UNIVERSITY OF CALIFORNIA PUBLICATIONS

IN

AGRICULTURAL SCIENCES

Vol. 3, No. 10, pp. 271-282 June 22, 1918

DOES CaCOa OR CaSO* TREATMENT AFFECT

THE SOLUBILITY OF THE SOIL'S

CONSTITUENTS?

BY

C. B. LIPMAN and W. F. GERICKE

In 1850, Thompson1 showed that when soil is shaken with a solution of sulphate of ammonia, calcium sulphate is brought into the solu- tion. Using this observation as a basis, Way2 proceeded, in a classical investigation, to study the nature of the phenomenon. He found that when the calcium sulphate goes into solution as observed by Thompson, there is an amount of base in the form of calcium and of other bases set free in the solution equivalent to the amount of ammonium base which is absorbed by the soil. From this fact and his observation that clay carries the constituent which thus reacts with the sulphate of ammonia, Way argued that there exist in the clay certain "double silicates" of the alkalies and alkali earths with aluminum, which are the active bodies in the reaction under consideration. He never proved that such double silicates actually exist in the "clay" of the soil, but believed them to be present there because his artificially prepared double silicates of calcium and aluminum, of sodium and aluminum, and others, behaved toward salt solutions like the clay, and lost their absorptive and reactive powers, like clay, on ignition. In contra- distinction to Liebig's view that the precipitation by soils of salts from solution constitutes merely a physical phenomenon, Way believed that the Thompson experiment, which typifies such soil-salt phenomena, represents, really, a chemical reaction. Way's view became generally

i Thompson, H. S., On the absorbent power of soils, Jour. Roy. Agr. Soc, vol. 11, p. 68, 1850.

2 Way, J. T., On the power of soils to absorb manure, ibid., vol. 11, p. 313, 1850, and vol. 13, p. 123, 1852.

272 University of California Publications in Agricultural Sciences [Vol. 3

accepted and has been taught and is still very largely taught in the agricultural colleges today under the subject of "fixation" or "ex- change" of bases in soils. The presence in the soil of double silicates or zeolites was thus assumed by soil investigators, and Hilgard gave the idea much prominence in connection with his methods and hypotheses on soil analysis. Further, the idea served as a basis for the use, by Lawes and Gilbert, of sodium sulphate and of magnesium sulphate in connection with the application of fertilizers to their experimental plots with the end in view of setting free potassium, from its silicate combinations in the soil, for use by the plant.

All of this has led to the statement, universally employed by authors of texts on soils, that the application of lime and gypsum to soils results, among other changes wrought by them, in the making "avail- able" of potassium and other ions* of a similar nature. As recently as 1907, Hall and Gimingham3 adduced experimental evidence on the interaction between clay and ammonium sulphate, which appeared to mark that reaction as one obeying the mass law, thus seemingly lend- ing support to the validity of Way's hypothesis. Hall and Giming- ham's evidence was soon shown by Cameron and Patten4 to be in- complete, however. They demonstrated that the mass law does not hold when a wider range of concentrations than that employed by the former investigators is tested and a new Ivypothesis was necessary to explain it. This was furnished by Van Bemmelen, who proved that absorption by soils was closely parallel to that by colloids which he had studied, and which may be explained by the formula y/m<=Kc1/n in which y is the amount absorbed by a quantity m of the absorbent, c the con- centration of dissolved substance when equilibrium is attained, and K and n are constants depending on the nature of the solution and the adsorbent. Such a formula has since been shown to hold for absorp- tion of phosphates by Prescott5 and for absorption of ammonium salts by Wiegner.6 In accordance with this conception of the soil as a colloid-containing body, the colloidal particles possess the power of holding ions which are adsorbed from salt solutions and give such ions up with relative facility to new solutions containing other ions for which they are substituted.

* In this case, and throughout this paper, the term "ion" is not used in the literal sense It is not intended to convey the idea that the authors believe that a given ioi by itself is absorbed or set free, for we are actually inclined to the belief that in these cases, as in absolu- tion by plants, not ions, but compounds, are absorbed as units.

•"• ITall, A. D., and Gimingham, C. T., The interaction of ammonium salts and the constituents of the soil, Trans. Chem. Soc, vol. 91, p. 677, 1907.

4 Cameron, F. K., and Patten, II. E., The distribution of solute between water and soil, .lour. I'hys. Chem., vol. 11, j). 581, 1907.

