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ThesisItem Open Access Fate of carbofuran applied to the soil basin of black pepper(Department of Soil science and Agricultural chemistry, College of Horticulture, Vellanikkara, 1996) Betty, Bastin; KAU; Wahid, P AAn investigation on the fate of carbofuran applied to the soil basin of black pepper (Piper nigrum L.) was conducted during 1992-1995 at the College of Horticulture, Vellanikkara. Laterite soils collected from the predominant pepper growing tracts of Kannur and Wayanad of Kerala state were used for the study. A field study was also conducted at the KADP farm attached to the College of Horticulture, Vellanikkara. The sorption of carbofuran in laterite soils and its persistence, influence of organic matter on the bio-availability of carbofuran, mobility of the insecticide in soil under field conditions and the effect of carbofuran on the growth of black pepper were assessed. The main findings of the study are given below. The sorption of insecticide in soil was found to be explained by Freundlich adsorption equation. The rates of sorption of carbofuran was not influenced by the organic matter contents . . An initial lag period was observed prior to carbofuran degradation in soil under laboratory conditions. Only one metabolite (3-hydroxycarbofuran) was detected as the product of degradation. The total content of 14C derived radioactivity was high in plants grown in soils with lowest organic matter content and vice versa. Hence, bioavailability of the insecticide is less in soils with high organic matter contents. So a discriminatory application of carbofuran is required depending on organic matter content of the soil. Thus for effective control of the pest in a soil with high organic matter content more quantity or carbofuran has to he applied than a soil with low content of organic matter. The residues of 14C-carbofuran absorbed plants left after HCl extraction, retained significant amounts of radioactivity which could be recovered following combustion. This indicated that determination of extraction efficiency by spiking or fortification of the samples with known quantities of insecticides would lead to overestimation of the recovery. The main metabolite of the carbofuran in the leaves was 3-hydroxy- carbofuran. Autoradiography of the bush pepper plants which was allowed to absorb 14C-carbofuran for 6 h showed that carbofuran was absorbed and translocated to the leaves and berry. Both carbofuran and hydroxycarbofuran were leached to the lower layers of soil (0-60 cm) during SW and NE monsoons. The content of hydroxycarbofuran was less than carbofuran in soils. In the foliage and berries carbofuran and the metabolite, 3-hydroxy- carbofuran accumulated. The content of hydroxycarbofuran was greater than that of carbofuran. As the harvesting time was delayed the content of residues also decreased. The early harvesting and use of immature berries may lead to more concentration of pesticide in the produce. This will lead to chances of more residue build-up in the human system.