How to enhance soil organic matter and how to maintain it

Soil organic matter is the result of the decomposition of plant and animal residues by microorganisms and consists of carbon-based compounds in the soil. During the process of organic matter formation by soil microorganisms, nutrients that can be absorbed by plants are released into the soil. It plays a particularly important role in the supply of nitrogen, phosphorus, sulfur, and iron.

The decomposition process is followed by processes of resynthesis and transformation of compounds that eventually form humus. This process is continuously carried out by soil organisms. Through these chemical transformations, the compounds resulting from decomposition are prevented from becoming insoluble. The role they play is significant; for example, humic substances help make iron available to plants even in soils with medium to high pH levels.

Organic matter is important because:

It stores and provides nutrients to the soil solution, where they are absorbed by plants.
It improves soil structure. In clay soils, it increases soil drainage capacity (by increasing the macroporosity of these soils).
It improves water-holding capacity. It increases water retention, especially in sandy soils, due to its absorbent properties
It encourages the presence of microorganisms.
Higher levels of soil organic matter translate into higher yields, greater stability, and increased profits.

Soil organic matter depends on its losses and its additions. If losses are greater, soil organic matter will decrease; if additions are greater, it will increase.

Losses of organic matter occur through soil erosion, water movement (transportation), and soil microorganisms (microbial decomposition of organic matter into carbon dioxide and organic compounds). The rate of microbial decomposition is influenced by temperature, moisture, oxygen, and other factors.
The addition of organic matter occurs through crop residues. Some crops leave minimal plant biomass, resulting in a reduction of soil organic matter. One of the most important methods of adding organic matter is through organic fertilizers (well-composted manure, peat, olive mill residues, sawdust, etc.).

Organic matter cannot be bought; it is built up year after year.

Organic matter is the single most important soil property that can be influenced through its management. Reducing the rate of decomposition is only half of the effort.

Awaken soil microorganisms by applying organic fertilizers (well-composted manure, peat, olive mill residues, etc.).

Do not assume that adding ten tons of manure per hectare will result in obtaining ten tons of soil organic matter. Approximately 10% of it becomes soil organic matter. As we mentioned, it is a demanding and time-consuming process.

Practice crop rotations that provide a diversity of microorganisms.
In fields with reduced organic matter that experience problems such as drought, salinity, and other issues, it is advisable to allow the soil to “rest” through crop rotation. It is beneficial to cultivate certain crops without harvesting them for one or two years (such as alfalfa, vetch, pasture grasses, peas, etc.).
If we observe earthworms, we can be confident about the microbial activity of the soil. The role of earthworms is important, as their castings provide nutrients such as calcium, magnesium, and nitrogen in forms that are readily available to plants. They also influence soil structure. There are crops whose residues contribute to increasing the activity of soil organisms, such as alfalfa, vetch, pasture grasses, and others. Additionally, reduced-depth tillage helps maintain a stable earthworm population.
To maintain soil organic matter, the root system also plays an important role. We want it to be healthy and as extensive as possible, so that it contributes to improved soil structure and, through its residues, adds organic material for decomposition.

To build up soil organic matter levels, more organic matter must be added than is lost.

The formation of organic matter is a slow process. It may require a decade of effort or more to significantly increase organic matter levels. Fortunately, the beneficial effects of these changes appear long before organic matter levels increase.