Guidelines For Using Manure On Vegetable Gardens
by: Val Hillers, Ph.D. , Extension Food Specialist
When fresh manure is used in a vegetable garden, there is a risk that pathogens that cause disease may contaminate garden vegetables. Pathogens (microorganisms which cause disease) that have been linked to manure applications include bacteria such as Listeria, Salmonella, andE. coli 0157:H7, as well as parasites such as roundworms and tapeworms.
The risk of manure application is greatest for root crops like radishes and carrots and for leafy vegetables such as lettuce where the edible part touches the soil. Careful washing and/or peeling will remove most of the pathogens responsible for disease. Thorough cooking is even more effective at killing pathogens on garden crops.
To reduce the risk of disease, we suggest these precautions:
- Composted manure is safest to use for gardens. You can either purchase composted manure or compost manure yourself. If you are composting manure, follow the American Organic Standards for compost production:
- the compost must reach a temperature of at least 130 degrees for a period of several days
- thoroughly mix the compost
- let the compost get to 130 degrees again
- If fresh (uncomposted) manure is to be used it should be applied at least two weeks before planting and roto-tilled or disked into the soil. The American Organic Standards state that unless manure is composted, it must be applied at least 120 days prior to harvest of products likely to be eaten raw.
- If the 120-day waiting period is not feasible, such as for short season crops like lettuce or leafy greens, apply only properly composted manure.
- For added safety, use water that meets drinking water standards to irrigate vegetables that are to be eaten raw. This is particularly important within one month of harvest.
- Thoroughly wash raw vegetables before eating.
- Do not use cat, dog, or pig manure in gardens or compost piles because parasites that can be in these manures may survive and remain infectious for people.