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Soil Moisture Monitoring
27 August 2021
2021 Issue 5
In this edition:

The soil moisture monitoring project, with the use of underground probes, provides real time soil water content data to Victoria’s farmers.
Monitoring sites have been set up in cropping regions throughout the state by Agriculture Victoria.
The sites record soil water content at one source point from 30 centimetres down to one metre as a reference point for a paddock.

Sites monitored include: Werrimul, Ouyen, Speed, Kerang, Birchip, Normanville, Lah, Bangerang, Taylors Lake, Coonooer Bridge, Raywood, Elmore, Youanmite, Hamilton, Lake Bolac, Tatyoon, and Sale.
Locations of Agriculture Victoria soil moisture monitoring sites

To access information provided in the graphs, log onto the new Agriculture Victoria soil moisture monitoring dashboard.

No login or passwords are required, and speedos are automatically updated.

Victorian rainfall deciles for May - July. Wimmera and Mallee received average rainfall in those three months but some areas of NE Victoria, Gippsland and Central highlands were above average.

Figure 1: May to July rainfall deciles for Victoria

A very dry April has been followed by average rainfall for the Wimmera, Mallee and North Central which has meant that there has been limited opportunities to bank large amounts of moisture over May, June and July.  Late to emerge crops have increased their water demands in the second half of August, while last year, similar water demands were experienced in the second half of July.

Victoria rainfall totals for August.

Figure 2: August month to date rainfall totals (26 August)

Less than 25 millimetre rainfall zones have not had rain to meet medium yield potential crop demands. Districts with the lower end of the 25 - 50 millimetre zone have not banked any further soil moisture during August but closer to 50 millimetres and above have seen positive moisture improvements.

Month rainfall percentages for August (month to date). The Wimmera and Mallee have 40-100 per cent of rainfall (month to date) and is on track for below average rainfall for the month.  It has been wet in East Gippsland and dry in the North East.

Figure 3. Month to date (26 August) rainfall percentages for Victoria

There will be large parts of the cropping areas that will be below average rainfall for August with current projections and limited forecast rain.  Crops will start depleting moisture reserves with below average August rain and create a moisture deficit that will increase crops reliance on spring rainfall.


Soil moisture monitoring sites rated by quartile moisture per cent (new product development for the Ag Vic SMM dashboard)

Figure 4. Soil moisture monitoring sites rated by quartile moisture per cent (new product development for the Ag Vic SMM dashboard)

Blue dots are sites above 75 per cent deep soil water storage and cover South West and North East Victoria and Gippsland. There are areas in Central Victoria that still retain good moisture profiles for this time of year. Profiles are generally wetter in the southern areas of the Wimmera and drier to the North. Mallee is low to medium, with previous hay rotations providing higher moisture values than crops that went to grain in 2020.

Speedo assessments

Soil moisture measurements collected by the Agriculture Victoria monitoring network indicate a range of low/moderate soil moisture conditions in the Mallee and Wimmera with some better patches in those regions due to isolated storms.  Southern parts of the Wimmera are moderate to high.  North Central and North East regions have depleted some of their moisture in the second half of August but still have medium to high deep soil moisture levels.  High yield potential crops are using the most water.

Gippsland and South West Victoria still have very wet sub soils.


Soil moisture speedos 26 August 2021.

Note -  use to monitor the changes to the sites relevant to you inbetween the next reporting period

Ag Vic SMM network site percentages. Werrimull 82%, Normanville 46%, Speed 90%, Ouyen 33%, Birchip 31%, Brim 30%, Sheep Hills 70%, Taylors Lake 74%.
Speedo soil moisture graphs
Werrimull soil moisture (30-100cm)
Werrimull Speedo, moisture currently 81%
Individual soil moisture trace from Werrimull, increases at 30-70cm.

The moisture profile at Werrimull continued to respond positively to July and early August rain and connecting to residual soil moisture from a low yielding oaten hay crop in 2020. This crop didn’t access all the available water and there are still some traces of water from the 50 millimetre thunderstorm on 1 January.  A dry second half of August has the wheat crop starting to use the easiest-to-access soil water at 30 - 40 centimetres.

Ouyen soil moisture (30-100cm)
Ouyen soil moisture is currently 31 per cent.
Ouyen individual soil moisture traces. Moisture improved down to 50cm during July but those gains have been used by the wheat in August.

The Ouyen site had some moisture improvements at 30 - 50 centimetres during winter but wheat is now depleting those reserves as rainfall doesn’t meet crop water requirements. Traces of residual moisture remain below this depth (left over from last year’s vetch hay crop).  Grain crops last year would be drier in this district (East of Ouyen).

