Stf.am Sti:i<ii.ization on W'ArKR-SoLuiu.K ]\Iatti:u in Soils. 2bi 



as compared with the yield in thi' extract of unheated soil and the 

 depressed transpiration. 



It is apparent that the soluble matter in the steamed soil, when 

 fresh and present in large amounts, contains substances injurious to 

 the growth of the wheat plant and that the injurious effect decreases 

 with the absorption of the soluble matter by the soil, or with the 

 further decomposition of this material. The luxuriant growth that 

 takes place later on the sterilized soil is evidently due to the large 

 quantity of soluble plant food. 



Effect of cropping on the soluble matter of steamed soils 

 Soils Nos. I and 2 were kept in the greenhouse after steaming, in pots 

 without and with plants. The unsteamed samples were kept in the 

 same way. In each pot a moisture content of approximately twenty- 

 five percent was maintained, whether the soils w^ere planted or not. 

 Other conditions to which they were subjected were the same for all. 



Table VII gives the results of analyses of the cropped and uncropped 

 soils upon standing for three months after steaming. Each soil is 

 compared with the same soil treated in the same manner except in 

 the matter of cropping, the uncropped soil being in each case upon 

 the line above the cropped soil. A lower percentage of any constituent 

 in the cropped soil is marked with a minus sign preceding the figures 

 representing the difference, which are placed on the line underneath 

 the two soils, while a higher percentage is marked with a plus sign. 



Table VII. — Showing Differences in Composition of Steamed and Unsteamed 

 Soils When Cropped and Not Cropped 