19] 8] Lipman-GericJce : CaCOs and CaS04 and Soil Solution 273

This idea has, however, been confused with the zeolitic hypothesis from which, in some respects, it is quite distinct. Due to both concepts, the teaching is still largely in vogue that CaC03 and CaS04 possess as one function in soils a power to set potash and other bases free from their insoluble combinations. In spite of the general acceptance of this view, however, some practical agronomists have called it in ques- tion and it seems necessary to determine if the hypothesis and the laboratory experiments used in support thereof are valid. Briggs and Breazeale7 have recently made an attempt to answer definitely the question as to whether or not lime or gypsum applied to soils does affect the potassium content of the soil solution produced by ortho- clase, pegmatite, or orthoclase-bearing soils in contact with water. They checked their results b}^ growing young wheat seedlings in the solutions produced by the treatment of the mineral or soil with lime or gypsum and water. As a result of these experiments, they con- clude that the "availability to plants of the potash in soils derived from orthoclase-bearing rocks is not increased by the addition of lime or gypsum. In some instances, a marked depression of the solubility of the potash in the presence of gypsum was observed." While the authors specifically refer to "soils derived from orthoclase-bearing rocks," the statement carries the implication, owing to the stated object of their investigation, that the potash-bearing silicates of any kind in soil are not likely to be affected in solubility by the addition to the soil of lime or of gypsum. The fact that this conception is con- trary to what one would expect from theoretical considerations regard- ing soil-solution reactions, appeared to render it desirable to investigate the subject farther. We therefore planned and executed the following experiment :

Calcium carbonate or calcium sulphate were each added to soils, and throughly mixed with them in the different cases as further indicated in the tables. The soils thus mixed were placed in pots in the green- house. Water was added to make optimum moisture conditions and such moisture conditions were maintained for a period of nine months. Three soils were used, viz : Oakley blow sand, Berkeley clay adobe, and a greenhouse soil, the latter having been originally made by admixing

s Prescott, J. A., The reaction between dilute acid solvents and soil phos- phates, Proc. Chem. Soc, vol. 30, p. 137, 1914.

s Wiegner, Georg., Zum Basenaustausch in der Ackererde, Jour. Landw., vol. 60, pp. 110 and 197, 1912.

7 Briggs, L. J., and Breazeale, J. F., Availability of potash in certain ortho- clase-bearing soils as affected by lime and gypsum, Jour. Agr. Ees., vol. 8, p. 21, 1917.

274 University of California Publications in Agricultural Sciences [Vol. 3

barnyard manure with the Berkeley clay adobe soil. The applications of CaC03 and of CaS04 were made on March 9, 1917, and in the manner and quantities indicated in the tables. Control soils, untreated with either lime or gypsum, were, of course, included in the experi- ment, but were otherwise treated like the other soils. The soils in all pots were sampled three times, at considerable intervals, as shown in the tables. The samples were taken so as to represent the whole depth of the soil layer in the pot and of different parts thereof. Eight hundred gram portions of these samples, in air-dry condition, were mixed with 1600 cc. of distilled water in large bottles and allowed to digest for six days with occasional shaking during every day. After six days, the solutions were filtered through Pasteur-Chamberland pressure filters and analyzed by gravimetric or volumetric methods for the constituents named in the tables. Large enough aliquots could be employed, owing to the method which we have devised and described above for mixing the soil and water, to insure accurate results by the standard methods of analysis intended for larger quantities of the same substances. We employed no checking system by means of germinating plants, such as that used by Briggs, because (1) we do not believe that a few days' growth of plants constitutes any reliable criterion regarding any factor in plant growth, and (2) the evidence obtained by Burd, Hoagland, and Stewart has demonstrated that for plants grown to maturity, an intimate relation holds between the nature of the soil solution and absorption of nutrients by plants grow- ing in such soil solutions in every stage of growth. In other words, we contented ourselves with trying to determine whether or not the soil solution is enriched with respect to potassium and other elements by the treatment of soil with CaC03 or with CaS04 as indicated by the composition of the soil extracts obtained by us. The results of the analyses of the soil extracts are shown in the subjoined tables, in which the amount of every ion sought and found in the solution is expressed in parts per million of the soil.

For the sake of greater simplicity and brevity, we shall at first discuss the tables separately.