Speed soil moisture (30-100cm)
Speed speedo showing 90%

There have been some moisture improvements at the site at Speed and will encourage the wheat crop to extend a root system to access the moisture banked from last year’s early terminated vetch crop.  Crop is late developing after a challenge to emerge, with low plant numbers, so biomass is low and water requirements small at this stage.

Normanville soil moisture (30-100cm)
Normanville speedo moisture currently 45%

Positive moisture improvements at this site during July and early August and the soil water profile peaked on the 10 August.  The vetch has been depleting moisture in the second half of August.

Birchip soil moisture (30-100cm)
Birchip speedos moisture currently 30%

Small deep soil moisture changes at the medium/heavy soil type at Birchip during winter, but has limited water losses as no crop was sown in the paddock this season.

Brim soil moisture (30-100cm)
Brim speedo moisture currently 31%

Moisture conditions peaked on 10 August and since then, the vetch has been using water as biomass is generated.

Sheep Hills soil moisture (30-100cm)
Sheep Hills speedo 68 per cent
Sheep Hill individual sensors that increase moisture at depths of 30-70cm during July.

The paddock is a late germinating canola crop. Water requirements were low through July and moisture infiltrated down to 70 centimetres.  Moisture was being used from mid-August.

Taylors Lake soil moisture (30-100cm)
Taylors Lake speedo soil moisture currently 74%

There have been some good soil moisture improvements in the past month on this heavy grey vertosol soil at Taylors Lake experiencing a wet winter. This paddock has gone back into pasture and recently germinated clover will have a low water requirement until biomass develops.

North Central
Coonooer Bridge soil moisture (30-100cm)
Coonooer Bridge soil moisture speedo at 72%.

The Coonooer Bridge site has the most mature crop growing of the Ag Vic network with wheat at early head emergence, the water demands are increasing and depleting the moisture reserves.  There will be a large moisture deficit created in the top soil/top horizon above the sensor zone.

Elmore soil moisture
Summed and separate soil moisture graph from Elmore showing wet conditions from 30-70cm.
Separate trace soil moisture graph from Elmore showing moisture being used from 30-90cm.

The Elmore monitoring site had the largest soil moisture improvements during July in the Agriculture Victoria network. During August it has had the largest soil moisture use of the probe network with canola progressing through stem elongation and flowering.  Moisture is being consumed at all depths and predominately at 30-90 centimetres, where the diurnal effects of day time moisture use can be clearly seen.

Photo of Elmore canola crop starting to flower.
Raywood soil moisture (30-100cm)
Raywood speedos current soil moisture 90%
Yield Prophet image from Raywood

The Agriculture Victoria SMM site at Raywood has a deep soil moisture profile around 90 per cent and the Yield Prophet model indicates similar amounts. .A moisture deficit is starting to build in the top horizon.

Raywood site photos

The Raywood field unit has had the modem replaced after ant damage during winter. The wheat crop is consuming water with increasing crop development. The Yield Prophet crop modelling program of this paddock shows plant water use at 1.5 - 2.0 millimetres a day. Soil core inspections identified solid root development down to 100 centimetres and excellent root structure at 20 - 30 centimetres that was able to hold the soil together (see photo above).

North East
Youanmite soil moisture (30-100cm)
Youanmite speedo moisture currently 97%
Youanmite individual sensor soil moisture graph has had soil moisture improvements during June and July but now just starting to use moisture at 30-40cm.

Youanmite stacked individual soil moisture graph – 2021 view

All the individual soil moisture traces have capacitance values that have hit their maximum value of 100 per cent in early August.  During the past three weeks, the wheat crop has been consuming small amounts of shallow moisture.

Gippsland cropping
Gippsland (Giffard) soil moisture (30-100cm)
Gippsland speedo moisture currently 100 per cent

The Giffard West site still has a wet deep profile.

South West
Lake Bolac SMM (30-100cm)
Lk Bolac  soil moisture levels at 88 per cent

Lake Bolac has a very wet sub soil moisture profile and has only just started using water at the surface.

Hamilton soil moisture (30-100cm)
Hamilton soil moisture speedo 100%

Hamilton has a wet full profile.

Yalla-Y-Poora soil moisture (30-100cm)
Yella-Y-Poora individual sensor moisture graph.  Moisture levels have infiltrated down to 80cm during July and have remained wet.

A new commissioned site at Yalla-Y-Poora to validate an existing monitoring point has reached field capacity during July after a sequential build up of soil water associated with frequent rain events during the growing season. After the deeper sensors responded to June and July rain, all sensor traces have 'flat lined' despite more rain, indicating that the capacitance sensor values cannot get higher.  This will  establish an upper limit for this new probe.


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