J. A. Prescott 227 



In fact, quantities of nitrate nitrogen have been found at Bahtini in 

 the soil of cotton fields quite sufficient for the growth of the crop to 

 the end of the season. The cotton crop in Egypt is not therefore usually 

 limited by the food supply. Table X illustrates approximately the 

 relationship between the requirements of the cotton crop and the amount 

 of nitrate formed in the soil by biological processes. 



Table X. 

 Nitrogen intake-oj llie collon crop and nitrate production in a cotton field. 



Pounds per acre. 

 May June July Aug. Sept. 



Nitrogen required by cotton crop i — 40 — liO 



Nitrates produced in surface soil 80 120 140 — — 



Root depth according to W. L. 



Ballsi 50 cm. !»0 cm. 150 cm. 180 cm. 200 pm. 



The distribution of nitrate between soil and subsoil has not been 

 followed up as yet. The movements of the salts in the soil with each 

 irrigation would afford some clue as to what happens to the nitrates 

 after they are produced. The only results obtained so far indicate, 

 as would be expected, that the amount of salt in the soil bears no 

 relationship to the amount of nitrate present. In each case the quantity 

 present is the outcome of dissimilar factors. The results of W. L. Balls 

 show that irrigation affects the moisture content of the soil down to 

 considerable depths, so that there is no reason to suppose that the nitrate 

 accumulated in the surface layer is never washed down far enough to 

 feed the plant. 



Table XI illustrates the lack of relationship between the amounts 

 of salt and of nitrate in the soil of the cotton field of 1917. 



Table XI. 



Amounts of nitrate and of sodium chloride in the surface soil 



of a cotton field. 1917. 



This Journal, 1913, 5, 469. 



