STUDIES OF NITROGEN FIXATION BY THE ROOT NODULE BACTERIA OF THE LEGUMINOSAE

Abstract

The root nodule bacteria of alfalfa, bean, dalea, pea, red clover, soybean, and sweet clover were cultured in a soil extract with 0.05-0.1% K2HPO4 and 1% glucose or sucrose. Sugar utilization of 5.4-36.0% occurred. Total N analyses were made on the cultures, using both the Davisson-Parsons method and the Gunning method modified to include nitrate N. The former method[long dash]more reliable for the determination of total N including nitrate N[long dash]gave no evidence of fixation of N beyond experimental error. The modified Gunning analyses showed an apparent fixation which is explained by a loss of nitrate N from the controls during analysis. When analyses were made by a reliable method of N determination, none of the 12 strains of nodule bacteria used fixed N in amounts above experimental error.