Optimal corn hybrid relative maturity is dependent on planting date in northern production systems

Abstract Climate change has allowed corn ( Zea mays L.) growers in northern regions to achieve early planting dates (PDs) but increase in extreme spring precipitations can cause significant delays. Current corn hybrid relative maturity (RM) decisions are based on only typical PD. It is important to understand how hybrid RM should be adjusted based on PD to ensure full utilization of the growing season. Field trials were conducted in Lansing, MI, from 2021 to 2023 to evaluate the impact of multiple PDs (late April to early June) and hybrid RMs (89–109 RM) on grain yield, partial returns, and phenology. Grain yield responded significantly to hybrid RM adjustment at day of year (DOY) 120, 130, and 150 with an average yield gain of 1.10, 0.75, and 0.55 Mg ha −1 for every 5‐unit increase in hybrid RM, with 62% of the gains explained by higher kernel number. At DOY 120, 130, and 150, partial returns increased by $229, $118, and $91.5 ha −1 for every 5‐unit increase in hybrid RM, respectively. With delayed planting, hybrid RMs matured quicker by compressing growing degree days (GDD) between 2.1 and 4.4 GDD per day of planting delay. Overall, growers in northern regions (40°–43° N) can benefit by using hybrids 5–10 units longer than the optimal RM under early planting. For late May and early June planting, maintaining the optimal RM or switching to 5 units shorter hybrids, respectively, is necessary to maximize profit and reduce risk of frost damage. We recommend additional research in different environments to provide quantitative RM adjustments based on PD.