SLOW RELEASE FORMULATIONS OF THE HERBICIDE MCPA BY USING CLAY-PROTEIN COMPOSITES

BACKGROUND: MCPA [(4-chloro-2-methylphenoxy) acetic acid] is a widely used herbicide showing a high leaching in the soil. In this study, clay-protein-based-formulations of this herbicide were designed to reduce the risk of water pollution resulting from conventional formulations. RESULTS: Clay-gelatin formulations of MCPA were prepared and the influence of synthesis parameters such as pH and the presence of a plasticizer (glycerol) on the active substance content and performance of the new formulations were examined. Differential scanning calorimetry (DSC) measurements provided information on the stability of the gelatin matrix in the gelatin-clay complex. Fourier transformed infrared (FTIR) spectroscopy showed that the herbicide was retained by the formation of hydrogen bonds with side amino groups of the protein backbone and polyion complexation. Clay-protein-based-formulations prepared at a pH below the isoelectric point (pI) value of the protein and in the absence of glycerol provided the slowest release of MCPA in water. Soil columns experiments showed a four-fold reduction in leaching and improved bioactivity in the upper soil layer for the new formulation compared to a commercial product used as a control. CONCLUSIONS: A reduction in the recommended dose of MCPA can be achieved by employing clay-gelatin, which reduces the environmental risk associated with herbicide applications