50 



Journal of Agricultural Research voi. xix, no. a 



Table III. — Effect of calcium sulphate on the solubility of washed soils held at low water 



content for jo days 



Inasmuch as acid phosphate contains both calcium sulphate and 

 calcium phosphate, a series was run in which the soils were treated with 

 a saturated solution of calcium sulphate, a N/io calcium phos- 

 phate, and also a combination of the two. After treatment the soils 

 were washed as in the series described above and let stand at the high 

 water content 30 days. At the close of the period the concentration of 

 the soil solution was determined by the freezing-point method. The 

 results are given in Table IV. 



Table IV. — Effect of calcium sulphate and calcium, phosphate alone and in com-bination 

 on the solubility of soils after jo days 



Kind of soil and treatment. 



Sandy loam: 



Treated with calcium sulphate 



Treated with calcium sulphate and calcium phosphate 



Treated with calcium phosphate 



Untreated 



Silt loam: 



Treated with calcium sulphate 



Treated with calcium sulphate and calcium phosphate 



Treated with calcium phosphate 



Untreated 



Freezing- 

 point 

 depressions. 



'C. 



3- 134 

 .094 

 .028 

 •035 



. 096 

 .084 

 .032 

 . 042 



A glance at the data composing Table IV reveals that the calcium 

 sulphate in the presence of the calcium phosphate is somewhat less active 

 in changing the rate of solubility of these soils than it is when used alone. 

 Moreover, where the calcium phosphate alone is added to the soils the 

 solubility is somewhat lessened. This is in accord with the results re- 

 ported by Bouyoucos.^ 



> BorrYOUcos, George J. rate and extent op soltjeility op seas under dipperbnt treatments 

 AND CONDITIONS. Mich. Agr. Exp. Sta. Tech. Bui. 44, 49 p. 1919. 