Tn table 1, we see the results obtained with the Oakley soil, from which it is clear that both lime and gypsum are without effect on the amount of water soluble potassium in that soil. The latter behaves in this respect like the Oatman soil from Riverside County in this state, which Brings and Breazeale have studied. There is little reason to believe, likewise, from the data under consideration that the water

1918]

Lipman-Gerlcle: CaCO-> and CaS04 and Soil Solution

Table 1. Oakley Soil

Treatment :	Date		Fe	Ca	Mg	S	K	P
Rate per acre kilograms	of samplin	g		In parts per mill	ion of dry	soil
Control	Apr. 9,	'17	1.0	16	2.3	17	9.1
500 CaCC-3	Apr. 9,	'17	3.6	23	3.9	16	8.1
1000CaCO3	Apr. 9,	'17	3.4	31	6.9	21	10.3
500 CaS04	Apr. 9,	'17	1.4	32	3.1	21	9.7
1000CaSO4	Apr. 9,	'17	1.4	63	1.0	20	10.7
Control	July 20,	'17	1.2	13	3.6	10	7.9	6.9
500 CaCC-3	July 20,	'17	2.0	27	6.7	10	7.8	5.8
1000 CaCOs	July 20,	'17	1.4	26	9.3	10	8.4	10.4
500 CaS04	July 20,	'17	1.4	26	1.6	23	8.3	5.5
1000CaSO4	July 20,	'17	1.4	62	0.9	45	6.9	8.1
Control	Dec. 24,	'17	1.4	24	1.3	19	8.8	6.7
500 CaCC-3	Dec. 14,	'17	1.4	31	1.3	14	9.1	7.2
1000 CaC03	Dec. 24,	'17	1.5	34	1.3	13	9.9	6.1
500 CaSo4	Dec. 24,	'17	1.0	44	1.7	30	7.3	6.7
1000CaSO4	Dec. 24,	'17	0.6	61	1.3	64	8.0	6.3
		Table 2.	Adobe Soil
Treatment :	Date		Fe	Ca	Mg	S	K	P
Rate per acre kilograms	of samplinj			In parts	5 per milli	ion of dry	soil
Control	Apr. 23,	'17	0.7	17	0.7		7.4
1000 CaC03	Apr. 23,	'17	0.7	25	1.4		12.8
1000 CaS04	Apr. 23,	'17	0.8	50	1.1		9.6
Control	July 20,	'17	0.7	32	2.1	32	9.7	7.2
1000CaCO3	July 20,	'17	0.7	34	4.2	31	15.0	7.8
1000CaSO4	July 20,	'17	0.7	78	2.1	124	12.4	7.5
Control	Jan. 2,	'18	1.6	47	2.6	32	8.3	5.6
lOOOCaCCv,	Jan. 2,	'18	1.6	46	2.6	31	8.8	6.1
1000 CaS04	Jan. 2,	'18	1.0	84		146	10.0	5.7
		Table	3. Greenhouse	Soil
Treatment :	Date		Fe	Ca	Mg	s	K	P
Rate per acre kilograms	of sampling		In parts	; per milli	on of dry	soil
Control	Apr. 20,	'17	7.8	83	9.3	40	14.4
500 CaC03	Apr. 20,	'17	15.5	112	19.5	42	15.3
lOOOCaCC-3	Apr. 20,	'17	8.3	115	25.5	49	25.4
500 CaSo4	Apr. 20,	'17	7.0	157	17.8	91	20.4
1000 CaS04	Apr. 20,	'17	7.8	210	6.7	106	27.0
Control	July 20,	'17	4.5	86	8.6	51	23.8	14.0
500 CaC03	July 20,	'17	7.8	91	20.6	86	25.0	12.3
1000CaCO3	July 20,	'17	5.6	104	24.3	82	38.6	12.3
500 CaS04	July 20,	'17	4.5	129	9.3	130	28.2	11.4
1000CaSO4	July 20,	'17	4.2	162	5.2	165	34.8	10.1
Control	Jan. 12,	'18	11.9	93	3.9	55	12.8	20.2
500 CaC03	Jan. 12,	'18	9.8	128	5.0	76	15.4	19.6
1 000 CaC03	Jan. 12,	'18	9.8	142	5.4	76	32.0	18.4
500 CaS04	Jan. 12,	'18	9.7	176	4.0	182	17.7	16.7
1000 CaS04	Jan. 12,	'18	9.8	171	4.3	219	22.4	17.1

