Nanoparticles based
on biodegradable polymers have been shown to
be excellent herbicide carriers, improving weed control and protecting
the active ingredient in the crop fields. Metribuzin is often found
in natural waters, which raises environmental concerns. Nanoencapsulation
of this herbicide could be an alternative to reduce its losses to
the environment and improve gains in its efficiency. However, there
is a paucity of information about the behavior of nanoformulations
of herbicides in environmental matrices. In this study, the stability
of nanoencapsulated metribuzin in polymeric nanoparticles (nanoMTZ) was verified over time, as well as its dissipation
in different soils, followed by the effects on soil enzymatic activity.
The physiological parameters and control effects of nanoMTZ on Ipomoea grandifolia plants
were investigated. No differences were verified in the half-life of
nanoencapsulated metribuzin compared to a commercial formulation of
the herbicide. Moreover, no suppressive effects on soil enzymatic
activities were observed. The retention of nanoMTZ
in the tested soils was lower compared to its commercial analogue.
However, the mobility of nanoencapsulated metribuzin was not greatly
increased, reflecting a low risk of groundwater contamination. Weed
control was effective even at the lowest dose of nanoMTZ (48 g a.i. ha–1), which was consistent with
the higher efficiency of nanoMTZ compared to the
conventional herbicide in inhibiting PSII activity and decreasing
pigment levels. Overall, we verified that nanoMTZ
presented a low environmental risk, with increased weed control.
With extensive use of herbicides in agricultural areas, the risk of contamination of groundwater and surface water by these products has become a worldwide concern. Practices of application or maintenance of soil organic residues that have begun to be used in agriculture for soil nutrition have demonstrated other benefits besides nutrient supplementation, such as reduced mobility and increased soil degradation of herbicides. Because it is the final destination of herbicides, soil and its constituents, especially organic matter in tropical soils, play a prominent role in processes that encompass the dynamics of herbicide molecules. In this context, it is necessary to know the influence of the organic matter and its constituents on the behavior of the herbicides. This review discusses the main relationships of organic matter in the retention, transport, and transformation processes of herbicides in the soil, as well as the interference in the weed control effectiveness of these products. Because of this, knowing the influence of organic matter in the various processes related to the behavior of herbicides in the soil allows us to adopt more appropriate management practices regarding both weed control and remediation of contaminated areas. However, despite the wide range of information on the subject in the literature, each situation is distinct due to the wide variation in the behavioral response of the products to the different types of organic material present in the soil.
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