Pig Manure For Compost: Can You Use Pig Manure For Gardens?
By: Anne Baley
Old-time farmers used to dig pig manure into their soil in the fall and let it decompose into nutrients for the next spring’s crops. The problem with that today is that too many pigs carry E.coli, salmonella, parasitic worms and a host of other organisms in their manure. So what’s the answer if you’ve got a ready source of pig manure and a garden that needs feeding? Composting! Let’s learn more about how to compost pig manure for use in the garden.
Can You Use Pig Manure for Gardens?
Absolutely. Add pig manure to your compost pile and allow it to rot long enough and hot enough. It will break down and kill all the organisms it might carry that are a danger to your health.
Compost is known by many gardeners as “black gold” for the amount of good it does in a garden. It aerates the soil to allow roots to go through easier, helps retain moisture and even adds many nutrients growing plants need. All this is created by turning unwanted garbage from your house and yard into a compost pile or placing it in a compost bin.
Pig Manure for Compost
The key to how to compost pig manure is that it needs to work at a high heat and be turned frequently. Build a pile with a good mix of ingredients, from dried grass and dead leaves to kitchen scraps and pulled weeds. Mix the pig manure in with the ingredients and add some garden soil. Keep the pile moist, but not wet, to get the decomposition action going.
Compost needs air in order to transform, and you give the pile air by turning it. Use a shovel, pitchfork or rake to dig down into the pile, bringing bottom materials up to the top. Do this at least once a month to keep the action going in your compost pile, and let it work for at least four months before you use it.
The best timing for using pig manure in the garden is to build a fresh compost heap in the fall when you’re cleaning up the garden and yard at the end of the season. Turn it over every three or four weeks until the snow flies, then cover it with a tarp and let the compost cook all winter.
When spring arrives you’ll be treated to a pile of rich compost, ideal for working into your soil. Now you’re ready to use your pig manure fertilizer in the garden.
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Read more about Composting Manures
NPK Values of Common Farmyard Manures – Cow, Horse, Pig, Chicken, Sheep & Rabbit
Let’s take a look at the N-P-K values of the most common farmyard manures. These are pretty variable according to the diet the animals have had, how long it has been rotted for etc but it gives a reasonable idea.
|N Nitrogen %||P Phosphorus %||K Potassium |
Using Manure "Wisely"
Question. Mike: I have manure available to me—horse and chicken—and am wondering how to best use them as fertilizer. Both are mixed with bedding material (straw and pine shavings). Do I have to compost this, or can I put the manure directly onto the garden? And do I need to add any other fertilizer to balance it out? I know manure is high in Nitrogen, and I don't want to end up with a lot of lush greenery and no flowers! Thanks.
- ---Lena in East Hampton, Connecticut
- --Benjamin in Bass River, NS, Canada
- ---Kathy in Albuquerque
Lets start with a definition. I'll try and do this delicately: The word "manure" refers to the solid waste the animal was all done with, plus the liquid waste, AND the material put down to cover the floor to make it less slippery by capturing Numbers One and Two. Typically, this bedding is straw, spoiled hay, wood shavings or some other carbon-rich material. So, you guys don't have manure and bedding, you have true 'manure'.
The waste is nitrogen-rich and the bedding is carbon-rich. Those of you who paid attention during compost class know that this perfect blend is all complete and ready for composting. And yes, composted it must be. Any manure can injure plants while it is still fresh, by 'burning' or dehydrating them. Yes, some farmers do use fresh manure on their fields, but they typically spread it in the Fall, so it will break down and be safe by Spring planting time. But this is a VERY inefficient use of the material. And it is extremely nasty on the smelliness end you will regret it greatly if you try this at home, kids.
And there's no reason to—manure composts VERY easily. Already that perfect combination of nitrogen and carbon, it quickly becomes a beautiful, crumbly, black, odor-free soil amendment. No container necessary—the best way to compost manure is in a big pile out in the open. (Fill that wonderful composter with shredded leaves and house and yard green waste instead!)
Don't worry unlike with spreading, manure will not waft any unpleasant odors after its first piled up. And it will have no odor at all when it's done and ready to use, even while you're turning it into the soil or shoveling it around your established plants, which is how you should use it when it is finished.
And while I wouldn't fill an entire composter with the stuff, small amounts of manure can certainly be added to a compost pile of shredded fall leaves or a mixture of shredded leaves and other green waste. And added it should be—many experts feel that adding some manure to such a pile creates the highest quality compost. You can use fresh or composted manure in such a situation, although fresh manure will help a slowpoke pile cook up much faster, especially in cool weather.
