Question

Which of the following weeds are helpful in control of soil erosion by wind and water?
(A) Cynodon dactylon
(B) Imperata cylinderica
(C) Agropyron repens
(D) Cassia tora
Choose the correct answer from the options given below:

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

Hint:

Monocotyledonous grasses with fibrous, stoloniferous, or rhizomatous root systems are excellent soil binders.
Conversely, erect tap-rooted annual dicots (like Cassia tora) offer minimal soil-binding capacity.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Soil erosion by wind and water occurs when soil particles are detached and transported by kinetic forces.
Plants, including certain weeds, help control erosion by binding soil particles with their root systems, increasing organic matter, reducing the velocity of runoff, and physically protecting the surface.
Creeping grasses with extensive rhizomes, stolons, or fibrous root systems are particularly effective at binding soil.

Step 2: Detailed Explanation:
Let us evaluate each weed species listed:
- (A) Cynodon dactylon (Bermuda Grass):
This is a perennial, creeping grass that propagates via stolons and rhizomes.
It forms a dense, carpet-like sod over the soil surface, providing excellent protection against water runoff and wind. It is widely used to stabilize bunds and embankments.
- (B) Imperata cylindrica (Cogon Grass):
This perennial grass has an extensive, aggressive underground rhizome system.
These rhizomes form a dense underground network that binds soil particles together, making it highly effective at stabilizing slopes and degraded lands.
- (C) Agropyron repens (Quackgrass):
A perennial grass characterized by its long, creeping, pale-colored rhizomes.
Its dense underground system excels at reinforcing soil structures against erosive forces.
- (D) Cassia tora (Sickle Senna):
This is an erect, herbaceous, annual dicotyledonous weed.
It has a taproot system and grows vertically rather than spreading horizontally. It does not form a dense soil-binding mat, making it ineffective for erosion control compared to rhizomatous grasses.
Thus, the species that help control erosion are (A), (B), and (C).

Step 3: Final Answer:
Therefore, the correct option is (A), which represents (A), (B), and (C) only.