Optimal soybean maturity group selection is influenced by planting date in northern production systems

Abstract

Changing climate conditions have resulted in a shift towards longer growing seasons in Michigan and other northern U.S. states, providing soybean [Glycine Max (L.) Merr.] growers an opportunity to achieve early planting dates (PDs). However, increasingly variable spring precipitation may result in a wide range of PDs. Current soybean maturity group (MG) recommendations are based only on optimal PD and may not fully utilize the available growing season. To determine how MG selection should be adjusted based on PD, six varieties ranging from MG 1.0 to 3.5 were planted on four PDs (from late April to late June) during the 2018 and 2019 growing seasons at two locations in Michigan. Seed yield increased by an average of 286, 171, and 73.0 kg ha−1 for each 0.5-MG increase when planting was conducted on day of year (DOY) 120, 140, and 160, respectively. When planting was delayed to DOY 180, there was a yield reduction of 51.4 kg ha−1 for each 0.5-MG increase. The increase in yield from using a late MG in early planting was correlated with an increase in seeds m−2 which was mainly driven by a consistent increase in cumulative growing degree days during pod and seed set. Results from this study indicate that soybean growers can increase seed yield and profitability by adjusting MG selection based on PD such that the maximum available growing season is utilized. Specifically, using a late MG when planting early and an early MG in late-season planting can maximize yield and profits.