EFFECT OF THE GROWING PLANT 139 



effect of the crop on the temperature or moisture content of the soil. 

 There appears to remain only the possibility that the growing plant 

 has a direct effect on the decomposition processes going on in the soil. 

 Unfortunately field experiments alone do not enable us to decide this 

 question and the systematic laboratory investigation has still to be 

 undertaken. These effects are reflected in the crop. Numerous field 

 experiments show the very beneficial effects of fallowing. Whether 

 these are wholly the result of the increased bacterial activity or 

 whether other factors come into play has not yet been determined. 



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