Permanent living mulches based on species mixtures can bridge the gap between organic and conservation agriculture practices in Mediterranean vegetable systems

This study investigated permanent living mulches as a strategy for integrating conservation agriculture practices into organic vegetable systems. Permanent living mulches were established using mixtures of perennial legumes ( Trifolium repens L., Lotus corniculatus L.) and self-reseeding species ( Trifolium subterraneum L., Medicago polymorpha L.) to exploit complementary growth cycles, improve weed suppression, and increase mulch persistence. The system was tested in a three-year rotation of broccoli, aubergine, fennel, and tomato under organic management in central Italy. Vegetables were transplanted into the living mulches using strip tillage without fertilizers, while two controls followed standard organic management with soil tillage, fertilization, and inter-row or inter- and intra-row weeding. The study assessed living mulch development, weed suppression, changes in weed community composition, and crop yield. Permanent living mulches suppressed weeds effectively during the first two years, and self-reseeding species increased total mulch biomass and improved weed suppression. However, mulch biomass declined over time while weed biomass increased, reducing agronomic benefits. Broccoli and aubergine yields were comparable to the fertilized and weeded controls, whereas fennel and tomato yield was substantially lower under living mulches. Weed communities also shifted, with Polygonum aviculare L. and Kickxia elatine (L.) Dumort. declining, Picris hieracioides L. and Lolium perenne L. increasing, and Cyperus rotundus L. remaining stable. Distinct communities developed between strip-tilled intra-rows, dominated by annuals, and mowed inter-rows, dominated by perennials. Permanent living mulches can therefore support the integration of conservation agriculture practices into organic vegetable systems, although periodic tillage may be needed to manage perennial weeds and maintain long-term system performance.