Mutual Effects of Rottboellia cochinchinensis and Maize Grown Together at Different Densities

A greenhouse experiment was performed to test whether competition, and possibly allelopathy, were involved in Rottboellia cochinchinensis–maize interactions in two soil conditions: fertilized and unfertilized. Changes in morphological and physiological growth parameters for each species were determined by classical plant growth analysis. The dry weight and total leaf area of maize grown with Rottboellia decreased significantly as the density of the weed or maize plants increased, particularly under unfertilized conditions. At high densities of Rottboellia, regardless of fertilization, its root biomass allocation was 38% greater than the stem and leaf biomass allocation. In contrast, in unfertilized conditions, Rottboellia biomass allocation was higher in leaves than in roots and stems at high densities of maize or Rottboellia. Relative crowding coefficient values indicated that maize had a competitive advantage over Rottboellia. Mutual allelopathic effects of maize–Rottboellia interactions were not fully demonstrated because plant relative yield values were not significant among treatments. When the density of Rottboellia increased, its total leaf area and total dry weight significantly decreased, greater than when the density of maize increased. These results indicate that intra-specific competition between Rottboellia plants was greater than inter-specific competition with maize. High densities of maize significantly reduced the total leaf area of maize and Rottboellia. Reductions in the total leaf area of maize were greater under unfertilized conditions. The results showed that maize was more affected by fertilization than by the density of plants.