238 NITRIFICATION 



the roots of which may absorb the plant-food as rapidly as it is made 

 available. 



The loss of nitric nitrogen from irrigated soil may be prevented 

 by the judicious use of irrigation water. Experiments at the Utah 

 Station covering a period of fourteen years have demonstrated that 

 the application of fifteen or twenty inches of irrigation water, 

 distributed throughout the season, to deep soil causes little, if any, 

 loss of nitric nitrogen from such a soil, whereas applications of from 

 twenty-five to thirty-seven inches similarly distributed causes consid- 

 erable diminution in the crop yield. This decrease in crop yield due 

 to excessive quantities of water, up until the soil becomes water- 

 logged, is largely due to the rapid washing of the nitric nitrogen 

 beyond the feeding area of the plant roots. 



REFERENCES. 



Lohnis: "Handbuch der Landwirtschaftlichen Bakteriologie." 



Lafar: "Handbuch der Technischen Mykologie," Dritter Band. 



Kossowiez: "Agrikulturmykologie," I Bodenbakteriologic. 



Warington, Robert: "Six Lectures on the Investigations at the Rothamsted 

 Experimental Station," U. S. Dept. Agr. Off. Exp. Sta. Bui. 8. 



Voorhees, Edw. B. and Lipmani, Jacob G.: "A Review of Investigations in Soil 

 Bacteriology," U. S. Dept. Agr. Off. Exp. Sta. Bui. 194. 



Chester, Frederick D.: "Bacteria of the Soil in Their Relation to Agriculture." 

 Penn. Dept. of Agri. Bui. 98. 



Greaves, J. E., Stewart, R., and Hirst, C. T.: "Influence of Crop, Season, and 

 Water on the Bacterial Activities of the Soil." Jour. Agr. Rsch., vol. ix, pp. 293-341. 



Gibbs, W. M.: The Isolation and Study of Nitrifying Bacteria. Soil Science, 

 1919, vol. viii, pp. 427-481. 



