Leaching

Leaching is the downward transport of dissolved substances through soil as water percolates. It removes soluble materials from upper layers and can carry them into groundwater.

Soil water: Water held in or moving through soil pores. Percolating soil water dissolves substances and carries them downward.
Soil acidification: The decline of soil pH through processes that increase acidity or remove base cations. Leaching can remove calcium, magnesium, and other base cations, leaving soil more acidic.
Soil salinity: The accumulation of soluble salts in soil at concentrations that can restrict plant growth. Excess salts are often managed by flushing them downward through the root zone.
Runoff: Water that flows over the land surface rather than entering the soil. Runoff moves dissolved and suspended material across the surface; leaching moves solutes downward.
Infiltration: The entry of water from the ground surface into soil. Infiltration supplies the water that may later percolate and leach solutes.
Nitrate pollution: Contamination of water or soil by excessive nitrate concentrations. Nitrate readily dissolves and can leach from fertilized soils into groundwater.
Saline soil reclamation: The restoration of salt-affected soil, commonly by leaching salts below the root zone and providing drainage. It applies controlled leaching to remove salts that impair crop growth.
Erosion: The detachment and transport of soil or rock by water, wind, ice, or gravity. Erosion removes soil particles, whereas leaching transports substances dissolved in water.
Percolation: The movement of water through connected pores in soil or rock. Leaching occurs as percolating water transports dissolved substances through soil.
Groundwater contamination: The presence of harmful substances in groundwater. Leached chemicals can pass through soil and reach underlying aquifers.

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