What is Compost?

Compost is the product resulting from the biological decomposition of organic material that has been sanitized through the generation of heat and stabilized to the point that it is beneficial to plant growth.  It has the ability to improve the properties and the physical structure of soil and will vastly improve the chemical composition of soils and growing mediums.

Compost, when fully reconstituted, bears no physical resemblance to the raw materials from which it originated!  It serves the purpose of a plant fertilizer but is not typically referred to as such.   Compost is produced through the activity of oxygen requiring microorganisms.  In order to grow and multiply these microbes require oxygen, moisture and food.  The microbes generate heat, water vapor and carbon dioxide as they break down raw materials into a stable soil conditioner.   The heating stage also kills the weed seeds, thus sanitizing and allowing a high rate of decomposition.  Soon after there will be a low temperature stage, that allows the compost to stabilize and decompose at a slower rate.  The microbes found in compost are also able to degrade some toxic organic compounds, including petroleum.

There are many uses for compost in large quantities.  The restoration of native wetlands is one.  Compost simulates the rich organic matter found in wetlands, encouraging the re-establishment of native plant species.  Coarse composts have also been used as mulch for erosion control, supplementing or replacing more conventional materials.

For most of us though, compost is used in much smaller quantities.   Even in small quantities, compost has many beneficial qualities. It improves the soil structure, porosity and density, resulting in a better plant root environment.  It increases infiltration and permeability of heavy soils, thus reducing erosion and runoff with the improved water holding capacity, and reducing water loss and leaching in sandy soils.  The organic material supplies beneficial microorganisms to soils and improves and stabilizes soil pH.  Compost can be used as a filter media for storm water treatment and has been shown to minimize leaching of pesticides in soil systems.

Compost is a very useful component for improving compacted, disturbed and unirrigated soils.  A good example could be a building site, where heavy equipment has compacted the soil and various building materials have mixed in with the existing soil, creating a site of poor quality, void of nutrition, compacted and possibly lacking any topsoil at all. It would be very difficult to establish any plantings.  The addition of compost to such a site would supply both beneficial microbes and nutrition, allowing for an on-going nutrient cycle to be established.

Making your own compost

When choosing a site for a compost pile, an area generally out of sight of the garden is good, but easily accessible to add to the pile, and empty when ready for use.  A compost bin should have a lid to keep the warmth in, and easy access to the compost by slats or movable panels, and a capacity of at least 10 cubic feet to generate sufficient heat. Plastic bins are generally more efficient than wooden ones; they conserve moisture and reduce the need to water frequently.

Almost any vegetable waste may be composted.  A small tub with a tight fitting lid can be kept in the kitchen.  Teabags, coffee grounds, potato peelings, citrus peels etc. can be put in the bin and added to the compost when convenient. No meat, grease or cooked foods should be used — these attract vermin.  When making compost, never use plant remains that have virus infections or perennial weeds — both are difficult to control.

To make a compost pile — build up a mixture of nitrogen rich material, such as grass clippings and carbon rich material, such as bark and shredded paper, preferably in a 1:2 proportion.   Thick layers of grass clippings will inhibit air movement.   Pruned clippings can be used, but woody stems should be shredded first.   Use only young weeds with no seeds!

To speed up the process of decomposition, add additional nitrogen such as commercial compost starters or preferably manure (horse or cow), which has the advantage of containing high levels of soil organisms.  Use alternating layers of organic material and manure.  If the material in the compost heap is very acidic (oak leaves and/or pine needles) microorganisms will not work efficiently — adding lime will make it more alkaline.

This process of making compost generates a high temperature, which encourages the natural breakdown of organic matter to operate quickly and also helps kill weed seeds, some pests and diseases.

To heat up sufficiently, a compost pile should be at least 1 cubic yard, but 2 cubic yards is preferable.  Compost reaches its maximum temperature in about 2-3 weeks and matures in about three months.   Turning the pile will speed up the process and ensure complete breakdown.  Turning introduces oxygen — a necessary component.

An ammonia odor indicates the compost is too rich in nitrogen; a smell of rotten eggs means the pile lacks air.

It may be necessary to water the compost from time to time.  A very long dry period can spell disaster to a compost pile, so a slow dribble for a long period can add the necessary moisture.   To avoid further drying out, place black plastic over the pile to help generate and keep heat in as well as the moisture.

Composting enables you to recycle your yard wastes, returning organic matter to the soil and providing some nutrients for healthy plant growth.  The total volume of waste discards, or garbage, picked up by your garbage collection service every week can be reduced by almost 15% a year. In the long run, composting helps you reduce what you discard, improve your garden, and even save money.

Click here for information from the Master Composters web site
on how to build your own composting bins