Grazing Winter Wheat: I. Response of Semidwarf Cultivars to Grain and Grazed Production Systems

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Abstract
Most wheat (Triticum aestivum L.) research in west Texas is conducted in ungrazed wheat that is managed solely for grain production (grain system). In contrast, most commercial wheat is planted early and grazed by cattle (Bos spp.) prior to management for grain production (grazed system). The objective of this research was to understand cultivar × production system interactions. Four semidwarf cultivars, TAM 105, Newton, Vona, and TAM 108, were grown in irrigated grain and grazed production systems for 3 yr. Grazed wheat headed 2.3 d later, had 57 and 62% as much above‐ground biomass and leaf area at heading, was 80% as tall, and yielded 80% as much as wheat grown in the grain system. There was a significant cultivar × system interaction for grain yield 2 yr (P = 0.088 in 1982, P = 0.001 in 1984) caused by differential cultivar response to yield constraints such as lodging, winterkilling, and shattering. In the 3‐yr combined analysis there was no cultivar × system interaction; however, the cultivar × system × year interaction for grain yield was significant (P = 0.003) because yield constraints within systems were not consistent across years. In 1984, extra fertilizer and insecticide reduced grain yield of TAM 108 by 18% (P = 0.001) in the grain system due to increased lodging while having no measurable effect on grain yield in the grazed system. If production systems frequently differ in type or degree of yield constraints, then breeders and agronomist must be concerned with cultivar × system interactions.