228 Xitrljieation in Eiiypt'ian Soih 



Nitrification in a maize field. 



The Egyptian maize crop grows exceedingly rapidly- -in some 

 sixty to eighty days the whole of the nitrogen required by the crop 

 has been taken up and in consequence nitrification in the soil has to be 

 very active to keep up with the requirements of the plants. Maize 

 practically always follows the summer fallow or "sheraqi" and the 

 period of ten days between the irrigation of the sheraqi and the sowing 

 of the crop does not allow of much nitrate accumulation. Two cases 

 were observed in 1917, one plot unmanured after wheat, and a second 

 plot unmanured after bersim. After the first irrigation the amount of 

 nitrate in the soil increased from 6 parts to 13 parts per million in nine 

 days; during the period of growth the amount of nitrate in the land 

 after bersim rose at first to 15 parts and then fell gradually to 5 parts 

 per million as the maize took up increasing quantities of nitrogen, 

 later rising again to 15 parts per million during the period of maturation 

 of the crop. The corresponding plot after wheat shows a more steady 

 content of nitrate, about 10 parts per million of dry soil. In neither 

 case is there any marked accumulation of nitrate. The higher values 

 obtained in the earlier and later stages after bersim reflect the higher 

 nitrogen content of the soil after a leguminous crop. See Table XTI. 



Agricv Itural oferafions . 



June 28. First irrigation of sheraqi. 



July 7. Ploughing and seed sowing. 



July .30, August 17, Sept. 20, Oct. C. Irrigations. 



Oct. 28. Maize harve.sted. 



The amount of nitrate found in the surface soil of a maize field is 

 frequently the outcome of factors other than those usually considered 

 in the case of similar studies made under English conditions. Maize is 



