Fluvisol

A Fluvisol is recognised by evidence of its water-laid origin: distinct layers of contrasting texture, buried organic material, and an irregular distribution of organic matter with depth, all reflecting deposition rather than in-place soil development. This youthful, stratified character sets Fluvisols apart from more strongly weathered soils.

Fluvisols form where flowing or standing water repeatedly deposits sediment, chiefly on the floodplains and deltas of rivers, along lake margins, and in coastal and estuarine settings. Each flood or high-water event can add a fresh layer of sediment, so the soils remain young and layered. They are found worldwide along major and minor watercourses, and are especially extensive in the great river deltas of Asia and in floodplains across all inhabited continents.

Stratification

Alternating layers of sand, silt, and clay reflecting successive depositional events rather than soil-forming horizons.

Fertility

Frequently good, as fresh sediment can supply nutrients, though it varies with the source material of the alluvium.

Drainage

Ranges from well drained on higher river terraces to poorly drained in low delta and backswamp positions.

Youth

Minimal horizon development because the soils are geologically young and the parent sediment is repeatedly renewed.

Managing Fluvisols largely revolves around water: exploiting their fertility and level terrain while managing the flooding and, in low positions, the poor drainage that come with a floodplain setting.

• Use flood control, embankments, and drainage where flooding or waterlogging threatens crops
• Exploit the level terrain and reliable water supply for irrigated cropping, including wetland rice in low, wet positions
• Match crops to the drainage of each part of the floodplain, from well-drained levees to wet backswamps
• Guard against contamination where river sediment may carry pollutants from upstream

Fluvisols support a wide range of crops thanks to their fertility and level, well-watered position. Wetland rice dominates low, seasonally flooded Fluvisols, particularly in Asian deltas, while better-drained river plains are widely used for wheat, maize, sugarcane, and intensive vegetable production such as tomatoes and onions.