Crop rotation
A simplified crop rotation dominated by cereals adversely affects the organic matter content required for humus formation. Unfortunately, such crop rotations are prevalent on Polish farms. Below is a list of plants that have negative and positive effects on the soil's organic matter content.

Cereals, predominant in cultivation, result in the degradation of over half a tonne of organic matter per hectare, while root crops are more detrimental, depleting 1.4 t/ha of organic matter.

Natural fertilizers
As evidenced by the table above, 1 ton of manure does not significantly increase organic matter in the soil. However, a dose of 25 t/ha of fertilizer notably enhances organic matter content to 1.75. Additionally, natural fertilizers contain specific amounts of valuable nutrients utilized by crops.

Harvest residues
Any crop residue positively impacts increasing the content of organic matter and humus in the soil. For root crops or cereals, it mitigates the reduction of humus content. Post-harvest, sugar beet leaves (80 t/ha yield) leave around 60 t of residue per field, containing 3–4 kg of N, 0.8–1 kg of P2O5, 5–6 kg of K2O, 0.8–1 kg of MgO, and 0.3 kg of pure S. Proper stubble processing is crucial to maximize the benefits crop residue provides to the soil.

Depth of cultivation
Shallow cover allows crop residue on the soil surface to protect it from water and wind erosion, functioning as a natural mulch that reduces water evaporation from the soil surface. Surface residue can stimulate the activity of surface soil microorganisms. A disadvantage of shallow cover is that pests use the residue as a shelter or food source. Surface residue may decompose more slowly than residue incorporated into the soil. Residue buried deep in the soil may decompose more quickly due to better contact with soil microorganisms. Incorporating organic matter into deeper layers improves soil structure and health at greater depths. Deeper cultivation can remove surface residue, making the soil more susceptible to erosion. Lack of mulch from surface residue can lead to faster evaporation of water from the soil.

Farming - which tools to choose?
Improper agricultural techniques can significantly contribute to the degradation of organic matter in the soil. For instance, if straw is ploughed up after harvest and poorly mixed with the soil in excessively humid conditions, it will resurface with the next crop and decompose, resulting in its loss. Therefore, each cultivation should aim to mix crop residues with the soil as effectively as possible. Ideally, this should be done to a depth of 30 cm using a three-beam Rolmako U436 cultivator. Remember that cultivating excessively wet soil is more detrimental than cultivating dry soil. Overly moist soil conditions will lead to anaerobic decomposition of crop and plant residues, resulting in rot instead of mineralization and humification. Consequently, humus will not form from such residues. Similarly, residues left on the soil surface will not convert into humus. A significant amount of straw after harvest, such as from high-yield cereals or corn, is challenging to mix in a single pass using a disc harrow or gruber. In such cases, double cultivation is required: initially to a shallow depth, around 5 cm, to minimize water evaporation and pre-mix the residues, followed by a greater depth, at least 15 cm, for thorough mixing. An exception to this rule involves using a combination of tools, including the front three-point linkage with a ProCut or TurboCut double knife roller in conjunction with any disc harrow. To achieve deep incorporation of straw in a single pass, utilize the aggressive angle of attack of the discs of the heavy stubble harrow U671. For shallow cultivation, optimal results are achieved with the SpeedCutter disc harrow equipped with a front knife roller. It is advisable to make passes at an angle to the previous pass.

Terminology
CO₂ - Carbon dioxide - a gas essential for plant photosynthesis.t