Efficiency of sokoto rock phosphate as a fertilizer source for maize production in Southwestern Nigeria

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Abstract
The study on agronomic efficiency of Sokoto Rock Phosphate (SRP) and water Soluble Single Super Phosphate (SSP) as a phosphorus (P) fertilizer sources for maize (Zea mays L. Van TZSRY) was carried out on Iwo Soil Series (Oxic Tropudalf) in the field. The initial (1989) and residual (1990) effects of the two sources of P were assessed. The treatment consist of the control. Two P sources applied at the rates of 25, 50, 100, and 200 kg ha‐1 and their mixtures in equal ratios at the rates of 50 and 100 P ha‐1. The available P was slowly released from SRP in the first year of trial. In the second year however, the SRP supplied significantly higher P than the SSP. The effectiveness of the different rates of SRP in increasing maize grain yields in the initial experiment followed the order of SRP25 > SRP50 > SRP100 > SRP200 while the residual effect after one year on yield was as follows: SRP50 > SRP100 = SRP200 > SRP25. The optimum grain yields of 5.9 and 5.1 tonnes ha‐1 were obtained with SSP at the rate of 50 and 100kg ha‐1 in the initial (1989) and residual (1990), respectively. The optimum grain yield could not be ascertained in the initial (1989) experiment for SRP because the yield declined as the rates of SRP increased. But in the residual (1990) effects, it was 4.9 tonnes ha‐1 at the rate of 50kg ha‐1. The relative agronomic efficiency values ranged from ‐500% to 0% and 150% to 100% in the initial and residual effects, respectively. This indicates that Sokoto Rock Phosphate was more effective in supplying P for maize growth in the second than the first year of the experiment.