Horse manure in gardens

Making And Using Horse Manure Compost

Horse manure is a good source of nutrients and a popular addition to many home gardens. Composting horse manure can help your compost pile become super charged. Let’s look at how to use horse manure as fertilizer and in the compost pile.

Is Horse Manure Good Fertilizer?

Readily available in many rural areas or through reputable suppliers, horse manure makes a suitable and inexpensive fertilizer for plants. Horse manure can give new plants a jump start while providing essential nutrients for continual growth. It contains adequate amounts of organic matter and can be applied in various ways. It’s also slightly higher in nutritional value than cow or steer manure.

How Do I Use Horse Manure as Fertilizer?

Fresh manure should not be used on plants, because it can burn their roots. However, well-aged manure, or that which has been allowed to dry over winter, can be worked into the soil without the worry of burning.

While it may be more nutritional, horse manure may also contain more weed seeds. For this reason, it is usually better to use composted horse manure in the garden. The heat produced from composting can effectively kill most of these seeds as well as any harmful bacteria that may be present.

Composted horse manure can also be used in the garden any time of the year. Simply toss it over the garden area and work it into the soil.

Horse Manure Compost

Composting horse manure is not any different than traditional composting methods. This process does not require any special tools or structures. In fact, small amounts of horse manure can be easily composted using a shovel or pitchfork.

In addition, a simple, free-standing pile can be easily turned into compost. While adding additional organic materials to the pile can create a more nutritional fertilizer, it is not always necessary. Adding just enough water to keep the pile moist while turning it at least once a day can produce optimal results as well. Frequent turning helps to speed up the composting process. Covering the pile with a tarp can help keep it relatively dry, but still moist enough to work with, as well as retain necessary heat.

There is no set ideal time for how long to compost horse manure, but typically it takes two to three months if done properly. You are better off looking at the compost itself to see if it is ready. The horse manure compost will look like soil and will have lost its “manure” smell when ready.

Although it’s not required, composted horse manure can provide better results in the garden. Soil aeration and drainage can be greatly improved, which ultimately results in the healthier growth of plants.

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

Mike: My spouse and I are setting up a veggie garden, and have access to a hill of cow manure and straw (it’s up to eight years old; no odor). We brought home several bags to work into the soil and have also begun filling a composter with the stuff, but it’s gonna take a while before it’s ready. Can we use the manure as compost? Thanks.

    –Benjamin in Bass River, NS, Canada

Will composted manure burn plants like chemical fertilizer? I have access to cattle manure that’s been processed for a long period of time at a facility near here.

    —Kathy in Albuquerque

Answer. Thanks all three of you! I’ve wanted to do a detailed piece on “manure” for a while now, and you asked just the right questions to propel me along.

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.

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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 also lower 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.)
  • If the animal is a meat eater, like a dog, cat, lion or tiger, do not use the material in any form; even meat-eaters that are kept indoors can harbor dangerous parasites that are completely absent in ‘veggie manures’. That’s right—no dog or cat pet poop should EVER go in the compost! If you already made that mistake, don’t use the compost; and wear gloves when you toss it into the woods or otherwise dispose of it.

Manure Nutrients

SERIES 19 | Episode 06

When it comes to adding body to the soil there’s nothing like natural manure as a soil conditioner. It’s a preferred option because, as the manure breaks down, it adds valuable humus to the soil and this helps to store nutrients and water.

Whether it’s cattle in the paddock or free-range chooks, any critter with a diet of grass or vegetable scraps, will produce manure that reflects the nutrient balance that plants need from the soil.

Manures are available in many guises. Ideally you can collect it yourself but there are also packaged products from the nursery and manure which can be bought from the farm gate. All are fantastic for building up organic matter in the soil. But it’s critical to realise that there can be great variation in nutrient content between different manures.

The three most commonly available manures for your garden are:

  • Cow manure, which tends to have a low nutrient analysis because, like sheep manure, it comes from animals grazing on grass. This makes it great as a general purpose soil conditioner; and great for phosphorous-sensitive native plants when it’s well rotted.
  • Horse manure tends to provide a step up in nutrient levels because these animals are often fed supplements. This makes it a great tonic for vegetable and flowerbeds.
  • Chook manure usually has the highest nutrient content because of the intensive nature of the diet. Laying hens are often fed calcium supplements, to strengthen the eggshells, and that makes their manure particularly good as a clay-breaker. Remember that farm gate chook manure is often mixed with bedding materials, such as sawdust, which greatly dilutes nutrient levels. Chook manure always has a higher nitrogen level, making it great for fertilising lawns and for use in the vegie garden. But it also has a higher phosphorous level, so using it long term on native plants, such as banksias, grevilleas and waratahs, can kill them.

Can you use dog poo or kitty litter in the garden? Unfortunately it’s not a good idea – particularly in the vegetable garden – because their droppings often contain pathogens harmful to humans.