Now let's take a look at the differences between the various barnyard manures. Note that this is GENERAL information things like the age of the animals involved, how they're kept and fed, and the type of bedding are all going to affect the outcome. (Shredded newspaper, for instance, will produce much lower quality compost than the other bedding we've mentioned.) But in general:
- Cow manure is the 'coldest' that is, the least Nitrogen rich. But that's not a bad thing too much Nitrogen gives you big plants with few to no fruits and flowers. And cow manure is the most balanced of the barnyard manures, making it very appropriate for all garden uses.
Horse manure is 'hot' richer in Nitrogen and physically warm to the…eh…'touch' so to speak. It is alsolower in the 'fruiting and rooting' nutrients Phosphorus and Potassium, which is why we always warn people not to use horse manure on flowering plants. Use it on non-flowering, nitrogen-hungry plants like lawns, corn, potatoes, garlic, and lettuce but not on tomatoes, peppers, flowers, and such. This IS generally the manure most widely available to gardeners, however so at the very least, take it and incorporate it into your compost, where it will lose its fruit-and-flower inhibiting power.
Sheep. I was surprised in my research (yes—I looked stuff up this week!) to see that this is even 'hotter' than horse, with about half again as much nitrogen. But it is equally rich in Potassium, making it much more balanced. Sheep are smaller (and people say I'm not observant!) and less numerous than horsies, so I don't imagine you'd ever be offered much. But take what you can get, and use it sparingly. It's balanced, but rich.
Poultry. Hotter than hot! More than twice as hot as horse manure, so a little goes a long, long way. Mix small amounts of this material well into your compost piles and the result will be a powerful organic fertilizer. Again, keep the amounts small—and even then, keep an eye on any fruiting and flowering plants that receive this gift. If they get big but under-produce otherwise, back off a little. But feel free to use fairly large amounts on Nitrogen hungry plants like sweet corn.
"Other" If the poop-producer is a vegetarian (rabbit, gerbil, guinea pig, llama, elephant, rhino, etc.) go right ahead and incorporate it into your compost pile. (Warning—elephant pies are the size of a football, composed of mostly undigested roughage, and take forever to break down. I recommend helping things along with a machete and/or baseball bat. But once it is finally done, the resulting compost keeps the deer MILES away.)
Cooperative Extension Publications
Updated and revised by Richard Kersbergen, Extension Professor and Cooperating Professor in Animal and Veterinary Sciences.
Originally Developed by Mahmoud El-Begearmi, Extension Professor.
Reviewed by Beth Calder, Extension Professor and Assistant Professor of Food Science and David Handley, Extension Professor and Cooperating Professor of Horticulture.
For information about UMaine Extension programs and resources, visit extension.umaine.edu.
Find more of our publications and books at extensionpubs.umext.maine.edu.
Publicity about E. coli outbreaks has made people more aware of the risk of food-borne illness. As a result, many people are asking about the safety of using manure on vegetable gardens.
Animal manure can contain bacteria such as Listeria, Salmonella, and E. coli 0157:H7, as well as roundworms and tapeworms. These tiny organisms are called pathogens because they may cause disease. Pathogens can pass from animal manure to humans through direct contact between contaminated manure and fresh fruit and vegetables.
Note: some people may be more at risk for food-borne illness and should not eat uncooked vegetables from manured gardens. Those who should be most careful include pregnant women, the elderly, very young children, and those with health issues such as cancer, kidney failure, chronic liver disease, diabetes, or AIDS.
To reduce the risk of disease transmission, food safety experts suggest that you follow these safe gardening practices:
- Use composted manure. Composting manure with your yard and garden waste help reduce the risk of contaminating your garden vegetables with pathogens. Ensuring that your compost pile reaches a temperature of 140°F will further reduce the risk. For more information on home composting, contact your University of Maine Cooperative Extension County Office. Commercially processed manure, available in garden centers, should indicate on the package if it is pathogen-free.
- Never use cat, dog, or pig manure in vegetable gardens or compost piles. Parasites that may be in these types of manure are more likely to survive and infect people than those in other types of manure. It is also important to keep your pets out of your vegetable garden.
- Use water that meets safe drinking standards to irrigate your vegetables (for water testing information, contact your UMaine Extension County Office). This is most important within one month of harvest. If you use any water that is not drinkable (potable), such as water from old dug wells or rain barrels, to irrigate your garden, it is best to use drip (trickle) irrigation to both conserve water and minimize the contamination of leafy vegetables that can occur with overhead irrigation. Information on simple trickle irrigation techniques is available at your UMaine Extension county office.
