Pre‐Plant and In‐Season Nitrogen Combinations for the Northern Corn Belt

Abstract

Core Ideas Starter fertilizer strategies must sufficiently supply N until sidedress time to influence success of in‐season N application. Applying the majority of N at V11 did not increase yield potential and may be best utilized as a rescue application in the northern Corn Belt. Increased 5×5 starter N rates (>45 kg N ha −1 ) may be required when full SD is applied at V11 to maintain yield potential. In variable weather conditions splitting N applications (i.e., multi‐pass systems) improved synchrony of N application with corn N uptake. In‐season N applications offer greater flexibility to address climate variability and better synchronize N availability with corn ( Zea mays L.) uptake, but deliberating between V4 vs. V11 sidedress (SD) application requires validation. A six site‐year study investigated multiple N placement and timing strategies on corn growth, yield, and profitability. The three primary strategies involved pre‐plant incorporated (PPI), in‐furrow (IF) (7.8 kg N ha −1 ), or subsurface banded N fertilizer below the furrow (5×5) (45 kg N ha −1 ). Treatment combinations within the IF and 5×5 starter N strategies included SD at V4, V11, or 50:50 (split) V4 and V11. The PPI strategies involved 100% urea, 25:75 blend of urea with polymer‐coated urea, and poultry litter applied at 2.2 Mg ha −1 plus SD N at V11. There were few yield and profitability benefits to late‐season N application. The 5×5 strategy stabilized both yield and profit variability whereas the IF strategy occasionally reduced yield when SD was delayed from V4 to V11. Split N applications (i.e., multi‐pass) increased yield 4.4 to 16.1% compared with a one‐pass PPI strategy in 4 of 6 site years. Increased starter N rates (>45 kg N ha −1 ) may be required when full SD is applied at V11 but N source must be cost effective. When using IF and 5×5 strategies at N rates in the current study, in‐season SD N applications were required prior to V11. The V11 timing may be considered as a rescue application in northern corn regions but not standard practice.