Forage and nitrogen yield of barley-pea and oat-pea intercrops

Barley (Hordeum vulgare L.) and oat (Avena sativa L.) have been intercropped with field pea [Pisum sativum subsp. sativum var. arvense (L.) Poir.] to increase forage yield and quality. Our objective was to evaluate the effects of two barley and two oat cultivars and seeding rates of cereal-pea intercrop on forage production, crude protein (CP) concentration, and N yield. A field experiment was conducted in 1993 and 1994 under dryland management in both fallowed and continuously cropped, no tillage environments. 'Bowman' and 'Horsford' barley, and 'Dumont' and 'Magnum' oat, were each sown at 93, 185, and 278 kernels m(-2) with 'Trapper' pea at 40, 80, and 120 seeds m(-2), in all possible rate combinations. The cereal cultivars also mere sown alone at 185 kernels m(-2). Cultivars developed for forage production (Horsford, Magnum) produced as much or more forage than cultivars developed for grain production (Bowman, Dumont) across sole-crop and intercrop plots (P less than or equal to 0.05). Forage yield was unaffected by intercropping when the cereal crop was sown at the sole-crop or greater rate. Less forage was produced by intercrops when the cereal component was sown at half the sole-crop rate. Forage yield was not affected by the pea seeding rate, but CP concentration increased with increasing seeding rate of pea in three of four environment-years. Forage N yield was unaffected by intercropping. These data indicate that the cereal component in barley-pea and oat-pea mixtures should be sown at a sole-crop or greater seeding rate for maximum forage production. Forage CP concentration can be increased as the relative proportion of pea seed to cereal kernels sown in a mixture is increased, but forage N yield may not be affected, since the cereal component contributes more to yield than the pea component.