Can Pre-Plant Polymer-Sulphur Coated Urea Replace the Need of Split N Application?.

Urea-based fertilizers are the most common nitrogen (N) source for corn production in Brazil. However, they are susceptible to losses when applied on the soil surface, and therefore to low N use efficiency (NUE). Split N application, use of slow release N and incorporation of N-fertilizers are recommended practices to improve NUE. The objective of this study was to evaluate the effect of N fertilizer application time and source (polymer-sulphur coated urea (PSCU) and non-coated urea (NCU)) on corn biomass accumulation, nitrogen uptake and grain yield. A study was completed at two locations with contrasting soil texture, location 1 with 140 g kg^-1 clay and location 2 with 600 g kg^-1, and evaluated for 2 consecutive years in the state of Sao Paulo, Brazil. The experimental design was a complete randomized block design with four replications. A combination of fertilizer source and application time was evaluated for a total of 4 treatments. Treatments included: (1) PSCU+U (70:30 ratio) incorporated before planting; (2) NCU incorporated before planting; (3) NCU split applied (30% incorporated before planting and 70% side-dress applied at V4); and (4) a control with no fertilizer N. Application rate was 180 kg N ha^-1. Both locations showed significant response to N application. Biomass accumulation, N uptake and corn grain yield increased with the use of blended PSCU+U application at location 1 in both years, and at location 2 in the second year, in comparison with treatments with U. Across site-years analysis showed that N fertilizer application as NCU pre-plant incorporated was equivalent in yield to split NCU application. The use of PSCU+U pre-plant incorporated showed overall higher yields.