4. Discussion
The market for agrochemicals designed for use on irrigated rice crops is
dynamic. Around a decade ago the residue most commonly detected in areas
cultivated with irrigated rice was the herbicide quinclorac. Although it did not
represent a risk of environmental impact (Resgalla et al., 2007), the use of this
product on irrigated rice fields has reduced, mainly due to the loss of
agronomic efficiency in relation to the predominant weed species in the fields.
Market strategies and efficiency of use appear to determine the sales cycle of
products more than their environmental risks. The use of the herbicide
bentazon, as an alternative for the control of weeds resistant to other
herbicides, has increased in the southern region of Brazil in recent years. As
its use has intensified an increased frequency of the presence of residues has
been observed, as well as an increase in the concentrations detected in water
samples collected from the river basins.
There are few studies on the presence of pesticide residues in the waters
surrounding the rice crop in Brazil. However, in the south of Brazil,