Storing compost for fresh produce cropping systems

The new proposed produce safety rule part of the Food Safety Modernization Act is fairly prescriptive about storing and preharvest application of compost.

Compost can greatly contribute to overall plant and soil health, adding beneficial bacteria and fungi as well as providing organic material and available nutrients. From a food safety perspective, improperly prepared compost from animal manure, animal mortality or post-consumer food residue used in growing fresh produce can be a hazard. According to Michigan State University Extension, proper storage of composted animal-derived materials is essential to ensure a reduced risk of contamination. The newly released produce rule as part of the Food Safety Modernization Act is fairly prescriptive as to what constitutes appropriate storage conditions under the rule.

The proposed produce safety rule as part of the Food Safety Modernization Act proposes that storage of the final composted product be done in a manner that prevents a reintroduction of fresh animal derived materials. From the produce rule’s perspective, ensuring that animals do not have access to compost piles and avoiding the mixing of piles of different ages are important to the integrity of the final product.

Properly composted material requires a preharvest interval of 45 days after application when it is applied in a way that minimizes crop contact. If the compost with animal-derived materials is not properly made or not maintained after creation in a manner that ensures a recontamination event does not occur, it must be treated like raw manure. The preharvest application window for raw manure under the proposed produce safety rule is nine months prior to harvest.

As of March 4, 2013, these compost guidelines are proposed and not final. The final rule regarding compost use in fresh produce may vary, so it is important to stay aware of what is finally decided. You may comment on the proposed guidelines.

If you have specific questions about food safety aspects of compost use or have difficulty tailoring GAPs to your farm, contact the Agrifood Safety Work Group at or 517-788-4292.

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