Nitrogen use efficiency and N2O emissions vary according to seasonal water supply across different cereal production systems of south eastern Australia

• Published in: Geoderma Regional 2022-06, Vol.29, p.e00498, Article e00498
• Main Authors: Wallace, Ashley J., Armstrong, Roger D., Grace, Peter R., Scheer, Clemens
• Format: Article
• Language: English
• Subjects: 15N Recovery; Barley; Calcisol; Dryland; Greenhouse gas; Irrigation; Luvisol; Solonetz; Vertisol; Wheat
• ISSN: 2352-0094; 2352-0094
• DOI: 10.1016/j.geodrs.2022.e00498

Application of nitrogen (N) fertiliser is vital to the productivity of grains production systems. However, losses can result in negative environmental impacts as well as having a significant impact on farmer profitability. Such losses can vary significantly, therefore it is important to benchmark nitrogen use efficiency (NUE) across a range of environments to better understand opportunities for improvement. Using a combination of 15N mass balance and monitoring for gaseous N2O flux we undertook an assessment of NUE at 29 sites spread across a range of management systems in semi-arid and temperate environments of south eastern Australia. An N rate experiment was established at each site, testing three different in-season application rates with N surface applied as urea. Timing and rates were determined in relation to farmer practice for the broader paddock. Loss of fertiliser N averaged 29% (ranging from 5 to 54%) and while daily N2O flux rates represented a fraction of this, peak flux rates ranged from 52 to 132 to 376 g N2O-N/ha/day across low/ medium rainfall, high rainfall and irrigated regions respectively. Crop recovery of applied N ranged from 3 to 65% and was positively correlated with agronomic efficiency of N application. •Benchmarking of NUE and N2O emissions from cereal production was undertaken across environments and management systems.•Fertiliser N was important to productivity, however overall loss of N applied in season can be high (5–54%).•NUE and N2O emissions varied across seasons, environments and management, but was primarily driven by water supply.•Highest loss of applied N was measured under irrigation or in high rainfall environments.•Dry seasonal conditions lead to low NUE due to poor crop uptake, resulting in high levels of residual N in the soil.