Competitive hability of plants for the use of environmental resources is affected by their morpho-physiological characteristics. There is no agreement on which rice plant characteristic is the most important in determining its competitive ability against weeds. This research aimed to identify flooded rice plant characteristics that contribute the most to its competitiveness. Thus, a field experiment was carried out during the 2000/01 growing season in Cachoeirinha, RS, to compare the behavior of eight rice genotypes, grown in the absence or presence of the EEA 406 rice genotypes, simulating a red rice infestation. Rice plant characteristics in the absence of competition were evaluated and at harvesting time, grain yield decrease was determined for each rice genotype, due to competition effect. The analysis of multiple linear regression and simple linear correlation showed that the ability of a cultivar to shadow the soil 60 days after seeding (DAS) was the variable more closely related to its competitive potential, and that this characteristic was especially associated with rice plant shoot matter accumulation at 15 DAS.
competition; interference; red rice; soil coverage; growth rate