Finished compost. It should take around three months, perhaps longer in the winter when microbial activity slows. You will know your compost is ready when the material looks evenly textured, crumbly, dark-colored like dirt, and is earthy-smelling.
Compost is ready or finished when it looks, feels and smells like rich, dark earth rather than rotting vegetables. In other words, it should be dark brown, crumbly and smell like earth.
Although the composting process will occur naturally over several months or years, with human help the entire process can be completed in as little as 4-6 weeks. Four essential ingredients are needed: oxygen, moisture, and a proper Carbon:Nitrogen ratio.
Adding too much compost may be harmful, especially in vegetable gardens. You can apply too much compost at one time or over several years. Too much compost in soil stunts plant growth. It also may create water pollution.
What is this? If you want to enrich your soil, add a portion of compost every spring. Work about an inch of compost into the first few inches of soil for an annual nourishing treat. Add your compost in the fall if your goal is to improve your soil's structure.
As a rule of thumb, actively decomposing materials should be turned every three to four days. Materials with slowed microbial activity can be turned less often. In tumblers, turning two times a week resulted in higher temperature and faster decomposition than turning once a week or once every other week (Figure 1).
Mix four parts soil with one part compost. You may also top dress perennial flower gardens with no greater than 1/4 to 1/2 inch of compost. A soil mix for this use should be around 10 percent. To obtain a 10 percent mixture, you should mix 9 parts soil to 1 part compost.
Disadvantages of composting organic residues include loss of nitrogen and other nutrients, time for processing, cost for handling equipment, available land for composting, odors, marketing, diversion of manure or residue from cropland, risk of losing farm classification, and slow release of available nutrients.
Vegetable root crops such as beets, carrots, radishes, and potatoes are particularly sensitive to adding horse manure. Salad greens are another vegetable type that can be damaged or burned by applying horse muck to the soil.
It will lose much of its value if materials are left to decompose too long. The more time compost is left to sit around, the more “colloidal” it becomes. In other words, it becomes more and more compact as the composting microbes continue to feed on the waste materials.
Manure that is piled and left alone will decompose slowly. This can take three to four months if conditions are ideal. It can take a year or more if the starting material contains a wide carbon:nitrogen ratio (as is the case when manure contains wood chips).
2 Fresh manure can also contain bacteria that could contaminate any edible plants growing in or near it. Manure needs to be composted or let rot for at least six months to a year before it is ready to be used in the garden.
Fresh, non-composted manure will generally have a higher nitrogen (N) content than composted manure. However, the use of composted manure will contribute more to the organic matter content of the soil. Fresh manure is high in soluble forms of N, which can lead to salt build-up and leaching losses if over applied.
Composting livestock manure reduces many of the drawbacks associated with raw manure use. It's also less likely to cause nutrient imbalances. The composted manure can safely be applied directly to growing vegetable crops.
Simple organic activators you may have on hand are lime (limestone), blood meal (yes, it's dried blood), fish meal, and poultry, rabbit, and horse manure. Rabbit food (pellets) and dry dog food are also organic activators that are often have on-hand.
Too much carbon material will slow down the composting process. Too much nitrogen will make the green material start rotting, and maggots will appear. Only add grass clippings in thin layers as too much green grass clippings will clump and slow down the composting. Get the correct combination of air and water.
Compost is rich in nutrients and therefore increases the fertility of the soil. Although fertilizers also increase fertility, they are artificial chemicals that can pass through the soil to the water, and these chemicals can be fatal for aquatic life. It increases crop yield and disease resistance in plants.
Compost can be added directly on top of the soil when introduced as a mulch layer for the plants. For a more immediate benefit, work the compost into the soil.
On its own, it doesn't provide all the necessary nutrition your backyard plants need. This is why I typically recommend mixing topsoil with other materials such as compost, manure and coco coir (optional, for raised beds) when filling new raised beds.
Decomposition will be complete anywhere from two weeks to two years depending on the materials used, the size of the pile, and how often it is turned. Compost is ready when it has cooled, turned a rich brown color, and has decomposed into small soil-like particles.