450 NATURE AND PROPERTIES OF SOILS 



ly so rapid as to make this fertilizer almost as quickly effec- 

 tive as sodium nitrate. 



While the nitrogen of ammonium salts is quickly changed 

 to the nitrate combination in a well-drained soil, some plants 

 seem to prefer ammoniacal nitrogen to the nitrate form. Kell- 

 ner 1 in 1884 and later Kelley 2 demonstrated that rice plants 

 growing on lowland soils use ammoniacal nitrogen rather 

 than other forms. On upland soils, however, it is presumable 

 that rice plants utilize nitrate nitrogen, which would indi- 

 cate that some plants, at least, may adapt themselves to the 

 use of a more abundant form of nitrogen. 



Hutchinson and Miller 3 found that peas obtained nitrogen 

 from ammonium salts as readily as from sodium nitrate, but 

 that wheat plants, although able to obtain nitrogen directly 

 from ammonium salts, grew much better in a solution con- 

 taining nitrates. One feature brought out by the numerous 

 experiments with ammonium salts is the difference between 

 plants of various kinds in respect to their ability to absorb 

 nitrogen in this form. 



249. The artificial fixation of nitrogen. 4 — The vast store 

 of atmospheric nitrogen, chemically uncombined and very 

 inert, will furnish an inexhaustible supply for plants when it 

 can with reasonable economy be combined in some manner to 

 give a product that can be commercially transported and 

 that will, when placed in the soil, become available without 

 liberating substances toxic to plants. The importance of the 



1 Kellner, O., Agrikulturchemische Stvdien uber die Beislcultur ; 

 Landw. yers. Stat., Band 30, Seite 18-41, 1884. 



2 Kelley, W. P., The Assimilation of Nitrogen by Bice; Haw. Agr. Exp. 

 Sta., Bui. 24, pp. 5-20, 1911. 



3 Hutchinson, H. B., and Miller, N. H. J., The Direct Assimilation of 

 Inorganic and Organic Forms of Nitrogen by Higher Plants; Centrlb. 

 f. Bakt., II, Band 30, Seite 513-547, 1911. 



4 Norton, T. H., Utilization of Atmospheric Nitrogen; U. S. Dept. of 

 Comm. and Labor, Special Agents Ser., No. 52, 1912. 



Knox, J., Fixation of Atmospheric Nitrogen; New York. 

 Slosson, E. E., Creative Chemistry, Chaps. II and III: New York, 

 1920. 



