Effects of green manure cover crops (Canavalia ensiformis L. and Mucuna pruriens L.) on seed germination and seedling growth of maize and Eleusine indica L. and Bidens pilosa L. weeds

In Lab bioassays and Pot culture, we studied the allelopathic potential of aqueous extracts (0, 1.25, 2.5, 3.75 and 5 % wv-1 ) of green manure cover crops [jack bean (Canavalia ensiformis L.) and velvet bean (Mucuna pruriens L.)], on the germination and seedling development of weeds [goosegrass (Eleusine indica L.), blackjack (Bidens pilosa L.)] and maize (Zea mays L.) crop. 25 seeds of each weed or 10 maize seeds were separately sown in pots (soil + powdered green manure of jack bean and velvet bean mixed at 1%). Germination of both weeds was inhibited by the aqueous extracts in the order: leaf extract > stem extract > root extract. Soil amended with the green manure of jack bean and velvet bean reduced the emergence and growth of weed seedlings but had little adverse effect on maize. LC-MS revealed the presence of phenolics such as kaempferol in the tissues of both cover crops. Most of the phenolics demonstrated allelopathic activity on blackjack and goosegrass seeds. The jack bean and velvet bean extracts were phytotoxic to weeds (goose grass and black jack) but not to maize