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

Soil suction pressure, also known as soil water potential or soil moisture tension, is a measure of the tenacity with which water is held in the soil. It indicates how much effort (negative pressure or suction) plants must exert to extract water from the soil.

• Tensiometers (option a): These are instruments specifically designed to measure soil water tension or matric potential (suction pressure). A tensiometer typically consists of a porous ceramic cup connected to a water-filled tube and a vacuum gauge or pressure transducer. The porous cup is buried in the soil. As the soil dries, water is drawn out of the ceramic cup, creating a vacuum (negative pressure) in the tube, which is measured by the gauge. This measurement directly reflects the soil suction.
• Lysimeter (option b): A lysimeter is a device used to measure the amount of actual evapotranspiration (ET) released by plants (usually crops or trees). It typically consists of a block of soil (often with vegetation) isolated from the surrounding soil, with instruments to measure water inputs (precipitation, irrigation) and outputs (drainage). It does not directly measure soil suction pressure.
• Infiltrometer (option c): An infiltrometer is an instrument used to measure the rate of water infiltration into soil. Common types include single-ring and double-ring infiltrometers. It measures how fast water enters the soil, not the suction pressure within the soil.
• Piezometers (option d): A piezometer is used to measure the piezometric head or hydraulic head (groundwater pressure) at a specific point below the water table in an aquifer. It measures positive pore water pressure in saturated soils, not the negative suction pressure in unsaturated soils.

Therefore, tensiometers are the appropriate instruments for measuring soil suction pressure or soil moisture tension. \[ \boxed{\text{Tensiometers}} \]