106 IRRIGATION PRACTICE 



had a distinctly beneficial effect upon the formation of 

 nitric nitrogen. The greatest total production was 

 observed when 15 inches of water were applied. The 

 greatest production to the inch of water was found, how- 

 ever, when the minimum quantity of water was used. The 

 use of the maximum quantity of water, 25 inches, decreased 

 the total yield, and gave the smallest yield of nitrates per 

 inch of water used. A medium quantity of water appeared 

 best, therefore, for the activity of the nitrifying organisms. 



In the same investigations, it was found that the con- 

 centration of the soil solution, in nitrates, was always 

 greater as more irrigation water was used. 



In view of the tremendously great importance of soil 

 life in the maintenance of soil fertility, it should be care- 

 fully studied under the conditions of irrigation. 



REFERENCES 



CAMERON, F. K. The Soil Solution. Chemical Publishing Company, 



Easton, Pa. (1911). 

 CAMERON, F. K., and GALLAGHER, F. E. Moisture Content and 



Physical Condition of Soils. United States Department of 



Agriculture, Bureau of Soils, Bulletin No. 50 (1908). 

 CAMERON, F. K., and BELL, JAMES M. The Mineral Constituents 



of the Soil Solution. United States Department of Agriculture, 



Bureau of Soils, Bulletin No. 30 (1905). 

 CLARKE, F. W. The Data of Geochemistry. Second edition. United 



States Geological Survey, Bulletin No. 491 (1911). 

 COLLINS, W. D. The Quality of the Surface Waters of Illinois. 



United States Geological Survey, Water Supply Paper No. 



239 (1910). 

 CUSHMAN, A. S. The Effect of Water on Rock Powders. United 



States Department of Agriculture, Bureau of Chemistry, 



Bulletin No. 92 (1905). 

 DOLE, R. B. Analyses of Waters East of the 100th Meridian. 



United States Geological Survey, Water Supply Paper No. 236 



(1909). 



