JOMALOFACMaiLTlALlSEARCH 



Vol. XIX Washington, D. C, April 15, 1920 No. 2 



EFFECT OF CALCIUM SULPHATE ON THE SOLUBILITY 



OF SOILS 



By M. M. McCoOL, Professor of Soils, and C. E. Millar, Associate Professor of Soils, 

 Michigan Agricultural Experiment Station 



Additional information on the rate of formation of soluble salts in 

 soils as affected by different factors is desirable. One phase of the sub- 

 ject of special interest is the immediate and residuary effects of fertil- 

 izing materials on soils. It seems that aside from its theoretical interest 

 such information should be of assistance in accounting for results that 

 are obtained from the use of certain substances under field conditions. 

 We have interviewed several of the earlier settlers in southern Michigan 

 and have been informed by them that calcium sulphate was used rather 

 freely by some farmers during the earlier stages of the State's agricul- 

 tural development. The general impression of those whom we inter- 

 viewed is that the application of calcium sulphate resulted favorably 

 for a time, increasing the yields of small grains and clover, but later on 

 failed to bring the desired results ; hence this substance came to be looked 

 upon as a soil stimulant. Some farmers are using it on wheat and clover, 

 although the amount so consumed is relatively small. According to 

 early reports, which are to be considered in a later publication, similar 

 conditions existed in the agricultural regions of some of the eastern 

 States. 



Because of the experiences of the early agriculturists, the increasing 

 interest in the fertilizing value of calcium sulphate, and the widespread 

 use of acid phosphate, which contains appreciable amounts of the sul- 

 phate, it was considered advisable to investigate the effect of the sul- 

 phate both alone and in junction with calcium phosphate on the formation 

 of soluble salts in soils, as well as the effect on the carbon-dioxid 

 production. The freezing-point method was used to determine the 

 former, and the titration method the latter. 



METHOD OF PROCEDURE 



In determining the effect of the chemicals on the rate of formation of 

 soluble salts, 200 gm. of the soils in question were brought into contact 



Journal of Agricultural Research, Vol. XIX, No. 2 



Washington, D. C. Apr. is, 1920 



tv Key No. Mich.-io 



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