Preventing Contamination

How To Prevent Contamination and Commingling on Organic Farms

Summary: To maintain organic certification, farms must prevent commingling (mixing) of organic and non-organic products and avoid contamination from prohibited substances like synthetic pesticides or treated wood.

This includes proper storage, equipment cleaning, buffer zones, and detailed recordkeeping—especially for split or parallel operations.

What Is Commingling and Contamination?

Under USDA Organic rules, certified organic operations must have systems in place to:

• Prevent commingling (mixing) of organic and non-organic products
• Prevent contamination from prohibited materials, like unapproved pesticides, treated wood, or synthetic fertilizers

These practices are required by the USDA National Organic Program (NOP) and reviewed during your annual organic inspection.

How to Identify Risk Areas on Your Farm

Look for places where organic crops could be exposed to non-organic crops or prohibited substances. Risk increases when you:

• Store organic and non-organic crops in the same area
• Reuse containers or equipment without cleaning
• Use custom services (planting, harvesting, spraying) for both organic and conventional fields
• Apply or store prohibited materials near organic areas
• Use shared or off-farm equipment without proper cleaning

Storage and Transport Requirements

Labeling Bulk/Nonretail Organic Containers

Containers used for storing or shipping bulk organic products must include:

• Product identified as organic
• A lot number or unique ID linking to your audit trail

Do I Need a Certified Transporter?

No. Transporters do not need to be certified as long as:

• The product is sealed and clearly labeled before pickup
• No relabeling, repackaging, or processing (including controlled atmosphere) occurs during transit

On-Farm Storage

Keep your crops from commingling or contamination by:

• Segregating organic and non-organic products
• Using clean containers, bins, and storage areas
• Keeping detailed records

Off-Farm Storage

Off-farm storage must be:

• At a certified organic facility, OR
• At an uncertified site only if:
  • Products arrive sealed and tamper-evident
  • No repacking or relabeling occurs
  • The facility completes Oregon Tilth’s Independent Storage Information Sheet

Treated Wood in Storage Areas

Treated wood must not come into contact with organic crops. If used in a storage building:

• Create a physical barrier (bins, distance, etc.)
• Avoid any direct exposure to crops or soil

Preventing Equipment Contamination

Using the same equipment for organic and non-organic crops increases contamination risk. Your Organic System Plan (OSP) must include:

• A list of shared equipment
• Documented clean-out procedures (e.g., pressure washing, purging)
• Cleaning records
• Preventative plans for leased or custom-hired equipment

What Inspectors Will Review:

• Equipment logs
• Cleaning procedures
• Post-harvest handling plans
• Use of shared tools and machinery

Buffer Zones: A Key Tool for Preventing Contamination

Buffer zones protect organic crops from neighboring non-organic land. You may need a buffer if your farm borders:

• Conventional crops treated with synthetic inputs
• Roadways with runoff risks
• Neighboring properties applying prohibited materials

Requirements:

• Buffers must be visible on your farm map
• Crops grown in buffers cannot be sold as organic
• Equipment used in buffers must be cleaned before use in organic fields

There is no set size for buffer zones. Factors include:

• Land slope and drainage
• Wind direction
• Crop type and planting density
• Type and proximity of prohibited inputs nearby

Treated Wood: What You Can and Can’t Use

Prohibited:

• New treated wood in contact with soil, crops, or livestock
• Structures such as:
  • Animal shelters
  • Feed or crop storage
  • Livestock fencing or gates
  • Stakes or posts touching soil or crops

Allowed (with restrictions):

• Pre-existing treated wood structures, if:
  • Contact with organic crops/livestock is prevented
  • Barriers or distance are in place
• Isolated treated wood outside of organic zones may be permitted, but you must:
  • Use a buffer zone
  • Avoid contamination risk
  • Never use creosote-treated wood

Split and Parallel Operations

Organic farms may also grow non-organic crops—but extra care is required to maintain certification.

• Split operation: Grows different organic and non-organic crops
• Parallel operation: Grows the same crop as both organic and non-organic (higher risk)

Requirements:

• Clear documentation of handling, storage, and transportation
• Equipment cleaning and segregation plans
• Strong buffer zones
• Enhanced recordkeeping to avoid confusion or contamination

Final Reminders for Preventing Contamination

• Identify and document all risk areas
• Keep clear labels on everything (containers, equipment, storage bins)
• Always clean equipment and document it
• Use buffer zones effectively and keep them on your farm map
• Never allow treated wood near soil, crops, or livestock without barriers

Your Organic System Plan is your main tool to demonstrate compliance. Keep it updated, accurate, and tailored to your operation.