UNIVERSITY of Western Australia research has found farmers need to be careful applying sulphate of ammonia onto recently limed soils due to the potential for substantial nitrogen losses.
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The UWA research, part of a Grains Research and Development Corporation project into fertiliser management, found that putting out sulphate of ammonia on limed paddocks could increase nitrogen volatilisation meaning less N for crops.
The practice is most common ahead of a canola phase, where the sulphate of ammonia is used to boost sulphur levels, critical for canola, along with providing nitrogen.
Project lead UWA associate professor Louise Barton said there was a high risk of volatilisation when sulphate of ammonia is applied onto the surface of recently limed soils particularly in dry periods when there is insufficient follow-up rain to move the sulphate of ammonia below the surface of the soil.
Ass Prof Barton said the N losses could be significant in conducive conditions.
"Losses after three weeks ranged from less than one to 20 per cent of the nitrogen applied," she said.
"The greatest losses occurred from the limed soils under a 'low' break-of-season rainfall, with losses more than halved under a 'high' break-of-season rainfall scenario."
In addition she said that applying ammonium sulphate onto a dry soil prior to sowing a second crop that contained residual lime from the first glasshouse study also produced a risk of volatilisation.
GRDC sustainable cropping solutions manager - west, Rowan Maddern, said the project provided valuable data for growers looking to cut losses both for environmental and financial reasons.
"Given the increasing reliance on nitrogen fertilisers in WA, and greenhouse gas emissions associated with their production and use, understanding whether this is a significant loss pathway is important," Dr Maddern said.
"Growers should consider these initial findings when applying lime and sulphate of ammonia in their nutrition programs," he said.
Meanwhile, a major fertiliser business is upbeat about progress with a new nitrogen inhibitor.
Incitec Pivot Fertilisers has been working with the inhibitordimethyl pyrazole glycolate (DMPG), to try and reduce nitrous oxide (N20) emissions from nitrogen fertiliser.
Nitrous oxide is a potent greenhouse gas with a warming potential 273 times that of carbon dioxide (CO2).
Results showed N2O equivalent GHG emissions (kg/ha) more than halved over 36 days as a result of applying a DMPG based product compared to just using nitrogen fertiliser.
Rather than volatilisation, which occurs primarily in dry conditions, work was done on denitrification, which happens in high soil moisture conditions.
IPF vice president, agronomy and innovation, Charlie Walker said IPF was at the frontier of helping farmers to minimise GHG emissions.
"DMPG works by inhibiting nitrifying bacteria in the soil, slowing down the conversion of ammonium N to nitrate which is more prone to losses like denitrification and leaching," Mr Walker said.
"Where nitrogen losses are minimised, there is the potential for growers to have a positive return on investment on the use of inhibitors such as DMPG," he said.
"Alternatively, growers may be able to reduce nitrogen inputs under some circumstances."