276 University of California Publications in Agricultural Sciences [Vol. 3

soluble phosphorus and the water soluble sulphur in that soil have been affected by CaC03 and the first by CaS04. The calcium content of the solution is affected by both CaC03 and CaS04, as would be ex- pected, but which does not necessarily have to occur. On the other hand, the water soluble iron content of the soil appears possibly to be slightly affected by the CaC03 treatment, at least in the first sampling; and the magnesium content of the water extract shows, it seems to us, very distinct accretions, through the CaC03 applications, in the first and second samplings. The effect seems to have dis- appeared, however, by the time the third sampling was made and a new equilibrium is probably established. On the contrary, gypsum seems to depress the amount of water soluble magnesium in the soil solution of the Oakley soil. This appears to be definitely true by the time the period of the second sampling has been reached, and less definitely in the period of the first sampling with the larger gypsum application. Just as the tendency to increase in amount in the soil solution through the instrumentality of the treatment seems to char- acterize both the ions, magnesium and iron, in the periods up to and including the second sampling, a reverse tendency is manifested by these ions by the time of the third sampling. In the soils treated with CaC03, there is a definite decrease in magnesium, in the solution, in the period named and the iron content of the same soil solutions seems to decrease simultaneously. Yet the other ions do not seem to have been affected in that way in the same period, but have either remained stationary or have shown increases. These rather marked changes evidenced by the figures of the second and third samplings are even more distinct in the cases of the other soils, to which reference will be made below.

In the Berkeley clay adobe soil, the data for which are given in table 2, conditions are quite evidently not the same as in the Oakley soil. While the potassium content of the latter soil's solution remained unaffected by the application of either CaC03 or CaS04, that of the former soil seems to us to be definitely increased by both CaC03 and CaS04 in the first two samplings and by CaS04 alone in the last sampling. The greater effect in that direction is clearly induced, how- ever, by CaC03. The iron content of the soil solution in the clay adobe soil remains entirely unaffected by the treatment which is accorded the soil. The phosphorus content of the soil solution affected by CaCOa may, perhaps, be slightly increased in both the second and third samplings, but the data do not give us leave to be certain on

1918] Lipman-GericJce : CaCO-^ and CaSO± and Soil Solution 277

that point. The calcium and sulphur content of the soil solution behave as one would expect without experiment in the clay adobe soil treated with CaS04, but the calcium content of the same soil treated with CaCOg is affected to a small degree in some cases and not at all in others. The magnesium content of the clay adobe soil solution behaves similarly to that of the Oakley soil solution, but the increases due to CaC03 treatment of the soil are not as large in the former as in the latter. Again CaS04 seems to be without effect in that direction. In general, the behavior of the clay adobe soil solution, as judged by our analyses, parallels that of the Oakley soil solution in the third samp- ling, a condition of equilibrium, and, in general of a more dilute solution, having been attained. That does not hold, however, for the soil treated wTith CaS04. In general, therefore, the results obtained by us with the clay adobe soil, among other things, show a lack of agree- ment between our results and those of Briggs and Breazeale regarding the effect of CaC03 and CaS04 on the potassium content of the soil solutions in question.

Coming finally to a consideration of the greenhouse soil, we find in table 3 some very interesting data, and the most definite of any sub- mitted in all the tables, inasmuch as the changes due to soil treatment are so much larger than those characterizing the other soils. Con- sidering the data for potassium first, we find that marked increases in the amount of that ion in the solution of the greenhouse soil are induced by the larger application of CaC03 and by both the smaller and larger applications of CaS04. Moreover, even the smaller appli- cation of CaCO?> seems to induce the solution of definitely larger amounts of potassium than those found in the solution of the untreated greenhouse soil. In the periods of the first two samplings, the iron content of the soil extract seems to have been increased by the CaC03 applications, but not by the CaS04 applications. Moreover, the smaller CaCOg application seems to have been much more effective in that direction than the larger application. By the time of the third sampling, the effects just mentioned appear to have vanished, and in fact, it is possible that they have been supplanted by a depression in the amount of iron in the soil extract. The general direction taken by the effects of the soil treatment on the calcium content of the soil extract is wrhat one would expect a priori. The results indicate, how- ever, the inaccuracy of the method of determination considered, in the large, since the relations between the CaC03 and CaS04 applications in small and large amounts do not maintain themselves constant.

