Comparative Assessment of Phosphorus Fertilization and Rhizobia Inoculation on Soybean Production in the Guinea Savanna Zone of Ghana

In the Guinea savannah zone of northern Ghana, the soils are reported to be declining for agricultural productivity. In these farming communities that depend on soybean production for their livelihoods, resource-poor farmers are not able to afford purchases of high cost inorganic phosphatic fertilizers to enhance the crop's production. The need arises to identify efficient practices and strategies and research into alternative means of enhancing soybean production to improve food security. This Randomized Complete Block Design as an experimental tool was employed to carry out a research in the Guinea savanna zone of Ghana (Tolon District) to assess the agronomic and economic productivity of rhizobia inoculation use in soybean production. Treatments used for the experiment were sole soybean production, soybean + recommended phosphorus (P) fertilize rate, soybean + inoculums, and soybean + P + inoculum. A planting distance of 60*10cm was used during planting. Each treatment was replicated three times. Growth and yield data were collected on plant height, nodule number and dry weight, shoot dry weight, pods number and dry weight, grain yield, 100 seed weight and nodule effectiveness. The results revealed the existence of significant difference in grain yield between treatments (p = 0.011). Soybean + inoculation + P gave the highest yield of 3.6 t/ha followed by soybean + inoculation (3.17 t/ha), soybean + P (2.97 t/ha) and soybean only (2.6 t/ha) respectively. Significant difference was also observed for number of pods between treatments (p= 0.01), with soybean + inoculation + phosphorus recording the highest followed by soybean + inoculation, soybean + phosphorus and soybean-only treatment respectively. However, use of sole inoculation in soybean production was associated with the least production cost, high revenue generation and high benefit/cost ratio. As rhizobia inoculation of soybean produced higher yields and is comparatively cheaper than phosphorus application, inoculation is suggested for the resource poor farmer in Northern Ghana.