Adverse impacts of allelopathy in agricultural systems

Literature reporting the allelopathic potential of weeds and crop residues is cited. A weed for which there is considerable evidence in support of allelopathy is Elymus repens, inhibiting growth and decreasing yields of many temperate crops including Trifolium spp., Medicago sativa and barley. Several compounds (p-hydroxybenzoic acid, vanillic acid and tricin) have been implicated as the allelochemicals responsible. Residues of Vigna unguiculata, Melilotus alba, wheat, rye, maize, Lens culinaris, Pisum sativum, and chemicals in the bark of peach trees (amygdalin) and apple trees (phloridzin) also cause growth inhibition. The physiology of allelopathic growth inhibition is discussed in relation to its action on nitrification and nitrogen fixation with particular reference to E. repens.