How Fast Does Compost Turn Into Soil?
Compost typically decomposes from a month to a year, but you can make your own in as little as a week! How fast it decomposes depends on your garden conditions. Let’s break down your dirt with native plant gardener Jerad Bryant.
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Compost is the best amendment for your garden! It’s alive, rich in nutrients, and adds structure to existing garden beds. Live compost contains worms, fungi, bacteria, and bugs that eat big particles, turning them into smaller ones for your plants’ roots.
This amendment decomposes quickly when it’s full of living creatures. Turning compost, adding grass clippings, and using small pieces help speed up decomposition by feeding them. They eat and reproduce, quickly consuming raw material and turning it into rich, crumbly humus.
Quick compost needs a lot of labor and can be difficult to maintain. Cold compost is a good option for gardeners with less time for turning, as it still decomposes rotting scraps into valuable dirt over a long period. This method requires less work than hot piles and is an invaluable option for excess waste.
Let’s explore the different kinds of compost and how long they take to morph into soil.
The Short Answer
Anything decomposes with time, but composting speeds up the natural process. You can have ready soil in as little as 18 days. How long before mulch decomposes depends on temperature, oxygen, moisture, and microbe activity. Manipulate these factors to either speed up or slow down how fast the raw materials turn into ready soil.
Cold compost takes six to twelve months to turn into usable soil. Although it takes longer than hot piles, it’s easier to do and works well in many different garden conditions.
The Long Answer
There are a few ways to speed up this natural, biological process. You can manipulate your pile to facilitate quicker results.
Small Chunks Are Best
Large debris like tree branches, clumps of wet scraps, and thick leaves slow down the composting process. Their large nature prevents microbes and critters from breaking them down into tiny particles. When you tear these items up, you make it easier for compost organisms to eat them.
I use my hands to tear garden scraps into smaller pieces. This works well for weak plants, but you may need a strong tool for other items. Use loppers or a saw to break up large tree branches into wood-chip-sized pieces. You’ll need a broad fork for turning the pile—it doubles as a mulch stabber for separating kitchen scraps.
Some items slow down decomposition and make turning piles impossible! These include the following:
- Large pieces of meat
- Long vines
- Dairy products
- Live plants that spread through rhizomes
Keep these things out of your piles, and use small chunks—the smaller, the better!
Hot Compost Is Quick
When in a hurry, try a hot composting pile. This method gives you usable soil in a few weeks, with regular turning and watering. Feed your pile as you would feed a plant; grant it water, air, and nutrition.
Use the rapid composting method to activate soil organisms into a frenzy. You’ll need a pile that’s 3x3x3’ in dimension, with an equal ratio of greens to browns. Greens add nitrogen; think things like kitchen waste, yard waste, and farm animal manure. Browns, like straw, newspapers, and dead leaves add carbon and structure.
Turn hot piles daily for finished compost in two weeks. Stab them with a broad fork and rotate the materials. Turn them every other day, and they’ll be ready in about three weeks. They should steam with hot moisture as you turn them. Maintain a moisture level of 50% the entire time—you’ll want the piles to resemble wrung-out sponges that are moist but not soggy.
Cold Compost Takes A Long Time
A lazy method I love to use is cold decompsition. These piles decompose mulch over many weeks with less work from the gardener. You can expect ready soil around six to twelve months after making a fresh pile. As its name suggests, this method lacks the hot steam that hot compost uses to break up raw materials rapidly.
To make cold piles, assemble ones the same size as hot ones. You may use an equal ratio of browns to greens, although it will require extra turning. Use a ratio of 2:1 or 4:1 browns to greens for cold piles with little disruption. Water them so they’re moist but not soggy, then let them be. You’ll only need to turn them over once a month, but you can do it as often as you’d like. The more often you turn, the quicker your cold piles produce usable products.
Bins help keep compost tidy and facilitate quicker decomposition by adding height and depth to your piles. Use chicken wire wrapped around wooden planks to make a simple bin. Another DIY option is with chemical-free wood pallets. Stack them on their sides to form three walls, then drill or tie them together. Place your mulch in the center, turning it as needed.
Speed It Up With Amendments
Some amendments boost breakdown speeds by feeding microbes, fungi, and bugs the nutrients they crave. These additions are protein-rich and help facilitate quicker decomposition.
If your piles have pieces that don’t seem to be decomposing, consider adding one of these finely shredded organic amendments to speed it up:
- Grass clippings
- Soy meal
- Oatmeal
- Alfalfa pellets
After you add a good amount of these inputs, avoid adding new materials for a few days. Feed your piles oxygen by turning them frequently, and water them when they dry out. You’ll have humus-rich soil in a few days or weeks after adding these amendments.
If you lack patience like me and want a usable amendment in less time, you can use the parts of the piles that have already decomposed. Move a pile over, and underneath will be black, crumbly humus ready for use. After a few days, move it over again, and there will be more humus-rich dirt on the bottom for the taking.
Seasons Affect Decomposition Rates
Cold winters cause most animals to hibernate, sleep, or die. Microorganisms are no different, and they slow down as ambient temperatures drop during fall and winter. If you make a fresh pile in the fall, it won’t be ready until the next spring through summer.
Start hot compost during early spring and you’ll have humus-rich soil for your garden in a few weeks! Warm temperatures awaken sleepy worms, bacteria, and fungi into action. They voraciously feed on raw mulch as you give it to them.
Summer piles also work well, so long as they have a few weeks before fall wet and cold arrive. Make sure to keep them moist, especially when drought is an issue.
What If It’s Not Working?
Compost piles may not work as fast as you’d like them to sometimes. It usually stems from a ratio imbalance of greens to browns and is easily fixable. There are two common issues, reluctance and smelliness.
If your heap is reluctant to decompose, it needs more green material. Add small chunks of kitchen scraps, grass clippings, or alfalfa pellets to it, and turn well. Then, water it so the organisms have moisture to drink. Often, too little water is why compost takes so long to turn into soil.
If your decomposition heap is smelly, it needs more brown materials. Add fallen leaves, shredded wood or paper, and straw. Turn it often after adding them, then water if it seems dry. The solution for most issues is to fix the ratio, water less or more, and turn your compost often.
