Comparing nitrogen timing and sidedressing placement strategies on corn growth and yield in Michigan

Abstract

Spring and summer weather volatility plus poor N use efficiency emphasize the importance of improving corn (Zea mays L.) N management strategies. Synchronizing N application with crop uptake and flexibility for in-season sidedressing placement options may reduce N losses. Field studies in Michigan evaluated four N timing strategies: broadcast pre-emergence (PRE), sidedressing at V4 to V6 (0:100), a 50:50 split between preplanting incorporation and sidedressing at V4 to V6 (50:50), and 40 lb N acre–1 applied 2 inches below and laterally from the seed at planting followed by sidedressing at V4 to V6 (2 × 2). Within the 0:100, 50:50, and 2 × 2 strategies, the two sidedressing placement methods included coulter injection (CInj) and Y-drop surface application (YD). The PRE N strategy and YD placement were applied with and without a urease inhibitor (UI). During dry soil conditions following application, N timing, sidedressing placement, and their combinations did not affect grain yield. The agronomic efficiency (AE) of applied N increased by 11.2 to 13.5% with 2 × 2 and 0:100 compared with 50:50 and PRE and increased by 7.8% with CInj over YD, suggesting greater application efficiency with delayed N application and CInj placement. Grain yield, net economic return, and AE were not affected by UI. Midseason N applications allow greater flexibility and adjustments to rate and placement but uptake may be restricted with limited soil moisture. The benefits of YD surface placement may be better realized with adequate surface moisture or as late-season rescue N applications.