Compost is a mixture of partially decomposed plant material and other organic wastes such as orange peels and coffee grounds. Using compost in the garden:
Reduces waste in our landfill.
Decreases the bulk density of the topsoil and increases moisture retention in soil.
Promotes increased root and leaf development as well as flower, fruit or vegetable production.
Saves money by reducing the need for fertilizers and pesticides.
Prevents the erosion of valuable nutrient-rich topsoil.
It's easy to compost in your own backyard! To learn how, read more below or attend a composting workshop or demonstration.
There are six building blocks for compost:
- Biology. The compost pile is really a teeming microbial farm. Bacteria start the process of decaying organic matter. They are the first to break down plant tissue and also the most numerous and effective composters. Fungi and protozoa soon join the bacteria and somewhat later in the cycle, centipedes, millipedes, beetles and earthworms do their part.
- Material. Anything growing in the yard can be composted. This plant material has carbon and nitrogen which microbes use as food.
- Surface Area. The more surface the micro-organisms have to work on, the faster materials decompose. Shredding leaves or chopping garden wastes will speed up the decomposition process.
- Volume & Temperature. The composting process generates a lot of heat, up to 160°. This heat means that the compost pile is working effectively and decomposing very quickly. A large compost pile insulates itself and holds heat better.
- Moisture & Air. Micro-organisms need air and water to survive. They will thrive in a pile that is turned on a regular basis, and has the moisture of a wrung-out sponge.
- Time. A pile that's made with the proper materials and provided adequate volume, moisture, surface area and air, will make finished composting in just a few short weeks. If one of these components is neglected, compost will still result, but at a much later date.
The How-to's of Building a Compost Pile
Composting piles are made up by layering different plant materials together. Micro-organisms feed on this plant material and leave behind compost. To build a compost pile, layer materials as outlined below.
Five Layers of a Compost Pile
- Layer 1.
- Four to six inches of chopped brush or other coarse material set on top of the soil will let air circulate around the base of the pile.
- Layer 2.
- Three to four inches of grass clippings or hay. This material should be damp when added to the pile.
- Layer 3.
- Three to four inches of leaves, straw or corn stalks. This material should be damp when added.
- Layer 4.
- (Optional) One inch of soil will add micro-organisms to the middle of the pile.
- Layer 5.
- (Optional) Two to three inches of animal manure, or one cup of 10-10-10 fertilizer or bloodmeal will provide a "nitrogen boost" to speed decomposition. Add water if the manure is dry.
Repeat layers until the pile is about four feet high or the bin is almost full. To help speed the decomposition process, you can add four to six inches of straw or dirt to the top. Scoop out a basin in the top to catch rain water, or lay a piece of plastic over the top to help retain moisture. Products sold as bacteria activators and compost innoculants are not necessary for successful compost.
Kitchen vegetable scraps can be added to the pile, however, these items are more likely to draw pests and should be avoided if the pile is not well maintained. Other items to avoid are: cat and dog manure, peanut butter, mayonnaise, sour cream and other processed or non-plant materials.
C:N Ratios: "Greens" vs. "Browns"
Average C:N Ratios for Organic Materials
The micro-organisms in compost use carbon for energy and nitrogen for protein synthesis. The proportion of these two elements should average about 30 parts carbon to one part nitrogen. Most materials available for composting don't have this ratio, so to speed up composting, the goal is to balance the numbers. For instance, a mixture of one-half leaves (40:1 ratio) could be used with one-half grass clippings (20:1 ratio) to make a pile with the ideal 30:1 ratio.
In the simplest terms, you can consider low carbon items as "green" and high carbon items as "browns," then it's just a simple matter of balancing the greens and browns. The chart below will help you balance your C:N ratio.
- Alfalfa hay
- Grass clippings
- Rotted manure
- Good Compost
- 25 to 35:1
- Corn stalks
- 40 to 80:1
Composting is a science based on guess work. Ideally a compost pile's outside will be warm, moist and earthy-smelling. When it's not, it means that one or more of the six components listed at the beginning of this article are out of balance. Chart B will help you correct the problem. If there is a problem with your compost pile, don't worry; compost will still result, but you'll have to wait longer.
There are many books about composting; look for them at book stores, garden centers and the public library. Your county extension agent can also answer your composting questions.
|The pile is wet and smells like rotten eggs.||Not enough air; pile too wet.||Turn it; add course, dry waste such as straw or corn stalks.|
|The center is dry and contains tough, woody wastes.||Not enough water in pile. Too much woody material.||Turn and moisten; add fresh green waste; chop or shred the pile.|
|The pile is damp and warm right in the middle, but nowhere else.||Pile is too small, or too dry.||Collect more material and mix into a new pile; moisten.|
|The pile is damp and sweet-smelling, but will not heat up.||Lack of nitrogen. The compost may be done; check and see!||Mix in fresh grass clippings or nitrogen fertilizer.|
|The pile has an ammonia odor.||Too much green material. Lack of nitrogen.||Add high carbon materials, such as straw, wood chips or sawdust.|
|Pests (raccoons, rats and insects) are attracted to the pile.||Meat scraps and fatty foods are present.||Remove meat and fatty foods from pile. Cover pile with layer of soil. Turn the pile to increase temperature.|
For more information, call the City of Lincoln Waste Diversion and Recycling Office: 402-441-8215.