Step 1: Understanding the Concept:
A drip irrigation system is a micro-irrigation system that consists of a network of pipes to deliver water directly to the root zone of plants. The system has different components that operate at different pressures. The question asks for the typical pressure rating for the "lateral pipes."
Step 2: Detailed Explanation of Drip System Components:
1. Mainline and Sub-mains: These are the larger diameter pipes that carry water from the pump and filter unit to the different parts of the field. They operate at a relatively higher pressure.
2. Lateral Pipes: These are the smaller diameter pipes (typically 12mm to 16mm polyethylene tubing) that run along the rows of crops. The drippers or emitters are attached to or are an integral part of these laterals.
3. Pressure Regulation: The pressure from the mainline is reduced before the water enters the laterals. Drip irrigation is a low-pressure system. The drippers are designed to operate efficiently at a low pressure to provide a slow, controlled release of water.
4. Operating Pressure:
The pressure in the mainline might be 2.5 to 4.5 kg/cm$^2$.
A pressure regulator is used to reduce this pressure for the laterals.
The typical operating pressure for the drippers, and therefore within the lateral pipes, is quite low, usually in the range of 0.7 to 1.5 kg/cm$^2$.
5. Let's analyze the options based on this standard operating range:
1.0 kg/cm$^2$: This value falls directly in the middle of the typical operating range for drip laterals. (1.0 kg/cm$^2$ is approximately 1 bar or 14.2 psi).
2.5, 3.5, and 4.0 kg/cm$^2$: These are pressures typical of the mainline or of sprinkler irrigation systems, not drip laterals. Drippers would not function correctly at these high pressures.
Step 3: Final Answer:
The usual pressure rating for lateral pipes in a drip irrigation system is around 1.0 kg/cm$^2$. Therefore, option (A) is the correct answer.