Effect of Nitrogen Rate and Split Application on Maize Yield in Oyo State

The timing of nitrogen application significantly affects nitrogen use efficiency and maize yield because late-season nitrogen availability is critical during grain filling, and evaluating split nitrogen application versus single application for maize in South West Nigeria provides important practical guidance for farmers. This study investigated the effect of total nitrogen rate and application timing on maize grain yield at Ogbomoso South LGA, Oyo State, South West Nigeria. A 3x2 factorial experiment examined three nitrogen rates (60, 90, and 120 kg N ha-1) and two application timings (single basal application and split application at planting plus 5 weeks after emergence) in a randomised complete block design with three replications during the 2023 growing season using SAMMAZ 53 variety. Plant height at tasseling, total above-ground dry matter at harvest, and grain yield were measured. Results showed that split nitrogen application consistently outperformed single application at the same rate for grain yield. At 90 kg N ha-1, split application produced 4.87 tonnes per hectare versus 4.12 t ha-1 for single application, a 18.2 percent advantage. The 120 kg N ha-1 split treatment produced the highest overall yield (5.14 t ha-1) but the cost-benefit ratio at 90 kg ha-1 split was more favourable. No significant interaction was found between rate and timing for plant height. The study recommends 90 kg N ha-1 in two equal splits as the most cost-effective nitrogen management strategy for maize production in Oyo State and advocates for its incorporation into state extension fertiliser management guidelines.