Weed Species Composition and Abundance in Conservation vs. Conventional Tillage Sunflower Fields

Abstract

Comparative field assessments of weed species composition and abundance were conducted in sunflower (Helianthus annuus L.) systems under conservation and conventional tillage practices to evaluate shifts in weed community structure and dominance patterns. Field surveys across representative plots recorded higher weed density and species richness under conservation tillage, with a marked increase in perennial and broadleaf species compared to conventional systems dominated by annual grasses. Dominant taxa included Cyperus rotundus, Amaranthus viridis, Parthenium hysterophorus, and Echinochloa colona, indicating habitat-specific weed shifts influenced by soil disturbance intensity and residue retention levels. Multivariate analysis using ordination techniques revealed clear separation of weed communities between tillage regimes, with conservation systems exhibiting higher evenness and functional diversity indices. Reduced soil inversion and increased surface residue in conservation tillage were associated with suppressed emergence of light-dependent weed species and enhanced persistence of rhizomatous perennials. Findings underscore the importance of integrated weed management strategies tailored to tillage-induced ecological shifts in sunflower production systems for sustainable crop protection. Weed seed bank dynamics further reflected greater stratification in conservation tillage fields, where minimal soil disturbance promoted surface accumulation of viable propagules and prolonged germination flushes across cropping stages. Herbicide efficacy also varied across systems, with reduced penetration and altered spray-soil interactions in residue-rich plots contributing to inconsistent control outcomes in conservation tillage. Overall, the study highlights that tillage system-driven habitat modification plays a central role in shaping weed assemblages and their competitive interactions with sunflower crops. These insights support site-specific integrated weed management planning in diverse agroecological conditions.