Relationship between plant uptake of pesticides and water-extractable residue in Japanese soils

Abstract

The relationship between pesticide concentrations in Komatsuna (Brassica rapa var. perviridis) shoots and the extractable concentrations in soils by a sequential soil-extraction method was investigated in 8 pesticides and in 4 soils. Concentrations of many pesticides in Komatsuna shoots showed higher positive correlation with water-extractable than with total-extractable soil concentrations. We also examined the effects of the soil-aging periods (SAPs) between pesticide applications and sowing on pesticide concentrations in Komatsuna shoots. Pesticide concentrations in Komatsuna shoots and soil-water extracts decreased with increasing SAPs. These results imply that estimating the pesticide concentrations in crops based on water-extractable concentrations in soil and setting the appropriate SAPs prevent contamination of crops by pesticide residues in soil. However, the correlation between pesticide concentrations in Komatsuna shoots and water extracts in soils, and the effectiveness of pesticide reduction in Komatsuna shoots by setting long SAPs differed according to the pesticide type. Hence, the applicability of the water-extraction method should be verified for each pesticide.