International Journal of Current Microbiology and Applied Sciences
ISSN: 2319-7706 Volume 2 Number 8 (2013) pp. 60-72
An assessment for the need of soybean inoculation with Bradyrhizobium japonicum in some sites of Kasungu district, Central Malawi
, P.C.Nalivata, G.Y.Kanyama-Phiri and M.W.Lowole
Lilongwe University of Agriculture and Natural Resources, Bunda College Campus, Department of Crop and Soil Sciences, P.O. Box 219, Lilongwe, Malawi *Corresponding author e-mail:
Soybean is one of the most important legume crops in Malawi. Over the years, yield of soybean has mostly fallen below an optimum level which is attributed to a number of factors including poor nodulation with the native rhizobia available in the soil. An on-farm study was done to assess the need for soybean inoculation with Bradyrhizobium japonicum in five sites of Mkanakhothi Extension Planning Area (EPA) of Kasungu district, Central Malawi. The trials included inoculated soybean plot, un-inoculated soybean plot and un-fertilized maize plot that was used in the estimation of biological nitrogen fixation using the nitrogen difference method. The treatments were arranged in a randomized complete block design. Results showed significant differences (p < 0.05) due to both inoculation and site effects. Inoculation of soybean significantly (p < 0.05) increased nodule numbers per plant and nodule dry weight in all sites by ranges of 75 to 90% and 25 to 53% respectively. Biological nitrogen fixation (BNF) increased by 74 to 87% (26 to 56 kg N ha -1 ) in inoculated soybean as compared to the un-inoculated soybean (5 to 9 kg N ha -1 ). Grain yield was also significantly (p < 0.05) higher in inoculated plots as compared to un-inoculated plots with ranges of 524 to 1868 kg ha -1 for inoculated soybean and 246 to 905 kg ha -1 for un-inoculated soybean. From this study it can be concluded that although soybean has commonly been grown in the EPA inoculation is still needed to all the sites. Application of different starter doses of N, different rates of P fertilizer and soil liming should be considered for further research in Mkanakhothi EPA of Kasungu district and similar agro-ecological zones in the country in order to improve BNF and yields of soybean. 
Inoculation; Biological nitrogen fixation; Brady - rhizobium japonicum; Nodulation; Soil fertility