Critical Timing of Weed Removal in Dry Bean as Influenced by the Use of Preemergence Herbicides

Abstract

Abstract The critical timing of weed removal (CTWR) is the point in crop development when weed control must be initiated to prevent crop yield loss due to weed competition. A field study was conducted in 2018 and 2020 near Scottsbluff, NE to determine how the use of preemergence herbicides impacts the CTWR in dry bean. The experiment was arranged as a split-plot, with herbicide treatment and weed removal timing as main and sub plot factors, respectively. Herbicide treatment consisted of no-preemergence, or pendimethalin (1070 g ai ha–1) + dimethenamid-P (790 g ai ha–1) applied preemergence. Sub-plot treatments included season-long weed-free, weed removal at: V1, V3, V6, R2, and R5 dry bean growth stages, and a season-long weedy control. A four-parameter logistic model was used to estimate the impact of time of weed removal, for all response variables including dry bean yield, dry bean plants m–1 row, pods plant–1, seeds pod–1, and seed weight. The CTWR based on 5% yield reduction was estimated to range from the V1 growth stage [(16 d after emergence (DAE)] to the R1 growth stage (39 DAE) in the no-PRE herbicide treatment. In the PRE-applied treatment, the CTWR began at the R2 growth stage (47 DAE). Dry bean plants m–1 row was reduced in the no-preemergence treatment when weed removal was delayed beyond the R2 growth stage in the 2020 field season. The use of preemergence-applied herbicides prevented a reduction in the number of pods plant–1 in 2020, and the number of seeds pod–1 in 2018 and 2020. In 2018, the number of pods plant–1 was reduced by 73% when no-preemergence was applied, compared to 26% in the preemergence-applied treatment. The use of preemergence-applied soil active herbicides in dry bean delayed the CTWR and preserved yield potential.