Safety Tips for Growing Food with Animal Manure

Growing food with animal manure can produce a healthy and vibrant garden. Here are a few tips for doing it safely…

Although humans have been growing food with animal manure for thousands of years, modern-day gardeners sometimes feel squeamish about it. It is true that improperly handled manure can carry diseases, but if you choose the right types of manure, and make sure it is well-cured before using, it is not only safe to use when growing vegetables, but one of the best sources of natural fertilizer that you can find.

Before using animal manure in your garden, you will want to make sure the manure is well-composted, and you will want to find a trustworthy source so that you can avoid any herbicide residues, growth hormones, heavy metals, and other undesirable substances that may be common in manure from, say, conventionally-raised livestock. The best source of manure for garden use is from animals raised organically and fed on pasture. Not only will your manure be richer and more nutritious, but it will also be safer to use on your garden – and to consume the food that is grown with it.

Of course, the best source is obviously from your own animals! (Now that we have chickens, we add their bedding to our compost pile every time we clean out the coop, creating a big lovely pile of rich compost by the time we use it a year later.) But if you have to buy manure for your garden, just make sure it’s from a farmer you trust, who uses organic and regenerative farming methods.

Here are a few tips for safely using animal manure in your vegetable garden:

…The same safety guidelines for poultry manure apply to other garden-worthy manures, which may come from cows, goats, horses, rabbits, sheep, or other grass eaters. Manures from carnivores or pigs should not be considered because they can host pathogens and parasites that can infect humans and can’t be composted away.

Spreading or digging in raw manure is an option in the fall because more than four months (120 days) will pass before the manured soil produces an edible crop. By then the manure will have decomposed and pathogenic Salmonella and E. coli bacteria in the manure will be vanquished by time, exposure, and soil-dwelling microbes. In the U.S., National Organic Standards allow for a shorter, 90-day waiting period for tall crops with edible parts that do not come into contact with the soil, for example, sweet corn or staked tomatoes.

…One of the challenges of using animal manures directly in the garden is guessing at how much to use, which varies with the type of manure and the next crop to be planted. Root crops often react badly to fresh manure of any kind, evidenced by twisted carrots and scabby potatoes. Composting manure before you use it, or simply allowing it to rot, reduces health risks and benefits the garden, too.

…Simply aging a manure pile for three months can kill about 60 percent of the weed seeds present, and bacterial counts start to drop within days after the manure leaves the animal. Then, when the aged manure is mixed into the soil, soil microorganisms clear out residual bacteria in about a month.

Yet the safest approach is to compost manure until it heats up, either by itself or combined with other materials. Bacterial counts plummet at about 100°F (37°C), while temperatures above 122°F (50°C) will kill many weed seeds. Hot composting animal manures can solve two problems at once.




Rose S.

An avid gardener since childhood, I love sharing my passion for gardening with others! I have gardened in a number of different climates and settings, from large fenced garden plots, to tiny patio and container gardens, and I firmly believe that everyone can learn to grow at least some of their own food - no matter where you live. Growing your own food can help you take control of your own health and food supply, and there has never been a better time to get started!

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