If you check the term soil structure in the BENCHMARKS glossary, the definition will be the following:

The arrangement of soil particles into aggregates which form structural units. Size, shape, and distinctness are used to describe soil structure.

Adapted from: SoilCare Project (2023) Glossary. Available at: https://www.soilcare-project.eu/resources/glossary (Accessed: 10 July 2023).

Soil is a complex system in continuous evolution, resulting from the interaction 🤝 of several factors. This interaction refers to the way particles are grouped into aggregates (also called peds). They are cemented or bound together by physical, chemical , and biological processes.

It is important to not confuse the structure of the soil with the texture of the soil. While the structure measures the arrangement of the particles and the space between them, the texture is an approximation of the relative quantities in the soil of sand, clay or silt particles. Two soils can have the same texture but not the same structure, and can act very differently due to this.

Why it is important to have a good soil structure?

Having said all of this, this question appears. And there isn’t just one answer. A good soil structure helps with root 🌳 support, nutrient availability of the soil 🌱, biological activity 🐛, water management 🌊 or air circulation 💨 among others. The factors affecting this structure are also not only one.

• Clay
• Organic Matter
• Iron and aluminum oxides
• The type of exchange bases
• Calcium Carbonate
• Agricultural processing

When these factors interact with each other, many different results come along. For example, clay, when combined with iron and aluminum oxides, forms a structure that isn’t stable and can break down in wet conditions. However, when clay mixes with organic matter, it creates stable clay-humic complexes that endure. But then, we ought to see which type of clay we are working with. This happens with all the factors interacting at the same type in very different conditions. So, taking all of this into account, we can determine that structure is a dynamic property, as even the strongest aggregates are susceptible to disintegration by physical, chemical and biological agents. The genesis of one soil structure can coincide with the destruction of another.

• Physical agents: Among the physical factors, alternating humidity and dryness, and similarly frost and thaw, induce tensions in the aggregates that, acting on the points of least resistance, can overcome the bonds and consequently break their integrity. Compression contributes to the aggregation of incoherent particles but, when it is too extreme, it can lead to aggregate failure. It is easy to see how the use of heavy vehicles in agriculture and the normal trampling of human beings in an urban environment can lead to a compaction of the surface layers of the soil, which brings with it numerous consequences that are also harmful to human health, such as the production of dust during the dry season or surface water stagnation during the wet season that, in extreme cases and certain environments, can lead to flooding.

• Chemical agents: The disintegrating action of chemical factors is important as it can influence the destruction of cements and various binders. Inorganic compounds are hardly alterable: only strong acidity can solubilise them, making them unsuitable as cement. Organic substances are much more attackable, with physical, chemical and biological oxidation phenomena acting mainly on them.

• Biological agents

📈 Enhancing Soil Structure: Evidence-Based Management Practices

Here are some basic management practices for improving soil structure.

1. Organic Matter Management: One of the fundamental practices for improving soil structure is the incorporation of organic materials, such as crop residues, compost and cover crops, which contribute to the formation of stable aggregates; in addition, the decomposition of organic residues by microbial activity releases substances that act as adhesive agents for soil particles, promoting aggregate stability.

2. Crop Rotation and Diversification: Monoculture can lead to a degradation of soil structure over time, as a result of the continuous stress on specific plant nutrients and increased vulnerability to pests and diseases, while crop rotation with different root structures and nutrient requirements contributes to the development of a diverse and resilient soil microbiome, which plays a crucial role in the decomposition of organic matter, nutrient cycling and the creation of stable soil aggregates.

3. Conservation Tillage: Traditional tillage can alter soil structure by breaking up soil aggregates and promoting soil compaction. Conservation tillage methods, such as minimum tillage or no-till farming, have been shown to preserve soil structure.

4. Cover Cropping: The incorporation of cover crops in agricultural systems is a practice to improve soil structure as cover crops protect the soil surface from erosion, increase the organic matter content and promote root growth. In addition, the root systems of cover crops help break up compacted layers, allowing better water infiltration and root penetration.

5. Soil Amendments: Some soil amendments, such as gypsum, lime and biochar, can play a crucial role in improving soil structure. These soil improvers address issues related to soil pH, nutrient availability and microbial activity. In particular, gypsum has a positive impact on clay soils by promoting flocculation and reducing compaction. Lime, on the other hand, can help neutralise acidic soils, improving microbial activity and indirectly improving structure. Biochar, a carbon-rich material, improves soil structure by increasing water and nutrient retention capacity.

In essence, having a good soil structure it’s the key to a resilient ecosystem, promoting healthy plant growth, nutrient cycling, and overall environmental sustainability.

To achieve this goal 🏆, it is imperative to implement effective management practices aimed at enhancing soil structure, thereby establishing a cornerstone for sustainable agriculture and ecosystem vitality. By integrating organic matter, embracing diversified cropping systems, employing conservation tillage techniques, utilizing cover crops, and applying suitable soil amendments, we can cultivate resilient soils conducive to robust plant growth, thereby fostering enduring environmental sustainability 🌿.

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