2017-08-16 / School News


“The ‘Safe’ Scoop on Poop”

Dung or manure (i.e. poop) has been used by farmers through the ages and is valuable for the garden for many reasons. Manure contains micronutrients as well as “NPK”-nitrogen, phosphorus, and potassium which are critical to plant health. It also contains — large amounts of humus, a bulky, fibrous material that comes from hay/grass fibers in the animal droppings particularly of large grazers. It has many advantages: it improves the soil by increasing air circulation, water infiltration and moisture-holding capacity as well as decreasing compaction. It also helps build organic matter by acting like a reservoir allowing nutrients to work, and it’s a valuable source of microbial activity allowing bacteria to convert nutrients into forms that are more useable by plants.

There are however some important manure safety guidelines to keep in mind. Animals vary in their ability to digest and absorb their food. Digestion processes do not kill bacteria that are harmful to humans. Fresh manures can contain bacterial pathogens such as E. coli, salmonella, listeria and parasites such as roundworms and tapeworm that can infect humans. Never use uncomposted animal manure on existing plants. The most important safety guideline is that all types of manure should always be composted.

There are several composting options. It can be added to your general cold compost slowly over several days or weeks, allowing plenty of air to circulate in the compost bin. Add other organic matter like grass clippings, leaves and water to break up the manure and speed curing. Turn the compost regularly as you add more manure. Stop adding the manure two months before you plan to use it in the garden. You’ll know the manure is well composted when it produces no heat and loses most of its objectionable odor. When dry it is dark colored, fine and crumbly like good soil. It can also be left in a big pile all on its own. The pile should be at least 3’x3’x3’ and turned periodically (like general compost, it will take 8-12 months to break down). Of course, the best method is to add it to hot compost. A report from Colorado State University Cooperative Extension says that, “to be on the safe side, manure should be hot composted at 130 to 140 F° for at least five days. Then the hot composting should be followed by a curing period of two to four months to get rid of any pathogens that survived the heat.” The National Organic Program provides the following guidelines on land used to grow crops for humans: any raw animal manure must be composted and incorporated into the soil at least: “120 days before harvesting any leafy green crop or root crops and 90 days before harvesting any above ground fruiting crops that don’t make soil contact (such as caged/staked tomatoes).”

Other safety considerations include: not using manure from pigs, dogs, and cats. If the animal is a meat eater, do not use the material in any form. If you use composted manure, thoroughly wash and brush raw vegetables and fruits in running water right before eating — even fragile fruits. Peel root crops like carrots and potatoes. Of course, always wear boots and gloves. Following these simple guidelines will improve the safety of your harvest.

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