Question

Soil suction pressure and soil moisture pressure can be measured by

• A. Tensiometers
• B. Lysimeter
• C. Infiltrometer
• D. Piezometers

Hint:

• Soil suction pressure (or soil water potential, matric potential, soil moisture tension) indicates how tightly water is held in the soil.
• Tensiometers are specifically designed to measure this suction pressure in the unsaturated zone.
• Lysimeters measure evapotranspiration.
• Infiltrometers measure infiltration rate.
• Piezometers measure groundwater pressure (positive pressure below the water table).

Answer 1

The Correct Option is A

To determine which instrument is used to measure soil suction pressure and soil moisture pressure, we need to understand what these pressures represent and how each instrument functions.

1. Understanding the Concepts:

- Soil Suction Pressure (Matric Potential): The negative pressure or tension in the soil water caused by capillary forces and adsorption of water molecules to soil particles. It represents the energy required to remove water from the soil.
- Soil Moisture Pressure: Another term related to the energy status of water in the soil, closely related to soil suction.
- Tensiometer: A device used to measure the soil water tension or matric potential. It consists of a porous ceramic cup connected to a vacuum gauge or transducer.
- Lysimeter: A device used to measure the amount of water that percolates through the soil profile. It is used to study water balance components like evapotranspiration and drainage.
- Infiltrometer: A device used to measure the infiltration rate of water into the soil. It helps determine how quickly water enters the soil.
- Piezometer: A device used to measure pore water pressure in saturated soil or groundwater levels.

2. Evaluating the Options:

- Tensiometers are specifically designed to measure the tension with which water is held in the soil, which is the soil suction pressure or matric potential.
- Lysimeters measure water movement through the soil profile but not the suction pressure.
- Infiltrometers measure the rate of water infiltration into the soil but not the suction pressure.
- Piezometers measure pore water pressure, typically in saturated conditions, and are not suitable for measuring suction pressure in unsaturated soils.

3. Determining the Correct Instrument:

Given that soil suction pressure and soil moisture pressure are related to the tension or energy status of water in unsaturated soil, the appropriate instrument to use is a tensiometer.

Final Answer:

Soil suction pressure and soil moisture pressure can be measured by Tensiometers.