Abstract

Experiments were conducted with 3 local strains of Rhizobium (collected from sites in Kerala where leucaena had been introduced) and 3 exotic strains. Soil (pH 5. 7) was collected from the KFRI campus (where leucaena had not been planted) and sievedits pH was adjusted either upwards (with lime) or downwards (with sulfur) . A summer trial was undertaken with soil of pH values 3. 2, 3. 7, 5. 7, 7. 0 and 7. 8, and a winter trial with pH values 3. 7, 4. 1 and 5. 1. Seeds of L. leucocephala var. K8 were inoculated with peat based Rhizobium and dibbled into the soil samples in bags. Seedlings were harvested after 75 days and biomass, height, fresh weight of nodules and appearance recorded for all treatments and for uninoculated controls. In the winter experiment germination and survival of the seedlings were normal at pH values of 5. 7, 7. 0 and 7. 8, but the seedlings showed some yellowing and stunting at pH 5. 7. In the winter experiment, growth was generally better (possibly