Evaluation method of weed suppression by rice plant.

Greenhouse experiments were conducted to develop an evaluation method for determining the suppressive effects of 10 rice cultivars (ACI423, Chungmyungbyeo, Daelipbyeol, Hwajinbyeo, IACI65, Keumobyeo, Nonganbyeo, PI312777, Sathi and Taichung Native I) on 3 weed species (Echinochloa crus-galli, E. crusgalIi var. praticola and Monochoria vaginalis). Twenty-eight days old rice seedlings (6 to 7-leaf stage), grown at saturated, no drainage pot, were clipped above 3–4 cm from the soil surface. Weeds sown around the clipped rice stem, named ratoon sowing screening method, showed varietal suppressive difference to the 3 weed species. Sathi, ACI423 and P1312777 showed better suppressive activity to weed seedling growth than Nonganbyeo and Keumobyeo. Weed suppression by one plant of each rice cultivar could be evaluated using a cell size of 2.5x2.5 cm by clipping of rice seedling 29 days after sowing.