Irrigation Engineering

Step 1: Match each irrigation term in LIST I with its closest association in LIST II.
- A. Infiltration opportunity time: This is the length of time that water is present on the soil surface, allowing it to infiltrate. It is directly related to the III. Time of ponding.
- B. Surface irrigation: This is a broad category of irrigation methods (including basin, border, furrow) where water is distributed over the soil surface by overland flow, primarily driven by gravity. It is a form of IV. Gravity irrigation.
- C. Check basin irrigation: This method involves creating small, level basins surrounded by bunds. It is particularly well-suited for irrigating orchards or I. Tree crops.
- D. Cropped area irrigated: The total area of crops irrigated by a canal system is related to the total area the system is designed to serve, which is known as the II. Command area.
Step 2: Compile the correct pairings.
- A III
- B IV
- C I
- D II
This combination corresponds to option (C).

Step 1: Evaluate each statement about border irrigation design parameters.
- Statement A: The width of a border strip is chosen based on the land slope and the size of farm machinery. A range of 10 to 25 m is a typical, reasonable range for many conditions. This statement is generally correct.
- Statement B: Sandy and sandy loam soils have very high infiltration rates. To ensure water reaches the end of the border before it all infiltrates, the border length must be kept relatively short. A range of 30 to 90 m is too long for these soil types; lengths are usually shorter. This statement is likely incorrect.
- Statement C: Medium loam soils have moderate infiltration rates. This allows for longer border lengths than sandy soils. A range of 100 to 180 m is a suitable and common recommendation for these conditions. This statement is correct.
- Statement D: Clay loam and clay soils have low infiltration rates. Water travels a long distance before infiltrating, so border lengths can be very long. A range of 120 to 350 m is appropriate for these heavy soils. This statement is correct.
Step 2: Conclude the correct combination.
Statements A, C, and D represent correct design principles for border irrigation. Statement B suggests lengths that are too long for coarse-textured soils.
Therefore, A, C, and D is the best combination.

Step 1: Match each soil-water term in LIST I with its correct definition in LIST II.
- A. Soil water not available to plant: This refers to water held so tightly by soil particles that plant roots cannot extract it. This is the definition of II. Hygroscopic water.
- B. Soil column occupied by root zone: The region of soil directly influenced by plant roots and their associated microorganisms is called the I. Rhizosphere.
- C. Vertical entry of water into soil: The process of water entering the soil surface from above is called III. Infiltration.
- D. Tensiometer: This is an instrument used for the in-situ IV. Soil moisture measurement, specifically measuring the soil water potential or tension.
Step 2: Compile the correct pairings.
- A II
- B I
- C III
- D IV
This combination corresponds to option (D).

Step 1: Relate water holding capacity to soil properties. Water holding capacity is the ability of a soil to hold water against the force of gravity. It is primarily determined by the soil's texture, which dictates the size and number of pores, and the total surface area of the soil particles.
Step 2: Compare the properties of the given soil types.
- Gravelly and Sandy soils: Have large particles, large pore spaces (macropores), and low surface area. Water drains through them very quickly, resulting in low water holding capacity.
- Loamy soils: A mixture of sand, silt, and clay, having a moderate water holding capacity.
- Clayey soils: Composed of very fine particles (\textless 0.002 mm). This results in a vast number of small pore spaces (micropores) and an extremely large total surface area. These properties allow clay soils to hold a large amount of water through adhesion and cohesion.
Step 3: Conclude which soil has the maximum capacity. Due to its fine texture, large surface area, and micropore structure, clayey soil has the highest water holding capacity among the given options.

Step 1: Visualize the flow of water in a drip irrigation system.
The system is designed to take water from a source, pressurize it, and distribute it through a network of pipes to the plants.
Step 2: Arrange the components in the order of water flow.
1. E. Pump and prime mover unit: This is at the water source. The pump pressurizes the water to push it through the system.
2. A. Main line: A large diameter pipe that conveys the main water supply from the pump to the field.
3. C. Sub-main: Smaller pipes that branch off from the main line to distribute water to different sections of the field.
4. B. Laterals: Small diameter tubes that branch off from the sub-mains and run along the rows of plants.
5. D. Emitter: The final component, attached to the laterals, which discharges water in slow drips at the base of each plant.
The correct sequence is E A C B D.