FACTORS INFLUENCING RELEASE AND DISTRIBUTION OF CARBOFURAN FROM GRANULES INTO SOILS

Manipulation of soil concentrations of pesticides may he achieved by controlling the rate of release of the active agent from solid formulations. Such controlled release granules have reduced losses in delivery of soil pesticides, such as carbofuran, leading to lower application rates in the field and less leaching hazard. A high carbofuran content (35%) solid formulation was based on by-product lignin modified with polyvinyl chloride (10%) and which can degrade in the soil and thus release completely the active ingredient. As part of a series, studies on factors influencing the release and fate in soil of carbofuran delivered in this form were performed on granules and thin flake formulations of the lignin-based carbofuran matrix under static water and various non-leaching soil conditions at constant temperature. Two agricultural soils were used; one originating in Northern Britain and the other from Sudan. Release and distribution of the carbofuran from the formulations into the soil was evaluated over 17 weeks according to the soil type and water content. Comparison was also made for the two particle sizes used and with release under sink conditions of water immersion. Results indicated that certain soil properties influenced the release kinetics and that the rate was correlated with moisture content of each soil type. However, the kinetics fitted a model that was generally valid for all the environments studied.