ALLELOPATHY IN FORAGE CROP SYSTEMS

Secondary plant metabolites and their degradation products are importa nt in all agroecosystems including those with forage crops. Allelopath y affects cropping systems and interseeding of one species into establ ished sods of another. Autotoxicity and heterotoxicity are types of al lelopathy. Alfalfa (Medicago saliva L.) has been investigated as both an autotoxic and heterotoxic species. Reestablishment of alfalfa immed iately after alfalfa has usually resulted in poor stands due to autoto xicity, and several other forage species also exhibit autotoxicity. Ma ny forage species have shown heterotoxicity, both between forage speci es and weed species. Several investigators have identified various all elochemicals and/or families of allelochemicals as being responsible f or allelopathic reactions. Identifying such chemicals would aid in dev eloping resistant forage cultivars and in maintaining a productive and profitable crop. Crop rotation, cover-crop management, interplanting, double cropping, no-till planting, and nonrotational cropping systems are involved with allelopathic effects. Some alfalfa cultivars posses s some resistance to these allelochemicals. Therefore, a breeding prog ram could provide resistant germplasms. Various forage grasses and som e weed species have demonstrated allelopathic effects on alfalfa, and alfalfa has allelopathic effects on some weed species. This alone may provide an insight for herbicide studies in alfalfa production.