ABOVEGROUND AND BELOW-GROUND INTERFERENCE OF WHEAT (TRITICUM-AESTIVUM) BY ITALIAN RYEGRASS (LOLIUM-MULTIFLORUM)

Greenhouse experiments in central Texas assessed the relative importan ce of above- and belowground interactions of semidwarf Mit wheat and M arshall ryegrass during vegetative growth. One experiment used partiti ons to compare the effect of no (controls), aboveground only belowgrou nd only, and full interaction for 75 d after planting (DAP) one wheat and nine ryegrass plants in soil volumes of 90, 950, and 3,800 mi. The results with the different soil volumes were similar. Wheat growth in the aboveground interaction only did not differ from controls. Howeve r, the full or belowground only interaction of wheat with ryegrass red uced wheat height, leaf number, tillering, leaf area, percent rural no nstructural carbohydrates in shoot, and dry weights of leaves, stems, and roots 45 and 75 DAP compared to controls. Wheat in full and belowg round interaction only did not differ from one another in growth. A re placement series experiment of 56 d also showed that the competitive a dvantage of ryegrass was relatively greater in root than in shoot grow th. No allelopathic response of wheat to ryegrass occurred. While the tallness of the semidwarf wheat minimized aboveground interference by ryegrass, the root growth of the thinner and more fibrous roots of rye grass greatly enhanced its belowground competitiveness.