THE CLIMATE KELPIE BLOG: Probing the value of soil moisture monitoring

Posted by BCG on 10th June 2021

Modern banking apps let us check our balance any time, which is important if you need to make a withdrawal. Soil moisture is just like money in the bank – great if you’ve got it, but when you are hoping to convert it into grain or feed it’s handy to know whether there is enough to meet your needs.

Soil moisture probes can bring the convenience of a banking app to the soil moisture bank. This information can help with decision making across a range of areas including nitrogen management, irrigation planning and marketing.

NSW grower Nick Beer uses soil probes to plan his cotton watering program.

Keeping track of cotton irrigation

Cotton grower Nick Beer says that the decision to install in-season moisture probes has revolutionised how he manages the watering program for his irrigated cotton. Based at Spring Ridge in the NSW Liverpool Plains, he grows irrigated and dryland cotton, sorghum, wheat, barley, chickpeas and faba beans.

“We grow somewhere between 500 and 800 hectares of irrigated cotton each summer. Everything is overhead irrigated, so we need to be on the front foot and keep the water up to the crop. If we get behind, we just can’t catch up.”

Our probes measure water to 90cm and we start watering once the moisture gets down to 35cm. before we installed the probes, we had to push in a hand probe or dig a hole. With paddocks spread over 15 km, the associated rain gauges provide valuable intelligence. Rainfall can vary from 20mm at one end of the property to 50mm at the other end, so we need to know which paddocks to water first.

With these probes, water stress is a thing of the past.

– Nick Beer

Nick Beer

Measuring moisture in a dryland scenario

Both Agriculture Victoria (AgVic)and the Western Australian Department of Primary Industries and Regional Development (DPIRD) manage a network of permanent soil moisture probe at sites around the state. Both networks measure soil moisture, at 10cm intervals, between 30cm and 100cm.

A DPIRD soil-moisture probe was installed at grain grower, Andrew Todd’s Dowerin property in WA’s Central Wheatbelt around eight years ago, using funds from the GRDC and the WA government’s eConnected Grainbelt Project.

Andrew says the probe has confirmed that calculations based on rainfall data and known water use efficiency provide a good guide for management decisions.

“Probably the main eye opener for me was the massive increase in the amount of water the crop needs as it moves into the reproductive phase.”

The network has now been refurbished and the data made available online. Further development by DPIRD as part of eConnected Grainbelt is underway to improve the accessibility of this data and make it available to industry partners.

The DPIRD soil moisture probe at Andrew Todd’s dryland property at Dowerin, WA has demonstrated the massive increase in the amount of water the crop needs as it moves into the reproductive phase.

The AgVic soil moisture monitoring probes have been in continuous operation for 10 years and is supported by industry-specific interpretation through newsletters targeting the cropping, dairying or livestock pasture industries. Users can subscribe or view live probe data online via extensionAUS for 17 cropping and 18 pasture sites.

Andrew Wall is in a prime position with one of the AgVic probes just over his back fence, and another five in the local area. Andrew and his wife Penny run dryland mixed-farming business at Raywood in North Central Victoria producing wheat, barley canola, and oaten hay along with sheep grazed on lucerne pastures or crop.

“We have consistent soil types in this area, which means that when we cross reference the rain gauges with the probe data we can be fairly confident about what is happening in the soil.”

They sow early as the warmer soils boost crop establishment, and crop grazing in winter prevents the crop from flowering too soon, reducing the risk of frost damage. 

“Knowing where the moisture was this year gave us the confidence to sow early despite a dry start. We knew it would take about 10 to 15 mm to get the crop started and about 25mm in total to get the roots down to the stored soil moisture.”

“In the past the data has informed nitrogen management decisions. We could see that topdressing in late August was not worthwhile as there wasn’t enough moisture in the profile to support the additional growth.”

Pasture management planning

Shelley Field uses an Agriculture Victoria soil moisture probe to guide pasture irrigation decisions on the family’s Yarram dairy farm in Victoria.

Yarram dairy farmer Shelley Field has one of AgVic probes under a centre-pivot spray irrigator. She says that the probe definitely saves the business money, because the information from the probe has given them the confidence to reduce irrigation frequency. They have been able to use information from the probe to guide their irrigation plans for other paddocks on the property.

“In the past we would dig a hole to decide whether it was time to irrigate, but now we just check the soil moisture levels on the phone making it both easier and more accurate,” said Shelley.

The Fields’ grass-fed dairy is mostly sown to permanent pasture, but in the last year the probe also helped them to track the water needs of a summer millet crop sown as part of their paddock renovation program.

“In February, we debated irrigating but the information we had from the probes, combined with a good forecast for upcoming rain, gave us the confidence that we had enough moisture in the profile to hold off. Given how wet things got after the rain event, we were more than happy with the decision.”

Shelley says the probe has really helped them learn more about their soil water needs and “has certainly helped to settle a few arguments around the farm”.

Agriculture Victoria agronomist Dale Boyd says that the probes are a valuable tool to add to the toolbox, but the data needs to be interpreted carefully. He advises producers to ground truth the data by digging the odd hole and to compare it with other tools such as the Grains Research and Development Corporation’s (GRDC) SoilWaterApp (SWApp).

Regardless of industry, the value of the soil moisture monitoring needs to be investigated on a case-by-case basis and its value depends on careful interpretation and cross-referencing against other management tools.

More information

Agriculture Victoria

Department of Primary Industries and Regional Development (DPIRD)

Producers

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