If seed sizes vary within a lot, what adjustment should be considered to achieve uniform coating?

• A. Ignore the variation and apply a standard rate.
• B. Increase the coating thickness uniformly for all seeds.
• C. Use a different pesticide with no regard to size.
• D. Calibrate treatment rate per seed size to achieve uniform coating.

Answer: (D)

When coating seeds, the amount of coating needed depends on the seed’s size because larger seeds have more surface area and mass than smaller ones. If seed sizes vary but you use a single application rate, some seeds will be under-coated while others receive more than needed, resulting in non-uniform coverage.

Calibrating the treatment rate per seed size directly addresses this. By adjusting the amount of coating to match each size category (or using equipment that automatically adjusts dosing based on seed size), you achieve a more consistent coating thickness across all seeds. This improves protection where intended and reduces waste or potential phytotoxicity from over-application.

Ignoring size variation, or simply increasing thickness for all seeds, won’t fix the unequal coverage and can cause over-treatment of small seeds or under-treatment of large seeds. Choosing a size-based calibration ensures uniform coating throughout the lot.