Organic carbon serves as a nutrient for microorganisms, which produce ingredients that form valuable humus. Organic carbon is merely organic matter introduced into the soil. However, introducing organic matter into the soil does not guarantee its transformation into humus, as some carbon is lost through CO2 evaporation and leaching of the smallest mineral fractions that would otherwise create a sorption complex with organic carbon in humus.

Soil organic carbon is a key component of soil organic matter, essential for the health and function of soil ecosystems. Organic carbon primarily originates from plant and animal debris decomposing in the soil. During decomposition, organic matter is transformed into more stable compounds, such as humus. Soil organic carbon levels vary based on soil type, climate, vegetation, land management practices, and other factors. Soils are among the world’s largest carbon reservoirs. Enhancing soil organic carbon levels is a critical tool in combating climate change, as they absorb and store CO2 from the atmosphere. Practices such as sustainable cropping (no-plough, ultra-shallow, and strip-till), composting, using cover crops, and reducing tillage can increase soil organic carbon levels.

Functions of organic carbon:
- soil structure: organic carbon enhances soil structure, promoting the formation of aggregates, which improves the conductivity of water and air in the soil
- water retention: increases the soil's ability to retain water
- nutrient demand: serves as a source of energy for soil microorganisms, which release nutrients available to plants during the mineralization process
- soil buffering: organic carbon can act as a buffer by stabilizing soil pH.

In summary, organic carbon is a crucial component of soil that impacts its health, structure, functioning, and carbon sequencing ability. Supporting practices that enhance soil organic carbon levels benefit both the environment and farmers. These goals can be achieved through no-plough cultivation methods using the Rolmako U436 three-beam tillage cultivator or the U624 chisel plough. Ultra-shallow cultivation with the SpeedCutter disc harrow or Rolmako knife rollers effectively increases soil carbon sequencing. For initial post-harvest crops, the SpringExpert mulch harrow is ideal for reducing evaporation and stimulating undesirable weeds and volunteers. Sustainable agriculture includes methods and cultivation simplifications that reduce field passes, such as using a tractor's front linkage and combining implements in crop combinations (e.g., cultivation with fertilization or sowing).

C : N (carbon : nitrogen) ratio
This parameter will determine the rate at which the mineralization of matter introduced into the soil will occur. The less nitrogen in the soil, the slower this process will occur. Therefore, we must reckon with greater carbon losses from organic matter and consequently with a much slower formation of humus. In our climate zone, the correct carbon-to-nitrogen ratio in the soil is between 10:1 and 12:1. It is generally constant but may undergo momentary strong fluctuations depending on what organic matter we introduce into the soil. In this zone, the C:N ratio can also be determined. The least beneficial is cereal straw at 80-100:1, while the best is fermented manure or crop residues of legumes, 20:1 and 24:1 respectively. Microorganisms are responsible for the mineralization of organic matter introduced into the soil, and for this, they need nitrogen (building their own proteins during reproduction). If there is little of it in the soil and the C:N ratio, e.g., of plant residues, is wide (straw after cereals), mineralization occurs slowly. Then farmers also use a small dose of nitrogen, e.g., on stubble, to speed up the process—about 5 kg N (nitrogen) for every ton of straw. This element will be used by microorganisms, but it will return to the soil after they die. Nitrogen is a key nutrient for plants. The C:N ratio (carbon:nitrogen) in organic matter affects the rate of its decomposition. Matter with a low C:N ratio (e.g., fresh grass) decomposes quickly and releases nitrogen into the soil. Matter with a high C:N ratio (e.g., dry leaves, straw) decomposes more slowly, and microorganisms can "consume" available nitrogen from the soil (immobilization). Managing organic matter and its processes in the soil, as well as maintaining the right levels of nitrogen, C:N ratio, and calcium, are key to maintaining healthy and productive soil.

High C:N ratio (above 20:1): this indicator suggests that organic matter is rich in carbon relative to nitrogen. In such conditions, soil microorganisms require more nitrogen to decompose organic matter, potentially leading to "nitrogen starvation" for plants due to competition with microorganisms for available nitrogen.

Low C:N ratio (below 20:1): this ratio indicates that the organic matter is nitrogen-rich relative to carbon. Soil microorganisms can rapidly decompose such matter, releasing nitrogen in a form accessible to plants.

The importance of calcium in the soil
Calcium (Ca) is a fundamental macronutrient for plants and plays a significant role in the soil ecosystem. It is a key component of plant cell walls, enhancing the integrity and stability of cells, which influences plant strength and structure. Calcium ions facilitate the formation of soil aggregates, improving soil structure. Aggregation enhances soil porosity, enabling better water and root penetration and aeration. Carbonate lime is commonly used in agriculture to neutralize acidic soils. The reaction of carbonate lime with soil acids produces CO2, water, and calcium ions, which become available to plants. Calcium is vital in activating specific enzymes essential for various metabolic processes in plants. It is involved in intercellular communication processes crucial for stress responses, such as during drought. Calcium can compete with other cations, such as magnesium (Mg), potassium (K), and sodium (Na), for plant uptake. The correct balance of these cations is critical for plant health. Proper calcium levels in the soil support healthy soil microflora, which is important for decomposing organic matter and cycling nutrients.

In summary, calcium plays a pivotal role in the soil, affecting both plant physiology and soil properties, including its microbiome. Proper management of calcium levels is crucial for sustaining a healthy and productive soil ecosystem.

Periodic soil content studies
Soil inspection and testing are essential activities for farmers aiming to optimize crop yields and maintain soil health. Below is fundamental information about soil testing and key indicators. Soil testing involves regularly collecting soil samples from various parts of the field to evaluate its quality and health. This may include assessing soil structure, nutrient content, and other indicators such as humus or C:N ratio.

How to conduct a soil test:
- select appropriate locations in the field for sampling. Avoid unconventional locations (e.g., former compost pile sites).
- utilize soil sampling tools such as a spade or probe (sampler)
- collect samples from various depths and locations in the field
- send samples to an accredited laboratory for analysis
- upon receiving the results, consult a soil expert or agricultural advisor for interpretation and recommendations

In summary, soil organic carbon testing is essential to evaluate the level of organic matter, which is critical to soil health. Organic carbon, the primary component of organic matter, indicates soil health and fertility. Regular soil testing aids farmers in making informed decisions about fertilization, liming, and other soil management practices, contributing to improved crop yields and long-term soil health.

Terminology
CO2 - carbon dioxide - is a gas essential for plant photosynthesis.
Reservoir - a collection of resources that can be utilized.
Soil aggregates - lumps of various shapes and sizes with differing durability, formed in the soil by the merging of individual mineral grains. They constitute the soil structure.
Microbiome - the community of microorganisms present in the soil.
Soil microflora - increases plant resistance to diseases and is responsible for a more effective supply of nutrients and bioactive substances.