Spring-planted mixtures of spring and winter cereals in a silage/fall pasture system have been shown to extend the grazing season in the Parkland of the Canadian prairies. Experiments were conducted at Lacombe, Alberta to determine the effects of planting date on yield and yield components of spring-seeded spring oat (Avena sativa L.), winter wheat (Triticum aestivum L.), winter triticale (X Triticosecale Wittmack) and winter rye (Secale cereale L.). The cereals were grown as monocrops or as binary mixtures of the oat and winter cereals. Treatments were planted in early May and mid-June and harvested twice for forage. The initial harvest for early and late planting dates occurred when oat reached the early-milk and heading stages, respectively. Regrowth was harvested in mid- to late September. The planting date x treatment interaction did not affect (P ≤ 0.05) annual yield (initial + regrowth) even though oat was harvested at different developmental stages. Averaged over treatments, late planting reduced annual yield by 42%. The annual yields ranked: mixtures = oat monocrop > winter cereals. Late planting date reduced the initial yield of all treatments, but the winter monocrops were reduced less than oat. Oat dominated the initial yield of all mixtures. Although oat tiller density was lower in the mixtures than monocropped oat at the initial cut, oat constituted a greater proportion of the mixture than would have been expected from the seeding ratio (1:1). A larger tiller weight in the oat mixture vs. the monocrop may have compensated for low tiller density in the mixture. Mixture regrowth yields tended to be greater in late-planted treatments and were dominated by the winter cereals. Although the winter cereal component of the mixture had more tillers at the regrowth cut, they still had lower yields when compared with their respective monocrops. Thus, late planting reduced annual yields of mixtures and monocrops, but did not limit regrowth of winter cereals in mixtures given equal regrowth periods. Key words: Oat, winter rye, winter wheat, winter triticale, forage yield, tillering
Grain yield of maize varieties of different maturity groups under marginal rainfall conditions