424 Biochemical Studies of Heated Soils [Mar. 



Experiment I. Ten pots of common unfertilized New York 

 soil were prepared; two of these were kept as controls and two 

 heated to a temperature of 90° C. for two hours, two to a temperature 

 of 120° for the same length of time, two to 150° and two to 170° C. 

 From one series of pots, extracts were taken by percolating equal 

 amounts of distilled water through each pot. Approximately the 

 same amount came through in each case. One hundred c.c. were 

 taken from each pot to be used for analytical purposes, As has 

 been previously noted, the extracts of heated soils are of a brown 

 color. In this series of experiments it was observed that the color 

 varied directly with the temperature; the control being colorless, 

 the extract from the soil heated to 90° being slightly colored, the 

 color becoming deeper in each case as the temperature increased. 

 The results of the chemical analyses of these extracts are given in 

 Table i (page 419). 



The other series of pots of soil which had been similarly heated, 

 but not extracted, were watered and planted with oats, the same 

 number of seeds having been placed in each pot. After about two 

 weeks the following results were obtained : the control and pot of 

 soil heated to 90° showed practically the same growth ; that heated 

 to 120° showed considerable acceleration ; and beyond this the growth 

 was retarded, the retardation in the pot heated to 150° and that 

 heated to 170° being nearly equal. The accompanying photograph 

 (Plate VII) shows the control, the pot heated to 120° C. and that 

 heated to 170°, the contrast being greatest at these points. 



Experiment II. In order to check the results obtained in one 

 of the experiments just described, a second series of pots of ordi- 

 nary New York soil were set up and heated in the manner already 

 stated. In this case the series consisted of an unheated control, and 

 three others heated to 90°, 150° and 180° C. respectively. Oats 

 were planted as usual and their condition noted, after germination 

 and about two weeks' growth had been made. In this series the 

 soil heated to 120° did not show the slight gain over the unheated 

 control that was noted in the earlier experiments, but the higher 

 temperatures produced the same retarding eflfects already found. 

 In this and previous experiments the soils heated to 120° and above 



