90–120-day rule

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A rule for use of manure on crops (to prevent contamination with pathogens).

Manure should be properly composted to reduce pathogens to safe levels. However, if raw, uncomposted manure is used, it should be incorporated into the soil a minimum of either 90 days or 120 days prior to harvest.

  • 90 days when edible parts of growing crops do not contact the soil (e.g. taller crops like corn)
  • 120 days when edible parts of growing crops touch the soil (e.g. crops like watermelon)



James Peth

James Peth

James Peth, MS, MPH, PhD is an Assistant Prof. in Food Science and Human Nutrition at Colorado State University in Fort Collins, Colorado.