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  • Sam Koerner

What is Organic Matter in healthy soil?

Updated: Jun 21

An integral part of a healthy soil is Organic Matter (OM). OM comes from a various range of sources however the most common ones are dead plant and animal material. Other sources include plant exudates and waste from organisms that are active in the soil.

The image below shows an image of a month-old thermophilic compost pile. The bulk of the items visible in this picture are plant material (yet to be broken down into OM), however there are also several patches of complex acids present (splotchy-looking brown areas on slide).

organic matter under microscope

Without OM, our soils cannot easily form structure which in turn enables aerobic microbes (beneficial) to build aggregates and cycle nutrients into a plant available form.

OM can vary from simple carbon chains through to incredibly complex carbon chains. An example of simple chained OM are sugars, amino acids and some proteins, whereas ulmic, fluvic and humic acids are much more complex in nature. I will delve into how these simple vs complex compounds interact with different biology types in later blogs, but a quick explanation is bacteria can consume simple chains, whereas fungi are required to break down complex chain OM.

In chemistry form a simple chain OM (bacterial food) can exist in the form of a basic sugar, as pictured below:

chemistry symbol

Whereas if we compare this with a complex chain OM (fungal foods) we can see that is much more complex. This is only a very small part of a humic acid molecule.

healthy soil chemistry

It is very common to find simple chain OM in soil, whereas in a lot of agricultural soils complex chain OM are less present due to a multitude of reasons that we will cover later on!

I trust this has assisted you in understanding why Organic Matter (OM) is such an important component of a healthy soil.



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