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Why can salt buildup cause irrigation projects to fail?
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land reclamation
The Yser River flowing through reclaimed farmland in Belgium.
Irrigation projects often fail due to salt buildup because all irrigation water contains dissolved salts. As water evaporates from the soil or is transpired by plants, these salts are left behind and accumulate in the soil profile.123
This accumulation causes project failure through several mechanisms:
- Dehydration: High salt concentrations in the soil make it difficult for plants to absorb water. Through osmosis, water may actually flow out of plant roots and into the soil, leading to dehydration and inhibited growth.12
- Toxicity: Some dissolved salts can be directly toxic to plants when absorbed through the roots.2
- Soil Degradation: In a process called cation exchange, sodium ions can be adsorbed by clay particles, rendering the soil sticky when wet and hard or cloddy when dry. This creates a "sodic soil" that is nearly impervious to water and root penetration.2
To prevent failure, irrigation systems must maintain a favorable salt balance by ensuring that salts are removed through drainage and leaching with excess nonsaline water.23