(a) Each certifying agency shall determine that genetic purity and identity are maintained at all stages of certification including seeding, harvesting, processing, and labeling of the seed.

(b) The unit of certification shall be a clearly defined field or fields.

(c) One or more field inspections shall be made (1) previous to the time a seed crop of any class of certified seed is to be harvested, and (2) when genetic purity and identity can best be determined. The field shall be in suitable condition to permit an adequate inspection to determine genetic purity and identity.

(d) A certification sample shall be drawn in a manner approved by the certifying agency from each cleaned lot of seed eligible for certification. Evidence that any lot of seed has not been protected from contamination which might affect genetic purity, or is not properly identified, shall be cause for possible rejection of certification.