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Why should irrigation water contain low levels of dissolved salts?
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land reclamation
The Yser River flowing through reclaimed farmland in Belgium.
Irrigation water should contain low levels of dissolved salts because all irrigation water inherently carries some salt, which accumulates in the soil as water evaporates or is transpired by plants.123
Maintaining low salt levels is critical for several reasons:
- Preventing Dehydration: Plants absorb water through their roots via osmosis. If soil salinity is too high, the osmotic pressure causes water to flow out of the plant roots and into the soil, leading to dehydration and inhibited growth.12
- Avoiding Toxicity: High concentrations of certain dissolved salts can be toxic to plants when absorbed through the roots.2
- Maintaining Soil Structure: High levels of sodium ions can be adsorbed by clay particles, creating "sodic soils." These soils become sticky when wet and hard when dry, rendering them nearly impervious to water and root penetration.2
- Ensuring Salt Balance: For agriculture to be sustainable, the amount of salt leaving an area through drainage must equal or exceed the amount received in the water supply. Using water with high salt content accelerates the accumulation process, necessitating costly land reclamation efforts like leaching.32