Rice crop in the state of Rio Grande do Sul is characterized by the presence of water layer on the soil, which can cause pesticide runoff during the occurrence of rainfall. Thus, proper irrigation management can reduce pesticide transport into the environment. The objective of this study was to evaluate the effect of different irrigation managements on water runoff, transport and dissipation of clomazone, thiamethoxam, imidacloprid, trifloxystrobin, and propiconazol. The treatments were arranged in a factorial scheme and consisted of continuous flooding, intermittent flooding, and flushing irrigation (factor A) and by the application of the pesticides listed above (factor B). Total water runoff, and pesticide transport and dissipation rate were evaluated. Due to the larger rainfall storage, compared with continuous flooding, intermittent flooding and flushing irrigation provided a reduction of 53 and 95% of water runoff, resulting, respectively, in a reduction of 49 and 64% of the total mass transported into the environment in relation to the total applied in the field. The pesticide mass transported was lower than 3% of the total amount applied. Based on these results, it could be concluded that intermittent flooding and flushing irrigation minimize pesticide transport into the environment.Since the highest pesticide concentrations occur close to application time, it is of fundamental importance to conduct proper irrigation management providing maximum permanence in the environment.
environmental contamination; half-life water dissipation; runoff
