Soils of the European Union - European Soil Portal - Europa

4.23 VertisolsGeographical distributionVertisols cover more than 36,000 km 2 (0.88%) of the European Union. Vertiols tend to be found in the southern countriesof the EU. They form dominant soils in 160 polygons, associated soils in 54 cases and inclusions to 399 associations.The Reference Soil Group has three soil units in the EU with Chromic and Haplic types accounting for 95% of their totalarea. (Table 4.23., Figure 4.23)Table 4.23 Area of the second level units of VertisolsUnits in the Reference Soil Groupin the EUCodes ofsoil unitsArea in the EUkm 2Chromic Vertisol VRcr 12878Haplic Vertisol VRha 1823Pellic Vertisol VRpe 21746Chromic Vertiol is characteristic for the Mediterranean and Balkan countries. Haplic Vertisols can be found in Cyprus (asdominant soils in their mapping units) and in Italy (in inclusions). The Pellic type is widespread throughout the countrieswith Vertisols, except in Cyprus. Largest Pellic Vertisol proportions are found in Hungary, Romania and Bulgaria.35.33%59.67% 5.00%VRcrVRhaVRpeGlobal referenceFigure 4.23 Share of the second level soil units in the area of VertisolsVertiols develop within depressions, in level to undulating landscapes, mainly in tropical, semi-arid to (sub)humid andMediterranean climates with an alternation of distinct wet and dry seasons. Sediments that contain a high proportion ofsmectitic clay or products of rock weathering that have the characteristics of smectitic clay are prerequisite of Vertiolformation.Vertisols cover 3.35 million km 2 world-wide.Vertisols shrink and swell upon drying and wetting. Deep wide cracks form when the soil dries out and swelling in the wetseason and creates polished and grooved ped surfaces (slickensides) or wedge-shaped or parallel-sided aggregates in thesubsurface vertic horizon. The landscapes of a Vertisol may have a complex micro-topography of micro-knolls and microbasinscalled gilgai.Vertisols with strong pedoturbation have a uniform particle size distribution throughout the profile but texture may changesharply where the substratum is reached. Dry Vertisols can be very hard, while wet Vertisols are very plastic and sticky.The agricultural use of Vertisols is depending on their physical characteristics, and ranges from very extensive use throughsmallholder post-rainy season crop production to small-scale and large-scale irrigated agriculture. Cotton is known toperform well on Vertisols. Tree crops are generally less successful because roots find it difficult to establish themselves inthe subsoil and are damaged as the soil shrinks and swells.Vertisols of the world are also known as black cotton soil (USA), regur (India), vlei soil (South Africa) and margalites(Indonesia).56