He is a soil scientist with a research focus on nutrients, soils and agro-ecosystems. He is recognised internationally for his contributions to improved nutrient and fertiliser management, particularly in pasture and grazing-based animal production systems in Australia. His areas of expertise include quantifying nutrient flows, transformations and use efficiency at the whole-farm and within-farm scale; the development of national interpretation guidelines, tools and indicators which meet industryand community needs for environmental performance and farm productivity; improving fertiliser decisions through soil and plant testing and interpretation, andinnovative soil test development;utilisation of animal manure and milk processing waste streams. He published more than 70 peer-reviewed articles as lead author or co-author, over 20 invited book chapters and technical bulletins, and more than 100 conference papers.
He has extensive international collaborations with researchers in the USA, Canada, China, New Zealand, United Kingdom and Europe. He is a contributor to the International Task Force on Reactive Nitrogen (TFRN), the FAO Livestock Environmental Assessment Program - Nutrient Technical Advisory Group and Task Leader for the UNEP supported Towards INMS program. He is international leader of the INMS project 1.1.2 which involves 23 government and university research scientists from dairy regions globally and has led the development and delivery of the project since 2016.
He was the Organising Secretary of the 7th International Nitrogen Initiative conference held in Melbourne in 2016 and is a member of the International Advisory Committee for INI2020, to be held in Berlin in May 2021. He also initiated and coordinated an International Symposium on Intensification of Animal Industries in Melbourne in December 2018.