Question

Given below are the two statements.
Statement I: Porous shelter-belt is more effective than dense shelter-belt in controlling wind erosion
Statement II: Tillage operation should be carried out across the prevailing wind direction.
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement I is incorrect but Statement II is true

Hint:

Porous windbreaks ($40-50\%$ porosity) are superior to dense solid barriers because they prevent turbulent leeward eddies.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Wind erosion control relies on reducing near-surface wind shear velocity using biological windbreaks/shelterbelts and roughness tillage perpendicular to prevailing winds.
Key Formula or Approach:
\[ \text{Shelterbelt Protection Zone} \approx 20 - 30 H \quad \text{(for 40--50\% porous barrier)} \]

Step 2: Detailed Explanation:
1. Statement I: A semi-permeable (porous, 40--50% optical density) shelterbelt allows part of the wind to filter through smoothly without creating strong turbulent low-pressure vortex eddies on the leeward side, extending the downwind protected zone up to 20--30 times the tree height ($20-30H$), compared to only $10-15H$ for a solid/dense barrier. Hence, Statement I is true.
2. Statement II: Carrying out tillage operations across (perpendicular to) the prevailing wind direction creates ridges and clods that trap detached saltating sand grains and increase aerodynamic surface roughness. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Both Statement I and Statement II are true, corresponding to option (A).