This project seeks to benchmark nitrogen-use efficiency (NUE) and to explore the management options that may yield significant improvements in NUE. Better NUE is important for both farm productivity and greenhouse gas abatement – nitrous oxide emitted during denitrification has high global warming potential, and for irrigated cotton, especially on heavy alkaline clay soils that waterlog, denitrification causes most nitrogen (N) loss. This PhD project specifically focuses on southern New South Wales as to date there is a lack of research quantifying NUE and N losses in southern areas, with consideration of their differing soil types, soil-water holding capacity, and rainfall patterns. New bank less irrigation systems used more commonly in southern NSW, also present opportunities for NUE benchmarking.