Spatial distribution of C-14-benazolin residues and two tracers in lysimeters in comparison to a field plot experiment

Lysimeter studies with undisturbed soil cores are an important tool to inve stigate the fate of pesticides in agricultural soils. However, lysimeters d o not account for lateral flow patterns or for important differences in the hydrology of zero-tension systems. The aim of this study was to compare th e transport behaviour and residue pattern of C-14-benazolin applied to zero tension lysimeters and field plots. The soil and climatic scenario investi gated represented a realistic worst-case scenario (soil with <1.0% Corg, > 70% sand and > 800 mm precipitation/year). The transport experiment with th e C-14-labelled benazolin took 2.5 years. Six months before the final soil sampling date, the tracers chloride and brilliant blue were also applied. T he average amount of pesticide that leached through the three replicates of both systems was almost identical. Analysis of soil samples indicated that the amount and the spatial distribution of the C-14-residues of benazolin observed in the lysimeter test system were the same as in the undisturbed f ield. The vertical distribution of both tracers in the lysimeters correspon ded to the patterns observed under field conditions. The results showed tha t transport and degradation of pesticides can be assessed sufficiently prec isely by using lysimeters.