If you do intend to use raw manure as a soil amendment or fertilizer source on your garden, follow these guidelines:
- Apply raw manure at least 120 days before harvesting a crop that has the potential for soil contact (leafy greens, root crops, etc). The USDA National Organic Program (NOP) standards allow a 90-day period between manure application and harvest for crops that don’t have direct contact potential with soil.
- For some gardeners in Maine, the best time to apply raw manure to your garden may be in the fall after harvest incorporate it into the soil and plant a cover crop to hold nutrients over the winter. This should be done before October 1 for good cover crop establishment.
- Never use raw manure as a sidedress to growing plants. Manure that is incorporated and distributed throughout the soil has a much lower risk of passing pathogens to the growing crop.
- Consider the source if you still want to use raw manures in your garden. Are the animals in the herd or flock healthy? Is there a parasite problem that requires regular deworming? Does the farm use antibiotics as a regular component of their feeding program?
In the Kitchen
- Make sure your hands are clean when handling produce. Regularly wash your hands with soap and water, especially when picking produce and bringing it into the kitchen for direct consumption or processing.
- Use proper hand-washing techniques, such as washing for 20 seconds with hot, soapy water and thoroughly scrubbing fingernails, hands, and between fingers. Dry hands thoroughly with a clean towel or single-use paper towels. Always wash hands after using the bathroom, changing diapers, and handling animals.
- Wash and peel your garden vegetables. All produce should be washed very well before you eat it. The risk of contamination is greatest for crops like radishes, carrots, and leafy vegetables such as lettuce, where the edible parts touch the soil. Washing with clean water and peeling will remove most of the pathogens that can cause illness. Fully cooking the vegetables will kill any remaining pathogens.
- Always wash with clean, potable water. Do not use soaps or chlorine washes to wash produce. Vegetable wash products are not necessary, and have not been found to be any more effective than clean water.* When washing or rinsing vegetables, don’t use water that is colder than the produce by 10°F or more.
*Crowe, Kristi, Alfred Bushway and Mahmoud El-Begearmi, 2004. Bulletin #4336, Best Ways to Wash Fruits and Vegetables. Food Safety Facts. Orono, ME: University of Maine Cooperative Extension.
This information is adapted from Guidelines for Using Manure on Vegetable Gardens with the permission of Washington State University Extension.
Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.
Call 800.287.0274 (in Maine), or 207.581.3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit extension.umaine.edu.
The University of Maine is an EEO/AA employer, and does not discriminate on the grounds of race, color, religion, sex, sexual orientation, transgender status, gender expression, national origin, citizenship status, age, disability, genetic information or veteran’s status in employment, education, and all other programs and activities. The following person has been designated to handle inquiries regarding non-discrimination policies: Sarah E. Harebo, Director of Equal Opportunity, 101 North Stevens Hall, University of Maine, Orono, ME 04469-5754, 207.581.1226, TTY 711 (Maine Relay System).
Animal manures and animal manure-based composts are rich in plant nutrients such as Nitrogen (N), Phosphorous (P) and Potassium (K) and provide organic matter that conditions the soil. While they can make excellent soil amendments for the home gardener, it is important to use them effectively and safely.
Manure or Compost?
There are no regulations or standards in New Hampshire that govern the many labels that can be used to describe soil amendments (“manure”, “aged manure”, “rotted manure”, “composted”, etc.). For the purposes of this fact sheet, “compost” refers to any mix of organic materials that has been partially decomposed to the point where its nutrient content is stable. This typically implies an active process, where the organic materials are managed carefully to speed decomposition. “Manure” refers to waste from livestock (including poultry, cattle, or horses), usually mixed with bedding such as sawdust or wood shavings and/or feed waste. Manures may be fresh – that is, they have not decomposed at all, or they may have decomposed (or “aged”) to varying degrees.
Generally, plant nutrients in manures and composts are measured in terms of pounds per wet ton it takes a lot of these materials to provide enough nutrients for plant growth. Nutrient content varies widely depending on the type of manure and the amount and type of bedding in it, and the ingredients in compost. While gardeners can use some general guidelines for nutrient content (see table below), the most accurate way to determine fertilizer equivalency is to have the material tested.
While most of the nutrients in manures and composts behave similarly in the soil to nutrients from commercial fertilizers, nitrogen is an exception. First, much of the nitrogen is not immediately available to plants, but instead becomes available slowly, as microbes digest it. Also, the availability of nitrogen depends on the ratio of carbon to nitrogen (C:N ratio). If the ratio exceeds 30:1, then most of the nitrogen is immobilized, or unavailable to plants, for an extended period. Manures or unfinished composts that contain a high proportion of bedding like wood shavings or sawdust have a high C:N ratio. This type of material “borrows” nitrogen from the soil as it decomposes, and the result is that garden plants may not have the nitrogen they need to grow.
