Effect of Soil Types and Mixtures on Nodulation of Some Beans and Groundnut Varieties (Report‪)‬

INTRODUCTION Biological fixation of atmospheric nitrogen is estimated to account for ~90% of the 100 to 140 Tg of nitrogen (1Tg = [10.sup.12] g [10.sup.6] metric tons]) fixed annually in terrestrial environments. The remaining 10% was fixed abiotically, primarily by lightning [1, 2, 3]. Human activity, especially the generation of ammonium compounds for agricultural fertilizers, fossil fuel consumption, and increased planting of legumes, contributes an estimated 140 Tg of additional fixed nitrogen each year [4, 5]. Biological nitrogen fixation is catalyzed by prokaryotes only, so far as it is known. The enzyme complex responsible for nitrogen reduction is called nitrogenase. It is irreversibly inactivated by oxygen. Hence the process requires conditions that are anoxic or nearly anoxic [4].