EFFECT OF RED RICE, DESICCATED BY NON-SELECTIVE HERBICIDES, ON IRRIGATED RICE: H. GRAIN YIELD AND OTHER AGRONOMIC CHARACTERISTICS

Abstract

Red rice (Oryza saliva L.) is considered the most serious weed in rice crop in Rio Grande do Sul. Severaltechniques are employed to decrease its infestations on irrigated rice, among them, the use of minimum tillage. The objectiveof this research was to evaluate the effects of red rice chemical management on grain yield and agronomic characteristics ofirrigated rice in minimum tillage system, as well as to define the time in which such management can be performed. To reach thispurpose, a field experiment was conducted in 1996/97, with the following treatments: red rice desiccation periods (10, 6, and2 days before, and 2 days after rice sowing), non-selective herbicidas (sulfosate, at rates of 825 and 1650 g/ha, and paraquat at400 g/ha), plus controls without herbicide application (with and without start nitrogen fertilization), and systems of irrigatedrice sowing (in presence and in absence of red rice residues). The results showed that the presence of rice residues interferednegatively on grain yield of rice, especially when sowing occurred dose to herbicide application. Sulfosate, especially at thelow rate, caused reductions in most of the parameters evaluated.