Competitive interactions of wheat withPhalaris minororRumex dentatus: A replacement series study

A replacement series study was conducted to evaluate the interference interactions between the weeds Phalaris minor or Rumex dentatus and wheat at two nutrient levels to test for changes in the competitive relationships of the weeds with varying nutrient availability. Plants were established in a mixture with proportions of 4:0, 3:1, 2:2, 1:3 and 0:4 (wheat: weed) plants per pot. The weeds exhibited clear differences in growth attributes and competition indices from wheat. Rumex dentatus showed significantly higher values for all growth attributes, relative yield, aggressivity and biomass. Both weeds performed better than wheat at high nutrient levels. Nutrient stress changed the intensity of competition between weeds and wheat, but did not change the weeds’ positions in the hierarchy. Therefore, although the competitiveness of P. minor and R. dentatus appears to be lower under poor nutrient conditions, they outcompete wheat irrespective of nutrient availability. Overall, the findings of the study suggest that wheat is more susceptible to resource competition from R. dentatus than P. minor.