Cropping System Affects Polymer-Coated Urea Release and Corn Response.

Preplant applied urea-based fertilizer management in high-residue no-till (NT) corn (Zea mays L.) is challenging due to potential N loss. Field research in Missouri: 1) evaluated the effects of polymer-coated urea (PCU) application timing, cropping system, and placement on urea release for corn, and 2) determined corn yield response to PCU on claypan soils following wheat (Triticum aestivum L.) cropping systems [reduced till corn following wheat, no-till corn following wheat with double-cropped (DC) soybean [Glycine max (L.) Merr.], and no-till corn following wheat with a frost-seeded red clover (FSC) (Trifolium pratense L.) cover crop]. Urea release from PCU was <35% from fall through winter (November-January) and <20% for early preplant (February-March) applications until 1 April. By 1 August, less urea was released from surface applications of PCU in some instances with a surface application following FSC or DC soybean, but were generally greater than urea released in the absence of soil. No-till corn with PCU at 168 kg N ha^-1 increased yield 1.01 to 1.32 Mg ha^-1 compared to urea following DC soybean and FSC. Grain yields were similar within no-till cropping systems with PCU, anhydrous ammonia, and sidedressed urea ammonium nitrate (UAN) at 168 kg N ha^-1. Farmers should not reduce PCU rates 50% in high-residue (DC soybean or FSC), no-till production systems in order to maintain high yields. Several N sources such as PCU, anhydrous ammonia, and sidedressed UAN worked similarly in high-residue, no-till systems, though no differences among N sources were observed in a reduced-tillage system.