Symbiotic Nitrogen Fixation in a Grazed Tropical Grass–Legume Pasture

Abstract

THE importance of legumes as symbiotic nitrogen-fixers in the pastures of temperate regions is generally recognized, and considerable data are available to show the contributions made to the soil nitrogen supply by these legumes. Very little information of this nature, however, is available in the case of legumes growing in tropical pastures. Tropical legumes are often considered to be inefficient nitrogen-fixers; in instances where this is so, it is probable that inoculation with the appropriate Rhizobium strain or the supplying of deficient nutrients, or both, will increase fixation efficiency. Results obtained from an experiment on the Faculty of Agriculture Farm, University College, Ibadan, indicate that under suitable conditions the legume in a pasture growing under equatorial conditions may contribute amounts of nitrogen to the soil similar to those added by legumes in temperate pastures.