226 Nitrification in Egyptian Soils 



In 1918, a further study was made on a piece of land, which was 

 under experiment for the sowing date of cotton. The land was rather 

 rich and nitrification was followed up on the soil of plots sown on the 

 1st February, 1st March and the 1st April. The land was too dry before 

 the irrigation of the cotton crop to allow of any bacteriological activity 

 and it was possible to compare land under cotton with the corresponding 

 fallow piece waiting for irrigation after a month's interval. Considerable 

 quantities of nitrate were observed, up to 60 parts per million. The 

 results indicate the rapid accumulation of nitrate that is possible in 

 an Egyptian cotton field far in excess of the immediate requirements 

 of the plant. See Table IX. 



Table IX. 

 Amountfi of nitinle found in the surface soil of cotton plots soirn on different 



dates. 1918. 



Irrigations — February plot: February 1, March 1. April II, May 23, June 14. 

 March plot: March 1, April 11, May 23, June 14. 

 .\pril plot: April 1, May 23, Juno 14. 



The amount of nitrogen required by the cotton crop is stated by 

 Foaden and Mackenzie^ to be 59 pounds per acre. The writer has made 

 two rough determinations of the nitrogen recjuired at early stages of 

 growth. The amount of nitrogen required in the first two or three 

 months is more than supplied by nitrates produced in the sui'face soil. 



' W. C. Mackenzie and G. P. Foaden. MdJiiins in Egypt anil Soil ExhauMion, Cairo, 

 1896. 



