Using lysimeters to evaluate the relative mobility and plant uptake of four herbicides in a rye production system.

Information regarding pesticide mobility is critical for the evaluation of pesticide management practices. Lysimeters have been used worldwide to assess the transport and plant uptake of solutes under relevant moisture regimes and crop production practices. We used repacked field lysimeters to evaluate the leaching and plant uptake of the herbicides pendimethalin, clopyralid, mecoprop (MCPP), and dicamba following fall and spring application to soil cropped to winter rye (Secale cereale L.). In most fall and spring trials, mass loss of herbicide through leaching was <3% of the amount applied. On the basis of this 6 year experiment, it appears that clopyralid is the most mobile of the tested herbicides in this soil, followed by dicamba, mecoprop, and pendimethalin. None of the herbicides was present in rye grain or straw at concentrations that exceed current E.U. or U.S. tolerances.