Abstract
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.
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