Splitting the N application into two or more timings may improve corn (Zea mays L.) grain yield and N recovery relative to a single-N application. A 49 site-year study across eight U.S. Midwestern states compared the effect of an at-planting (single-N application) and two split-N applications [45 (45+SD) or 90 kg N ha−1 (90+SD) at planting with the remainder of the total rate (180 or 270 kg N ha−1) applied at V9]. For split-N applications, soil and plant responses were similar between 45+SD and 90+SD 93–98% of the time, indicating the at-planting N rate of 45 kg N ha−1 may be all that is needed in most cropping scenarios. Splitting the N application compared to a single-N application changed soil NO3–N at VT and post-harvest <35% of the time and plant N uptake and grain yield <15% of the time. Split-N applications had greater grain yield in areas with uniform precipitation around the sidedress timing (Shannon Diversity Index >0.56–0.59) to incorporate N in the root zone, and in coarse-textured soil (sand content >4–10%) that had greater potential for N loss. Single-N applications produced greater grain yield in soils with more total N (>2.1–2.4 g kg−1) to support N mineralization and greater cation exchange capacity (CEC) (> 27–31 cmolc kg−1), silt content (>66–74%), or clay content (>24–37%) to improve nutrient and water retention. Decisions on nitrogen application timing should be made based on soil parameters and typical weather conditions around the sidedress timing.
Bibliographical noteFunding Information:
We would like to thank DuPont Pioneer for funding this research. The authors thank the graduate students [Matt Schafer (IN), Curtis Ransom and Gregory Bean (MO), and Christopher Bandura (WI)], supporting scientists [Matt Yost (MO); Dan Barker (IA); Lakesh Sharma, Amitava Chatterjee, and Norm Cattanach (ND); Todd Andraski (WI); and Tim Hart (DuPont Pioneer)], field technicians [Matt Volkmann (MO); Jason Niekamp and Joshua Vonk (IL); Glen Slater (NE); Andrew Scobbie, Thor Sellie, Nicholas Severson, Darby Martin, and Erik Joerres (MN)], and cooperating farmers and research farm personnel for their help in completing this project. Mention of trade names or commercial products in this publication is solely for the purpose of providing information and does not imply recommendation or endorsement by the affiliated Universities or the U.S. Department of Agriculture.
© 2020 The Authors. Agronomy Journal published by Wiley Periodicals, Inc. on behalf of American Society of Agronomy