FATE OF CARBOFURAN IN SELECTED SOILS OF SRI LANKA
DOI:
https://doi.org/10.31357/fesympo.v0i0.1258Abstract
Carbofuran (2,3 dihydro 2,2 dimethyl 7 benzofuranyl methyl carbamate) isthe most popular pesticide used in Sri Lanka. The fate, degradation anddissipation, of carbofuran was determined in four soil groups in Sri Lanka inorder to study the persistence of pesticide in soils after application.
Red yellow podzolic soils (Nuwara Eliya), Alluvials (Pugoda) and Regosols(Kalpitiya and Negombo) types were selected for the experiment.
For the degradation analysis, 10 g of each soil was incubated under 70% ofmaximum water holding capacity and 28 0 C of temperature at 13 hours lightand 11 hours dark conditions. 0.05 DCi of 14Cring labelled carbofuran (98%of chemical purity) was added to each soil sample and incubated in the aboveconditions. Liberated CO2 collected to an alkaline solution was analyzed byusing Liquid Scintillation Counter after 0, 1,3,5, 7, 14,28,56,90 days.
For adsorption studies, 5 g of soil mixed with Ippm pesticide solution wasshaken for 16 hours in the room temperature. The supemant collected aftercentrifuging was analysed using High Performance Liquid Chromatographhaving 18C Apollo column.
Carbofuran mineralization percentage was below 7.5% in all soils after 10days but a significant different showed in Kalpitiya regosols, which had arapid mineralization rate than other three soils. After 20 days mineralizationin Kalpitiya was 12.5% and in Pugoda it was 7.5%. After 90 days Kalpitiyaregosols showed over 60% of mineralization and in other three soils it wasbelow 50%. During 90 days incubation period only 10% mineralization wasshowed in Nuwara Eliya red yellow podzolic soils.
In the adsorption study K, value obtained were 1.64 for Nuwara Eliya, 0.63for Kalpitiya, 0.2 for Pugoda and 0.11 for Negombo. Hence Nuwara Eliyahas the highest adsorption rate and Negombo exhibited the lowest.
Nuwara Eliya has the highest organic matter among the selected soils andpesticide sorption can be expected to be the highest to Nuwara Eliya soils.
The microbial degradation is expected to be high in soils having high organicmatter but the degradation rate was highest in sandy soils in Kalpitiya. Henceit can be seen that chemical and other degradation is higher than microbialdegradation of pesticides in soils in Sri Lankan conditions.
