Effect of Polymer Coated Urea, Irrigation, and Drainage on Nitrogen Utilization and Yield of Corn in a Claypan Soil

Abstract

Slow‐release N fertilizers, such as polymer‐coated urea (PCU), may increase crop N use and reduce NO3–N leaching. Research was conducted to evaluate NO3–N concentrations of soil water samples in noncoated urea (NCU) and PCU treated plots under different water management systems, and to determine differences in crop yields and N utilization among water and urea management systems. Water management treatments included: no irrigation or drainage (NIN), no irrigation and drainage with subsurface drain tiles 6.1 m apart (NID), subirrigation and drainage with tiles 6.1 m apart (SUB), and overhead irrigation with no drainage (OND), which were split into preplant‐applied NCU or PCU at 0, 140, and 280 kg N ha−1. Water samples from suction lysimeters at a 45‐cm depth in soil treated with PCU had 51 to 63% lower NO3–N concentration than NCU 59 d after application (DAA), while NCU had 85 to 92% lower N concentration than PCU 153 DAA. In 2005, N uptake was ranked OND > SUB ≥ NID = NIN for PCU and NCU treatments. Grain yield for water management systems was ranked NID = SUB ≥ OND ≥ NIN in 2004 and OND > SUB > NID ≥ NIN in 2005. No grain or silage yield differences between PCU and NCU treatments when applied at similar rates were observed in either year. This study showed no increase in N uptake by the crop with PCU compared with NCU; however, PCU reduced subsoil NO3–N concentration early in the season, which may reduce NO3–N leaching.