YIELD AND YIELD COMPONENTS OF CORN INTERSEEDED WITH COVER CROPS

The rising costs of pesticides, soil erosion, and environmental pollut ion associated with corn (Zea mays L.) production have led to consider ation of alternative production methods. Growing cover crops with corn could address these problems. Field experiments were conducted in 199 3 and 1994 at l'Assomption and Macdonald in Quebec to determine the ef fects of interseeding 12 cover crops on corn yield and yield component s. Fall rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), a m ixture of red clover (Trifolium pratense L.) and ryegrass (Lolium mult iflorum Lam.), a mixture of white clover (T. repens L.) and ryegrass, subterranean clover (T. subterraneum L.), yellow sweetclover (Melilotu s officinalis Lam.), black medic (Medicago lupulina L.), Persian clove r (T. resupinatum L.), strawberry clover (T. fragiferum L.), crimson c lover (T. incarnatum L.), alfalfa (Med sativa L.), and berseem clover (T. alexandrinum L.) were seeded 10 and 20 d after corn emergence. The experimental design was a split-plot, randomized complete block with four replications at each site. The mainplots were the cover crop plan ting dates; the subplots were the 12 cover crop treatments and 3 contr ols (hand weeding, chemical weeding, and no weeding). Seeding the cove r crops either 10 or 20 d after corn planting did not affect corn grai n yield. Chlorophyll fluorescence measurements (F-v/F-m) indicated tha t corn plants were stressed when interseeded with crimson clover (P < 0.05). When there was competition for moisture, crimson clover was fou nd to be too competitive with corn st the seeding rates used in this e xperiment. Corn yield was less affected by the interseeded cover crops under conditions of adequate rainfall. No consistent differences in c orn grain yield components were found for cover crop treatments.