A PAIR of satellites has been put to work monitoring soil moisture levels in Victorian paddocks so farmers can make informed decisions to help them through drought.

Agriculture Victoria senior research scientist Dr Elizabeth Morse-McNabb said until now it was difficult, time consuming and expensive to regularly monitor soil moisture across a paddock using conventional point sensors.

“However the recently launched Sentinel 1A and 1B satellites can measure topsoil moisture across the globe every six days and sees through night skies and dense cloud cover,” she said.

“Importantly for our farmers the mapping resolution is useful at the paddock scale.

“So we set out to find how accurate the satellite measurements were and what topsoil moisture told us about soil moisture in the root-zone.”

Dr Morse-McNabb said five research sites were established in the high rainfall zone of south-west Victoria with a grid of sampling points for topsoil moisture and a set of probes from the surface down to 1.5 metres to examine the root-zone moisture.

“Between December 2014 and October 2015 we used probes and collected soil over a period that covered the full range from extremely dry to very wet and then extremely dry again, and it worked,” she said.

“The topsoil moisture measurements closely matched the satellite measurements and were able to predict root-zone soil moisture. We used the root-zone measurements to predict spring-summer pasture growth as the 2015 drought took hold.

“Our producer group successfully used these forecasts to make decisions on reducing stocking rates and/or boosting pasture growth with timely applications of nitrogen,” she said.

Dr Morse-McNabb said nitrogen fertiliser was a major cost to most farmers and managing it better was critical to increasing farm productivity, profitability and reducing environmental impacts.

Agriculture Victoria researchers say a 10 per cent increase in nitrogen fertiliser efficiency will save Victorian grain producers $17 million per year, while a three per cent increase in nitrogen efficiency would be valued at $24,000 per dairy farm and $9.6 million for Victoria a year.

This project was delivered by researchers from Agriculture Victoria and Monash University.

Source: Agriculture Victoria