Concept:Underground drainage removes excess water through pipes placed below the soil surface, leaving the surface clear for farming operations.
Explanation:In this system, perforated pipes are buried under the ground to collect and carry away surplus water.
No open ditches or surface channels are formed.
So the land remains even and free from obstructions.
This makes it easy for tractors, planters, and harvesters to move freely across the field.
It also reduces the risk of machinery getting stuck or damaged.
The other options are not direct advantages of underground drainage because it does not primarily control weeds, improve soil texture, or add organic matter.
Answer:It allows for free movement of farm machinery.