Investigations on main harmful weed species and their agroecological management methods and allelopathic effects of cover crops in citrus orchards of çukurova region

Achieving sustainability in citrus cultivation increasingly requires the adoption of agroecological methods as alternatives to herbicides for effective weed management. This study aimed to identify such agroecological methods for weed management and to analyze the dynamics of weed species in the region. Field surveys were conducted in 111 citrus orchards in the Çukurova Region during the 2021 and 2022 growing seasons to assess weed species composition and distribution. A total of 106 weed species belonging to 29 families were recorded. The most common and major problematic species were Horseweed (Conyza canadensis L.), Common Purslane (Portulaca oleracea L.), Common Mallow (Malva sylvestris L.), and Sow Thistle (Sonchus oleraceus L.) respectively. In addition, studies were conducted in mandarin orchards in 2020 and 2021 to evaluate the effectiveness of various cover crops sown between the tree rows. The evaluated cover crop species comprised Vicia sativa L., Hordeum vulgare L., Secale cereale L., Poterium sanguisorba L., Onobrychis sativa Lam., Raphanus sativus L., Vicia villosa L., as well as various combinations thereof. Results indicated that Vicia villosa L., Secale cereale L., Vicia sativa L., and Hordeum vulgare L. were the most effective cover crops when grown as monocultures. Among the mixtures, the combination of H. vulgare + V. villosa and S. cereale + R. sativus + V. villosa provided the highest levels of weed suppression, achieving approximately 99% and 96% weed control, respectively. In-row weed management strategies included the application of mulch textiles, mowing (motorized trimmer), and both organic and synthetic herbicides. Among the evaluated applications, mulch textiles achieved by complete (100%) weed suppression and were identified as the most effective method. This was followed by organic herbicides, including clove and cinnamon oil as well as amino acid salt formulations, which demonstrated efficacy comparable to that of synthetic herbicides. Laboratory studies evaluating allelopathic potential of Vicia sativa and Vicia villosa extracts demonstrated that they inhibited the germination of Lepidium sativum L. (Garden Cress) seeds by 95%, while no inhibitory effect was observed on Lolium multiflorum L. (Italian Ryegrass). In conclusion, the findings suggest that cover crops, with their competitive traits and allelopathic potential, are effective in suppressing weed populations, offering a sustainable alternative to herbicides in citrus cultivation. Keywords: Agroecology, Cover crop, Allelopathy, Weed, Management.