6 Best Lime For Composting Manure On Organic Farms Old Farmers Swear By
Lime is key to composting manure on organic farms. Explore the 6 best types used by farmers to balance pH, reduce odor, and accelerate decomposition.
Nothing transforms a farm’s soil faster than well-made manure compost, but getting it right can be a balancing act. One of the oldest tricks in the book is adding lime, a practice that separates good compost from great compost. Understanding which lime to use, and why, is a key skill for any farmer serious about building healthy, productive soil from the ground up.
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Why Add Lime to Your Manure Compost Pile?
Adding lime to a manure pile isn’t just an old habit; it serves a few critical purposes. Manure, especially when mixed with bedding like wood shavings or straw, tends to become acidic as it breaks down. This acidity can slow down the beneficial bacteria and fungi that are doing all the hard work of decomposition.
A light dusting of lime neutralizes this acidity, creating a more hospitable environment for those microbes. This helps the pile heat up faster and break down more completely. It also helps manage odors—particularly the sharp smell of ammonia—by converting it into a more stable form of nitrogen that stays in the pile instead of gassing off into the air. Think of it less as an "ingredient" and more as a "catalyst" for the natural process you want to encourage.
Soil Doctor Pulverized Lime for pH Balance
When most old-timers talk about "liming the pile," they’re referring to standard pulverized agricultural lime. This is finely ground calcium carbonate, the same stuff that makes up limestone and chalk. It’s the straightforward, no-frills workhorse for raising the pH of your compost.
Improve plant growth with this OMRI-listed dolomite lime, providing essential calcium and magnesium while raising and stabilizing soil pH. The ultra-fine powder ensures a rapid reaction, perfect for preventing blossom end rot in tomatoes and peppers.
Its main job is to counteract the acidity that builds up as organic matter decomposes. Because it’s a fine powder, it has a lot of surface area and gets to work relatively quickly. The biggest downside is the dust; on a windy day, you’ll end up wearing more of it than the pile does. But for its low cost and effectiveness, basic pulverized lime is the go-to choice for simple pH management.
Espoma Organic Dolomitic Lime for Magnesium
Correct acidic soil and encourage vibrant pink hydrangea blooms with Espoma Organic Garden Lime. This pelletized dolomitic lime improves plant growth, maximizes fertilizer performance, and is approved for organic gardening.
Sometimes your soil needs more than just a pH adjustment. Dolomitic lime is your tool for that job. It contains not only calcium carbonate but also a significant amount of magnesium carbonate. This is crucial if your farm’s soil is naturally low in magnesium, a key nutrient for photosynthesis.
Before you reach for dolomitic lime, it’s wise to have a basic soil test done. Adding too much magnesium can throw off the critical calcium-to-magnesium ratio in your soil, which can make other nutrients less available to your plants. But if you know you have a deficiency, incorporating dolomitic lime into your manure compost is an incredibly efficient way to deliver both calcium and magnesium in a plant-available form.
Down to Earth Oyster Shell for Slow Release
If you’re worried about shocking your compost pile’s ecosystem, oyster shell flour is the gentlest option available. Made from finely ground oyster shells, it’s a pure source of calcium carbonate that breaks down very slowly. This gradual release provides a long, steady buffering effect on the pile’s pH without causing any drastic swings that could harm microbial life.
This isn’t the product you use for a quick fix on a sour-smelling, acidic pile. Instead, oyster shell is for farmers playing the long game. It enriches the final compost with a slow-release source of calcium that will benefit your soil structure for years to come. It’s an excellent choice for building foundational fertility in your garden beds.
Oldcastle Pelletized Lime for Easy Spreading
Pelletized lime is simply pulverized lime that has been mixed with a binding agent and formed into small, easy-to-handle pellets. The practical benefit is enormous. There’s virtually no dust, making it much more pleasant and safer to work with. You can spread it evenly with a scoop or your hand without worrying about the wind carrying it away.
The pellets dissolve when they get wet, releasing the fine lime particles into the compost pile to do their work. You pay a small premium for this convenience, but for many small-scale farmers, the reduction in mess and waste is well worth the extra cost. It’s the same effective ingredient, just in a much more user-friendly package.
Hardwood Ash: The Old-Timer’s Free Liming Agent
Before bagged lime was readily available, farmers used hardwood ash from their wood stoves. Wood ash is a potent, fast-acting liming agent that also supplies a healthy dose of potassium and other trace minerals. Best of all, it’s free. This is why you’ll still see old farmers swearing by it.
However, you must use it with care. Wood ash is more caustic than agricultural lime and can raise the pH very quickly, potentially harming the compost microbes if over-applied. Never use ash from treated, painted, or manufactured wood. A very light sprinkle between layers is all you need; treat it like a powerful spice, not a main ingredient.
Hydrated Lime: A Fast but Cautious Choice
Hydrated lime, also known as slaked lime or builder’s lime, is the heavy artillery of liming agents. It’s extremely caustic and reacts very quickly to raise pH. While some guides might mention it for quickly "sanitizing" a pile or neutralizing intense odors, it’s a tool that comes with serious trade-offs.
Its aggressive action can kill off a wide range of beneficial microbes, effectively sterilizing the compost and stalling the decomposition process. It also causes a rapid release of nitrogen as ammonia gas, meaning you lose valuable fertility into the atmosphere. For most organic composting situations, the potential damage to the pile’s biology far outweighs the benefits. It’s best left on the shelf unless you’re dealing with a specific problem like a disease outbreak and know exactly what you’re doing.
Applying Lime Safely and Effectively in Compost
How you add lime is just as important as which type you choose. The goal is not to create a white, layered cake. You want to incorporate it evenly throughout the pile to buffer acidity everywhere.
The best method is to add a light dusting with each new layer of manure and bedding you add.
- Spread a 6-8 inch layer of manure and bedding.
- Use a small scoop or can to sprinkle a thin, even layer of lime over the top—think of it like dusting a cake with powdered sugar.
- Water the layer lightly to moisten the materials and activate the lime.
- Repeat with each new layer.
Always wear a dust mask, especially when working with pulverized or hydrated lime, as the fine particles can irritate your lungs. A little goes a long way. For a typical pile the size of a pickup truck bed, you might only use 10-20 pounds of lime in total, distributed throughout.
Ultimately, the right lime for your compost pile depends on your specific goals—whether you need fast pH correction, a gentle long-term amendment, or a boost of magnesium. By choosing the right tool for the job and applying it thoughtfully, you can turn a simple manure pile into a powerhouse of fertility for your entire farm. It’s one of those small adjustments that yields big results season after season.
