Weed community responses and maize productivity under different weed control approaches

Abstract

Effective weed control is essential for maize productivity, but its success depends on weed community composition and intervention timing. This study evaluated how control method and timing affected weed communities, maize growth, and grain yield. A field experiment with eight treatments and three replications was arranged in a randomized complete block design in 2024. Treatments comprised weedy and season-long weed-free controls, pre-emergence and post-emergence herbicides, hand weeding, and three sequential combinations. Weed density, biomass, and species composition were assessed at 20 and 55 days after sowing (DAS), together with maize growth and yield. Seventeen weed species from 11 families were recorded. The community was dominated by Cyperus rotundus L., Eleusine indica (L.) Gaertn., Mazus pumilus (Burm.f.) Steen., and Alternanthera sessilis (L.) DC., although their relative importance changed over time. Weed responses were mainly species-specific and were not consistently explained by life cycle. At 20 DAS, treatments containing pre-emergence S-metolachlor reduced weed biomass by 61.1–65.2% relative to the weedy control. At 55 DAS, pre-emergence herbicide and hand weeding alone provided 53.8 and 66.2% control, respectively, whereas sequential programmes provided 87.7–99.3% control. Post-emergence atrazine + mesotrione alone reduced weed biomass by 98.2% at 55 DAS; however, because it was applied at 40 DAS, it provided no early-season control. Grain yield was significantly lower in the weedy control (3.1 t · ha⁻¹) than in all weed-control treatments, with the highest yields in the sequential and season-long weed-free treatments. Weed biomass was more strongly negatively associated with grain yield at 55 DAS (R² = 0.759) than at 20 DAS (R² = 0.324). Overall, treatment timing and complementary interventions were important for maintaining weed suppression and maize productivity, while species-specific responses should guide control selection.