Manure is a valuable nutrient source, but if poorly managed, it can also be a wellspring of bacterial contamination for crops.

Lindsay Gilmour, Kimberly Raikes and Rodette Jones discussed contamination pathways and prevention methods during a Feb. 23 webinar presented by Future Harvest CASA.

Farmers need to recognize potentially hazardous situations, assess the situation and find methods to eliminate the risks of contamination, said Jones, who manages the Filbert Street Community Garden in Baltimore.

The closer a food product grows to the ground, the more vulnerable it is to contamination, Gilmour said. Leafy greens and squash, for example, would be in the manure splash zone.

When preparing to plant a field or lot, consider some possible problems. How was the land previously used? Was it a catchall for trash? A chicken pen? A compost site?

If you are not sure or suspect the land may be contaminated — a special concern for urban lots — test the soil.

Additionally, look at the nearby fields and woods, and see which direction the runoff and prevailing winds flow. A strong storm could wash manure particles downhill, and the woods may harbor animals that could contaminate the field.

The farm’s own livestock may be contamination risk if they are on pasture. There are dangerous bacteria in animal manure as well as in blood, urine, saliva, feathers and hide.

If goats or free-roaming chickens wander through the vegetable patch, they may spread contaminants in their wake.

If a farm has both livestock and crops, plan to limit access to the crops by fencing in the fields or fencing animals.

Consider, too, the possibility of farmworkers carrying contaminants from the chickens or cows into the garden beds or crop fields.

If the paths that access various areas of the farm travel through contaminants, the workers can easily carry those contaminants on their boots, even if they use the hand-washing stations.

Contamination Prevention Tips

There are several ways to avoid manure contamination.

Standard operating procedures should be clearly posted around the farm.

The farm hands should participate in the writing of these procedures. In so doing, they will get a thorough understanding of the procedures and will be invested in making them work.

Farmers should be ready to clean up when accidents happen.

A first-aid kit should be on hand to dress cuts on humans and animals. Farmers should provide hand-washing stations with water, soap, sanitizer, paper towels and a bin with a lid for disposal of towels and other items. Disinfectant foot baths might be useful when placed at garden and field gates.

Farms should keep equipment used in crop production away from livestock areas.

That equipment may be identified by color coding the handles. Coding flags can also be placed at the crop sites to remind workers which tools are to be used there.

Keeping water sources clean and safe from contamination may require some planning.

If a creek is accessible to the livestock, the banks should be fenced off or have riparian buffers. The buffers are excellent for protecting the stream banks, trapping nutrients, and encouraging pollinators to linger on the farm.

Fencing, though useful for excluding livestock from cropland, can be costly and requires regular maintenance.

Riparian buffers, by contrast, require an initial investment of time cleaning up the banks so that native plants and trees can thrive.

To watch the full Future Harvest CASA webinar, visit


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