Tensiometer

Technology Explainer

Tensiometers measure the matric potential of soil water. They consist of a porous ceramic cup connected to a water-filled tube and a vacuum gauge. The matric potential, which reflects soil moisture tension, is measured directly.

Accuracy

High quality Tensiometers have good accuracy of matric potential, which measures how much pressure a plant needs to apply to extract water from the soil.

Price

A Tensiometer is quite cheap, making it affordable to most operations.

Installation & Maintenance

The installation of Tensiometers is fairly simple and does not take a great amount of time or technical expertise.

However, Tensiometers are extremely maintenance heavy. A tensiometer needs to be topped up with distilled water periodically. Furthermore, after every growing season a tensiometer should to be removed from the soil and cleaned to ensure optimal functionalty.

Soil Types

Tensiometers do not work well in sandy soils. One of the characteristics of sandy soil is that it cannot hold on to water very well. Hence, the moisture safe range that a tensiometer can show is very small, leading to greater likelihood of plants suffering under water stress.

Measurements

A tensiometer will only show matric potential. Matric potential is a measure of how hard/easy it is for plan roots to extract water from the soil.

Summary

Direct Measurement: Tensiometers provide a direct measurement of soil water potential, which is useful for understanding plant water availability.

Inexpensive: They are relatively low-cost and simple to use.

Limited Range: Tensiometers are most effective in wet to moderately dry soil conditions and are less useful in very dry/sandy soils.

Maintenance: They require regular maintenance, such as refilling with water and ensuring the ceramic cup is free of air bubbles.

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