Soybean Light Interception and Yield Response to Row Spacing and Biomass Removal

Biomass removal effects on soybean [ Glycine max (L.) Merr.] light interception and yield under different row spacings have not been documented. Objectives for this study were to evaluate biomass removal, light interception, seed yield, and yield components of soybean under seven clipping treatments. Treatments in this study were clipping at V5, R1, R4, V5 + R1, V5 + R4, R1 + R4, and V5 + R1 + R4, and a control in 18‐ or 20‐cm and 76‐cm rows. In 1998, a dry year, biomass removal exhibited a negative linear relationship with seed yield in narrow rows ( r 2 = 0.62). A row spacing–clipping interaction was observed. In wide rows, clipping at V5 or R1 produced a compensatory response by increasing yield 12 and 5%, respectively. Generally, soybean in 76‐cm rows maintained seed yield by adjusting the number of pods or seed weight, except when clipping occurred at V5 + R4 or at three growth stages. In 1999, under severe moisture stress, row spacing influenced seed yield. Averaged across clipping treatments, narrow rows yielded 16% more (301 vs. 254 g m −2 ) than wide rows. Generally, soybean yield declined as clipping timing was delayed and as clipping frequency increased in narrow rows, except when clipping occurred at V5 + R1. Clipping at V5 and V5 + R1 did not affect yield in wide rows. All other clipping treatments suffered yield reductions ranging from 20 to 58%. A quadratic relationship ( R 2 = 0.83) was observed between biomass removal and seed yield.