Improving soil physical properties and effect on tree legume seedlings growth under barren soil

Nitrogen is one of the major elements available to plants through biological nitrogen fixation, which has received much attention in recent years. The present study aims at improving tree legumes viz., Albizzia lebbeck, Pithecolobium dulce, Sesbania grandiflora, Albizzia amara, Enterolobium saman, Erythrina indica, Leucaena leucocephala, Acacia mellifera, Pongamia glabra and Acacia auriculiformis through dual inoculation with arbuscular mycorrhizal fungi and suitable rhizobial isolates. Rhizobial isolates viz., AcM05 (from A. mellifera), AlL01 (from A. lebbeck ), EnS08 (from ( E. saman), LeL02 (from L. leucocephala ) and ErI06 (from E. indica) were characterized. Dual inoculation with Rhizobium and Glomus fasciculatum increased the nodule nitrogenase activity (36-213%), dry matter yield (156-279%), total nitrogen content (12-159%) and total chlorophyll content of leaves of A. mellifera (125-395%) compared to single inoculation with either Rhizobium or G. fasciculatum alone. Initially the soil had high potassium content (115mg/kg soil) and low nitrogen (14mg/kg soil) and phosphorous (1.1mg/kg soil) content. Dual inoculation significantly enhanced the nitrogen (60.0mg/Kg soil) and phosphorous (24.3mg/Kg soil) contents of soil, but to a lesser extent with respect to potassium content (155mg/Kg soil). In conclusion, it may be stated that tripartite association not only enhances plant growth but also improves the nutrient status and activities of soil enzymes.