State soil moisture monitoring – 2015

Dale Boyd
Department of Economic Development, Jobs, Transport and Resources (DEDJTR)
Peer review: Graeme Anderson, Dale Grey (DEDJTR)

Background
Crop potential and cropping inputs are increasingly being subject to greater instability and uncertainty due to seasonal variability. There are increasing examples of soil moisture probes installed in dryland cropping system in Victoria with interest from both service providers and farmers. This technology is being used to gain a greater understanding of seasonal conditions through a repeatable measurement in the soil rather than estimates based on rainfall.

Key messages
• Northern Mallee started the 2015 growing season with soil moisture to depth after conserving water from two significant rain events in January and April.
• Other parts of the state failed to accumulate soil moisture to depth which exposed large areas to the spring finish.
• Previous soil moisture data shows periods to build moisture are Summer/Autumn and winter. In Spring, crop water requirements generally exceed rainfall so soil moisture reserves are drawn down, particularly rapidly in low decile springs.
• In 2015, crop inputs on monitored paddocks were reduced with the low potential yields projected. Rapid soil moisture depletion could be tracked through September and projected crop lower limit was expected around flowering time (critical growth stage).
• Decisions to salvage crops for hay instead of grain were made on the basis of soil moisture conditions, crop dry matter and spring forecast conditions.
• The crop at Werrimull was taken to grain with moisture available through grain-fill but Wimmera and Central Victorian crops had higher crop salvaging percentages compared to usual. Soil moisture probes proved useful as one of the tools for this decision making.