Compost

Proper, Aerobically Decomposed Organic Matter

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We all know how to make compost, right? We've been doing it for years, no?

As a rule, no. There may be some things that we could all learn to make better, more beneficial compost. Ways of ensuring there are no, or far fewer, detrimental organisms and compounds, no pathogenic organisms and eliminating viable seeds from the finished compost.

There are mantras of “never put diseased plants in your compost pile” or “never put animals in your compost pile”. This is malarkey, in relation to true aerobic, thermophilic compost production, though it is good advice for piles of “putrid organic matter”. Properly composted, “anything which once was alive can be composted”.

Compost, The Definition

The term compost was defined in the late nineteenth into early twentieth century by Sir Albert Howard, a British botanist working for the British government in India. Sir Howard is recognized as the great-grandfather of organic horticulture, and recognized that the farmer must feed the soil rather than feed the plants and that the soil will reward the farmer in like kind. He went on to define compost as “aerobically decomposed organic matter”. This implies the pile is to be constructed in such a fashion as to entrain oxygen, and the pile is turned when necessary in order to maintain proper oxygen levels. Temperature at the core of the compost pile is commonly used as the indicator for necessary turning. Anything less is, to quote Dr. Ingham of the Soil Food Web Inc., “putrid organic matter”.

Per Websters:

Putrefaction: 1 : The decomposition of organic matter; especially : the typically anaerobic splitting of proteins by bacteria and fungi with the formation of foul-smelling incompletely oxidized products.

Additionally, ensuring proper pile temperatures through maintaining the proper ratio of carbon-rich to nitrogen-rich materials, combined with judicious turning ensuring proper aeration, results in temperatures beyond the survival range of pathogenic and detrimental organisms and seeds incorporated into the compost materials. This ensures a safe product with no seeds to germinate and cause weed issues when used.

Organic Growers Topically Get It Wrong

After six-plus decades of the “green revolution”, the thought processes of chemical agriculture have become all-pervasive. Organic growers have begun to think like chemical farmers. Often is heard the mantra of making good, mineral rich compost to “re-mineralize the soil”. This is a misconception. As we learn in the study of soil, there are more than adequate quantities, and diversity of minerals in the base constituent soil particles for optimum plant growth, with very, very few exceptions.

The goal of composting is to produce a dense, diverse population of bacteria, fungi, protozoa, nematodes, micro-arthropods and more. Additionally, to promote conditions to produce beneficial species of these creatures while reducing numbers of detrimental species. Additional nitrogen is also a beneficial component for a directly applied amendment. Available nitrogen in the soil being in the form of a water soluble compound, rather than the water insoluble mineral compounds, leaches from the soil readily when adequate organic mater and organism are not present to keep it in place, and even then it is ultimately lost and must be replaced regularly.

Of course, diverse, mineral rich compost will result in more diverse microbial populations and is never a bad thing to achieve, but mineral content is not the key to a soil building amendment, but rather bio-diversity is key. Mineral density is, however, a requirement when producing compost for the base of a planting mix for container use. In which case amendments such as basalt rock dust, added to the mature, finished compost are also helpful.

Component Materials and Engineering Compost For Desired Result

Building the successful compost pile requires an appropriate mix of brown or woody, carbon rich materials, green, nitrogen rich materials and smaller quantities of high-nitrogen materials, resulting in a mixture with an overall ratio of about 20-30 : 1, carbon : nitrogen.

Brown,or woody material, is high-carbon material, with a carbon to nitrogen ratio of 60:1 or greater, typically much greater. Brown materials include those such as wood chips, straw, fallen leaves, shredded cardboard or paper, etc. Most common brown materials will exhibit C:N ratios in the hundreds : 1.

Green plant materials contain the living sugars, enzymes, proteins and so on which contain higher concentrations of nitrogen, typically about 30:1. It is notable that material which is harvested green and then turns brown when dried for storage, is still green for composting purposes. The sugars, proteins and so forth are still present and the material may be stored safely for future use as long as it remains dry.

High nitrogen materials make a compost pile “kick”, causing robust microbe growth and heat with only small additions. They fall into a C:N range of near 10:1 or less. Typical high nitrogen materials include fresh animal manures, leguminous plants (grown with active rhizomatous nodules), seeds and a select group of plants including alfalfa (a legume), comfrey and stinging nettle.

As mentioned previously, utilizing a wide verity of input components when composting results in more microbial diversity, it also results in greater organic nutrient diversity. The components may be varied and altered in order to promote specific types and numbers, or ratios, of organisms needed to achieve balance within the soil being treated.

For a more thorough discussion of the makeup and function of the soil biome may like to visit the Soil Life page.

Aeration, Regular Turning Is A Necessity

One of the most crucial points in the production of good compost is maintaining the aerobic condition of the pile. Even a small portion which is repeatedly not turned and mixed will produce detrimental, anaerobic, organisms resulting in “putrid organic mater” in lieu of compost.

Core Temperature of the Pile

Fortunately we have been provided by nature with a highly accurate and reliable indicator by which to gauge the need for turning the pile. Microbes within the pile, particularly bacteria, produce heat as they consume products, grow and reproduce. This results in a steady increase in pile temperature, that is to say core temperature. As microbial populations increase they use-up the available oxygen at a predictable rate which presents as a corresponding temperature increase. Once a core temperature of 155° F to no higher than 165° F   is attained, the pile must be turned.

Mechanics of Turning the Pile.

As mentioned previously, the pile must be methodically turned in order to leave no portion un-aerated, additionally all portions of the composting material must spend adequate time in the "hot core" of the pile to ensure proper pasteurization. When turning, the top and outer areas of the pile are first removed and placed in position to make the new “center of the pile”, then the material in the center of the existing pile is placed on the outside of the new pile. This “inside-to-outside, outside-to-inside” procedure is conducted each time the pile is turned. During turning, is an excellent time to add water to the pile as well, if needed.

Among the requirements for organic compost production are that the temperature of a turned pile be maintained between 131°F and 170°F for a period of at least fifteen days and the pile be turned a minimum of five times while held within that temperature range. Turning between 155°F and 160°F ensures a temperature of greater than 131°F exists throughout the turning process.

While it is important to ensure that all material is cycled through the “hot” portion of the pile repeatedly, it is desirable to keep the number of turns to a minimum in order to preserve nutrient and organism density, especially fungal mycelia, and, your pile should never exceed 165°F. At temperatures above this, there are anaerobic processes occurring that we want to prevent, producing detrimental acids, ammonias, organisms and other negative metabolites. There is also the remote possibility of spontaneous ignition within an anaerobic compost heap, similar to the ignition of improperly dried hay bales.

In Sumation

The production of compost is by no mean rocket science. However, the length of this very superficial overview of the procedures and processes indicates the intricacies of the process, and the need for a complete understanding of the systems and processes involved, in order to fully benefit from the wonderful gift of compost nature has given us.

Please feel free to reach out for individual consultation or, and assistance with production of high quality compost, testing of your compost and application.