Аннотация:Slow‐release N fertilizers, such as polymer‐coated urea (PCU), may increase crop N use and reduce NO 3 –N leaching. Research was conducted to evaluate NO 3 –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 NO 3 –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 NO 3 –N concentration early in the season, which may reduce NO 3 –N leaching.
