What is Compost, Exactly? It’s the Result of Composting, of Course!
This is my search for information about compost in its various forms – including humus, mulch, vermicompost, bokashi. These range from my original and straight-forward query, to questions about composting systems, about the micro-organisms and small creatures that transform the raw ingredients and about ways of utilizing the ‘black gold’ that is the result of the process.
What is compost?
Here are two straightforward dictionary definitions of the phrase.
The Oxford Dictionary (Eng. english) when asked, calls it:
- “decayed organic material used as a fertilizer for growing plants”
- “a mixture of compost or similar material with loam soil used as a growing medium”
- “a mix…’ of organic residues such as decomposed vegetation, manure, etc, used as a
So – what is compost? Compost, or humus, is a mulch of rotting, organic material – nothing more and nothing less. But, as they say in the ads, “Wait – there’s more!”
These uncomplicated definitions of the word bear no hint of the special nature of the product under discussion, or of the high drama that is taking place within the average pile and this is what really interests me.
By looking more particularly at the physical make-up of our compost, we can better understand the importance of its variations and how each type of compost may differ in both make-up and function. Probably the most recognised type, in nature, is humus. This is the substance found on forest floors, and is the result of years of almost undisturbed branch, leaf and fruit – fall being processed by some of the same creatures we need in our own garden bin. This symbiotic relationship between animal and vegetable matter, results in a gentle fertiliser that feeds the forest itself, and, at the same time a carpet of mulch that protects the root systems of the trees while keeping the soil moist and providing insulation. Cool, sweet-smelling humus has a beauty all of its own.
So, for a starter, in a back-yard heap, or in a worm farm inside, we should certainly find some of these basic ingredients – grass clippings, vegetable and fruit peelings and garden trimmings. These are easily dealt with and are known as ‘greens’ or ‘wet’ items. They are the source of the nitrogen which provides protein for our microscopic workers. We should also find items such as dry leaves, clean paper, cardboard, sawdust, twigs or hay. These are known as ‘browns’ or ‘dry’ ingredients and are the source of the carbon needed to provide necessary energy. We need to achieve a balance of these materials, and you will find a few different figures quoted. Some say 50-50, others say 2 or 3 parts brown to one part green, or 25:1 brown to green. I am sure there are reasons for these variations, but at this stage, let’s not get precious about it. My grand-dad did it by instinct and years of experience. I reckon he never measured or weighed a grass clipping in his life and after all, the humus in the forest makes itself extremely successfully without much bother at all.