How large do my buffer zones need to be?

It depends! The NOP doesn’t give specific space requirements for buffer zones. The buffers need to be large enough to prevent contamination. It is your responsibility to assess the risks and establish a sufficient buffer. The width of buffers depend on individual farm circumstances. For example a larger buffer may be needed, if adjacent land is sprayed by a plane, or airblast sprayer or where prevailing winds blow from a non organic field to an organic field. Area topography and natural features may also be utilized as a buffer. A buffer may be smaller if it includes a tree line to act as a barrier to drift. All crops harvested from a buffer zone must be sold as conventional.
Water runoff from conventional fields can contaminate organic crops. If the possibility of contamination exists, it will need to be addressed through drainage ditches, grassed waterways, use of filtering wetlands, etc.