RAS question
Which soil conservation technique involves building barriers across slopes?
Correct answer: (D) Contour bunding.
Contour bunding is the soil conservation technique that builds bunds along contour lines, or across a slope, to reduce runoff and soil erosion.
Explanation
Contour bunding is defined by the construction of bunds, or barriers, along contour lines on sloping land. The Journal of Soil and Water Conservation article explains that contour bunding creates a series of shallow storage basins on sloping fields by means of bunds on the contour, or at least across the slope. That design slows the movement of rainwater, stores rainfall after infiltration is accounted for, and helps prevent sheet erosion. This is why the technique is widely associated with semi-arid areas: the same structure that checks runoff also improves moisture retention for crop growth. The barrier is not incidental here; it is the core engineering feature of contour bunding.
Why the other options are wrong
- (A) Strip cropping alternates crops in strips, so its main method is crop arrangement rather than constructing bund-like barriers across a slope.
- (B) Shelter belts use rows of trees to block wind, whereas contour bunding uses barriers built across slopes to manage runoff and erosion.
- (C) Terrace farming cuts slopes into flat platforms, but the technique specifically centred on bunds along contours or across the slope is contour bunding.
Concept
Soil conservation under Indian physical geography depends on matching each erosion-control method to its actual mechanism. RAS often separates crop-based, wind-based and slope-runoff conservation techniques through small wording differences.