59 



TECHNICAL BULLETIN 3 

 FOUR PAPERS ON 



NITROGEN FIXATION AND NITRIFICATION IN VARIOUS 



SOIL TYPES. 



By HOWARD S. REED AND BRUCE WILLIAMS. 



(1) The Effect of Mineral Fertilizers on Nitrogen Fixation and 

 Nitrification in the Soil. 1 



The bacterial flora of soils which have received prolonged and definite 

 applications of mineral fertilizers has been the subject of rather meager 

 attention. The status of bacterial activities as regard inorganic substances 

 is imperfectly understood and, while a subject of considerable interest, it is 

 justifiably relegated to a secondary place in soil bacteriology investigations. 

 Yet to note the bacterial activities of any soil which has received "control" 

 treatment is eminently worth while since some condition may be observed 

 which exerts an unmistakable influence. This paper reports a study of 

 nitrification and nitrogen fixation on soils that had received annual applica- 

 tions of fertilizers for five years. 



Through the courtesy of Prof. T. C. Johnson an opportunity was af- 

 forded in 1913 to study the soils of some of the experiment plats of: the 

 Virginia Truck Experiment Station. The soil samples were taken from 

 twentieth acre plats which had grown various truck crops, none, however, 

 which should have exerted a peculiar influence on the bacterial flora. The 

 samples were carefully taken and immediately brought to the laboratory. 

 The fixation tests were made by incubating ten grams of soil in 100 c. c. 

 Ashby's solution for 21 days and making total nitrogen determinations for 

 the increase. For nitrification tests, 400 grams of soil in Erlenmeyer flasks 

 was incubated with 1 percent ammonium sulphate for six weeks, at the end 

 of which period nitrate determinations were made by the Iron-Zinc Reduc- 

 tion method. 



Tables I and II give the results of these tests. Under the column 

 " Annual Fertilizer Treatment " is given the amount of fertilizer the soils 

 received annually per acre for five years. The laboratory numbers are the 

 same for both tables. 



36 from the Laboratories of Plant Pathololgy and Bacteriology, Virginia Agr. Exp. Sta. 



