INFLUENCE OF NITRATES ON NITROGEN-ASSIMILAT- 

 ING BACTERIA^ 



By T. L. Hn^ivS,- 

 Research Bacteriologist, Idaho Agricultural Experiment Station 



INTRODUCTION 



REIvATlON Olf NITRATES TO VARIOUS FORMS OF PLANT LIFE 



The importance of nitrogen to plant life can not be overestimated. 

 It is one of several elements essential to plant growth, one, moreover, 

 which is apt to be deficient in arable soils. These facts are well brought 

 out by the almost innumerable investigations which have been made 

 concerning the source of nitrogen for plants. 



The influence of nitrate nitrogen on various plants has been the con- 

 trolling idea in many of these experiments. Very little attention has 

 been placed on the effect of nitrates on the lower plants, especially the 

 bacteria. Because of the relation that exists between higher plants and 

 bacteria it seems advisable to consider the effect of nitrates on the soil 

 bacteria. Indeed, progress in the knowledge of nitrogenous fertilizers 

 depends on a study of the effect of the fertilizer on the soil organisms as 

 well as on the higher plants. The action of fertilizers on the different 

 groups of soil organisms, the relation of these organisms to higher plants, 

 and the separation of the important from the unimportant groups are 

 some of the factors involved in the problem of soil fertility. 



REVIEW OF LITERATURE 



The relation of nitrates to the germination of seeds has been studied 

 by De Chalmot {iiy, who found that corn germinated in solutions con- 

 taining nitrate was more robust than com germinated under similiar 

 conditions without nitrate. He also noted that if too concentrated 

 solutions of nitrate were used germination was retarded rather than 

 hastened. The presence of nitrate also increased the amount of al- 

 buminous material in the seed. 



The direct influence of nitrate nitrogen on the growing plant is too 

 well known to justify any lengthy discussion here. Jost {26, p. 134) 

 gives the results of experiments made by Boussingault, who grew the 

 sunflower {Helianthus argophyllus') in sand with and without nitrate. 



'Major portion ot a paper submitted in partial fulfillment of the requirements for the degree of doctor of 

 philosophy in bacteriology in the Graduate School of the University of Wisconsin, December, J916. 



2 The \vriter wishes to acknowledge his appreciation oi the sugsiestions and criticisms obtained through- 

 out the progress ot this work from Prof. E. B. Fred and E. G. Hastings, of the University of Wisconsin. 



' Reference is made by number (italic) to "Literature cited." pp. 227-230. 



Journal of Agricultural Research, . Vol, XH, No. 4 



Washington, D. C. J^" '^- ^^iS 



1- Key No. Wis. — 10 



(X83) 



