Comprehensive Analysis of the Value of Single Versus Multiple Year (Season) Crop Residue Data for Establishment of Maximum Residue Levels (MRLs)

Disharmony currently exists in regulatory requirements regarding whether multiple seasons of field residue trials are necessary. This analysis used historical residue data to evaluate whether the year in which trials are conducted is a significant contributor to the overall variability in field residue data. It was concluded that residue behavior is highly variable in nature, regardless of the season, that variation of residue data compiled from multiple years is not statistically greater than data resulting from trials conducted within any one year, and that variation across years does not result in large systematic differences in residue values or resulting Maximum Residue Limits compared to trials conducted in any single year. Field trials conducted at a variety of locations across geographical regions will capture variability due to different environmental conditions and agricultural practices and provide a robust estimate of the spread of residues expected due to labeled use of a pesticide.