Leaching

Definition

Leaching is the downward movement of dissolved substances with percolating water. It can carry salts out of the root zone, which is useful on saline ground that drains freely, but it also removes nutrients such as nitrate and may pollute groundwater. It is strongest in sandy soils and after heavy rain or irrigation. It also strips basic elements such as calcium and magnesium, which contributes to acidification over time. See also: Salinity, Cation exchange capacity, Soil pH, and the guide "Salinization and Sodicity: When Salt Takes Over the Soil".