The proportions of plant nutrients in composts and manures are usually different from what plants require for growth. In particular, these materials often contain more phosphorus than nitrogen. Thus, gardeners that apply enough of these materials to meet nitrogen needs for their gardens will likely apply far more phosphorus than is needed. Over time, this can lead to very high levels of soil phosphorus.
What’s the problem with high phosphorus? Very high soil phosphorus is not toxic, and will not harm plants or people, but when phosphorus moves into surface waters, it can lead to algae blooms, which harm water quality and aquatic organisms.
In order to use manures and composts effectively and responsibly, start with testing your soil for pH and soil nutrient status. If soil phosphorus is in the low to optimum range (up to 50 ppm on the University of New Hampshire (UNH) soil test), feel free to use manure or compost to provide nutrients. If soil phosphorus test levels are very high (over 100 ppm on UNH’s soil test), consider using nutrient sources other than manure.
In the soil test examples below, Garden A has very high levels of phosphorus, because of a history of compost applications. While nitrogen and potassium fertilizers are still needed for crops in this garden, this gardener should not add more compost or manure, to avoid becoming a source of phosphorus contamination. In contrast, Garden B has probably had very little or no compost or manure added to it, since the soil phosphorus levels are quite low. In this case, the gardener could add composts or manures to provide nutrients and organic matter.
For all the benefits of using manure and manure-based composts in the garden, there are also some risks. Animal manures harbor pathogens harmful to humans, including E. coli, Salmonella, and Campylobacter bacteria, and Giardia or Cryptosporidium protozoa. These organisms can affect people when they consume crops contaminated with soil, and under certain conditions, they can be taken up into plant tissue.
The risk from pathogens is greatly reduced when manure is composted correctly. To ensure that pathogens have been killed, the compost pile must reach a high temperature (between 131°F and 140°F) for a sustained period of time (several weeks). The compost must also be turned regularly and carefully monitored so that all of the manure has been exposed to sufficient temperatures. In home compost piles and in unmanaged manure piles, this rarely happens. Aged manure is not the same as composted manure, and it is not safe to assume that pathogens in an aged manure pile have been destroyed.
Another strategy for destroying pathogens is pasteurization. Some commercial poultry manure products are processed in this way. Pathogens, begin to die once incorporated into garden soil, and research has shown that incorporating manure at least 120 days before harvest greatly reduces risks of food borne illness.
There have been many cases where vegetable gardeners have unknowingly used manure and composts that are contaminated with herbicides and have seen herbicide injury in their vegetable gardens. The herbicides of concern are broadleaf herbicides used on lawns, turfgrass, pastures, and hay crops. Some of these materials can retain herbicidal activity for a long time, even after passing through an animal’s digestive system, and even after the resulting manure is composted. Treated grass clippings, and compost made from treated grasses, can also retain residues. The herbicides do eventually breakdown and lose activity over time, particularly as they are exposed to microbes, heat and moisture. This can take place relatively quickly, or can take up to several years, depending on the situation.
On sensitive crops, these herbicides can cause poor germination and kill seedlings, and they cause new leaves to become twisted and malformed. Sensitive crops include a wide array of crops including tomato and other solanaceous crops, lettuce, beans and other legumes, strawberries, grapes, and most other vegetable crops.
If you purchase manures and composts, make sure to be aware of this possibility and get assurance that herbicides are not present.
To Minimize the Health Risks Associated with Using Manures in Home Gardens
- Wait at least 120 days after applying raw or aged manure to harvest crops that grow in or near the soil (root crops, leafy greens, strawberries). Wait at least 90 days for other crops.
- Once the garden is planted, avoid using animal manures unless they have been pasteurized or actively composted.
- Never use cat, dog or pig manure in your compost pile or your vegetable garden. These manures are more likely to contain parasites that infect humans than other manures.
- Wash vegetables before eating.
- People who are especially susceptible to foodborne illnesses should avoid eating uncooked vegetables from manured gardens. Those who face special risks from foodborne illness include pregnant women, very young children, and persons with chronic diseases.
While manures and composts are excellent soil amendments for the home gardener, gardeners should be aware of the potential environmental and health risks associated with using manures and manure-based composts. Regular soil testing can help gardeners avoid soil phosphorus buildup from continuously applying manures and composts to soils, and gardeners can follow some simple tips to reduce the health risks associated with applying fresh manures to vegetable gardens.
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