Starter Nitrogen and Growth Habit Effects on Late-Planted Soybean
1998
Starling, Michael E. | Wood, C Wesley | Weaver, David B.
In 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 interactiveffects 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.
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