Evaluation of six soybean varieties for response to inoculation with rhizobia in four impact zones of Malawi

Abstract The importance of soybean in small holder cropping systems cannot be overemphasized. Studies have shown that soybean play a role in reducing soil erosion, biological nitrogen fixation, pests and disease management and are also important sources of plant proteins. Despite the importance of soybean, production remains low in Malawi because of a number of factors which include the use traditional production practices and local seed. Studies are being conducted by N2Africa team in Malawi to test the response of six soybean varieties to inoculation in the four impact zones of Dedza, Kasungu, Lilongwe and Salima. Specifically, the research is aimed at determining the effect of inoculants on grain yield and biological nitrogen fixation with and without phosphorus application. Dedza and Kasungu represent medium to high altitude while Lilongwe and Salima represent medium and low altitude agro-ecological zones respectively. A total of 12 trials laid out in a split plot design, and replicated three times, are being carried out in the impact sites. The main plot has rhizobial inoculants treatment sourced from Mea in Kenya whereas the sub treatment structure is comprised of six soybean varieties namely Tikolore from IITA, Solitaire and Saprano from SeedCo, Makwacha and Nasoko from Department of Agricultural Research Services (DARS) in Malawi and PAN 1867 from Pannar Seed Company. Fertilizer was applied at the rate of 30kg phosphorus per hectare using Triple Superphosphate. Data being compiled include crop installation, establishment, flowering, pod setting, biomass and grain yield and nodulation which will be used to assess the varietal performance in heterogeneous environments as well as response to inoculation with rhizobium. Number and weight of active and inactive nodules based on sampled plants is being compiled to determine the response of different varieties to inoculation under different environments and consequently quantify biological nitrogen fixation. Soil samples before establishment and after harvest will be analyzed for nitrogen content and other relevant biophysical properties which will be used to determine changes in soil nitrogen levels and, together with rainfall data being collected, aid in interpretation of agronomic data results. Participatory variety selection with farmers is being done at two growth stages thus vegetative and physiological maturity, to determine farmers’ preference and selection criteria disaggregated according to gender. The results of participatory variety selection will be compared with agronomic data results. Data will be analyzed using Gensat, SPSS and MS Excel statistical packages.