If you’re lucky enough to have a source of fresh manure then you need to be careful because it can have salt levels high enough to burn plants. A tip to make it more manageable is to put the manure into a plant pot, run some water through it and this will dilute the nutrient levels. (It also allows any weed seeds in the manure to germinate, and they will quickly die before you’re ready to use it.) And what’s left is beautiful liquid manure. Dilute it so it looks like weak tea and you’ve got a wonderful tonic for your flower or vegetable garden.

When using manure, dig it into the garden as soon as possible. If it’s left sitting on the surface, much of the nitrogen, particularly from chicken manure, can be lost as ammonia gas. Just fork it into the topsoil, and the nitrogen will be available, in the short term, for any leafy vegetables, but the beautiful organic matter will break down and build up the nutrient and water-holding capacity in the soil. It’s good stuff.

How to use horse manure with no regrets

It may not smell the greatest, but your garden will thank you for using horse manure to help it flourish.

It’s a great option for the gardener, but you need to do some cooking before this poo turns into gold.

Horse manure makes a great addition to any garden, but it does have one big drawback for the gardener. Horses are somewhat inefficient as digestors – you will probably easily see a horse’s last meal in its droppings, whereas in a cow for example (that has four stomachs and is a careful digestor) you wouldn’t be able to tell.

This means it will contain weed and pasture seeds that you don’t want growing in your garden. Hot composting horse manure should take of weed seeds but it needs to be a carefully controlled hot compost. Many home gardeners don’t get a true hot compost mix brewing and so some seeds may remain.

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If you want to use it fresh on your rose garden, you run the risk of seeds sprouting. Some gardeners cover the manure with a mulch, others just hoe the weeds out as they appear. This approach does save you double-handling the manure, from car/truck to compost to wheelbarrow to rose garden – why not just let it compost down on site and handle the weeds as they emerge? If you wish to take that route, the recommended thickness of the layer of manure is 5-10cm.

Hot composting horse manure will save you all the hoeing, the danger of weeds setting seed and infesting your garden, and it will kill any pathogens in the manure, making it more safe for you to handle. That pathogen risk is why we wouldn’t recommend putting any manure onto a vegetable garden while fresh (although if you’re digging it into the soil and leaving it to rot down over winter, or not allowing edible parts of vegetables to come in contact with it, your risk of getting ill is minimised, especially if you wash and then cook the vegetables concerned.

Note: pig manure should not be used fresh at all in any garden due to its high level of pathogens, for the same reason you wouldn’t use cat, dog or human excrement.

On the NPK scale of fertiliser, horse manure tends to be around 0.7-0.3-0.60 but don’t be misled by its low scoring. It contains large amounts of organic matter that feed and build the soil as well. That information comes from the Rodale Insitute, a US organic gardening research group, but they add a rider, that these values will vary depending on the diet, health status and age of the horse, and whether bedding or other material is mixed in with it.

Most manure in its fresh state is too strong for most plants, with an alkaline level that is too high. However roses are pretty greedy and so are better able to handle the large amounts of available soluble nitrogen. That’s in contrast to most other plants that require a balanced mix of nitrogen, carbon and microbial activity (that compost will provide).

THE BEST WAY TO HOT COMPOST HORSE MANURE

You’ll need a good mix of compostable material, not just the horse manure, and reach a temperature of 80°C (and stay at that temperature for a couple of weeks).

To do this, it’s recommended you create a compost pile that’s at least 2m across at its base. If you use some old netting to form a circle (and put your compost pile inside it), you’ll create a pile that has enough mass to keep up that critical temperature for the required time. Build up a layer of horse manure around 15cm deep, making sure it is damp but not wet (spray it with the hose if you think it’s too dry).

At this point you could add a handful of nitrogen-rich granule fertiliser if you wish.

Then add a layer of brown material (eg, tree clippings, hay/straw) and make that layer about 20-30cm (it will compact). Your end goal is to have a pile of compost that is 50% manure, 50% other additives.

Repeat these steps until the compost pile is about 1m high. Leave it for at least six months. You can check it after a week to see if it’s steaming, or you can buy long thermometers at gardening stores to measure the temperature.

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This article first appeared in NZ Lifestyle Block Magazine. Discuss This Article

Managing and composting horse manure

Start with a good compost site

  • Choose a convenient location

  • Make sure the site won’t flood with water

  • Make sure the location meets the manure stockpile site requirements

The larger the pile, the easier it is to keep the composting process going.

The storage area doesn’t need walls, but walls will help contain the compost and allow air flow. You can use pallets, chicken wire, straw bales and slatted boards for walls.

You can use piles that aren’t turned if you allow air flow through perforated pipes. This air can be passive or forced with blowers. You can apply design guidelines for larger manure storage sites for smaller compost bins as well.

Get compost ingredients

Horse manure compost piles need these key elements.

  • Carbon: wood shavings, straw, sawdust, manure

  • Nitrogen: urine, manure, fresh plant material (lawn clippings, freshly pulled weeds), ammonium sulfate

  • Air: ⅔ of the pile volume should be air. Use large woodchips to fluff. Sift when done.

