Cropping System Affects Polymer‐Coated Urea Release and Corn Yield Response in Claypan Soils

Preplant‐applied, urea‐based fertilizer management in high‐residue, no‐till (NT) corn (Zea mays L.) is challenging because of potential N loss due to cool, wet conditions in the spring and dry conditions during the summer months. Field research evaluated the effects of polymer‐coated urea (PCU) application timing, placement and cropping system on urea release for corn and 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 in some instances from surface applications of PCU following FSC or DC soybean, but release was generally greater than in the absence of soil. No‐till corn following DC soybean or FSC had yields that were 1.01–1.32 Mg ha^?1 greater when grown with PCU compared to urea at 168 kg N ha^?1. 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 recognize that high yields may not be obtained if PCU rates are reduced by 50 % (84 kg N ha^?1) in high‐residue (DC soybean or FSC), no‐till production systems. Several N sources such as PCU, anhydrous ammonia and sidedressed UAN worked similarly in high‐residue, no‐till systems, although no differences between N sources were observed in a reduced‐tillage system.