Branch Dry Weight in Relation to Yield Increases in Narrow‐Row Soybean

Abstract

AbstractPrevious studies indicated total dry matter at R5 (TDM,R5) played a more important role in narrow‐row yield increases at late compared to optimal planting dates in soybean [Glycine max (L.) Merr.]. The objective of this study was to test the hypothesis that greater TDM(R5) in narrow vs. wide rows at late plantings stimulates yield by increasing vegetative branch dry matter (BDM,R8), branch yield components, and branch reproductive dry matter (BRDM). Field studies were conducted during 1987 and 1988 at optimal (May) and late (July) planting dates, with two commercial soybean cultivars (Forrest, Maturity Group V and Centennial, Maturity Group VI), and 100‐cm (wide) rows/normal plant population, 50‐cm (narrow) rows/normal plant population, and 50‐cm rows/high plant population. The test was conducted at Baton Rouge, LA on a Mhoon silty clay (fine‐silty, mixed, nonacid, thermic, Typic, Fluvaquents) soil. Narrow compared to wide row spacing resulted in greater BDM(R8) at both planting dates. However, increased BDM(R8) was correlated with whole plot yield (r2 = 0.92***, significant at P = 0.001) only at the late planting. Narrow‐row‐increased BDM(R8) was responsible for greater yield at this planting date because it was associated with increasing branch yield components which are reduced by late planting: branch number, total branch length, branch node number, and branch pod and seed production. In conclusion, data supported the hypothesis that the close association between narrow‐row‐increased TDM(R5) and yield at late plantings is related to increased branch dry matter and branch yield component production.