Weed Community Response to Halosulfuron‐Methyl in Bottle Gourd ( Lagenaria siceraria ) and Rotational Safety to Mustard (

ABSTRACT

Bottle gourd ( Lagenaria siceraria ) production is generally constrained by complex weed communities dominated by purple nutsedge ( Cyperus rotundus ). While halosulfuron‐methyl is widely used for sedge control, the quantitative understanding of how weed community dynamics influence crop yield and rotational safety in vegetable systems remains limited. A two‐year field study was conducted at the Punjab Agricultural University Regional Research Station, Abohar, to compare POST‐applied halosulfuron (52.5 and 67.5 g ai ha ⁻¹ ) with PRE‐applied pendimethalin (750 g ai ha ⁻¹ ), a hand‐weeded standard, a weed‐free, and untreated control in randomised block design. Halosulfuron at 67.5 g ha ⁻¹ reduced total weed biomass by 80% compared with the untreated control and was more effective than pendimethalin. Total weed biomass explained 88% (35 days after bottle gourd sowing; DAS) and 89% (55 DAS) of yield variation (−38 kg fruit per kg weed biomass; R ²  ≥ 0.88), and C. rotundus biomass alone accounted for 80%–84% of the variance in yield. Regression analysis further identified biomass thresholds associated with a 10% yield loss, highlighting the crop's high sensitivity to early‐season weed interference. Application of halosulfuron at 67.5 g ai ha ⁻¹ and hand weeding, both treatments produced 46–47 t ha ⁻¹ bottle gourd yield, about 89% of the weed‐free. To evaluate rotational safety for mustard, field emergence, early biomass and seed yield were assessed. Equivalence testing indicated that halosulfuron at 52.5 g ai ha ⁻¹ and pendimethalin were statistically equivalent to hand weeding for mustard emergence and early biomass. In contrast, the halosulfuron 67.5 g ha ⁻¹ did not meet the equivalence criteria, with large effect for emergence and seed yield, although ANOVA detected non‐significant treatment effect on mustard seed yield. Therefore, the higher halosufuron rate should be considered effective for sedge suppression in bottle gourd but require cautious approach for succeeding mustard crop.