CHEMICAL, CHANGES 233 



Water capacity 

 in volume per cent. 



Loam 34.4 



3^ loam and X peat 39-Q 



Sand 11.7 



Sand ^ and peat # 22.7 



Except with soils very rich in humus, the greatest production 

 will be secured only by extensive use of manures rich in organic 

 matter, or other measures suitable to enrich the soil in humus 

 materials. 



Action of Carbon Bisulphide on Bacterial Change. 1 Carbon 

 bisulphide applied to the soil during the growing season may 

 destroy or injure the crop, but if it is applied some time before 

 planting, it increases the fertility of the soil to a decided extent. 

 Its action appears due to its effect on the soil bacteria. In an 

 ordinary soil, the bacteria have reached a condition of equilibrium. 

 Carbon bisulphide destroys or injures the bacteria, and diminishes 

 the production of active nitrogen. In time, new bacteria develop, 

 but along different lines, and there occurs both an enormous in- 

 crease in number of bacteria, and an abnormal predominance of 

 certain species. The bacteria which prepare active plant food 

 are more energetic, and the fixation of nitrogen also takes place 

 to a greater extent than usual. The nitrogen is at first locked up 

 in the bacterial bodies, and so is useless to the plants, but it be- 

 comes active when they decay. Hence the action of the carbon 

 bisulphide is depressing if applied to a growing crop, but it acts 

 like a nitrogenous fertilizer to a succeeding crop. After a longer 

 or shorter time, the soil is more exhausted than it was at first. 

 This is probably due not only to the rapid transformation of the 

 more easily decomposed organic nitrogen of the soil into active 

 nitrogen, but also to the abnormal mixture of soil bacteria due to 

 the changed conditions. 



Treating the soil with toluene, and heating the soil, have similar 

 effects to carbon bisulphide. The heat, however, itself changes the 

 chemical composition of the soil, rendering both organic and in- 

 organic material more soluble. According to Russell, 2 the action 



1 Russell, Soil Conditions and Plant growth, p. 114. 



2 Jour. Agr. Science 3, p. in. 



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