Important research to help grain growers use nitrogen more efficiently is underway at Agriculture Victoria's Horsham SmartFarm.
Agriculture Victoria research scientist Kamal Adhikari said dryland cropping farmers commonly top dress urea as a nitrogen (N) fertiliser on their paddocks in anticipation of forecast rain.
'Urea represents one of farmers' single largest variable cost input,' Dr Adhikari said.
'Getting it right has major implications for on-farm profitability. The downside of urea fertiliser is that much of its benefit for a crop can be permanently lost in a process known as volatilisation.
'Volatilisation is where ammonia (NH3) gas is released from urea granules to the atmosphere.
'Losing nitrogen through volatilisation doesn't just have an economic impact on yields and profitability, it also affects the environment via greenhouse gas emissions,' he said.
Using the dynamic chamber method, Dr Adhikari hopes to assess ammonia losses. He has previously used this method in New Zealand to measure NH3 volatilisation of intensive dairy pasture systems and can see its potential for Australian dryland cropping systems.
He believes it has several advantages over other 'standard' micrometeorological methods such as alpha samplers.
'The dynamic chamber method only requires a small area to operate, so we can set up multiple plots with different conditions to study at the same time,' he said.
Dr Adhikari said although the primary aim of the study is to benchmark this new method against alpha samplers, it is already collecting data that may be useful to growers.
'Recently, we top dressed a paddock with urea in anticipation of a large rain front but we only received a fraction of the forecast rain,' he said.
'The urea granules had dissolved, but not enough to wash this urea into the soil where it could be used by the wheat.
'We suspect that some has been lost to volatilisation but by the end of this study, we will know exactly how much of the N was actually lost.'
Dr Adhikari hopes the research will lead to the creation of a decision support tool for growers to help understand the impact of urea top dressing, depending on how much rain is expected, when it's likely to fall and soil conditions.
