Abstract

Nodulation and growth of L. leucocephala was poor in soils with a low pH (5.5) and in degraded areas, especially in high ranges. However, nodulation was good in places where other leguminous crops (e.g. Mimosa pudica and Sesbania grandiflora) nodulated. Based upon the extent of nodulation and soil pH, Rhizobium was isolated from nodules of L. leucocephala growing at 6 localities in Kerala. Evaluation of these (as well as 7 exotic strains) showed that inoculation of seeds with Rhizobium increased seedling biomass and fresh weight of nodules. Rhizobium isolates from Nilambur, Nandiyode (Palghat) and Trivandrum were as good as the best exotic isolates. Among the latter, RCR 3878, RCR 3817 and TAL 582 were promising. Low pH (5.7) not only reduced thefresh weight of nodules and seedling biomass but also affected root growth and seedling establishment. As the soil pH increased, there was improvement in the fresh weight of nodules, seedling biomass, and the efficiency of nodules in increasing the biomass. The Rhizobium strain RCR 3817 was suitable for soil of pH 5.7; at pH 5.7, TAL 582 was suitable for seed inoculation. An isolate from Nilambur was as good as the exotic isolates at the pHs tested