Influence of time of emergence of wild oat on competition with wheat

Summary The influence of time of emergence of wild oat (Avena fatua L.) on its competition with wheat (Triticum aestivum L.) was studied, using boxes that allowed separation of root and shoot competition. The relative yield total for mixtures of wild oat and wheat, grown under different forms of competition and with different wild oat sowing times, was very close to unity, indicating that the two species competed fully for limiting resources. Wild oat was more competitive than wheat when the two species were sown simultaneously, due largely to its greater root competitive ability; the two species had similar shoot competitive abilities. When wild oat was sown 3 or 6 weeks later than wheat, wheat was more competitive than wild oat and the production of wild oat panicles was prevented. This was mainly the result of greater root competitive ability of the wheat, although shoot competitive ability was also greater. The effects of root and shoot competition were additive. It is concluded that in order to prevent the return of wild oat seeds to the soil, and hence obtain long‐term benefit, it is necessary to control the wild oat seedlings emerging within the first 3 weeks after drilling a wheat crop.