222 Nitrification in Egnptlan. Soils 



February 15tli and up to March fith there was no further increase in 

 the nitrate content of the soil probably on account of the relative dryness. 

 Immediately after the cotton was sown and watered the conditions 

 became favourable and in sixteen days the nitrates increased from 21 

 to 36 parts per million. Table III gives the results of the 1916-1917 

 observations. 



In the second series, carried out in 1917-1918, the maize was harvested 

 at the end of October and 13 parts per million of nitrate nitrogen were 

 present in the surface soil. In this case, however, the accumulation of 

 nitrate dm'ing the winter was negligible. The soil was poor and the 

 rainfall was less than in the preceding winter, so that there were few 

 favourable of)portunities when the moisture content of the soil was 

 sufficiently high for active nitrification. As with the field of 1917, as 

 soon as irrigation began, nitrification increased and an accumulation 

 from 14 to 28 parts per million was observed in 20 days. In Table IV 

 the results of the observations of the winter 1917-1918 are given. 



Table IV. 

 Nitrates infalloiv land in preparation for cotton. 1917-1918. 



Agricultural operations. 



Maize harvested October 28, 1917. 



The difference between the residts obtained in the two winters is 

 most probably explained by the difference between the rainfalls. In 

 the following Table V the official records of the Egyptian Ministry of 

 Public Works for the two stations nearest to Bahtim are given. 



