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ISHS Acta Horticulturae 664: IV International Symposium on Irrigation of Horticultural Crops

PERSISTENCE AND MOBILITY OF MALATHION AND PARATHION IN HORTICULTURAL SEMIARID SOILS

Authors:   L. Andrade, P. Marcet, E.F. Covelo, M.L. Reyzábal
Keywords:   Organophosphates content, Depth variation, Fluventic Haplustols, Petrocalcic Paleustols
DOI:   10.17660/ActaHortic.2004.664.1
Abstract:
The surrounding soils of Bahía Blanca were dedicated to intensive horticultural use six decades ago. Soils with different ages of horticultural use were evaluated for the effects of the organophosphate applications. The content of malathion and parathion at different soil depths at 44 sites from Bahía Blanca horticultural belt (Argentina) were determined. An alkaline soil pH, amongst other factors, favours the degradation of organophosphate pesticides, but this is not sufficient to compensate for annual applications repeated over a period of five decades. The highest values are found in the soils that have been cultivated for more than fifty years and the highest content at a depth from 0-5 cm (6659 and 11103 μg kg-1 of malathion and parathion respectively), indicating their low level of mobility. In soils that have received large amounts of these products over this period of time, they are found at all levels of the soil profile. The relative mobility of malathion and parathion depends more on their properties and the time that the land has been dedicated to intensive horticultural cultivation, than on the physicochemical properties of the soil or of the crop. The oldest farm showed the highest values (malathion contents: 6659, 6006, and 4936 μg kg-1, and parathion contents: 11103, 10254 and 9051 μg kg-1, at 5, 10 and 20 cm depth respectively) confirming their accumulation over time and their persistence due to the lack of biological degradation. The results indicate that these insecticides are immobile under semiarid conditions and show a relative high adsorption on soil particles.

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