In our previous article we established that carbon is at the epicentre of a complex interplay that exists between living matter, dead matter, organic matter and mineral matter; it's the key ingredient that makes a soil not only fertile - but healthy. Furthermore we explained how soil organic carbon promotes the small water cycle, which leads to more - and more effective - rainfall.
This is the second of a four-part series that explores the existential role of carbon in soil, and how soil carbon can greatly increase farm productivity.
Most farmers may not recognise soil carbon but do know soil organic matter, which is approximately 45% carbon. Other carbon in the soil is inorganic and includes carbonates (calcrete) and soots and chars. Both typically are small in farming systems and difficult to influence.
So what does carbon do chemically that helps soil, and the farmer, function better?
Well for one, organic matter is an impressive chemical regulator.
It stores excess nutrients, it imprisons toxic substances, it stops acids and alkaline being wayward (meaning it buffers pH) and feeds nutrients to microbes as well as roots at the desired rate.
Yes - organic matter buffers soil pH. It gives soil the ability to resist acidification or alkalinisation caused by synthetic fertilisers and hostile subsoils. Sounds good right?
Organic matter also accelerates nutrient cycling of C:N:P:S.
Organic matter provides a home and food for microbes. An active biome feeds the roots, and organic matter promotes exactly that - an active biome, which is also a powerful accelerator of carbon sequestration in soil. It provides a storage and slow release mechanism for nutrients, and the decay of it releases nutrients such as Amines (Nitrogen) and Phosphate - as well as trace elements, such as Zinc and Sulfur. Phosphate is released in soil through acidic excretions of microbes, which makes it available to plants. This severely reduces the need for fertilisers, and thereby reduces costs to grow pasture or crops.
Since we're in the mood for metaphors, organic matter also undertakes the role of garbage cleaner and chief policeman of the soil.
It moves the bad substances - poisons such as heavy metals, which become entrapped in clay or within the intractable zone of organic matter. It also stops excess but precious nutrients being washed away to groundwater or surface water, holding it for later release.
Organic matter is not only our chemical regulator of the soil but our efficiency driver of all chemical inputs to the soil needed for optimum plant production.
Building up organic matter has a direct impact on your bottom line - because it ensures all inputs are efficiently used.