Modelling predicts varied nitrogen responses

Author: Natalie Lee | Date: 18 Jul 2014

Image of Frank D’Emden from Precision Agronomics Australia briefing an audience on nitrogen ‘top-up’ decisions

Results from technology that measures soil moisture across the Western Australian grainbelt indicates that nitrogen fertiliser ‘top-ups’ applied in coming weeks could have variable yield benefits, depending on location.

“Analysis of sites hosting new soil moisture probes suggests that potential benefits range from nil to more than 0.5 tonnes per hectare,” Precision Agronomics Australia’s Frank D’Emden said.

He said nitrogen decisions made by growers in coming weeks would require careful assessment of subsoil moisture levels.

“This is due to the combination of well-established crops with variable soil moisture levels, marginal soil nitrogen levels and a decile 5 (average) rainfall outlook to the end of September,” Mr D’Emden said.

Mr D’Emden this year installed the 12 soil moisture probes, with basic weather sensors, under the Grains Research and Development Corporation (GRDC) Regional Cropping Solutions Networks (RCSN) project ‘Plant Available Water (PAW) information and tools for better crop management decisions’.

The probes trace growing season soil moisture levels every 10cm down the profile in the root zone.

“Sites for the probes were selected based on soil types being representative for the district,” Mr D’Emden said.

“The project aims to improve yield predictions and develop new reporting formats so growers can finetune their crop management decisions.”

Mr D’Emden said the yield response predictions were generated from Yield Prophet® modelling conducted at the end of June for the 12 moisture probe sites.

“This modelling suggested that responses to top-up nitrogen ranged from nil at the Beacon, Bonnie Rock, Southern Cross and Merredin sites - where soil moisture is marginal - to at least 0.5t/ha at the Coomberdale, Bindi Bindi, Dowerin, Lake Grace and Jerramungup sites - where soil moisture levels are reasonable,” he said.

“However, local grower experience suggests that some of the responses, particularly at Dowerin and Jerramungup, could be overstated.”

Data from the sites can be viewed at using the user name RCSN and password grdc (case sensitive).

Data from additional moisture probe sites installed in the Esperance port zone in 2013 is available at


Contact Details

For Interviews

Frank D’Emden, Precision Agronomics Australia
08 9072 0542, 0488 917 871


Natalie Lee, Cox Inall Communications
08 9864 2034, 0427 189 827

GRDC Project Code PRE00003

Region West