Abstract:
Two pot experiments were carried out in the glasshouse to determine the effects of density of wheat population, level of nitrogen fertilizer and degree of soil waterlogging on the competition between Wimmera ryegrass and wheat for nitrogen but not light, and for nitrogen and light up until the late tillering stage of wheat. Wheat competed successfully with ryegrass for nitrogen and for nitrogen and light, reducing tiller numbers and dry weight production of the ryegrass by up to 60 per cent. Competition from ryegrass had little effect on tiller and dry matter production of wheat. Increasing the density of wheat population had no significant effect on the yield of ryegrass when there was competition for nitrogen but significantly reduced yield when there was competition for nitrogen and light. Both species responded positively to nitrogen fertilizer and negatively to temporary waterlogging, but neither of these effects significantly changed the competitive relationship between the two species. These results are discussed in relation to the success of ryegrass as a weed in wheat crops.