Soybean maturity group and planting date influence grain yield and nitrogen dynamics

Abstract Manipulation of soybean [Glycine max (L.) Merr.] maturity group (MG) and planting date will increase the yield of a soybean crop while simultaneously influencing the potential soil‐nitrogen (N) credits. Variations in N returned to the soil by soybean can significantly affect the amount of fertilizer‐N needed for the subsequent crop. Four soybean MGs (3.5, 4.7, 5.4, and 5.6) were evaluated at optimal and late planting dates in Arkansas. Grain yield was significantly different among MGs in 2016 (P = .0012) and 2017 (P = .0004), with the 4.7 MG consistently yielding the highest at 3,232 kg ha−1. Plant total aboveground N uptake (TNU) increased with increasing grain yield (P = .0167) and was significantly higher when planted in an optimal planting window (P = .0004). The N removed from the cropping system through grain harvest (147–201 kg N ha−1) was significantly different among MGs in 2016 (P < .0001) and in 2017 was significantly influenced by the planting date × MG interaction (P = .0397). The net N returned to the soil through unharvested biomass (24–75 kg N ha−1) was not influenced by planting date (P = .7796) or MG (P = .3475); however, net N returned decreased as grain yield increased (P = .0522). An optimum planting date of a well‐adapted soybean MG produces the highest grain yield, TNU, and N removed from the cropping system, identifying a relationship that allows producers to achieve maximum profitability while minimizing inputs to the whole farm system.