April
2006
By
B. Rosie Lerner
Extension Consumer Horticulturist
Purdue University
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The Scoop on Poop
Gardeners have long used manure from various farm animals to fertilize
and enrich their soil. However, recent public awareness of food-borne
illnesses has left many gardeners wondering if using manure is safe.
There are a number of pathogens, including E. coli, salmonella, and listeria
that can be transferred to humans from animal manure. Some animal manure
may also contain parasites, such as roundworms and tapeworms.
If fresh manure is applied to the garden or compost pile, there is a high
risk of causing illness to the gardener, as well as anyone eating fresh
produce from that garden. Fresh manure can also be harmful to growing
plants, due to being too high in available nitrogen, thus burning roots.
It is safer for both plants and people to apply only composted, rotted
manure to an active garden bed. Manure should be composted for a minimum
of six months to reduce the risk of contamination. If fresh manure must
be applied, do so during the previous fall so that it has a chance to
decompose for as long as possible before the garden will be planted. Do
not apply manure to actively growing fruits or vegetables.
Root vegetables and other crops whose edible portion is harvested from
below ground pose the greatest risk of transmission, since they have the
most contact with potentially contaminated soil. Vegetables, such as carrot,
radishes, sweet potatoes, Irish potatoes, turnips, parsnips, onions and
beets, should be thoroughly washed and/or peeled to decrease risk.
Leafy vegetables, such as lettuce, spinach, cabbage, chard and other greens,
where the edible portion is in contact with soil, and especially crinkly
leaves that catch soil particles are also at high risk for contamination.
Some fruits may also be in contact with the soil, such as tomatoes that
are not staked or caged, and strawberries. Thorough washing and removing
outer leaves from heads of lettuce and cabbage will reduce risk. Thorough
cooking is the only way to eliminate the risk completely.
Manure from pigs, dogs and cats should not be used at all in gardens or
compost because they may contain parasites that can infect humans.
4-6-06
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