Estratégias de cultivo em área de arroz irrigado para controle de arroz vermelho: estudo de caso

Abstract

Red rice (Oriza sativa L.) is the most important weed in rice culture, which can reduce productivity. With the advent of the Clearfield® system, it became possible to control it using herbicides belonging to the imidazolinone chemical group. However, several cases of red rice resistant to these herbicides have already been identified, intensifying the problem especially when rice is sown in dry soil. The objective of this paper was to describe the potential of different cropping systems in rice areas to reduce the presence of red rice resistant to these herbicides, through a case study conducted in a field. The work was conducted in the city of Manoel Viana, located in the western border of Rio Grande do Sul, during the 2021/2022 crop year, using two treatments: minimum tillage (CM) and pre-germinated (PG). This commercial crop had been under minimal cultivation for several years prior to the implementation of the treatments. The presence of susceptible and resistant red rice was assessed in soil samples collected after the harvest of the 2021/2022 crop. The collections then were stratified, at the following depths: 0.0-0.15m and 0.15-0.30m. At the same soil collection points in each plot, rice was harvested to estimate grain yield (kgha-1), grain mass, and whole grain yield. We observed a higher number of red rice seeds present in the area cultivated in pre-germinated system, but only 7.95% of these seeds generated plants, in the previous crop. However, in minimum cultivation, 33.86% of seeds generated plants. This result, together with the higher average yield and percentage of whole grains, leads to the conclusion that the use of the pre-germinated system, besides reducing problems with red rice, can also improve the economic gain of the product.