Wheat and ryegrass competition for pulses of mineral nitrogen

Abstract

The ability of wheat to compete with annual ryegrass for pulses of extra nitrogen was examined by replacement series competition experiments. Nitrogen pulses were added to wheat and ryegrass monocultures and mixtures when wheat was at one of the following growth stages: first true leaf, two leaf, three leaf, four leaf and six leaf. Wheat competed effectively with ryegrass in terms of biomass accumulation if nitrogen was supplied before the three leaf stage. However, at the three to four leaf stage, wheat lost its ability to use mineral nitrogen effectively, while ryegrass maintained this ability at these same times. Thus, if mixtures of wheat and ryegrass are not supplied with adequate nitrogen in early phases of crop growth, ryegrass may predominate.