The organic matter cycle: what it is and why it is essential for your crops

Today we are talking about the most important element of our work: soil.
We often take it for granted, but understanding its characteristics and how to manage it, is crucial to get the most out of your crops and ensure the long-term health of your land.

What is soil and why is agricultural soil special?

Soil by definition is the portion of material within two meters of the Earth’s surface in contact with the atmosphere. It is a precious heritage, which is formed incredibly slowly: about 10 centimeters every 1000 years. An agricultural soil differs from a natural one by its fertility, that is, its ability to produce crops that are useful to humans. It is the ground that allows the roots of crops to spread and support growth.

The profile of your soil: the three horizons

In cultivated soil, three main layers (horizons) can generally be distinguished:

• Cultivated Layer: This is the surface layer, which is worked. The roots and biological activity are concentrated here. It is rich in nutrients, soft and well aerated.
• Subsoil: this is where the deepest roots are found, which mainly serve to anchor the plant.
• Bedrock: the underlying rocky layer, where the root system does not reach.

The depth of agricultural soil is a fundamental indicator of its productive potential. The deeper it is, the more productive it is! Maximum potential is achieved with active layers greater than 90 cm.

The fundamental components: Solids, Liquids and Gases

Soil is a complex system, a mixture of three phases: solid, liquid and gaseous. In fertile soil and under optimal conditions, the volume is divided as follows:

• Solid phase: approximately 52% of the total volume, composed mainly of minerals (48%) and organic matter (4%).
• Liquid phase (water): approximately 23%.
• Gaseous phase (air): approximately 25%.

The vital importance of the organic matter

Although it is a small fraction, organic matter (Humus) is crucial for soil fertility. Its presence is always positive because it improves the physical, chemical and biological quality of the soil.

Benefits of the Organic Matter (Humus) – Type of Properties:

• PHYSICAL: improves porosity and aeration for better root growth. Increases water retention, making more water available to plants.

• CHEMICAL: increases cation exchange capacity, retaining more nutrients in the surface layer.
• BIOLOGICAL: contributes to soil formation (pedogenesis), increasing fertility. It helps sequester carbon, reducing atmospheric carbon dioxide.

Organic matter is often evaluated based on its stable humus content. Classification of soils by humus content: Poor: 0.2% / Moderate: 3-5% / Rich: 11-15% / Very rich: >16%.

The “organic matter cycle” and the formation of humus

The organic matter (plant and animal residues, etc.) that enters the soil is attacked and decomposed by soil organisms. This process takes place in three main stages:

1. Demolition: macro and micro organisms begin to decompose the organic tissues.
2. Mineralisation: the complete degradation of organic compounds by microorganisms, which releases nutrients available to plants and carbon dioxide into the atmosphere.
3. Humification: compounds that are not completely degraded, are polymerised (aggregated) by microorganisms to form stable, dark molecules called humus.
   Humus is a colloidal, dark material with a very high-water retention capacity.

As we have seen previously, organic matter can come from two different sources:

• Crop residues (what remains of plants after harvesting), which are the most common source of organic matter in cultivated land.
• Green manure (intercropping and cover crops): specially sown, harvested and ploughed into the soil, their main purpose is to increase organic matter.

Proper management is essential to maximise the benefits and promote a healthy organic matter cycle. This is where our Alpego shredders come into play.

Finely shred residues (such as wheat straw or corn stalks) and distribute them evenly over the soil or lightly plough them in:

• Increases the contact surface: fine, uniform shredding exposes a larger surface area of residue to soil microorganisms, facilitating and speeding up the early stages of decomposition and mineralisation.
• Promotes nutrient distribution: the release of nutrients is more gradual and distributed.
• Helps with incorporation: well-shredded residues are easier to incorporate into the rhizosphere (the root zone) with subsequent tillage operations, such as ploughing or subsoiling, thus preparing the seedbed in the best possible way.

By using our professional Alpego shredders, models TR36 – TR36F and models TR56 – TR56F, we ensure that organic matter is managed in the most efficient way, transforming harvest residues into essential nutrients for the fertility and health of your soil.

These two processes (mineralisation and humification) are in balance. With the right cultivation practices, you can influence this balance, favouring one or the other depending on the needs of your crop.

Conclusion

Caring for agricultural soil and its organic matter is not only good practice, it is an investment in your productive future. Deep, well-structured soil rich in humus, with a balance between mineralisation and humification, is the key to successful cultivation.

Would you like to find out which Alpego mulcher is best suited to managing your crop residues and optimising the organic matter cycle in your soil?

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