Organic Matter Is The Foundation of Healthy Soil & There Are Two Types of Soil Organic Matter.
Table of Contents
This article is about the Two Types of Soil Organic Matter but let’s start by defining organic matter. It’s the living and dead material found in soil, including plant residues, animal waste, and microorganisms mainly bacteria and fungi).
It plays a critical role in soil health, influencing:
Soil structure: Organic matter improves soil structure by creating aggregates, which enhance water infiltration and aeration.
Nutrient cycling: It acts as a nutrient reservoir, releasing essential elements like nitrogen, phosphorus, and potassium as needed by plants.
Water retention: Organic matter helps soil retain moisture, reducing water run-off and erosion.
Soil biodiversity: It supports a diverse community of microorganisms, which are essential for nutrient cycling and soil health.
Carbon sequestration: Organic matter stores carbon in the soil, helping to mitigate climate change.
Two Types of Soil Organic Matter
The types of organic matter in soil, particulate and mineral associated.
Particulate Organic Matter (POM): This consists of plant residues, such as leaves, stems, fruit and roots, that are broken down by microorganisms. POM is a significant source of organic carbon and nutrients.
Mineral-Associated Organic Matter (MAOM): This is formed when organic compounds bind (adsorb) to mineral particles in the soil. MAOM is more resistant to decomposition and can be a long-term carbon sink.
Here’s the science bit …. Soil organic matter can be adsorbed* on to mineral surfaces in various ways. One common mechanism is outer-sphere complexation, where organic molecules are attracted to mineral surfaces through electrostatic interactions.
* Adsorbed Definition. The main difference is that adsorption takes place with the adhesion of particles onto the surface of a substance, while absorption involves the transfer of particles into another material (one substance absorbing another).
Confusion Alert. The key spelling difference here is the second letter. A b or a d. To confuse things even further I sometimes see the B or P being interchangeable .. adsorption or adsorbtion. No one promised it would be easy.
How To Increase Soil Organic Matter
Gardeners can increase soil organic matter through several practices:
Cover cropping: Planting cover crops between main crops helps to protect the soil from erosion, add organic matter, and improve soil structure. In my view soils should rarely be left bare … preferably never.
Reduced cultivation: Minimising cultivation reduces soil disturbance, preserving organic matter and promoting microbial activity. This also reduces CO2 release.
Manure application: Applying manure or compost to the soil adds organic matter and nutrients.
Conservation practices: This approach combines reduced cultivation, cover cropping/ green manuring and crop succession (including winter cropping) to improve soil health and sustainability.
By understanding the importance of organic matter and implementing appropriate practices, gardeners can enhance soil health, improve crop yields, and contribute to more sustainable gardening systems.
