Summer green manure effectively suppresses malignant weed growth in citrus orchards of the three gorges reservoir area

To clarify the dynamic changes resulting from summer green manure mulching on the growth of summer weeds in citrus orchards in the Three Gorges Reservoir area and to further optimize green manure planting patterns, this study evaluated five green manure species: Crotalaria spectabilis, Vigna radiata, Vigna unguiculata, Dolichos lablab, and Glycine max. Weed density, biomass, average weed control efficacy, soil seed bank size, weed species composition, and weed diversity indices were analyzed under summer green manure mulching in citrus orchard rows to investigate the effects of different species on weed diversity dynamics. The results showed that all five green manure mulch treatments effectively suppressed the growth of malignant weeds compared to the naturally occurring grass treatment. Among them, the V. unguiculata treatment reduced weed density by 77.79% and biomass by 75.91%, demonstrating the best mean weed control, followed by Vigna radiata and Dolichos lablab treatments. During the various growth stages of green manure, more weed species emerged, with perennial weeds such as Alternanthera philoxeroides, Artemisia argyi, Digitaria sanguinalis, and Cyperus rotundus being dominant. As the green manure crops matured, weed growth was mainly dominated by Eleusine indica, A. philoxeroides, D. sanguinalis, and occasional Echinochloa crusgalli, with a noted irregular pattern of occurrence. The comprehensive results demonstrate that summer green manure mulching can effectively inhibit summer weed occurrence in citrus orchards and can be promoted as a weed management strategy in the Three Gorges Reservoir area.