Organic matter
In our circumstances, organic matter typically comprises plant material and natural fertilizers incorporated into the soil. This includes crop residues, straw, manure, and fertilizers derived from sludge or post-fermentation pulp from biogas plants. The outcome—whether this material undergoes humus-forming processes or is lost—depends significantly on our management practices.

Organic matter can undergo two processes: mineralization and humification. Both are important. The first releases nutrients that crops can use, and the second produces humus, which is responsible for the soil's water retention capacity.

Mineralization
This is the transformation of organic compounds into minerals. It can occur through two processes: decay and putrefaction. Putrefaction occurs in aerobic conditions, such as in the top layer of soil with a high accumulation of organic matter, which is common in no-plough cultivation. It is also more prevalent in light soils that naturally contain more air and therefore more oxygen. During putrefaction, carbon dioxide is produced, along with water and ions such as sulfate, phosphate, or nitrate, which can be absorbed by plants. Decay, on the other hand, occurs in anaerobic conditions, typically in moist and colder soils. In this process, carbon dioxide, methane (CH4), hydrogen sulfide (H2S), and carbon disulfide (CS2) are released. The smell of rotting can be detected, for example, when plowing wet soil in waterlogged areas or ponds. Scientists in the 1970s discovered that as a result of rotting and decay, 20-30 kg of CO2 is released from each hectare.

Humification
This process is significantly more complex than mineralization. In simple terms, humification results in the formation of humus. It is a continuation of mineralization, involving two groups of compounds: one includes products formed during mineralization such as CO2, nitrates, or sulfates, and the other consists of difficult-to-decompose plant compounds like fats or lignins, and compounds synthesized by microorganisms, such as polysaccharides.
The processes of humification and humus formation are significantly influenced by:
- the quantity and quality of plant residues
- the species and quantitative composition of soil microorganisms
- the water properties of the soil
- the chemical composition of the soil and its grain size
The importance of organic matter and humus
Improving soil structure: humus promotes the formation of soil aggregates, enhancing its structure, water, and air conductivity.

Water retention: humus increases the soil's capacity to retain water, benefiting plants.

Providing nutrients: humus serves as a source of essential nutrients for plants.

Supporting microorganisms: organic matter acts as food for soil microorganisms, which perform crucial ecosystem functions.

What promotes the formation of humus?
Sustainable crop cultivation: ensuring a steady supply of plant residues.
Composting: the composting process accelerates the formation of humus from organic matter.
Mulching: applying a layer of plant residues to the soil protects it from erosion and promotes the formation of humus.
Reduced tillage: less intensive soil work preserves humus in the soil.

Factors leading to humus degradation?
Excessive tillage: destroys the soil structure and accelerates the decomposition of humus.

Excessive use of pesticides: can kill soil microorganisms responsible for creating humus.

Monocultures: growing one plant species for an extended period can lead to depletion of humus.

Droughts: lack of water inhibits the activity of microorganisms responsible for creating humus.

Summary:
The formation of humus is a complex and prolonged process, requiring at least 15 years for organic matter introduced into the soil to produce humus. This necessitates regular supply and appropriate agricultural technology. Humus degradation outpaces its synthesis, particularly on light soils that undergo regular ploughing without organic matter supplementation. In Poland, the humus content in such soils is often lower than 1%. Polish soils generally contain between 0.5 to 3.5-4% humus, with over half of them having less than 2%. Maintaining soil humus by farmers is a cornerstone of sustainable agriculture. Humus, as the primary nutrient source for plants, influences crop health, fertility, and quality. It enhances soil structure, increases water retention capacity, and supports soil microorganism activity. In conclusion, maintaining soil humus is crucial for long-term productivity and soil health, leading to improved yields and greater farm profitability. In the context of climate change and the increasing demand for sustainable agriculture, managing soil humus is both an economic and ecological priority. Sustainable soil management and humus maintenance are vital for crop quality and ecosystem health.

Terminology
Post-fermentation pulp - product of methane fermentation, is distinguished by its relatively high content of micro- and macroelements, nitrogen, phosphorus, and potassium in mineralized form, as well as high biochemical stability.
CO2 - carbon dioxide, is a gas essential for plant photosynthesis.