Ground-breaking international research has identified ways farmers can create mitigation strategies to efficiently manage nitrogen to meet production while reducing environmental losses.
The research, part of an international collaboration, was headed by Dr Garima Lakhanpal and her findings will be presented at the 10th international Nitrogen Conference in Japan in November.
Dr Lakhanpal is supported by the Grassland Society of Southern Australia to present at the conference.
Dr Lakhanpal completed her PhD last year through the University of Waterloo, Canada as part of a collaborative project fully funded by Teagasc, Ireland's national body for agriculture and food development.
All of her field work and data collection was based in Ireland, with her research focused on nitrogen dynamics in pasture-based dairy systems.
“Ireland has a lot of intensive dairy farming and the goal was to understand nutrient management and find a balance so farmers can meet their production requirements and reduce environmental losses specific to nitrogen,” Dr Lakhanpal said.
Her research focused on understanding the dynamics of the nutrient-specific nitrogen in intensive dairy farms and assessing the effectiveness of different mitigation strategies, such as restrictive grazing techniques, reducing inorganic or chemical fertiliser applications and using protected urea.
Restricted-duration grazing reduced nitrogen leaching and ammonia losses by 40 per cent and 24 per cent, respectively, when combined with lower inorganic and organic nitrogen inputs, highlighting its potential as an effective nitrogen mitigation strategy.
A key aspect of the work was to investigate legacy nitrogen which was achieved through deep soil coring and integrating results with multi-decade farm management data.
“We were able to quantify nitrogen stores sitting under the soil from years of application of fertilisers,” Dr Lakhanpal said.
“We traditionally focus on what is being applied and the impact on groundwater and subsequently rivers and water bodies but we’re missing what is actually being stored in the soil.
“I was able to quantify in my PhD what is being stored in the soil and how we can potentially use that as a free, available resource for the next application while reducing what we apply on the surface.
“Legacy nitrogen accumulations of 3,000–6,000 kg N ha⁻¹ were recorded within the upper 50 cm of soil in a well-drained dairy system.
“Despite reduced fertiliser inputs, pasture production remained high and was sustained in low-input paddocks, highlighting the potential contribution of existing soil nitrogen reserves.
“This could provide both economic and environmental benefits for farmers, while helping policymakers account for legacy nitrogen when setting realistic timelines and targets for achieving water-quality goals.”
Dr Lakhanpal said the research was targeted to dairy but was easily transferable to any other agricultural field.
“I’m excited about how I can use this knowledge and transfer it to Australian grazing systems and look at how pastures, including multispecies pastures, can improve efficient nutrient management approaches.”
Dr Lakhanpal finished her PhD in December and moved back to Melbourne in April.
She developed a connection with the Grassland Society of Southern Australia while drafting a research proposal with its vice-president Dr Paul Cheng at the University of Melbourne.
“It’s nice to have avenues for support and I am looking forward to representing the Society at the conference,” she said.
People interested in joining the GSSA can visit https://www.grasslands.org.au.