Bemgba Anjembe, M.T Adetunji and C.O Adejuyigbe
Four Alfisols in Benue state were examined to determine the solution phosphate concentration required to obtain optimum yield of soybean with the view of employing the SPC as a tool for the estimation of the P fertilizer requirement for soybean production on these soils. Soil inorganic P was fractionated using standard procedures. Sorption characteristics were determined in 0.01 M CaCl2 solutions of various P concentrations. For each soil, the amounts of P that gave 0.025, 0.05, 0.075, 0.100, 0.125, 0.150, 0.175, 0.200, 0.225, 0.250 mg kg-1 solution concentration were estimated from adsorption curves. In the greenhouse, 4 kg of soil from each location was placed in plastic pots. Amount of P estimated from sorption study was added as KH2PO4. The treatments were laid out in Randomized Complete Block Design (RCBD) and soybean seed variety (TGx 1448-2E) was planted and observed to maturity. At harvest, the shoot was dried, weighed, milled and digested in a 4:1 HNO3:HClO4 mixture and analyzed for P. Optimum solution P concentration (SPC) was determined for each soil in relation to yield. Field trials were conducted at Nor and phosphate fertilizer quantity that resulted in 0.0, 0.5 SPC, 1.0 SPC, and 2.0 SPC (as estimated from pot experiment) was added per plot and replicated thrice in RCBD. Soybean seeds were planted by drilling. At harvest, SPC that gave highest grain yield was evaluated for each soil and the quantity of P required (SPR) to achieve this concentration was calculated. High grain yield (t ha- 1) was obtained at 0.075 mg P kg-1 in Katsina-Ala (15), Utonkon (7.3), Akoodo-Mbakor (9.3) and Nor (8.7) in the green house experiment. The estimated SPC value also gave high grain yield (t ha-1) in the field trial at Nor (4.3). It was thus concluded that the highest P fertilization would be required at Utonkon (72.75 Kg P ha-1), Katsina-Ala (67.64). Akoodo-Mbakor and Nor (61.26) would require the least.
Share this article