Back U. R. Sangakkara and T. Higa
University of Peradeniya, Peradeniya, Sri Lanka and
University of Ryukyus, Okinawa, Japan
Full Paper (PDF File: 231KB)
Abstract
The effect of effective microorganisms (EM) on nodulation parameters and yields of bush bean and mungbean on soils with low and high populations of rhizobia were evaluated. Two soils were selected because of the adverse effects of high temperatures and dry conditions of the tropics on growth and maintenance of inherent populations of beneficial soil microorganisms. The experimental treatments included the use of fertilizer, organic amendments, and a control, with and without application of effective microorganisms. Estimates were made on the nodulating capacity, nitrogenase activity, and growth and yield of plants for each treatment.
Application of effective microorganisms significantly increased the most probable number counts of bacteria in soils, The greatest change was observed in soil with low inherent microbial populations. Nodulation and nitrogenase activity, characteristics of both legumes, were significantly enhanced, especially when grown in nutrient depleted soil. In addition, the beneficial impact was most prominent with bush beans which generally do not fix significant quantities of atmospheric nitrogen infertile and biologically active soils.
Addition of fertilizer decreased the process of biological nitrogen fixation. However, this adverse impact was reduced with addition of EM In contrast, application of nitrogen-rich organic materials had a significant beneficial impact on the process of biological nitrogen fixation, especially when applied with EM. The use of organic materials with a high C:N ratio did not increase the rates of nitrogen fixation, especially in the absence of effective microorganisms.