|Left corner: my first compost pile, 1972|
Compost can be used in many different ways. It can and should be dug into the soil at planting. It can be mixed with garden soil for potting purposes. It is a very successful topdressing around established plants. When applied to the soil surface, it will be integrated into the soil over time and create a more friable soil. In the shorter term, it makes an attractive mulch and will help to retard weed establishment.
|Compost used as mulch|
|Note that they are empty.|
What has to be achieved in a home compost pile is to allow the plant materials to decompose rapidly without excessive odor. Woody materials must be run through a shredder if they are to be added. Other plant parts will benefit from cutting into smaller lengths or chopping by hand into pieces (squash or other large fruit or tubers). Roots will not usually compost. Don't add diseased plants to a home compost pile, and no really weedy material that has seed pods. I strongly suggest that plant material is all that should ever go into the pile. No animal parts. Definitely no animal feces, including manure (that can be composted separately). In this comprehensive study of compost odors you'll note that the really bad stinks (those characteristic of putrefaction) derive from animal sources. Ammonia is a common problem in home compost piles (from degradation of high-nitrogen tissues like grass clippings) and fatty acids like butyric acid (detectable at low concentrations!) are noticeable when anaerobic bacteria take over (too wet, too little oxygen). It helps to understand that a compost pile is a little ecosystem. For details, here is this overview of microbial succession, but the point is that different bacteria and actinomycetes come and go through the process and the system needs to support them. In a very real sense, what you have is a fermentation reactor and like such a reactor, you need to have the proper substrate and environmental conditions to make it work.
Oxygen: Aeration is critical. The beneficial microbes involved in composting are engaged in active metabolism and will use up the available oxygen quickly. Then the process will shut down. This is why commercial composting operations turn the compost in windrows daily. Turning the pile at least once every couple of weeks during active composting is a good idea, and good exercise too.
Temperature: It is perfectly okay to add materials to a compost pile when it is cold, but don't expect anything. The pile will operate best within a range of 120-140° F internal temperature and the air temperature will affect that. The process will be most active in summer temperatures. If the pile is kept moist and turned frequently when it has the right nutrients, it should be at least pleasantly warm in the center.
|Layer the "greens and browns".|
All this effort occurs fairly automatically during the gardening year. You'll notice that after a time, the total volume has been reduced and new material is not decomposing very fast. This is a good time to quit adding material. Turn a pile once more, adding moisture, then let it sit. By the fall, you should have compost.