Moisture monitoring

Monitoring soil moisture helps to:

• time irrigation to avoid over- or under-watering
• match stocking rates to pasture availability
• plan fertiliser application and pasture renovation
• avoid waterlogging and improve drainage outcomes
• respond to seasonal shifts and forecasted rainfall.

How to monitor soil moisture

There are several practical methods available:

• Soil moisture probes. Installed in paddocks to measure moisture at multiple depths (typically up to 1 metre). These provide real-time data and are used across NSW in networks like the Hunter Soil Moisture Project and the Murray Valley representative sites. Probes can also measure soil temperature, rainfall and wind speed.
• Manual observation. Digging up soil and feeling for moisture remains a reliable method. Pulling plants and inspecting root zones can help assess whether irrigation is needed.
• Weather-based scheduling. Uses evapotranspiration data and crop factors to estimate how quickly soil moisture is being depleted. This method is especially useful for irrigators managing high-value crops.
• Remote sensing and plant-based sensors. These technologies measure canopy temperature, sap flow and stem growth to assess plant water stress. While more advanced, they can support strategic irrigation decisions.

Farming forecaster

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The Farming forecaster probes and platform provides free, easy to access regional weather data for farmers and their advisors.

Each site has:

• a full weather station with rainfall
• air and soil moisture and temperatures
• wind speed and direction.

It does not contain information on solar radiation.

Farming forecaster:

• shows how widespread rain has been
• shows how much rain has fallen in the different locations
• shows how soil moisture is declining or rising
• can predict grass growth
• can predict river heights for irrigation
• pre-empt flood level rises.

The amount of moisture monitored has a profound effect on how long to expect good plant growth and how much rain is stored in the soil profile.

Moisture monitoring advice for irrigators

If you’re irrigating, especially with flood systems, timing is critical. Delaying the first spring irrigation often leads to poor water-use efficiency and reduced yields. The key to get the timing right is to monitor soil moisture levels in the active root zone and irrigate before stress occurs. To do this you can:

• use probe data or manual checks to assess moisture at 30 cm depth
• use a matric potential reading of –60 kPa at 30 cm is a common trigger to irrigate
• prioritise paddocks with lighter soils, good crop potential or fast drainage
• be ready to order water and ensure channels and outlets are clear
• consider strategic irrigation if water is limited by focusing on critical growth stages like flowering and pod fill in canola, or head emergence in cereals.

If you’re using centre pivot or drip systems, small, frequent irrigations can be applied with minimal risk of waterlogging. These systems are especially valuable in seasons with limited water availability.

Getting started

If you’re not confident in interpreting soil moisture data, consider working with an agronomist or Local Land Services officer to help apply it to your irrigation decisions.