SOIL OEGANISMS 



427 



practical importance than nitrate reduction, yet even less is 

 known regarding the phenomena. Many different forms of 

 bacteria and fungi are probably capable of assimilating 

 nitrogen, but what conditions favor their activity in this re- 

 spect cannot be stated definitely.^ To make the problem more 

 intricate higher plants seem to be a factor to a certain ex- 

 tent in this type of nitrate disappearance. Seasofial influ- 

 ences also have been noted, which suggest the possibility of a 

 special nitrate assimilating flora. 



Nitrate accumulation always proceeds slowly on sod land, 

 especially if the soil is heavy. Lack of sufficient moisture or 

 unfavorable temperature relations do not always adequately 

 account for this phenomenon. An experiment at Cornell Uni- 

 versity '^ is typical of the conditions mentioned above. In this 

 case, maize and grass were grown side by side, the nitrates 

 being determined at frequent intervals during the season. 

 The nitrates are expressed in parts per million of dry soil for 

 the various months. 



Table XCIII 



nitrates in parts per million under maize and sod. 



cornell university. 



Month 



x3Lprii . . 

 May... 

 June. . 

 July . . . 

 August 



Nitrates, Parts per Million" Dry 

 Soil 



Maize Land 



40.3 

 194.0 

 186.7 



^ Murray has ioxind at the Washington Agricultural Experiment Sta- 

 tion that the addition of straw to the soil markedly aided the bacterial 

 utilization of nitrates. The numbers of bacteria increased without 

 reference to the groups present. 



Murray, T. J., The Effect of Straw on the Biological Soil Processes; 

 Soil Sci., Vol. XII, No. 3, pp. 233-259, 1921, 



* Unpublished data. Cornell Agr. Exp. Sta., Ithaea, N. Y. 



