Evaluation of competitive ability of the main cultivated rice varieties against red rice

There are several structural and technical factors that determine rice production. Among others, we have to take into account weed management. Red rice (=Oryza sativa L.) is undoubtedly one of the most troublesome weeds in rice production in some regions of Portugal. In order to be able to better control this weed, the knowledge of red rice biological behavior, in relation to different environmental conditions, is considered essential to bring out strategies of weed management fit for an integrated production of rice of a high quality. This experiment was conducted to study the competitive ability of the most important rice varieties (Ariete and Thaibonnet) against red rice, at 2 N rate and 4 densities of the weed. This research allowed besides understanding preliminarily if shattering is related only to the genetic features or depends also on agronomical or environmental conditions, such as N supply and condition of competition.