Every grower would be happy to have land with high OM values. Soil organic matter (OM) is one of the most important parameters that makes soil productive and creates unique conditions for the producer to achieve a fast return on investment.
Soil OM serves as a major reservoir of essential nutrients. Additionally, OM contributes to soil structure by promoting the formation of stable aggregates, which enhances soil aeration, water retention, and resistance to erosion.
Soil with higher OM values better withstands the negative impacts of poor weather conditions and lack of water supply. It has a buffer capacity for essential soil supplies like water, air, and nutrients, making them readily available in case of immediate shortages due to a lack of supply.
Soil organic matter consists of plants, animals, and microorganism materials and is a key component in carbon storage. During the process of photosynthesis, plants absorb CO₂ from the atmosphere and convert it into organic matter. When plants die, this organic matter becomes part of the soil.
If soil OM is such an important parameter, can we increase it quickly? Can we see the difference within a few years if we decide to do so? Organic matter is not uniform and consists of several fractions that behave differently in soil and can be managed differently with varying outcomes.
These fractions are Free OM, Light OM, Intra-aggregate OM, and Mineral-associated OM. Each plays its own role in the soil organic matter complex and has a different “life cycle.” For instance, Free OM is very labile in soil, with a turnover time ranging from minutes to days. On the other hand, Mineral-associated OM, which makes up about 60% of total soil OM, is very stable, with a usual turnover time of over 100 years.
All these fractions transform from one to another at different speeds, conserving or releasing nutrients, carbon, and energy. Using well-known practices to increase soil OM content—such as applying manure, compost, humic fertilizers, straw, and other residues—helps to increase the light fractions of soil OM quickly. Unfortunately, light fractions often make up a smaller percentage of soil OM and may not result in a significant and visible difference within a short time after application.
On the other hand, the slow transformation of light fractions into stable OM makes soil OM very important and slow to change despite human or natural activities. This stability is a proven fundamental soil feature that supports yields for future generations.
Nowadays, we consider soil OM as a form of soil carbon storage to conserve carbon from the atmosphere. This process is called carbon sequestration. The carbon involved in soil OM fractions, starting with labile OM, transforms over time into stable fractions, conserving carbon for longer periods and naturally regulating the Earth’s climate.