The objective of this research was to determine the influence of populations and relative emergence timings of red rice or of rice cultivar EEA 406 considered as a mimicker of red rice, on grain yield of rice crop and to compare explicative variables, to identify which one provides a better adjustment of data to the retangular hyperbolic model. Thus, two field experiments were carried out during the 1999/00 growing season. Treatments were arranged in a factorial design, consisting of three relative emergence timing (-9, 0, and 8 days in relation to the emergence of IRGA 417 cultivar) and by plant populations of red rice (Experiment 1) or of the mimicker cultivar (Experiment 2). The non linear regression model of retangular hyperbole was tested to describe the relation between rice grain yield loss and explicative variables. Anticipation of emergence of the red rice or of its mimicker cultivar, in relation to rice emergence, increased crop grain yield loss. Red rice showed greater competition potenctial with rice than the mimicker genotype. Plant population and soil coverage by the competing genotypes presented better adjustment than dry weight as explicative variables, in the mathematical models used to estimate grain yield loss in flooded rice.
Oryza sativa; interference; empirical models; explicative variables
