1912] 



Fred J. Seaver and Ernest D. Clark 



419 



extracts of unheated soils. The organic matter thus made soluble 

 is always greater in amount than the inorganic matter, but the latter 

 is also considerably increased. We now turned our attention to a 

 study of the effect of exposing the soil to different intensities of 

 heat for the same period of time. The manner of handling the soil 

 for these experiments was as follows : Ordinary loamy soil from 

 this vicinity was placed in pots properly labeled with the various 

 temperatures to which they were to be heated. They were all 

 placed in a large hot-air sterilizing oven and were heated until the 

 thermometer in the soil indicated 90 . This temperature was main- 

 tained for two hours, when the pot marked 90 was removed. The 

 temperature was then increased to 120 , and maintained there for 

 two hours, when the corresponding pot was taken out. This 

 process was repeated in each case until the different series of heated 

 soils were obtained. The extracts of the various soils were then 

 prepared by percolating 3 kg. samples of the soils with about two 

 liters of distilled water. We saved the first 350 c.c. that came 

 through and used two 50 c.c. portions for the determination of sol- 

 uble matter and total nitrogen. The remainder of each extract was 

 reserved for cultural experiments with seedlings, etc. 



TABLE I. 



Effect of Different Temperatures upon the Soluble Matter in Soils 



TABLE 2. 



Conditions Similar to Those Stated in the Heading of Table 1 



