Response of Sorghum (Sorghum bicolor L.) to Residual Phosphate in Soybean-Sorghum and Maize-Sorghum Crop Rotation Schemes on Two Contrasting Nigerian Alfisols

The effectiveness of finely ground Sokoto Rock Phosphate and Morocco Rock Phosphate to enhance productivity of maize- (Zea mays L.) Sorghum (Sorghum bicolor) and soybean- (Glycine max L.) Sorghum crop rotation schemes was evaluated using Single Super Phosphate as reference fertilizer. The experiments were carried out in the screen house of the Department of Agronomy, University of Ibadan, in February and June 2013. The experiments involved 2 × 2 × 4 × 3 factorial in a Completely Randomized Design. In the first and second croppings, the slightly acidic loamy sand still produced higher biomass than the strongly acidic sandy clay loam. On average, MRP was more efficient than SSP for maize dry biomass but, for soybean dry biomass, MRP was less efficient than SSP in the two soils. Sokoto Rock Phosphate was less efficient in the two location soils compared to SSP for the test crops. There was no difference in performance of P-sources in the second cropping. Soybean-Sorghum crop rotation scheme produced greater Sorghum biomass than maize-Sorghum crop rotation scheme. It is evident that pH and clay contents of soils as well as the rotation crop concerned influence the efficiency of finely ground soluble phosphates in crop rotation schemes