The chapter on soil discusses the process of rock weathering until the formation of silicates, oxides and soluble salts. Secondary clay minerals are formed from these basic components, as kaolinite, illite and montmorillonite and aluminum silicates, containing m. in. iron, magnesium and potassium.
A characteristic feature of clay minerals is the ability to absorb water and swell, while drying up and shrinking. If they are sufficiently moist, they can be kneaded like plasticine. They retain water in the soil and bind soluble salts. This property is especially characteristic of montmorillonite, which is due to its large internal surface (600—800 m2/g) and swelling capacity. Clay minerals are abundant, e.g.. in bentonite in Lower Bavaria. Bentonite (the name comes from the discovery site in Fort Benton, USA) includes approx 50% montmorylonitu, 15—20% illite and 5—10% kaolinite. It was formed as a result of the weathering of volcanic necrosis in the Tertiary period.
Both clayey meals are used in agriculture and horticulture, and rocky. Soil organisms, especially earthworms, play a big role in mixing and the formation of complexes
clay-humus. The addition of clay to light sandy soils is particularly advantageous, but also for heavy calcareous soils; this significantly improves soil structure and water management, resulting in a richer harvest. Loam is a good binder for sandy or calcium-rich soils, which is also important in natural pest control methods. In horticulture, bentonite flour should be used in small doses, but often. It can be spread directly on the soil surface within the time limit depending on the succession of plants in the applied crop rotation, and, if plants are sown for green manure, per capita. The dose of 200-400 kg / ha is sufficient, the flour can be mixed with organic fertilizers or Algomin. The easiest way is to add bentonite to the compost per dose 3 kg in 1 m3 of compost mass. It is then absorbed and processed most quickly by soil organisms. Too high doses of bentonite inhibit these processes, and the compost becomes greasy and compact. Bentonite is also added to the spray liquid to increase its adhesion and to the lime solution used to whiten the trunks of fruit trees..