234 Nitrljiditioii in Egyptian Soils 



niti'iiication under the wheat itself for the ultimate requirements of 

 the crop. 



Ejfecl of a growing cmp on nitrification. 



It has been suggested that the growing crop influences the biological 

 activity of the soil. The general opinion seems to be that nitrification 

 in a cropped soil is not so active as in the corresponding fallow soil. 

 In the case of the maize crop, however, T. L. Lyon and J. A. Bizell^ 

 suggest that the effect of the crop is to stimulate nitrification. In the 

 case of Egyptian soils it is almost impossible to compare cropped soils 

 with fallow soils under field conditions owing to the enormous variation 

 in the water content of these soils. A number of data from pot ex- 

 periments are available, however, and are of .sufficient interest to be 

 included in this paper. 



Table XIX. 



Effect of iiiuizc cro'p on nitrification in lite ^uil. 

 Fbf exjierimenl. i917. 



Tablk XX. 



Effect of a wheat crop on nilrificatiou in (he noil. 



Pot exferiment. f917-1918. 



Nitrogen Nitric nitrogen Total nitric 



in crop found in pot nitrogen produced 



gm. " gm. gm. 



1-38 1-38 



0-73 0-94 1-US 



1-37 0-70 207 



1-34 0-61 204 



FaUow pot 3-68 3-68 



Fallow pot 1-38 



— 1-87 



— 2-61 



— , 3-68 



' J oar II. Franklin Inst., 1911, Jan. 



