J. A. Prescott 



223 



Table V. 

 Rainfall near Cairo, 191(i-J917, mm. 



Abbassia 

 Giza 



Abbassia 

 Giza 



()i;t. 

 0-0 

 0-0 



Oct. 

 0-0 

 00 



In the first winter the rainfall was not only higher than in the second 

 winter but was distributed as a small number of fairly heavy showers. 

 At Abbassia 25 mm. fell on January 2, 3 and 4, 1917, and 7-0 mm. on 

 February 10 and 11. In 1917-1918 more frequent, but very light rains 

 were the rule; in only one or two cases did more than one millimetre 

 fall in one day. Further in 1918 the bulk of the rain fell in March when 

 the cotton was already growing on the land under observation. In 1917 

 the wettest month was January. 



It is possible that the nitrification is not continuous, but occurs 

 only after showers heavy enough to supply the necessary soil moisture. 

 This would explain the differences observed between the two winters. 



The bersim catch crop. 



The growing of a single cutting of bersim during the winter preceding 

 the cotton croj) is very common as the extra fodder so obtained is very 

 valuable. The amount of nitrogen returned to the soil in the excrements 

 of the animals feeding on this crop together with the crop residues has 

 been estimated by the writer to be not more than 5-5 to 65 pounds per 



Table VI. 

 Nitralcs in fallow soil after bersim catch 



crop. 



1918. 



* The subsoil contained nitrates: 13-7 parts per million. Irrigations were given on 

 March 4 and May 16. 



15—2 



