Allelopathic effects of rye, brown mustard and hairy vetch on redroot pigweed, common lambsquarter and knotweed

In bioassays, the water extracts of rye, brown mustard and hairy vetch biomass were toxic to target species, suggesting the release of phytotoxins from plant biomass. The toxic effects on germination were extracts concentration dependent. Root growth was more affected than shoot growth. We found that allelopathic inhibition of weeds occurred through different toxic mechanisms: (i) reduction in seeds germination, (ii) lengthening the germination process and (iii) slow growth of seedlings. All these factors may reduce the plants population in the field and thus their competitive ability. In terms of inhibition of weeds germination and particularly root growth of seedlings, the test crop followed the order: brown mustard > rye > hairy vetch. Their weed suppressing ability may be used in future weed management strategies. Weed control may be further improved with proper cultural practices, i.e. delaying the time of residue incorporation into soil in spring if soil biota rapidly inactivates toxic allelochemicals and increasing cover crop biomass through seeding density or fertilization.