• Introduction
• Recent SMM observations
• Speedo assessments
• Speedo soil moisture graphs
  • Mallee
  • Wimmera
  • North Central
  • North East
  • Gippsland cropping
  • South West

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.

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.

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.

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.

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.

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.

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.

Note -  use extensionaus.com.au/soilmoisturemonitoring to monitor the changes to the sites relevant to you inbetween the next reporting period

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.

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).

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.

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.

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.

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

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.

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.

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.

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.

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.

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).

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.

The Giffard West site still has a wet deep profile.

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

Hamilton has a wet full profile.

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.