|(a) Care must be exercised in planting to avoid mixing of the variety in the seeding equipment and in the transporting vehicle. The applicant must see that these machines are thoroughly cleaned in order to safeguard the purity of the seed. Identity of the seed must be maintained at all times. (b) Every field for which certification is requested shall show evidence of good management and shall show that reasonable precaution has been taken to control contamination by other varieties. Constant roguing must be practiced throughout the season. The right is reserved to reject a field on general certification principles when weeds, diseases, or lack of good management make accurate inspection difficult or impossible.