SOME RELATIONS OF CERTAIN HIGHER PLANTS TO THE 

 FORMATION OF NITRATES IN SOILS 



T. Lyttleton Lyon and James A. Bizzell 



{Received for 'publication September 1, 1912) 



INTRODUCTION 



There are several forms in which nitrogen occurs in soils. The 

 uncombined nitrogen of the soil air constitutes the largest supply 

 because of its diffusibility with the atmospheric air. Next in amount 

 is the nitrogen of organic compounds, ranging from .05 to .3 per cent on 

 ordinary arable land and always slightly, but appreciably, soluble in soil 

 water. In upland cultivated soils the nitrogen of nitrate salts forms the 

 next largest supply, but rarely exceeds 20 per cent of the total com- 

 bined nitrogen of the soil. Curiously enough, the heavy, and conse- 

 quently poorly aerated, soils usually contain more nitrates' than do 

 lighter soils, and Fischer (1911)* has found that nitrate formation is 

 more rapid in such soils. In forest, swamp, and inundated soils the 

 nitrogen of ammonium salts and nitrites forms a larger proportion of 

 the soil nitrogen than does the nitrate nitrogen, but in well-aerated soil 

 these compounds exist in very small quantities. 



The utilization of nitrogen in these various forms by agricultural plants 

 has furnished the incentive for a large amount of able and important 

 experimentation, which has resulted in the definite and final demonstra- 

 tion of certain facts and in the partial solution of some questions relating 

 to the agricultural availability of nitrogen in its various soil conditions. 

 The utilization of atmospheric nitrogen by leguminous plants, for instance, 

 has been established beyond question; but the extent to which this form 

 of nitrogen may be utilized by other plants, or the identity of the plants 

 that participate in its use, are subjects on which opinions differ and which 

 are still being investigated. The study of the degree to which the nitrogen, 

 of organic compounds is available to higher plants has enlisted the efforts 

 of numerous investigators and has been only partially worked out. 



While nitrate nitrogen is generally conceded to be the form best suited 



* Dates in parenthesis refer to bibliography. 



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