Starter Nitrogen and Growth Habit Effects on Late‐Planted Soybean

Abstract

AbstractIn the Gulf Coast region of the southeastern USA, soybean [Glycine max (L.) Merr.] is often planted in a double‐cropped system following corn (Zea mays L.). In this system, soybean planting date is delayed from the optimal range (mid‐May to mid‐June) to late July, causing a substantial yield reduction. Potential grain yield response has led to increased interest in indeterminate growth habit and N application for late‐planted, double‐cropped soybean systems. Our objective was to determine the interactiv effects of growth habit (determinate and indeterminate stem termination types) and starter N (0 and 50 kg ha−1) on soybean growth and yield when planted following corn in a double‐crop system. Three Maturity Group VIII soybean genotypes [the near‐isolines Au86‐2397I (Dt1Dt1, indeterminate) and Au86‐2397D (dt1dt1, determinate) and a determinate check cultivar, Cook] were planted in late July in seven Alabama environments during 1995 and 1996. Starter N increased R1 dry matter for both Au86‐2397D and Au86‐2397I by 0.50 Mg ha−1. Au86‐2397I had 1 cm greater average plant height at the R1 developmental stage and 14 cm greater height at R8 than Au86‐2397D. Au86‐2397I yielded 0.16 Mg ha−1 more than its determinate near‐isoline. Application of starter N decreased the number of nodules per root, but increased plant N concentration and dry matter yield. Grain yield was increased on average by 0.15 Mg ha−1 with addition of starter N. In this study, an indeterminate genotype soybean coupled with application of starter N promoted greater soybean growth and yield in a late‐planted, double‐cropped system.