Effects of Split Application of Urea Fertilizer on Soil Chemical Properties, Maize Performance and Profitability in Southwest Nigeria

Background: Since N fertilizer applied to maize (Zea mays L.) is prone to loss by leaching, it is important to derive an application time during the phenology of maize when the fertilizer is most efficiently and effectively used by the crop with minimal losses. Objective: Hence, experiments were carried out in 2014 at two locations in Osogbo southwest Nigeria to determine the effects of split application of N fertilizer on soil chemical properties, maize performance, and profitability. Methods: The treatments were: (i) control, (ii) 120 kg N ha-1 Applied at Planting (AP), (iii) two split applications (SA) of 120 kg N ha-1 {90 kg N ha-1 applied AP + 30kg N ha-1 at thirty Days After Planting (DAP) [90 + 30]}, and (iv) three SA of 120 kg N ha-1 {60 kg N ha-1 applied AP + 30 kg N ha-1 thirty DAP + 30 kg N ha-1 at tasselling[60+30+30]}. The four treatments were arranged in a Randomized Complete Block Design with three replicates. Results: Results indicate that at both sites, SA three times (60+30+30) has the most improved soil chemical properties, growth and yield of maize relative to other methods. The yield parameters increased in the order: control < 120 kg N ha-1 applied once < 90+30 < 60+30+30. Using the mean of both sites, 60+30+30 increased yield of maize by 15.3%, 37.1% and 138.2%, respectively compared with 90+30, 120 kg N ha-1 applied once and the control. Optimum returns were recorded by 60+30+30 with net return of ₦ 227,600 and a benefit cost ratio of 3.67:1 while the application of 120 kg N ha-1 applied once has a return of ₦ 157,200 with a benefit ratio of 2.9. These results show that farmers would benefit by making more profit by adopting the method of SA of N fertilizer three times (60+30+30). Conclusion: Therefore, for improved soil chemical properties, growth, yield and profitability of maize, N fertilizer application should be structured in accordance with this pattern of uptake to avoid losses by leaching and therefore ensure that N level in the soil is high at the critical stage of N demand.