Soil degradation in dry land agricultural zones is often caused by poor irrigation management leading to secondary salinization. Arrange the following steps in the correct chronological order to describe the biological and physical sequence of soil salinization, starting from the human activity to the final physiological impact on crops.
- 1Application of excessive irrigation water containing dissolved mineral salts to poorly drained agricultural land
- 2Rise of the water table causing upward capillary transport of saline water toward the topsoil horizon
- 3Evaporative loss of moisture from topsoil, depositing high concentrations of crystallized mineral salts in the root zone
- 4Increase in soil hypertonicity, inducing root cell plasmolysis and physiological drought in growing crops
Answer
The correct sequence begins with the application of excess irrigation water containing dissolved salts, followed by the upward capillary movement of saline water as the water table rises, then the evaporation of surface moisture leaving deposited salts in topsoil, and concludes with elevated soil hypertonicity leading to root plasmolysis and physiological drought.
The process begins with human irrigation introducing dissolved salts into poorly drained soil. As groundwater levels rise, capillary action transports saline water upward toward the surface layer. Extreme evaporation under warm atmospheric conditions removes pure water, leaving concentrated mineral salts in the upper root zone. Finally, the hypertonic environment creates a negative solute potential gradient that pulls water out of plant root cells, causing plasmolysis and physiological drought.
Step-by-Step Solution
Key Concept
Secondary Soil Salinization and Physiological Drought