Effect of sample preparation on the estimation of residue levels of sprayed pesticides in separate analyses of turnip roots and leaves: inclusion or exclusion of the root-shoot junction.

The effect of inclusion or exclusion of the root-shoot junction on the estimation of pesticide residue levels in turnip roots and leaves was investigated. Turnips grown at two experimental sites were sprayed with six pesticides. At residue analysis, the turnips were divided in three segments: roots (R), leaves (L), and root-shoot junctions (J). The highest pesticide residue amounts were found in leaves ≥93% of total, with minimal amounts in roots. Residue amounts in root-shoot junctions were intermediate between those of leaves and roots. Residue levels were calculated for the root plus root-shoot junction, and were higher than those in roots: (R+J)/R=1.0-9.0. In contrast, residue levels in the leaf plus root-shoot junction were lower than in leaves only: (L+J)/L=0.76-0.91. The results indicate that the position of the cut between root and leaves could greatly affect the estimated pesticide residue levels when roots and leaves are analyzed separately.