How Long Does It Take Cow Manure To Compost? [Ultimate Guide]


How long does it take cow manure to compost? It ranges from a week to a year. Depending on the size of the manure, the condition in which the manure is being composted and how long you intend to keep the manure. In this article, I covered the basics of composting cow manure, and how long it takes to get it fully composted.

Composting helps break down organic material into nutrient-rich soil that can be used in gardens or other places where plants are growing. Cow manure is good fertilizer. But fresh dung smells bad. It might be too hot for plants. And it might have too much salt in it.

Composting is a wonderful way to recycle organic material from many sources. And if you have a source of cow manure, you should move it quickly into the compost pile, so you can take advantage of the quality organic fertilizer. You can use composted cow manure on any plant, including flowers, vegetables, fruits trees and more!

Composting cow manure is easy to do and eliminates the odor and converts excess nitrogen into plant-available forms (leaving you with finished compost). You can speed up the process of composting cow manure by turning the material more often or by adding something that will help retain water, like grass clippings.

Covering the manure with a tarp or black plastic helps retain moisture and speeds up decomposition. It might take as short as two weeks or as long as two months to compost cow manure. Covering the manure with a tarp or black plastic helps retain moisture and speeds up decomposition.

How long it takes to compost depends on many variables (outside air temperature, the moisture level of the manure pile, size of the pile). As a general guide:

-A properly managed and maintained aerobic composting system can take as little as three weeks to achieve a finished product while a low-temperature composting pile may take as long as six months or more.

-Anaerobic decomposition takes even longer, about four to twelve months.

Factors that Determine How Long a Cow Manure Compost

Outside air temperature.

When you are trying to compost cow waste, temperatures play a huge role in how fast your material will decompose. Cow dungs with lower temperatures have an increased risk of harboring harmful bacteria that can be passed on to humans and livestock. The introduction of air into a cow manure pile speeds up its decay. Warm air moves more quickly. Cold air moves more slowly.

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Moisture level in the pile

Manure that is moister will compost faster than drier manure because it produces heat as it decomposes, which speeds up the process. The wetter a compost pile, the faster it decomposes because water creates a desirable environment for microbes that break down materials in the pile into simpler components that plants can use. So you can speed things up by wetting down dry manure before adding it to your pile.

Size of the pile

A large pile retains more heat than a small pile. Warmer piles decompose materials faster.

Bedding or covering in the pile

Dark, carbon-rich materials like newspaper, cardboard, and sawdust slow down the heating of the manure pile because they don’t decompose as quickly as light-colored, nitrogen-rich materials like straw and grass clippings.

  1. A pile of grass clippings one-inch deep will heat up in about one week in the summertime.
  2. A pile of grass clippings two inches deep will heat up in about two weeks in the summertime.
  3. A pile of grass clippings three inches deep will heat up in about three weeks in the summertime.
  4. Grass clippings that are four inches deep will take about one month to heat up.
  5. Grass clippings that are six inches deep won’t get hot enough to kill weed seeds or pathogens in two months, even during the summertime.

Turning the pile 

Piles that are turned more often will decompose faster because more oxygen is made available to the microorganisms in the compost pile.  The more often your compost pile is turned over, the faster it will compost because air can get into the pile. This is known as “aeration.” If you do not turn your compost pile often enough, destructive bacteria can grow.

The danger with turning it too often is that the material may dry out. If it does, decomposition will stop and the material will be too dry for seed germination.

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How to Compost Cow Manure Aerobically?

-Start with a pile of porous brown material, such as straw, hay, or dried grass clippings.

-Add the cow manure to the bottom of the pile and cover it with brown material. This will prevent “scorching” by ammonia if any is present. Turning this mixture every few days, or building your compost heap in layers will speed up the decomposition process.

-To create heat and further break down materials, water the pile occasionally with a fine spray to keep it moist but not soggy. While cow manure contains substantial amounts of nitrogen, you may want to add additional nitrogen sources like grass clippings to help jumpstart your composting system.

