Secrets Underground

Soil fertility, a fundamental element of agricultural production, refers to the ability of the soil to provide the essential nutrients required by plants for optimal growth. This ability is directly related to the presence and availability of nutrients such as nitrogen, phosphorus, potassium, calcium, magnesium, sulphur and other elements in the soil.

In addition, soil fertility is inextricably linked to several factors such as soil structure, organic matter content, soil pH and, of course, the presence of beneficial micro-organisms.

Fertile soil is characterised by its ability to provide plants with the right amount and form of nutrients to grow healthily and produce high quality crops. Soil fertility is an essential pillar of agriculture and food production as it has a direct impact on crop yields and the long-term sustainability of agricultural land. Maintaining and improving soil fertility is therefore a key objective of agricultural management and environmental protection.

It is important to recognise that soil is a complex and dynamic ecosystem. The physical soil particles are saturated with living organisms that are in a state of continuous activity throughout the growing season.

Classification of soil organisms by size

Soil organisms can be divided into three main categories according to their size:

• Microfauna: This category includes organisms of minute size, ranging from 0.02 to 0.16 mm. Examples of microfauna include bacteria, fungi, actinomycetes, protozoa and algae.
• Mesofauna: Mesofauna includes organisms of moderate size, ranging from 0.16 to 10.4 mm. Examples of mesofauna are insects, springtails, mites, nematodes and molluscs.
• Macrofauna: Macrofauna includes larger organisms, larger than 10.4 mm. Examples of macrofauna are earthworms, insects, arachnids and small rodents.

Activities of soil organisms

Soil organisms play a crucial role in the functioning of the soil ecosystem and in supporting plant growth. Some of the main activities of these soil organisms are described below:

Decomposition of organic matter: Micro-organisms, such as bacteria and fungi, are responsible for decomposing organic matter in the soil, including fallen leaves and plant debris. This decomposition releases nutrients that are essential for plant growth.

• Nutrient cycling: Soil organisms actively participate in nutrient cycling by breaking down and releasing elements such as nitrogen, phosphorus and potassium into forms that are readily assimilated by plants.
• Improved soil structure: Earthworms and other burrowing organisms help improve soil structure by mixing and aerating the different soil horizons. This facilitates water infiltration and oxygen circulation, which benefits root growth.
• Pest and pathogen control: Some organisms, such as predatory nematodes and certain fungi, play an important role in controlling pests and pathogens that can damage plants.
• Humus formation: Organic waste processed by micro-organisms is converted into humus, a nutrient-rich substance that improves water retention and soil structure.
• Nitrogen fixation: Some bacteria, such as those that form symbioses with legume roots, have the ability to fix atmospheric nitrogen in the soil, making it a nutrient available to plants.
• Carbon storage: Soil organisms play a key role in storing organic carbon, which helps to mitigate climate change.

Abundance of Microorganisms in Soil

The number of micro-organisms in the soil is staggering. For example:

Conclusions

Soil fertility is a fundamental factor in agricultural production as it determines the ability of the soil to provide the nutrients necessary for healthy plant growth. This fertility is related to the availability of essential nutrients such as nitrogen, phosphorus and potassium, and is influenced by several factors, including the presence of beneficial micro-organisms.

Soil is a complex ecosystem inhabited by a wide range of organisms, from micro-organisms such as bacteria and fungi to macro-organisms such as earthworms. These organisms play a vital role in soil health and fertility. They are involved in decomposing organic matter, cycling nutrients, improving soil structure and controlling pests. They also contribute to carbon storage and atmospheric nitrogen fixation in the soil.

The abundance of micro-organisms in soil is staggering, with hundreds of millions per gram of soil. These organisms are essential for maintaining and improving soil fertility, which in turn influences agricultural productivity and long-term sustainability. Agricultural management and environmental protection focus on preserving this diversity and function of soil organisms.