Delay of harvest effects on forage yield and regrowth in spring and winter cereal mixtures

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Spring-planted mixtures of spring and winter cereals extend the grazing season and maximize dry matter yield if the initial defoliation is delayed until the milk stage of kernel development of the spring cereal component. However, fall regrowth may be less than spring-planted winter cereal monocrops. Research was conducted at Lacombe, Alberta to determine the effect of time of initial cut and winter cereal species on initial yield, regrowth yield and factors affecting regrowth (tiller density, water-soluble carbohydrate (WSC) and etiolated regrowth immediately post-cutting) of the winter cereal component of spring-seeded monocrops of fall rye (Secale cereale L.), winter triticale (× Triticosecale Wittmack) and winter wheat (Triticum aestivum L.) and in binary mixtures with spring barley (Hordeum vulgare L.). Treatments were planted in early May and harvested initially when the barley reached the boot (B), heads emerged (H), H + 2 wk, H + 4 wk and H + 6 wk stages. Three weeks after the initial cut a regrowth harvest was conducted. Initial yields of both mixtures and monocrops increased until approximately H + 4 wk and H + 6 wk respectively, with no differences due to species in the mixture. The effect of crop stage at initial harvest on regrowth was much larger than the species effect. Monocrop regrowth decreased almost linearly with delay of defoliation, while that of the mixture (winter and spring components combined) declined at a faster rate. Tiller density, WSC and etiolated regrowth also followed decreasing trends with time of initial cut in the monocrops and mixtures. These trends were due directly or indirectly to very low light intensities in the lower levels of the canopies of both cropping systems after H + 2 wk. Both initial and regrowth yields of the winter cereal component of mixtures involving rye and triticale were generally superior to those involving wheat. The ability of the winter cereal component to regrow in mixtures may be related to plant size and therefore ability to compete during initial growth. In general, the initial harvest of the mixture should occur no later than H + 2 wk of the spring cereal component in order to allow sufficient time for recovery of the winter cereal component after harvest. Otherwise, a spring-seeded winter cereal would be a better alternative for fall pasture. Key words: Delayed harvest, spring and winter cereals, forage yield, regrowth