Effect of Rhizobium inoculation on growth, modulation, and nitrogenase activity of some legume tree species

An experiment was conducted to study the effect of inoculation of Rhizobium suspension in Albizia procera (Roxb.) Benth, Albizia lebbeck (L.) Benth, and Leucaena leucocephala (Lam.) De Wit. seedlings grown in sterilized and nonsterilized soil media. Control treatments were maintained by non-inoculation. Inoculation response was observed strong in sterilized and modest in nonsterilized soil when compared to respective control treatments. Increase in height was found 105.07%, 63.42%, and 109% higher in sterilized soil and 52.1%, 68.6%, and 95.8% in non-sterilized soil for Albizia procera, Albizia lebbeck, and Leucaena leucocephala, respectively, after a period of 4 months. Nodule number increased up to 10.27 and 3.51 times in Albizia procera, 11.47 and 4.3 times in Albizia lebbeck, and 7.22 and 2.9 times in Leucaena leucocephala due to inoculation in sterilized and non-sterilized soil media respectively. Significant increase in nodule dry weight and nitrogenase activity was also recorded in both sterilized and non-sterilized soil for all the species tested. Nitrogenase activity per plant per hour was recorded 68.75, 11.58, and 13 times higher in sterilized and 6.7, 5.53, and 3.38 times higher in non-sterilized soil over control for the species respectively after 4 months. In the tree species tested the inoculation of Rhizobium showed higher productivity, modulation and nitrogenase activity than control suggesting the idea that application of Rhizobium suspension greatly enhances plant growth, modulation, and nitrogenase activity.