Serozem soils are common in Eurasia and the continents of North and South America. In Russia, gray soils are located in the southeast of its European part; they are found in Kazakhstan and Uzbekistan. Formed under dry steppes. Let's consider what gray soils are, their classification, characteristics, how they are formed, how they are used, what vegetation grows on them.
What are sierozems?
Gray soils are so named because they have a light brown-fawn color. They have a loose structure, a profile with unclear transitions between horizons, carbonate content, and are highly permeable to water. The parent rock is loam.
Distributed in foothill deserts of the subtropical zone. Gray soils are characterized by high bioactivity in the spring, when it is warm and the soil still retains moisture. This is explained by the saturation of the upper horizon with beneficial bacteria; the result of the activity of microorganisms is mineralization processes, among which the processes of nitrification and at the same time denitrification predominate.
Gray soils contain blue-green and green 1-cell algae, in addition to them live many insects, worms, termites and ants, spiders, reptiles, which also contribute to the formation of the upper soil horizon. Typical vegetation is grasses, sedges, and representatives of the Umbelliferae family.
Serozem soils contain 4% humus, the thickness of the fertile layer does not exceed 0.5 m. The surface of the soil is turfy, penetrated by the roots of perennial plants. After the humus horizon there is a transition layer, gray-fawn, silty-loamy, with many passages of worms and soil animals. Underneath it there is a carbonate-illuvial layer 0.6-1 m thick, dense, without shrew passages. The last horizon is yellowish-fawn; in its lower part, at a depth of 1.5 m from the surface, there are gypsum inclusions.
Type classification
Gray soils are divided into dark, light and typical; the classification is carried out according to the level of soil location above sea level. The dark ones are located in the foothills and highlands; light – at an altitude of 200-350 m; and typical - at an altitude of 400-1250 m. All types of soils have different humus content, predominant vegetation, and they are formed on different parent rocks.
How are they formed
Gray soils are formed under a hydrothermal regime, which is characterized by a short spring period, warm and humid, during which the growth of vegetation and the action of microorganisms are activated. As well as a long dry and hot summer period, during which bioactivity is greatly reduced.
Some of the main characteristics of gray soils are the active formation of humus and mineralization of organic matter in the spring, intrasoil weathering of primary minerals, accumulation of clay minerals in the upper and middle layers, low content of easily soluble salts, and low humus content.
How to use
Despite the small percentage of humus, the thickness of the humus horizon in gray soils is large - up to half a meter. Therefore, subject to irrigation, they are suitable for growing cotton, melons and vegetables, vineyards, corn, and beets. Measures to improve gray soils, in addition to irrigation: deep plowing and loosening, drainage.
Irrigated agriculture can greatly change soil-forming processes on sierozem soils. Irrigation creates a new water regime, accompanied by the deposition of clay particles in the horizons.
The content of mineral elements necessary for plant nutrition in gray soils shows that the amount of nitrogen is insufficient, but it is in a form accessible to plants. There is usually enough potassium and phosphorus; often in soils of this type there is an excess amount of sulfates and chlorides.
On gray soils it is necessary to apply nitrogen fertilizers, organic and mineral, and to take measures to prevent salinization. The fertility of gray soils is increased by sowing green manure, for example, alfalfa.
Serozem soils are found under a combination of certain climatic conditions of semi-deserts and such features as high spring activity of soil bacteria and animals, rapid growth and a short growing season of semi-desert vegetation. Serozems, after improvement and subject to regular watering, are suitable for agricultural use for growing grapes, vegetables and cotton.
