The Secret Life of Compost
Compost is a much desired material used to improve soil quality and texture. We dutifully save our kitchen scraps, place them in a bin or area with grass clippings, dried leaves and regularly water. Over time, the end product of this composted material is ready for application. How do individual scraps and leaves become one substance? What really goes on in a compost pile to turn unwanted egg shells and dried leaves into rich, fragrant material?
Composting is a process whereby living organisms consume and digest carbon-containing materials. These materials are called feed stock.
Feed stock, the scraps and clippings we put into the compost pile, are comprised of lignin, cellulose, sugars, starches, carbohydrates, chlorophyll and trace elements.
No batch of feed stock will have the same chemistry because every dried leaf, egg shell and vegetable has its own unique chemistry. Like snowflakes, every combination of feed stock is different.
Feed stock includes materials rich in carbon, nitrogen, oxygen and trace elements. Carbon-rich materials are the “browns” such as dried leaves, shredded newspaper or dry corn stalks. Nitrogen-rich materials are the “greens” and include grass clippings, vegetative scraps or garden debris.
A carbon to nitrogen ratio of 25-30:1 (25-30 parts carbon to one part nitrogen) works well for decomposing the materials within the feed stock. Compost with this ratio of feed stock materials will achieve the minimum temperature of 130-140 degrees Fahrenheit needed to eliminate plant pathogens during decomposition. This is the reason why the carbon to nitrogen ratio is so important to achieve usable compost. For detailed information about these ratios and how they are analyzed, visit Penn State Agricultural Science's example of a compost analysis report (https://agsci.psu.edu/aasl/compost-testing/compost-sample-report).Living organisms are needed to consume and digest the feed stock, thus creating compost. These organisms are present in nature and seek out food sources for survival. Three types of organisms (consumers) digest the feed stock. The primary consumers eat and digest organic feed stock. Primary consumers include bacteria, fungi, actinomycetes, nematodes, some types of mites, snails, slugs, earthworms, millipedes, sowbugs and whiteworms. Once the primary consumers have eaten they may move away or die. Secondary consumers are those who eat the primary consumers and include springtails, varieties of mites, feather-winged beetles, nematodes, protozoa, rotifera, and soil flatworms. Tertiary consumers eat the secondary consumers. This group includes centipedes, predatory mites, rove beetles, ants and carabid beetles.Creating your own compost site requires time, creativity and commitment. Select a location for the compost site. The location should allow for ease of accessibility and maintenance. This site can be designated land or a large container, bin or tumbler.
Place the feed stock in the area where it is to be composted. Start with two parts of the carbon-rich stock (“browns”) such as dry leaves, shredded newspaper or dry corn stalks. The unit of measure (parts) can be scoops, shovels, buckets, bushels, etc.; just be consistent in using the same unit of measure to assure similar proportions of “browns” and “greens.” The important result is the relative volume ratio of 2:1 browns to greens. Add one part of nitrogen-rich stock (“greens”) such as grass clippings, vegetative scraps or garden debris. Mix these materials thoroughly adding enough water to thoroughly wet the mixture.Continue the layering with feed materials in the two parts brown and one part green ratio. Mix and water until all materials are incorporated. Dinner is now served for the organisms that will compost the feed stock. Time is required for the organisms already present in the mixture to feed and reproduce and for others to arrive from the environment. You should be able to detect a temperature increase within the pile and to see some decomposition of the feed stock after a week or so. Continue to turn the composting material weekly. Add enough water to keep the batch damp like a moist sponge. The entire decomposition process may require three to twelve months to complete.
Finished compost is feed stock reduced by the living organisms to a dark-colored, soil-like texture that easily crumbles. No feed stock is readily identifiable. Finished compost has a musky, earthy smell. Allow the compost to cure until you are ready for garden application.Finished compost helps retain moisture in the soil, adds organic material which creates pathways for plant roots, adds nutrients, and reduces wastes that can be beneficially used.The secret to healthy compost is using feed stock with the proper carbon to nitrogen ratio that attracts and encourages reproduction of living organisms to decompose the feed stock while achieving the correct temperature to kill weed seeds and pathogens. Be discerning in your choices of feed stock materials to prevent weeds, pesticides and other contaminants that may actually cause more pain than joy in your gardening and landscape efforts. Penn State Extension offers additional resources on home composting (https://extension.psu.edu/home-composting-a-guide-for-home-gardeners). If you are interested in having your compost tested, see Penn State's Ag Analytical Services Lab website for fees and services (https://agsci.psu.edu/aasl/compost-testing). If you have questions about composting, call the Butler County Master Gardener Garden Hotline at 724-287 4761, Ext. 7 or email the Master Gardeners at butlermg@psu.edu.<i>Michael Pavelek II is a Penn State Extension Master Gardener of Butler County.</i>
