Irrigation Management.

Using Tensiometers 2

ll. Installation and placement of tensiometers (TO2-0801)

Tensiometers are irrigation management tools that can help you determine when to irrigate, which paddocks need to be irrigated first and whether irrigation water is being lost to deep drainage.

It is important that tensiometers are properly prepared and installed to avoid incorrect readings.

Preparing tensiometers for installation:

  • Fill the tensiometer with fresh, clean water and add a few drops of chlorine to stop algal growth.
  • Remove the reservoir cap and leave the tensiometer to soak overnight in a bucket of clean water.
  • Remove air from the gauge and tube using a vacuum pump or by pumping the reservoir of the "jet fill" types.
  • Refill the reservoir with clean water and replace the cap. Wrap the tip in a wet towel to prevent drying when transporting to the paddock.

Installing tensiometers:

  • Auger or drive a hole into moist ground with a standard piece of 1/2" pipe for an exact fit. This will ensure good contact with the soil and minimal root disturbance.
  • If the soil is dry, prepare a 'slurry' of soil and water and pour it down the augered hole.
  • Insert the tensiometer, pushing on the reservoir and not the gauge. Be sure it is inserted into the bottom of the hole.
  • Leave at least 2 inches between the bottom of the gauge and the soil
  • Hill up soil around the plastic tube and pack to ensure good soil contact and to provide drainage for surface water.

How many tensiometers do I need?

The number and length of tensiometers needed at each site depends on crop type and root depth. In sugarcane, it is recommended that two tensiometers of different lengths (30 cm and 60 cm) be installed 30 cm apart in the drill.

The shorter tensiometer is installed in the root zone to monitor crop stress. The longer tensiometer is installed below the root zone to determine if water is being lost to deep drainage

The number required on a block or farm depends on soil types, the irrigation system used and the accuracy required.

 

The Rural Water Use Efficiency Initiative is a joint venture between BSES, CANEGROWERS and the Queensland Government through the Department of Natural Resources and Mines. For more information, please ring your local Rural Water Use Efficiency Officer.