Question

Type of land requiring drainage:
A. Land having water table high
B. Water logging lands
C. Excessive moisture content below the field capacity
D. Humid regions having continuous high rainfall
Choose the correct answer from the options given below:

• A. A, B and D only
• B. A and B only
• C. A, B and C only
• D. A and C only

Hint:

Remember that drainage only removes gravitational water (water held at tensions looser than field capacity). Any moisture below field capacity is held by capillary forces and is highly beneficial for plants, meaning it should never be drained.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Agricultural drainage is the removal of excess gravitational water from the soil surface or root zone.
Drainage is required when the soil contains excess water that fills the pore spaces, displacing oxygen and causing root asphyxiation, which inhibits crop growth.

Step 2: Detailed Explanation:
Let us evaluate each land condition:
1. Land having high water table (A):
A persistently high water table saturates the root zone, preventing oxygen diffusion and root respiration.
This land requires subsurface drainage to lower the water table to a safe depth.
Therefore, A is correct.
2. Waterlogged lands (B):
Waterlogged lands have standing water on the surface or complete saturation of the root zone, which severely limits crop growth.
These lands require surface and subsurface drainage.
Therefore, B is correct.
3. Excessive moisture content below field capacity (C):
Field capacity is the amount of water held in the soil after excess gravitational water has drained away.
Any moisture content *below* field capacity means the soil pores contain a healthy mix of both air and water.
No gravitational or free water is present, meaning no drainage is required.
Therefore, C is incorrect.
4. Humid regions having continuous high rainfall (D):
Humid areas with frequent, heavy rainfall often experience surface ponding and root zone saturation because the soil cannot drain naturally fast enough.
These regions require surface and subsurface drainage to remove the excess rainfall runoff.
Therefore, D is correct.
Thus, the land types requiring drainage are A, B, and D.

Step 3: Final Answer:
The types of land requiring drainage are land with a high water table (A), waterlogged lands (B), and lands in humid regions with high rainfall (D).
Hence, the correct option is (A).