In-season N fertilization is increasingly being used as a management strategy to reduce risk of N loss to the environment. This study evaluated the optimal timing for a split N fertilizer application in corn (Zea mays L.) across different environments and soil textural classes in Minnesota. Treatments consisted of pre-plant (PP) urea applied at 0 to 270 or 315 kg N ha–1 on increments of 45 kg N ha–1 and five split applications (SA) of 45 kg N ha–1 urea ammonium nitrate as starter fertilizer and 90 kg N ha–1 of urea with an urease inhibitor applied at the V2, V4, V6, V8, or V12 stage of corn phenological development. Site-years were grouped according to grain yield response to fertilizer timing. Irrigated coarse-textured soils produced 1.5- to 1.9-fold greater grain yield when fertilizer was split applied from V4 to V12 due to improved synchrony of N availability to crop demand and reduced potential for NO3–N leaching. Rainfed, fine-textured soils had mixed results. Site-years receiving welldistributed precipitation produced greater grain yield when fertilizer was split applied from V2 to V8, but early season N deficiency reduced yield for the V12 application. Site-years with limited precipitation during the late vegetative through grain filling stages of corn had no improvement in grain yield or N use efficiencies for SA because dry soil conditions likely interfered with root development and made N fertilizer positionally unavailable to the crop. This study highlights that the success of SA is largely dictated by soil texture and precipitation.
Bibliographical noteFunding Information:
This study was funded by the Minnesota Corn Growers Association. The authors extend their appreciation to collaborating growers who allowed us to conduct this study on their farms, the Univ. of Minnesota Field Crew, and the many students who helped with this project.
© 2019 The author(s).