New tools improve use of soil moisture data
Neal Dalgliesh, a farming systems researcher with CSIRO, is pushing the case for increased use of soil water data in crop management as new technology and tools makes this information more functional.
Mr Dalgliesh, who has worked on the APSIM (Agricultural Production Systems sIMulator) model for more than 20 years, says experience shows that increased soil information increases the chances of achieving a season’s optimum yields and profits.
He says two key inputs into APSIM are a soil’s water-holding capacity and the amount of water in the soil at particular times during the season.
Mr Dalgliesh has to date trained 130 consultants in soil-water management. He has also determined the water-holding capacity for different agricultural soils across the country and is continually assessing new technologies for delivering soil information to growers.
Mr Dalgliesh says that while the knowledge of how much water is stored in the soil assists decisions on when and what to sow, the other important use is in fertiliser decisions.
He says that while knowing more about in-season soil-water availability is useful in its own right, it becomes even more valuable when used as an input into the decision-support tool Yield Prophet®.
This knowledge allows a grower to explore the risks of fertiliser strategies based on soil-water reserves ahead of seasonal weather conditions and long-term climate information.
However, the challenge is for growers and consultants to develop the skills and knowledge to take advantage of this information.
Mr Dalgliesh says this challenge is where current research comes in. Information on the water-holding capacity of an additional 245 soils has been added to the APSoil database (www.apsim.info/Wiki/APSoil.ashx), bringing the total to more than 900. The information is available through the database or Google Earth. APSoil is also accessed by Yield Prophet®.
The recently developed iPad application SoilMapp uses GPS to identify soil water-holding information for specific locations. It also incorporates the wider range of soil information collected by CSIRO and state organisations. “You can go anywhere in Australia and get an idea of what the soil you are standing on is likely to be,” Mr Dalgliesh says.
However, while SoilMapp might provide information on a soil’s water-holding capacity, it does not provide information on the seasonal dynamics of water availability for a specific place. For this reason there is a growing interest in field-based technologies that log soil water in real time, and in other electronic devices that speed up soil monitoring.
Several new field-based sensors, using technologies such as time domain reflectometry, are being tested. Mr Dalgliesh says this gives a reasonable estimate of soil water in a non-cracking soil but has been less successful on cracking clays.
Another technical hurdle is the conversion of the electronic signal produced by the device into something meaningful to a grower. CSIRO is developing the Soil Water Express system to convert sensor output into ‘millimetres of available water’. Mr Dalgliesh says the system needs more testing, but a beta version is available.
Another promising new technology being tested is EM38. This is used to measure salinity, but it can also provide a point-scale estimate of soil water. It has the advantage of being portable and providing almost instant measurements, making increased sampling replication easier.
The potential benefits of improved soil‑water management are known to be huge. A recent GRDC survey showed that a 10 per cent increase in yield, achieved through improved soil-water management over the 20 per cent of the area currently monitored for soil water each year, would provide an extra 114,400 tonnes of wheat worth $22.9 million (based on a price of $200/t).
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GRDC Project Code CSA00023