Crop field trials are conducted to determine the magnitude of the pesticide residue in or on raw agricultural commodities, including feed items, and should be designed to reflect pesticide use patterns that lead to the highest possible residues.

Objectives of crop field trials are to: (1) quantify the expected range of residue(s) in crop commodities following treatment according to the proposed or established good agricultural practice; (2) determine, when appropriate, the rate of decline of the residue(s) of plant protection product(s) on commodities of interest; (3) determine residue values such as the “Supervised Trial Median Residue” and “Highest Residue” for conducting dietary risk assessment; and (4) derive maximum residue limits (MRLs).  This Test Guideline requires one sample from treated plots at each sampling interval for crops that have eight or more crop field trials.

The test substance(s) should be stored under appropriate conditions for the study duration and applied soon after preparation or mixing. Test substance applications should not be made in strong wind, during rain or when rainfall is expected shortly after application. For all applications, the application rate should be expressed in terms of amount of product and/or active ingredient per unit area. At the end of each crop field trial, the (stored) samples are analysed for residue level (expressed for example in mg/kg).