  • Water: moisture like a wrung out sponge, wet but not dripping

  • Mix well: microbes have better access to materials with more evenly mixed materials

You can compost:
  • Manure

  • Garden waste

  • Some kitchen waste: vegetables, fruit, coffee grounds, unbleached coffee filters, tea bags, eggshells, bread, etc

  • Lawn clippings

  • Leaves

Don’t compost:
  • Diseased plants*

  • Animal mortalities**

  • Dog or cat feces**

  • Fats**

  • Meat**

* Many fungi and spores are not killed in the composting process. Adding them can spread the disease further.

** Experienced composters can compost these, but correct temperatures MUST be met.

Blend compost materials well

Mixing the compost gives the microbes access to the nutrients they need. Add water during mixing until it reaches the moisture level of a wrung out sponge. It’s hard to add water throughout the pile outside the mixing process.

Cook

Check the temperatures and remix the pile as needed. A correct mixture pile heats between 140 and 160 F and holds that temperature for 3 weeks. Use a temperature probe, which you can purchase from a farm store, to check the temperature. Turn the pile if temperatures exceed 160 F or when temperatures begin to decline.

A lower temperature usually means missing ingredients. Often these piles need more nitrogen or water. Remix after adding the needed ingredients.

The composting process is nearly complete when it doesn’t heat after mixing and you can’t recognize the original ingredients.

You may not be able to attain desired temperatures during winter in Minnesota. Stockpile manure over winter and resume composting in the spring.

Let cool

Compost curing occurs in the last 1 to 2 months during which time the temperature will reduce to ambient levels. The finished product will look like something between potting soil and large, dark brown wood chips depending on the material size. Finer material composts more quickly.

Use

You can use finished compost for the following.

  • Amending soil in a garden

  • Tree mulching

  • Potting soil

  • Fertilizer for the yard, pasture or hay fields

Never spread more than ½ inch of compost at one time when spreading compost on a yard, pasture or hay field.

Environmental Impacts and Benefits

Environmental Benefits: When managed properly, manure can be a valuable resource on a farm. Manure can be a source of nutrients for crop production and can improve soil quality. The organic matter present in manure can improve both tilth and water holding capacity of the soil. Manure can also be used as a fertilizer (N and P) for crops. However, most horse owners do not have enough land to use the amount of manure that is produced. Monitoring horse manure so that it does not cause environmental impacts is the goal of manure management.

Nutrients: When not managed properly, horse manure (feces and urine) can pollute the environment, mainly as ground or surface water pollution due to the nutrients nitrogen, phosphorus, and carbon (organic matter). These nutrients can reach waterways as surface runoff or leachate from the manure pile.

Nitrogen excreted from horses is usually present either as urea in urine, which is quickly converted to ammonia (NH3), or it remains in association with organic matter in the feces. Ammonia (NH3) can be volatilized into the atmosphere. If NH3 from horse manure comes into contact with surface waters, it can cause nutrient enrichment and excessive algae growth. This process is referred to as eutrophication. Eutrophication is the process of nutrient enrichment in a lake or slow-moving stream occurring when excess nutrients from manure, fertilization, sewage, etc. are deposited. This can result in waters rich in mineral and organic nutrients that promote a proliferation of plant life, especially algae, which reduces the dissolved oxygen content and often causes the extinction of other organisms. (Adapted from Concise Columbia Electronic Encyclopedia, 1999 & American Heritage Dic. of the English Language, 4th ed.) In the case of nitrogen, the excessive algae and conversion of ammonia to nitrate (NO3) causes a reduction in dissolved oxygen in the water, which can contribute to fish kills through oxygen depletion.

Nitrogen present in organic matter in the feces will be converted in the soil to ammonia and then nitrate, which can be taken up by plants. If plants do not take up nitrate it will easily move through the soil and can eventually leach into the groundwater where it can be a human health concern. Nitrate can also undergo the process of denitrification in the soil and be lost into the atmosphere as gaseous nitrogen (NO, N2O, or N2).

Phosphorus is also present in manure. When spread on the land it will not leach like nitrogen, unless the soil matrix where phosphorus binds becomes overly saturated with phosphorus. However, phosphorus will run off if applied at the wrong time of the year and/or when soil erosion occurs. This can lead to contamination of surface waters where it may cause eutrophication.

When manure is not properly incorporated into the soil, organic matter present in manure (contains carbon, nitrogen and phosphorus) can be a concern when it runs off into surface waters. Eutrophication and additional oxygen depletion may occur due to the decomposition of the organic matter.

Pathogens and Vermin: In addition to the above concerns, pathogens may be present in manure. Some of these are, E. Coli, Salmonella, and Cryptosporidium parvum, however the frequency of Salmonella and Cryptosporidium parvum are low in horse feces and there have been no known outbreaks of E. coli infections in humans attributed to horses. Internal parasite infestations in horses may also result from horse manure. Flies, dust, rodents, and odors may also be manure related concerns on horse farms. These problems can be minimized by proper design of housing and manure storage areas and care when turning or moving manure piles.

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