EVALUATION OF COVER CROP MIXTURES FOR USE IN VEGETABLE PRODUCTION SYSTEMS

Planting polyculture mixtures of cover crops can optimize the benefits of their use. Thirteen polyculture mixtures of cover crops were evalu ated in Columbus and Fremont, Ohio, to find a species mix that would e stablish quickly for erosion control, overwinter in Ohio, contribute s ufficient N and have a C : N ratio between 20:1 and 30:1 to optimize N availability for subsequent crops, be killable by mechanical methods, and have high weed control potential. All of the mixtures in Columbus had achieved 30% ground cover 1 month after planting, but only four o f the mixtures achieved this in Fremont due to poor conditions at plan ting. Above-ground biomass (AGE) accumulation in the mixtures ranged f rom 3631 to 13,642 kg.ha(-1) in Columbus, and 449 to 12,478 kg.ha(-1) in Fremont. Nitrogen in the AGE ranged from 74 to 269 kg.ha(-1) in Col umbus, and 10 to 170 kg.ha(-1) in Fremont. Weed cover in the cover cro p plots ranged from 1% to 91% eight weeks after cover crop kill in Col umbus, and 12% to 90% seven weeks after cover crop kill in Fremont. Be cause one or more species in each screened mixture was determined not to he suitable, none of the mixtures was optimum. However, information gained about performance of individual species within the mixtures is also useful. 'Nitro' alfalfa (Medicago sativa L.),ladino clover (Trif olium repense L.),subterranean clover (Trifolium subterraneum L.), Aus trian winter peas [Pisum sativum ssp. Arvense (L.) Poir], and annual r yegrass (Lolium multiflorum Lam.) did not overwinter dependably in Ohi o, Tall fescue (Festuca arundinacea L.), perennial ryegrass (Lolium pe renne L.), and orchardgrass (Dactylis glomerata L.) did not compete we ll with taller, more vigorous species, and were not persistent in the mixtures. Medium and mammoth red clover (Trifolium pratense L.), annua l and perennial ryegrass, and white and yellow blossom sweetclover [Me lilotus alba Desr., and Melilotus officianalis (L). Desr.], were not k illable by mechanical methods, Individual species that established qui ckly, were competitive in the mixtures, overwintered dependably, and w ere killed by mechanical methods were rye (Secale cereale L.), barley (Hordeum vulgare L.), crimson clover (Trifolium incarnatum L.), and ha iry vetch (Vicia villosa Roth.).