The impact of crop rotation and tillage practices on weed flora of cotton in the southern fertile crescent

Background: Weeds remain a key constraint in cotton systems of Southeastern Anatolia, and agronomic practices, including crop rotation and conservation tillage, may alter weed communities and pressure. Objective: The primary objective was to quantify the effects of crop rotation and tillage on weed flora (density/diversity, and key species) and cotton yield. Methods: Field studies were conducted at Harran University (& Scedil;anl & imath;urfa, T & uuml;rkiye) during 2021-2024 using three tillage methods [conventional tillage (CT), reduced tillage (RT), no tillage (NT)] and three cropping systems (cotton/cotton; cover crop [vetch + triticale]/cotton; wheat/ maize/cotton). Weed species, their densities/diversity, and cotton yield were recorded. Results: A total of 69 weed species (23 families) were recorded. Amaranthus palmeri, Sorghum halepense, and Physalis angulata were the dominant weeds. Weed density/diversity was highest under cotton/cotton (=50-120 plants m-2) and lowest under wheat/maize/cotton (=20-60 plants m-2). Weed density was significantly altered by tillage practices, and the highest (=60-140 plants m-2) and the lowest (=20-70 plants m-2) densities were recorded for NT and CT, respectively. The highest cotton yield (=5,940-6,670 kg ha-1) was recorded for cover crop/cotton, whereas cotton/cotton resulted in the lowest yield (=4,070-4,260 kg ha-1). Conclusions: Crop diversification reduced weed pressure compared with continuous cotton, and CT generally minimized weed density relative NT. However, crop rotation or tillage alone was insufficient for weed control. The findings support integrated weed management that combines cultural practices and herbicide programs. Nevertheless, longer-term trials years) are needed to confirm the results.