Application of Phosphorus Fertilizer on Soybean [(Glycine max L. (Merril)] Inoculated with Rhizobium and its Economic Implication to Farmers

The experiment was conducted during the 2012 farming season on the agricultural experimental field of the University for Development Studies, Nyankpala in the Guinea Savannah agro-ecological zone. The objective of the study was to determine the influence of Rhizobium inoculants and phosphorus (P) at different application rates on yield and yield components of soybean and also to determine the economically optimal application rate of phosphorus for soybean production in the Guinea Savanna agro-ecological zone. Two levels of inoculation regimes {un-inoculated (-In) and inoculated (+In)} were combined with three application rates of phosphorus (as Yaralegume) and a control (0kg P/ha, 15kg P/ha, 30 kg P/ha and 45 kg P/ha). The experiment was laid in a 2 x 4 factorial arranged in a Randomized Complete Block design with three replications. Parameters measured were crop emergence, plant height, canopy spread, number and weight of nodules, number of pods and total grain yield. The results obtained indicated significant differences in all the parameters measured. Phosphorus application at 45kg P/ha plus Rhizobium inoculants recorded significantly higher grain yield than the rest of the treatments. The economic analysis of the treatments also showed that combination of inoculation of soybean seeds with 45 kg P/ha was more profitable than the application of 45kg P/ha without inoculation. The study recommends inoculation of soybean seeds with Rhizobium inoculants and the application of phosphorus fertilizer at 45kg P/ha.