The soil is an independent natural body that was formed as a result of the combined activity of various external forces. What factors influence soil structure? These include plant and animal organisms, parent rock, age of the country, relief, and climatic conditions. The structure of the soil is also affected by human economic activities.
Physico-chemical factors of structure formation
People are often interested in what conditions are necessary for soil to form. Physical and chemical factors play a significant role. Under natural conditions, the coagulation of clay-colloidal components that are present in the soil structure is important.They are reversible and irreversible. The second option provokes the formation of aggregates that are resistant to moisture.
Irreversible coagulation is associated with the influence of absorbed cations. These include calcium, iron, aluminum. Also important is the mutual coagulation of soil colloids, which differ in positive and negative charges.
For example, colloidal compounds of aluminum and iron, as well as silica and humus, form strong coagels due to mutual coagulation. Also, irreversible coagulation can occur during freezing, thawing, and drying of soil hydrogels with irreversible loss of moisture. This process is accompanied by gradual crystallization.
In this case, coagulation can also be reversible. For example, coagulation of soil colloids and clays, associated with an increased content of potassium and sodium salts, provokes the formation of structural aggregates. However, they are not very resistant to water.
The reversibility of coagulation provokes the dispersion of colloids that had previously coagulated. If, during land irrigation, the environment becomes more alkaline and exchangeable calcium is replaced by sodium, structural aggregates in the soil disintegrate. This occurs under the influence of dispersion of colloidal material.
Physical and mechanical
Among this group of factors, pressure plays a significant role. The development of the root system, the movement of insects and animals, as well as the creation of chambers and burrows by them, leads to the appearance of pressure on the fine soil. This entails its aggregation.Swelling and increasing the volume of soil when wet has the same effect.
Further drying out of the soil mass leads to a reduction in volume, the appearance of cracks, and the occurrence of increased intracapillary pressure. Alternate swelling and contraction of the soil mass is considered one of the important mechanical factors in soil formation. The freezing of groundwater has a similar effect with an increase in volume and pressure. It is replaced by melting ice and a decrease in pressure.
Chemical
During soil formation and weathering, new chemicals appear and are transformed into an insoluble form. This can result in a water-resistant soil structure. For example, the accumulation of silicates of iron, magnesium, and calcium carbonate in the soil leads to the cementation of primary mechanical substances and their gluing. This causes the formation of waterproof aggregates.
Biological
Biological and biochemical factors are important for the formation of soils. The structure of soils and their water resistance are closely related to the accumulation of humus and the functions performed by microorganisms. The active formation of soil is due to the constant activity of bacterial microorganisms and fungi.
Soil formation is influenced by a large number of significant factors. The most significant ones include biological, chemical and physical.
