Soil nitrogen supply and N fertilizer losses from Australian dryland grain cropping systems

L. Barton, F. C. Hoyle, P. R. Grace, G. D. Schwenke, C. A. Scanlan, R. D. Armstrong, M. J. Bell

Research output: Chapter in Book/Conference paperChapterpeer-review

Abstract

There is a global imperative to satisfy the demand for grain production and minimize environmental impacts associated with applying nitrogen (N) fertilizers. Soil is critical to the regulation of N supply and loss from agricultural systems. We summarize field-based measurements of these pathways for Australian dryland (rainfed) grain cropping soils in three agroclimatic cropping regions. In situ net N mineralization rates have been widely reported from Australian dryland cropping soils, with up to 285 kg N ha− 1 mineralizing during the growing season and up to 190 kg N ha− 1 accumulating during the fallow between harvest and sowing of the next crop. Ammonia volatilization measurements are sparse and cover few Australian dryland cropping soils, with field-measured losses ranging from 0% to 34% of applied N. Nitrous oxide emissions have been quantified for all key Australian grain growing regions and the median annual rate is low (0.19 kg N ha− 1 yr− 1). Dinitrogen losses via denitrification are poorly understood with evidence that they may be substantial (> 50% of N fertilizer applied) from soils high in clay or organic carbon. Our understanding of nitrate leaching losses comes largely from coarse-textured, free-draining soils that have not received N fertilizer. Long-term studies investigating all key soil N supply and loss pathways and using a combination of field-based measurements, laboratory-based process studies, and modeling are required to advance our understanding of soil N supply and losses from contemporary and future dryland cropping systems in Australia.

Original languageEnglish
Title of host publicationAdvances in Agronomy
EditorsDonald L. Sparks
PublisherAcademic Press
Chapter1
Pages1-52
Number of pages52
Volume174
ISBN (Print)9780323989572
DOIs
Publication statusPublished - Jan 2022

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