278 University of California Publications in Agricultural Sciences [Vol. 3

This holds, of course, for the other soils as well as for the greenhouse soil, indeed, more markedly so. The phosphorus content of the soil extract is certainly not increased, in the two determinations made, by the treatment of the soil under consideration. In fact, while it is difficult to appraise it as such, there seems to be a slight depression in the amount of the phosphorus present in the soil extracts of the treated, as against those of the untreated soils. The magnesium is affected in the greenhouse soil similarly to the manner in which it was influenced in the other soils, but, as in the case of the potassium, the results are much more emphatic. It is quite evident that large amounts of magnesium go into solution through the influence on the soil of CaC03 throughout the period of the experiment, but especially in the periods of the first two samplings. CaS04, on the other hand, only increases the amount of magnesium when employed at the smaller application and then only in the period of the first sampling. With the larger application of CaS04, in the first sampling and with both applications in the second sampling, there seems to be evidence of a depression in the magnesium content of the soil extract. In the third sampling, the CaS04 treated soils seem to behave like the control and furnish another instance of the phenomenon noted above in the case of the other soils. The sulphur content of the soil extract is more markedly affected by the treatment in question in the case of the green- house soil than any other constituent thereof which we have deter- mined. That is, perhaps, not surprisingly so in the case of the CaS04 treatment, but it is to be particularly remarked how very great such increases are even with the CaC03 treatment. Unlike the cases of the other constituents of the soil extract, moreover, that of the sulphur shows the effect of treatment even at the third sampling.

General Discussion

From a general survey of our results, a few facts stand out clearly. Of the seven ions which we have determined in the extracts of the soils treated with CaC03 or with CaS04, all, with possibly one excep- tion— phosphorus — are affected by the treatment in one or more of the three soils, in the directions either of increase or decrease in amount in the soil solution. The ions are not all affected by the treatment in any one soil, however. It appears that the nature of the soil minerals. jis well as the organic matter content of the soil, and hence probably the partial carbon dioxide pressures, are important factors in deter-

1918] Lipman-GericJce : CaCO:> and CaS04 and Soil Solution 279

mining how CaC03 or CaS04 will affect the soil reactions and the precipitation or the greater solution of given ions in any soil. This marked disparity between the nature of soil reactions and their results in different soils, seems to have been but slightly appreciated, if at all. among soil investigators. We therefore find, on the one hand, the iterated and reiterated statements in our text-books respecting the effect that lime or gypsum, or both, exert on the available potash supply in the soil solution; and, on the other hand, such statements as that by Briggs and Breazeale to which we have made reference above, which deny directly or inferentially the effectiveness of lime and gypsum, in that direction, for a certain soil or a certain mineral ; and through the absence of comparison with other soils imply the denial of the existence of such effects in general. As is freqently the case in all matters, the truth lies between these extreme views. Potas- sium from the soil minerals is rendered soluble in greater quantity than normally by applications to the soil of both CaC03 and CaS04 in some soils, but not in others. Of the three soils which we have studied, two seem to us to show clearly the former and one the latter effect.

"Working also with only one soil (Dunkirk clay loam), Lyon and Bizzell,8 by the indirect method of studying drainage water from lysimeters, and by the possibly direct method of studying absorption by plants, showed, prior to the work of Briggs and Breazeale, that liming of soils does not increase the potassium content of the drainage water, or of plant substance. But, it should be noted too, that in other respects their results are also at variance with ours. For example, they found that the application of lime to soil (to be sure it was CaO and not CaC03) did not increase, and in general, actually depressed the amount of calcium in the drainage water and hence probably, though not necessarily, in the soil solution; whereas we have found the calcium content to be higher and distinctly so in all soil extracts but one from soils treated with either lime or gypsum regardless of the soil 's nature. In our opinion, these apparent disagreements are really only manifestations of the marked differences characterizing the physical-chemical systems which we call soils in equilibrium with water. When we consider soils as such systems, dynamic and not static in nature, and in addition apply to them the Van Bemmelen formula for absorption by colloids, it is not difficult to understand the

s Lyon, T. L., and Bizzell, J. A., Calcium, magnesium, potassium and sodium in the drainage water and from limed and unlimed soils, Jour. Amer. Soc. Agron., vol. 8, p. 81, 1916.

280 University of California Publications in Agricultural Sciences [Vol. 3

discrepancies in the reactions between different soils and CaC03 or CaS04, which we have been studying. While thus we are in apparent disagreement with the principle of the indirect results of Lyon and Bizzell regarding the effect of lime on the calcium content of the soil solution, we are not actually so. On the other hand, we are in actual agreement with them as regards the effect of calcium applications on the magnesium content of the soil solution. In all soils studied by us. we find increases of magnesium in the soil solution, due to CaCO., applications, but this does not imply that the same would hold for all other soils. Again, we are in agreement with the indirect results of Lyon and Bizzell regarding the sulphur content of the soil solution as affected by lime applications in the case of the greenhouse soil, but not in the case of the clay adobe soil, and probably not in the case of the blow sand.

