Weed Control Effect of Different Organic Mulches inMediterranean Vineyards

Weeds are a major constraint in Mediterranean organic vineyards, where tillage is the dominant under-vine management practice but entails high labour costs and negative environmental impacts. This study evaluated the effectiveness of four organic mulches derived from local agro-industrial by-products (almond shells, almond peels, walnut shells and wine pomace) compared with conventional tillage over two growing seasons in irrigated vineyards (Vitis vinifera L.) in NE Spain. Weed cover was monitored monthly and analysed at the community level, together with soil properties, mulch persistence and vine canopy structure, which was assessed using LiDAR. Lignified mulches (almond and walnut shells and almond peels) consistently suppressed annual weeds (< 5% cover) across both years, whereas tilled plots exhibited recurrent flushes and wine pomace allowed higher weed emergence. In contrast, perennial weeds, particularly Cynodon dactylon (L.) Pers., progressively dominated all mulched plots, eroding treatment differences by the end of the trial. The indicator species analysis confirmed distinct associations: disturbance-adapted annuals (e.g., Chenopodium album L., Sonchus asper L. Hill) with tillage, and aggressive perennials (C. dactylon, Convolvulus arvensis L.) with mulches. Mulch decomposition rate influenced performance: persistent shells provided long-term suppression, while fast-decomposing wine pomace mulch enhanced canopy vigour but lost effectiveness against weeds sooner. Soil chemistry at 0–15 cm was only marginally affected. Overall, organic mulches offer a sustainable alternative to tillage for annual weeds and can improve vine growth but must be integrated with complementary strategies to limit perennials.