Heavy clay soil is characterised by a very high clay content and strong cohesion between soil particles. These soils have a very narrow optimum tillage window because their moisture conditions change rapidly. When the surface soil dries excessively due to evaporation, it becomes hard and difficult to cultivate. Consequently, selecting the appropriate time for tillage is particularly important. Tillage performed when soil moisture is unsuitable can damage soil structure, reduce soil aeration, and adversely affect conditions for plant growth.
Humic acids are a group of complex, high-molecular-weight organic compounds found in humus-rich soils, peat, and lignite. They belong to the group of humic substances formed during the decomposition and transformation of organic matter in the soil. Unlike fulvic acids, which are soluble in both acidic and alkaline solutions, humic acids are soluble primarily in alkaline solutions. They have the ability to chelate metal ions, including heavy metals, thereby contributing to improved soil properties. Owing to their physical and chemical properties, humic acids are important components of soil, contributing to soil fertility, nutrient retention, and soil structural stability.
Humification is the biological process by which dead organic matter in the soil is partially decomposed and transformed into stable organic compounds, resulting in the formation of humic substances. This process is carried out by soil microorganisms and other soil organisms. Humification plays a fundamental role in the formation of humus, the stable fraction of soil organic matter that contributes to soil fertility and favourable soil properties. During humification, organic matter is not completely decomposed but is converted into more complex and stable compounds. Humification occurs simultaneously with mineralisation, during which plant-available nutrients are released from organic matter.
Humus is the stable fraction of soil organic matter formed through the decomposition and transformation of dead plant and animal residues by soil microorganisms and other soil organisms. Owing to its large surface area and high capacity to bind various substances, humus serves as an important reservoir and source of plant nutrients. It contributes to soil fertility by retaining nutrients and gradually making them available for plant uptake. In addition, humus improves soil structure and has a positive influence on the soil water, air, and thermal regimes. The formation of humus is a long-term process involving the decomposition, transformation, and stabilization of organic matter into stable organic compounds. The topsoil generally contains the largest proportion of humus reserves and provides a vital habitat for soil organisms.
