Insights from a comprehensive project tracking nitrogen fertilizer dynamics in soils and plants over three consecutive crop seasons will be presented at the 2025 Grains Research and Development Corporation Goondiwindi Update. Led by University of Queensland researcher Professor Mike Bell, the national project examines 12 sites, including four in the northern region: Gatton, Kingsthorpe, Tamworth, and Wagga Wagga.
The project aims to quantify grain yield, fertilizer N lost through volatilization and denitrification, and leaching of N below-crop root zones. Laboratory studies on stubble breakdown and N mineralization and immobilization support the field program. Data generated will be used to validate or enhance the N routines in APSIM, a widely used platform for modeling cropping systems, to improve the accuracy of predicting optimal N management strategies and fertilizer N dynamics in the Australian grains industry.
Collaborating with researchers such as Dr. Graeme Schwenke, Dr. David Lester, Prof. Peter Grace, Dr. Louise Barton, Dr. Mark Farrell, and Dr. Kirsten Verburg, Prof. Bell’s research addresses the low use of nitrogen in the year it is applied. The project, titled “Predicting nitrogen cycling and losses in Australian cropping systems,” spans from April 2022 to September 2026 and aims to quantify N losses in various forms and pathways.
The field research involves using N fertilizer enriched with stable N isotopes to track the fate of applied N over three consecutive cropping seasons. In the northern region, the project focuses on both summer and winter cropping, with sub-surface banding and spreading of fertilizer N in systems with different reliance on in-crop rainfall or stored water.
Preliminary findings from the project reveal insights into fertiliser N removal in harvested grain, with varying efficiencies of uptake by crops ranging from 10-75%. The fate of residual fertiliser N is being monitored over subsequent growing seasons to understand its impact on crop yields.
In the second crop season, preliminary assessments of the effects of residual fertiliser N on grain yields have been conducted. For example, at the winter-crop sites in Wagga Wagga and Tamworth, residual fertiliser N from the previous season led to significant yield increases in the second crop season. The research also delves into the responses to residual N at different rates and application times, shedding light on the effectiveness of different N management strategies.
The project aims to provide valuable insights into contrasting soil types and cropping systems to ensure sustainability and economic viability while meeting greenhouse gas emissions targets. By understanding the fate of fertiliser N in different cropping systems, the research will contribute to the development of more effective N management strategies for maximizing fertiliser N-use efficiency across diverse soils and farming systems.
To learn more about the 2025 Goondiwindi GRDC Grains Research Update and register for the event, please visit the provided link.
