Vertisols Soils: Dark Clays

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Vertisols are a group of heavy-textured soils which are found in the tropics, subtropics and warm temperate zones. They could be known Dark Clays and many different names mostly related to their dark color; Sixty percent of the Vertisols are in the tropics, 30 % in the subtropics and 10 % in colder regions. The major areas of Vertisols are found in Australia, India, Sudan, Chad, US, China, and Ethiopia. Vertisols are an important soil in agriculture, although they cover only a small area of the land surface. The major factor contributing to the productivity of Vertisols in semi-arid environments is their high ability to hold water; this important in areas of uncertain and variable rainfall. Vertisols have the ability to store sufficient water to carry crops through droughty periods is of great importance. However, some of their physical characteristics cause some problems for the cultivation of crops.
Vertisol are found in areas with average rainfall between 500-1000mm a year, but also found in very wet tropic where it rains up to 3000mm a year. The largest Vertisol are on sediments that have high content of semctite clays or on post-depositional weathering and on basalt plateaus. They are typically found in lower landscape locations; for example, the bottom of dry lakes, river basins and periodically wet lowlands. Depending on the parent rock and weather condition, they can occur on bottomlands, residual soil, or gently sloped hills sides.
Vertisols are mainly soils that have a high content of expending clay and that have at some time of the year deep wide cracks. They shrink when drying and swell when they become wetter. Vertisols are mineral soils that have a exist in a well-balanced supply of moisture or warmer soil temperatu...

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...e subsurface soil. The soil must have large cohesion to transfer pressures all the way to the soil surface for gilgai to form.
Morphological characteristics such as color, texture, composition, etc. are uniform throughout the solum. There is no movement of soluble soil components. A concentration of soft powdery lime may be existing in or under the vertic horizon. Gypsum can occur either uniformly distributed over the matrix or in layers of gypsum crystals. Vertisols have a uniform particle size distribution throughout the solum, but texture may change abruptly where the substratum is reached. Dry Vertisols are very hard while wet Vertisols are plastic and sticky (Jewitt et al. 1979). It is generally true that Vertisols are crumbly over a narrow moisture range but their physical properties are greatly influenced by soluble salts or adsorbed sodium (Fao.org, 2014).

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