Germination and growth management of some common annual weeds by phytotoxicity of selected vegetable crops

Phytotoxic effects of some vegetable crops including bean, cabbage, cauliflower, eggplant, pepper, potato, radish and tomato were investigated against Amaranthus retroflexus, Chenopodium murale, Eruca sativa, Malva sylvestris, Portulaca oleracea and Solanum nigrum weed species under laboratory and glasshouse conditions. Shoot extracts, foliage leachates and volatile materials of different crops significantly reduced seed germination and seedlings growth of different weed species in Petri-dishes. Leachates of cauliflower, pepper and potato were highly toxic to weeds. Extracts effects were concentration-dependent and roots were more inhibited than shoots. The effects of crops soil-incorporated dried shoot residues were varied on weeds and ranged from highly toxic to stimulatory. Residues of cabbage, cauliflower and bean were most toxic, while A. retroflexus, C. murale and P. oleracea were most sensitive weeds. Decayed residues of tomato, cabbage, bean and eggplant in the soil were most toxic to the tested weeds. Soil-applied extracts significantly reduced germination and growth of certain weeds. Growing weeds in the same soil after crops severely reduced shoot dry weight of most weed species with radish, cauliflower and bean were most toxic to A. retroflexus, C. murale and S. nigrum. Among weeds, M. sylvestris was most tolerant.