-You may notice too much heat building up in your pile. This can be a problem because it can damage the bacteria trying to do their work inside the pile. In this case, you’ll need to add more brown material or turn down the heat by increasing water and reducing nitrogen sources.

-When turning your pile, don’t worry if parts of the manure are still recognizable. These materials will be covered by other brown materials and decompose as you continue to turn and water the mixture.

-The finished product – rich, dark compost – is ready when the materials resemble soil and no longer smell or have a discernible manure texture.

-You may want to use a compost sifter. That will let you screen out larger pieces so they can decompose a bit more before being put on the garden, where it is less likely to burn plants. 

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How Long Does It Take Cow Manure To Compost: Stages & Composting Time

Cow manure composting is complete when all the materials are reduced to a fine, rich-smelling, crumbly (almost like chocolate cake) substance that no longer has any chunks or bits of visible animal waste in it. The time that it takes to reach this stage depends on how often you turn the compost pile and whether or not grass clippings were used in the mixture.

The following table shows various stages of decomposition for cow manure at different turning intervals.

Stage State/condition Odor Description Cured Description
Stage 1  Fresh or uncomposted fresh, unpleasant odor

 

Fresh manure is warm, moist, and crumbly. It can be shaped into patties or balls without falling apart.
Stage 2 Heating up

 

Strong, offensive odor; ammonia fumes may burn your eyes and throat.

 

The material appears steamy. It is drying. If you squeeze a handful, the liquid will ooze out.

 

Stage 3 Well-decomposed Earthy, damp, or musty smell The material is dry and crumbly, but still holds together in a clump when squeezed. Very few, if any, recognizable chunks of manure remain. 

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Cow Manure Composting By The Numbers 

To wash the salt out of cow manure, spread a layer on the soil with grass clippings or straw at least two inches thick. Water thoroughly and let it sit overnight. Then turn it over to dry more. Repeat this process until the salt is gone.

 

  1. If you plan to use your compost within a week, immediately after it’s made, just turn and moisten as needed.

 

  1. If you plan to use your compost within a month, cover it with a six-inch layer of straw or grass clippings and keep it turned and moist.

 

  1. If you plan to use your compost within a year, cover it with a six-inch layer of straw or grass clippings and keep it turned and moist for three months. Then let it sit undisturbed for the last nine months of the first year.

 

  1. If you plan to use your compost more than a year after it’s made, let it sit for two years undisturbed.

 

  1. A pile of fresh cow manure three feet high and three feet wide and three feet long will take about three weeks to decompose enough that it’s no longer smelly and there are no recognizable chunks of animal waste.

 

  1. A pile of fresh cow manure four feet high and four feet wide and four feet long will take about one month to decompose enough that it’s no longer smelly and there are no recognizable chunks of animal waste.

 

  1. If you add a pound of nitrogen-rich material (like blood meal, cottonseed meal, or fresh grass clippings) to the above pile every week, it will decompose in about two months instead.

 

  1. A pile of dry cow manure that is four feet high and four feet wide and four feet long will take about two years to decompose enough that it’s no longer smelly.

 

  1. A pile of dry cow manure five feet high and five feet wide and five feet long will take about three years to decompose enough that it’s no longer smelly.

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Conclusion

So How long does it take cow manure to compost? It depends! Cow manure is an excellent fertilizer for your garden. It’s packed with nutrients that will help your plants grow, but it also has some downsides like high ammonia levels and excess salt. That’s why we recommend starting with composted cow manure to make sure you get the most out of this great product! Start with a pile of porous brown material, such as straw, hay, or dried grass clippings. Add the cow manure to the bottom of the pile and cover it with brown material. This will prevent “scorching” by ammonia if any is present. Remember that turning this mixture every few days, or building your compost heap in layers will speed up the decomposition process.