound treatment, and then there is a gradual decline with the two heavier treatments. 592 II. S. Smith TABLE 7. Accumulation of Nitrates in Volusia Silt Loam after Seven Months (Moisture content, 30 per cent) Pounds of KCl to 2,000,000 pounds of soil Milligrams of nitrogen as nitrates in 100 grams of soil Series At time of setting up experi- ment After seven months 1 No lime; lime rcciuirement 3393 pounds CaCOs to 2,000,000 pounds of soil 200 500 1,000 2,000 2.00 2.00 2.00 2.00 2.00 6.06 5.55 4.88 3.77 2.32 II Lime requirement just satisfied 200 500 1,000 2,000 2.00 2.00 2.00 2.00 2.00 7.50 7.14 5.97 4.81 4.08 III 4000 pounds CaCOs to 2,000,000 pounds of soil in excess of lime requirement 200 500 1,000 2,000 2.00 2.00 2.00 2.00 2.00 9.76 9.09 8.69 7.01 6.45 With the twenty-one-days incubation period (tables 8 to 10), all of the soils in which the lime recjuirenient was just satisfied show the initial depression of nitrification with the 1000-pound treatment of the chloride. When ammonium hydroxide was the nitrifiable material added (table 10), altho the initial (h^pression occurred at this point the nitrates found in the heaviest chloride treatment exceeded those in the ciieck, indicating perhaps some action due to the basic nature of the hydroxide. In the Hagerstown soil treated with potassium sulfate (table 8), nitrification was depressed slightly b(^low that in the check with the heaviest sulfate treatment. This was not the case in the Dekalb soil (table !)), altho in the latter soil the 8000-poimd treatment caused less stimulation of the jirocess than did the 2000-pound treatment. Some Effects of Potassium Salts on Soils 593 TABLE 8. Nitrification in Hagerstown Silt Loam When Ammonium Sulfate Is Used (Moisture content, 24 per cent; incubation period, 21 days) Nitrogen as nitrates in 100 Nitrogen in (NH4)2S04 grams of soil nitrified Pounds of potassium salt to 2,000,000 pounds 21.2 milli- of soil Chock grams N Milligrams Per cent (milligrams) added (milligrams) (KCl) 3.11 13.98 10.87 51 27 200 2. SO 14.42 11.56 54.52 500 3.05 14 93 11.88 56.03 1,000 2.94 12.95 10 01 47 21 2,000 2. 82 10 94 8.12 38.30 3,000 2.83 8 . 28 5 45 25 70 (K2SO4) 3.87 17.18 13.31 62.31 200 3.60 16.80 13.20 62.26 500 3.35 17.52 14.17 66.83 1,000 4.06 19.03 14.97 70.61 2,000 4.40 21.60 17.20 81 . 13 3,000 4.48 17.64 13 16 62 07 TABLE 9. Nitrification in Dekalb Silt Loam When Ammonium Sulfate Ls I'sed (Moisture content, 24 per cent; incubation period, 21 days) Pounds of potassium salt to 2,000,000 pounds of soil Nitrogen as nitrates in 100 grams of soil Check (milligrams) 21.2 milli- grams N added (milligrams) Nitrogen in (NH4)2S04 nitrified Milligrams Per cent (KCl) ....... . 200 500 1,000 2,000 3,000 (K2SO4) 200 500 1,000 2,000 3,000 1.69 1.36 1.56 1.44 1 27 0.67 3.49 4.28 3.61 2.21 1.21 1.76 2.13 2.72 2.17 0.94 0.52 1.25 1.97 2.27 2.71 2.16 2 OS 3.62 3.58 4.76 5.55 5 74 4.82 2.37 1.61 2.49 2.84 3.58 2.74 8.30 10.04 12.83 10.23 4 43 2 45 11 17 7.59 11 74 13 39 16.88 12 92 594 R. S. Smith The beneficial action of lime is again brought out in table 10. Here it is shown that in the no-limc scries depression in the nitrification of ammonium hydroxide accompanied the application of potassium chloride. Wlien the lime requironKMit of the soil was just satisfied, the initial depression occurred with the 1000-pound treatment, and when lime was used in excess of the lime requirement the initial depression occurred with the 2000-pound treatment'. TABLE 10. Nitrification in Volusia Silt Loam When Ammonium Hydroxide Is Used (Moisture content, 30 per cent; incubation period, 21 days) Nitrogen as nitrates in Nitrogen i n NH4OH 100 grams of soil nitrified Pounds of KCl to Series 2,000,000 21.2 milli- pounds Check grams N MilU- Per of soil (milli- grams) added (milli- grams) grams cent I 6.05 8.19 1.94 4.7.3 No lime: lime requirement .3.393 200 5.88 7.41 1.53 3.73 pounds of CaCOa to 2,000,000 500 4.88 6.25 1.37 3.34 pounds of soil 1,000 4.54 6.00 1.46 3.56 2,000 2.70 3.50 0.80 1.95 7.09 11.11 3.42 SM II 200 5.58 10.96 5.38 13.12 Lime requirement just satisfied 500 1,000 5. 33 5.12 12.50 10.77 7.17 5.65 17.48 13.78 2,000 3.33 7.41 4.08 9.95 III 11.11 17.02 5.91 14.41 200 11.11 20.00 8.89 21.68 4000 pounds of CaCOs to 500 9.20 20.00 10.80 26.34 2,000,000 pounds of soil in 1,000 8.00 19.52 11.52 28.10 e.xcess of lime requirement 2,000 7.41 16.02 8.61 21.00 The results from the use of dried blood as the nitrifiable material are given in table 11. Here again the beneficial action of lime in counteracting the ill effects of potassium chloride is shown very strongly. It is possible that a longer incubation period would have allowed more nitrification in Series I. An acid condition is apparently very unfavorable to the nitrification of dried blood. Some Effects of Potassium Salts on S- Roy. Agr. Soc. England. Journ. 15:491-514. 1854 White, J. W. The results of long continued use of ammonium sulphate upon a residual limestone soil of the Hagerstown series. Pennsylvania State Coll. Agr. Exp. Sta. Ann. rept. 1912-13:55-104. (References on p. 99, 102-104.) 1914. Memoir 32, The Carbon Dioxidi- of the Soil Air, the third preceding number in this series of publica- tions, was mailed on August 19, 1920. LIBRftRY OF CONGRESS 002 762 348 7 • •j« ,