Arrange the following sequential stages in the process of soil salinization—a major form of environmental land degradation in semi-arid agricultural zones—from the initial human activity to the ultimate ecological impact.
- 1Excessive irrigation water is applied to farmlands with inadequate subsurface drainage systems.
- 2Dissolved mineral salts are drawn upward from subsoil horizons toward the surface via capillary action.
- 3High ambient temperatures drive rapid surface evaporation, leaving dissolved salts behind in topsoil.
- 4A dense saline crust accumulates on topsoil, causing severe osmotic stress, vegetation death, and land abandonment.
Answer
The correct sequence of soil salinization begins with excessive irrigation on poorly drained land, followed by capillary uptake of saline groundwater, surface water evaporation leaving salt deposits, and ultimately the formation of a toxic saline crust that causes crop failure.
The correct sequence follows the hydro-geological progression of land salinization. Over-irrigation on poorly drained agricultural land first saturates the subsurface. Capillary forces then pull the saline groundwater upward into topsoil layers. Rapid surface evaporation under hot, dry conditions removes pure moisture while leaving concentrated mineral salts behind. Finally, continuous salt accumulation forms a toxic surface crust that destroys soil structure and prevents plant water uptake.
Step-by-Step Solution
Key Concept
Soil Salinization and Land Degradation Mechanics in Semi-Arid Environments