Spatial distribution of 14C-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 investigate the fate of pesticides in agricultural soils. However, lysimeters do 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 the transport behaviour and residue pattern of C-14-benazolin applied to zero tension lysimeters and field plots. The soil and climatic scenario investigated represented a realistic worst-case scenario (soil with <1.0% Corg, > 70% sand and > 800 mm precipitation/year). The transport experiment with the 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. The 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 field. The vertical distribution of both tracers in the lysimeters corresponded to the patterns observed under field conditions. The results showed that transport and degradation of pesticides can be assessed sufficiently precisely by using lysimeters.