Correct Option (d):
Contour bunding is a soil and water conservation technique primarily employed on sloping or undulating agricultural lands. It involves constructing small earthen embankments or bunds along the contour lines (lines of equal elevation) of a slope. These bunds are designed to intercept surface runoff, reduce its velocity, and increase the infiltration of water into the soil. This process effectively minimizes soil erosion, conserves moisture, and prevents nutrient loss, making it suitable for rainfed farming areas with moderate slopes, such as parts of the Deccan Plateau in India.
The given options do not describe the typical application areas for contour bunding, which necessitates its use on sloping terrain for water erosion control.
Incorrect Options:
(a) Desert margins, liable to strong wind action:
In desert margins prone to wind erosion, techniques like windbreaks, shelterbelts, or strip cropping are typically used to reduce wind velocity and stabilize soil. Contour bunding is designed to mitigate water erosion on slopes, not wind erosion in flat or gently sloping desert areas.
(b) Low flat plains, close to stream courses, liable to flooding:
For low flat plains susceptible to flooding, flood control measures such as constructing levees, embankments, or improving drainage systems are implemented. Contour bunding is not applicable in such flat terrains as its primary function relies on slope to manage water runoff.
(c) Scrublands, liable to spread of weed growth:
Managing weed growth in scrublands involves methods like manual removal, chemical control (herbicides), or biological control, which are distinct from the physical soil conservation technique of contour bunding. Contour bunding does not directly address weed proliferation.