If we may repeat, therefore, we are apparently forced to conclude, from the results of our experiments and from such comparisons of them with those of others as we can make, that no general idea of the effect of CaC03 or of CaS04 on the potassium content of any other ion in the soil solution can be adduced from any one soil or from any one general kind of soil. In some soils, large accretions of soluble potas- sium to the solution may be obtained by CaC03 or by CaS04 applica- tions ; in others no increases may be obtained. This may hold for any ion, but does not preclude the probability that some ions may be rendered soluble in larger amounts by CaC03 in any soil. Whether or not the ions which are rendered soluble in greater amounts by the application to the soil of CaC03 or CaS04, or both, are also available in such larger amount to the plant roots is another question, an affirmative answer to which does not necessarily follow from such an answer to the question which we are discussing here. It is to be noted from our results, also, that the time of the year at which ions are sought in the soil solution, or at least the period elapsing between the application of CaCO., or of CaS04 to the soil and the sampling of the latter, are important factors in determining the results of one's findings and cannot be overlooked in any such investigations.

In anticipation of queries which may arise from readers of the fore- going discussion, we desire to make very clear and emphatic the follow- ing general statement. We do not believe that all of the data given by us in the tables are significant, because we appreciate the large error which probably attaches to our method of obtaining the soil extrad and of analyzing it. Our calculations are such, therefore, as

1918] Lipman-Gerichc: CaCOo and CaS04 and Soil Solution 281

not to be dependent, in any large degree, upon the significance of any isolated portion of our data. The table which we hold to be most significant is table 3 and the two chief conclusions which we desire to draw from our work are (1), that a soil may be distinctly affected, as regards the solubility of its constituents through its treatment with CaC03 or with CaS04 ; and (2) , that this is not necessarily so, however, and may hold for one soil and one constituent in one case, and not in another, depending on the nature of the physical-chemical systems dealt with and upon the composition of the soil mineral complexes. In these two conclusions from our experiment, one can find a reconciliation of the two diametrically opposed views with regard to the effects of CaC03 and CaS04 on soils and we offer our discussion as a contribu- tion to such a reconciliation.

Summary

From experiments to determine how CaC03 and CaS04 affect the water soluble iron, calcium, magnesium, potassium, sulphur, and phos- phorus in soils as determined by ordinary water extractions, the fol- lowing outstanding conclusions were drawn :

1. All soils do not behave alike when treated with CaC03 or with CaS04. They should not be expected to do so, considering th^ir mineral composition, the law of chemical equilibrium, and the nature of colloid action in soils. With this conception as a basis, the con- flicting statements in our literature on the effect of CaC03 and CaS04 on the soluble potassium supply in soils may easily be accounted for and each view may be regarded as correct under certain circumstances.

2. Potassium was found to be rendered more soluble by CaC03 and by CaS04 applications in clay adobe soil and in a greenhouse soil made therefrom, but not in a blow sand soil.

3. The soluble calcium content was increased in all soils studied by CaC03 or CaS04 applications. This does not prove that the same will hold true for all other soils.

4. The soluble magnesium content of all soils studied was increased by CaC03 treatment. It seems to have remained unaffected or even to have been depressed by CaS04 treatment in all but one case in each, the Oakley and the greenhouse soil with the small gypsum application.

5. The soluble iron content was probably increased in the solution of the greenhouse soil by the treatment in question. It seems also to

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University of California Publications in Agricultural Sciences [Vol. 3

have been so increased for a time in the blow sand, but not in the clay adobe soil.

6. The soluble sulphur content was increased in the solution of the greenhouse soil by CaC03 applications and probably also in that of the blow sand, due to similar treatment.

7. The phosphorus content of the solutions of the three soils studied seems to have remained unaffected by the treatments accorded the soils. The indications are, however, that a slight depression in the amount of the water soluble phosphorus may have resulted from the CaC03 or the CaS04 applications in one case. In this case also no generalization is attempted.

8. It seems that our current teachings on soils and plant physiology should be corrected with these results as a basis.

Transmitted June 4, 1918.