FERTILIZER PRACTICE 547 



466. Effects of nitrogen on plant growth. 1 — Of the 



three primary elements of a fertilizer, nitrogen 2 seems 

 to have the quickest and most pronounced effect, not 

 only when present in excess of the other constituents, 

 but also when moderately used. It tends primarily to 

 encourage aboveground vegetative growth and to impart 

 to the leaves a deep green color, a lack of which is usually 

 due to insufficient nitrogen. It tends in cereals to in- 

 crease the plumpness of the grain, and with all plants it 

 is a regulator in that it governs to a certain extent the 

 utilization of potash and phosphoric acid. Its application 

 tends to produce succulence, a quality particularly de- 

 sirable in certain crops. In its general effects it is very 

 similar to moisture, especially when supplied in excessive 

 quantities. 



The peculiarity of nitrogen lies not only in its absolute 

 necessity for plant growth, its stimulation of the vegeta- 

 tive parts, and its close relationship to the general tone 

 and vigor of the crop, but also in the fact that it was not 

 one of the original elements of the earth's crust. During 

 the formation of the soil it slowly and gradually became 

 present, brought down by rains and fixed naturally in the 

 soil itself mostly through the agency of bacterial action. 

 Even now it exists largely locked up in complex nitrog- 

 enous compounds of the humus and the less decayed 

 organic matter, and becomes slowly available to plants 



1 Discussions of the effects of the various elements on plants 

 may be found as follows : Russell, E. J. Soil Conditions and 

 Plant Growth, Chapter IT, pp. 19-50. London, 1912. Also, 

 Hall, A. D. Fertilizers and Manures, Chapters III, V, and VI. 

 New York, 1910. 



2 For a discussion of nitrogen in relation to crop yield, see 

 Hunt, T. F. The Importance of Nitrogen in the Growth of 

 Plants. Cornell Univ. Agr. Exp. Sta., Bui. 247. 1907. 



