THE ROLE OF ALLELOPATHY IN LEGUME DECLINE IN PASTURES .2. COMPARATIVE EFFECTS OF PASTURE, CROP AND WEED RESIDUES ON GERMINATION, NODULATION AND ROOT-GROWTH

Sterile cold water extracts of a range of residues from pasture, crop and weed species have been shown to exert allelopathic effects on subterranean clover and other species of pasture legumes, resulting in reduced germination, stunted growth of the radicle and reduced root growth and nodulation. Roots exposed to the extracts became discoloured and shortened with distorted and scant root hair formation which may result in reduced nodulation. Seedlings exposed to these allelopathic compounds were smaller, less robust and slower growing than the control seedlings and hence more susceptible to attack by plant pathogens.