Leaching potential of several insecticides and fungicides through disturbed clay-loam soil columns

Abstract

A laboratory study was conducted in order to determine the leaching potential of five insecticides and six fungicides commonly used during pepper cultivation by use of disturbed soil columns. The tested compounds were pyridaben, pyriproxyfen, tebufenpyrad, buprofezin and pirimicarb (insecticides/acaricides) and azoxyxtrobin, kresoxim-methyl, hexaconazole, tebuconazole, triadimenol, and pyrimethanil (fungicides). For this purpose, 100 µg of each pesticide were added to columns (n = 5) filled with 150 g of a clay loam soil and leached with 600 mL of 0.01 M CaCl₂ during 10 days. Finally, leachates and soil fractions were analysed for pesticide residues. For insecticides only pirimicarb was found in leachates (48% of the initial amount) while 55% was recovered from the soil layers. For the other studied insecticides, the percentage remaining in the top soil fraction was nearly the total amount added and therefore showing ‘non-leaching’ behaviour. In the case of fungicides 41% of triadimenol and 6% of pyrimethanil were found in leachates. The amount recovered in leachates for the other fungicides was lower than 2%, hexaconazole and tebuconazole exhibiting the higher retention on the upper layer of soil. Therefore, is extremely important to propose methods and conduct to avoid the potential adverse effect of pesticides behaving as ‘leacher’ compounds.

Keywords:

• aqueous/soil environment
• pepper protection
• pesticide mobility
• soil sorption constant

Acknowledgements

The authors acknowledge financial support from Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), of Spain, research project number RTA2005-00127-00-00.