Afluvisol in theWorld Reference Base for Soil Resources (WRB)[1] is a genetically young soil inalluvialdeposits . Apart from river sediments, they also occur inlacustrine andmarine deposits.[2] Fluvisols correlate withfluvents andfluvaquents of theUSDA soil taxonomy. The good natural fertility of most fluvisols and their attractive dwelling sites on river levees and higher parts in marine landscapes were recognized in prehistoric times.
Fluvisols are found on alluvial plains, river fans, valleys and tidal marshes on all continents and in all climate zones. Under natural conditions periodical flooding is fairly common. The soils have a clear evidence of stratification.Soil horizons are weakly developed, but a distincttopsoil horizon (but no mollic or umbric horizon) may be present.
Many dryland crops are grown on fluvisols, normally with some form of water control. On tropical Fluvisols with satisfactory irrigation and drainage paddy rice cultivation is widespread.
Some coastal lowlands have fluvisols with sulphidic material within the profile (a thionic horizon). Theseacid sulfate soils have severe constraints foragricultural use as low pH-values, toxicaluminium levels and high concentrations ofsalts. Tidal lands that are strongly saline are best kept under mangroves or some other salt-vegetation.
Major concentrations of fluvisols are found along rivers and lakes, e.g. in theAmazon Basin, theGanges Plain of India, the plains nearLake Chad inCentral Africa, and the marshlands ofBrazil,Paraguay and northernArgentina. Also in deltaic areas, e.g. the deltas of theGanges–Brahmaputra,Indus,Mekong,Mississippi,Nile,Niger,Orinoco,Po,Rhine,Rio de la Plata, andZambezi. Furthermore in areas of recent marine deposits, e.g. the coastallowlands ofSumatra,Kalimantan,Irian Jaya andPapua New Guinea.
Acid sulfate soils are found in the coastal lowlands ofSoutheast Asia,West Africa and along the northeast coast of South America (French Guiana,Guyana,Suriname andVenezuela).
