48 



Journal of Agricultural Research voi. xix, No. a 



with 500 cc. each of distilled water and the substance in solution, and 

 allowed to stand 24 hours with several thorough agitations. At the 

 close of this period the mass was transferred to filter paper in large fun- 

 nels. In some cases the soluble salts were reduced to a very low con- 

 centration by washing with distilled water, while in others the soils were 

 removed, after drainage had ceased, but otherwise treated in the same way 

 as in the former instances. The rate of formation of soluble substances in 

 treated and untreated soils was determined under two sets of moisture 

 conditions. The one which is here called low water content approx- 

 imated the so-called optimum condition for plant growth; and the other, 

 which is here called high water content, was secured by allowing i part 

 of soil to 0.7 part of water and provided sufficient moisture to saturate 

 the soil and leave a small column of about yi inch above it. 



Soils of the following description were used in all the experiments : 



Soil I, a silt loam, light phase, containing a large amount of organic matter. 



Soil 2, a heavy sand, rather low in organic content. 



Soil 3, a fine sandy loam with a medium supply of organic matter. 



Soil 4, a very fine sand containing a small amount of organic material. 



Soil 5, a very heavy silt loam with a very high content of organic matter. 



Soil 6, a silt loam well supplied with organic material. 



EXPERIMENTAL RESULTS 



The first series of experiments to be reported is the one in which the 

 soils were treated with calcium sulphate, drained, and made up to the 

 high water content, or i part of soil to 0.7 part distilled water. Treated 

 and untreated portions of each of the soils studied were placed in jelly 

 glasses, which were tightly covered and let stand in the laboratory. At 

 about 4-day intervals they were thoroughly aerated by stirring, the cov- 

 ers being removed for one-half hour or more. The soils employed were 

 air-dry and had been stored in the laboratory about 160 days. The 

 results are set forth in Table I. 



Table I .^Effect of calcium sulphate on the solubility of unwashed soils held at high water 

 content for various periods 



Soil 

 No. 



Condition of soil. 



Treated . . 

 Untreated 

 Treated. .. 

 Untreated 

 Treated . . 

 Untreated 

 Treated. .. 

 Untraeted 

 Treated. .. 

 Untreated 

 Treated. .. 

 Untreated 



Freezing-point depressions. 



After : 

 days. 



C. 



042 

 003 

 044 

 000 



043 



002 



04s 

 000 

 046 

 003 



045 

 008 



After 4 

 days. 



°C. 



o. 040 

 • 005 

 •045 

 . 004 

 .051 

 . 004 

 .050 

 . 002 

 .048 

 . 002 

 . 042 

 . 012 



After 6 

 days. 



"C. 



0.055 



.GOS 

 . 050 



• o°5 



• 054 

 . 006 

 .050 

 . 004 

 .051 

 . 004 

 .050 

 . 012 



After 8 

 days. 



C. 



058 

 on 



055 



007 



057 



007 



053 



006 



055 



006 



051 



or8 



After 10 

 days. 



"C. 

 0.063 

 .013 



•059 

 . 009 

 .058 

 .008 



•055 

 . 010 

 .058 

 . 012 

 .052 

 . 024 



After 30 

 days. 



091 

 024 

 080 

 on 



057 

 014 



138 

 017 



075 

 018 

 089 

 032 



