Equitensiometers

Equitensiometers

• Worldwide, the first highly accurate instrument for measuring soil matric potential (suction, soil moisture)
• Cover the whole range of soil water potential in which plant growth occurs ( 0 to -1500 kPa or 0 to -15 bar
• Maintenance-free for outdoor conditions, not affected by over-range
• Independent operation on a wide range of  soil types and conditions
• Very low power consumption
• Easy installation
• Data recording with data logger or display with simple voltmeter
• More than 5 years field testing

What is matric potential? 

There are two ways to measure soil moisture status, namely: Soil water content (SWC) and  soil water potential (ys).  Soil water content describes the amount of water in a given amount of soil relative to the mass of oven-dried soil. Metric potential (ym), defined as the amount of work that must be done per unit quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water, identical in composition to the soil water, from a pool at an elevation and the external gas pressure of the point under consideration (Glossary of Soil Science Terms, Soil Science Society of America (SSSA), July 2000). If the specified quantity is volume, the potential is referred to as pressure (Pascal). Matric potential (=suction, moisture tension resulting from combined effects of capillarity and ad-sorptive forces within the soil matrix) is the main component of total soil water potential. In non-saline soils the total soil water potential (ys) is equal to the matric potential.

Comparison of techniques for measuring matric potential

Techniques   Range (kPa)   Advantages   Disadvantages 

1. Resistance blocks  -100-  -700
2. Inexpensive
3. Must be calibrated individually by user 
4. Unreliable measurement

Just for rough estimating the matric

1. Psychrometer  -200- -10000   
2.  Useful in very dry soil
3. Measures  totals water potential   
4. Does not function in wet soil
5. Sensitive to temperature gradients in the soil 

Tensiometer  0- -85 

1. Relatively reliable   
2. Does not function in dry soil
3. Costly maintenance and service
4. Not suitable for monitoring water 

Equi-Tensiometer  0 00  

1. Relatively reliable
2. Covers the whole range of matric potential for plant growth
3. Maintenance-free 
4. No linear output