This precision tensiometer is used by commercial growers and research institutes to accurately measure water tension in potting soil.

• Stainless Steel Gauge — Accuracy and long life are ensured by a stainless-steel rustproof body and membrane vent for better temperature and elevation related compensation.
• Quick-Flo” Ceramic Tip — is designed for low tension applications where quick response to soil moisture variations in potting soil / growing media is needed.
• The LT 300 is 30cm in length, ideal for large sized containers or beds.
• Easily topped up with fluid without removing from the soil.

How it Works

The IRROMETER Model LT (Low Tension) is designed for use in large containers or growing beds, commonly used in greenhouses. Its design and insertion depth of up to 30 cm allows the LT to be installed deeper into the pot or bed compared to the MLT 120. With a range of 0-40 centibars (0-400 millibars), this instrument is for use in situations where very dry conditions with tensions above 300mbar are rarely expected. This model instrument is also well suited for conditions where rapidly changing soil moisture conditions need to be observed.

The IRROMETER operates on the tensiometer principle, which measures soil water tension. Soil water tension is the energy (vacuum) applied to the soil by the plant as it draws in water through transpiration. This force is measured in centibars (cb) or millibars (mbar) of tension with a high reading indicating the dry soil a low reading indicating the wet soil conditions.

The IRROMETER instrument consists of a sealed, fluid filled tube that is equipped with a porous ceramic tip and a special vacuum gauge. They are installed in the growing media with the tips placed at desired root zone depths. As the soil dries (increasing tension), fluid is drawn out of the instrument. This reduces the fluid volume in the IRROMETER, thus creating a partial vacuum which is registered on the gauge. The drier the soil, the higher the gauge reading. An irrigation application or watering event reverses this action. As water flows back into the soil (and the IRROMETER), tension is relieved in the soil and the instrument, resulting in a lower gauge reading (lower tension).

In effect, the instrument is indicating how hard the roots are working. Due to the IRROMETER’s unique principle of operation, no calibrations are necessary under normal operating conditions for different soil types. A gauge reading of 15 cb (kPa) indicates that the roots are extracting the same amount of moisture whether the crop is planted in sandy soil or non-soil growing media.

How to Use

The Irrometer LT 300 needs an Irrometer LT Service Kit for set up and maintenance. Many Irrometer LT 300’s can be set up and maintained with one Irrometer LT Service Kit.