Pools and Fluxes: A snapshot of nitrogen dynamics in Australian soils

Mark Farrell1, Diane Allen2, Ben Macdonald3

1 CSIRO Agriculture & Food, Adelaide, SA, 5064, mark.farrell@csiro.au

2 DSITI, Brisbane, Qld, 4001, diane.allen@dsiti.qld.gov.au

3 CSIRO Agriculture & Food, Canberra, ACT, 2601, ben.macdonald@csiro.au


Nitrogen (N) uptake by plants has been researched for well over a century, and continues to be of central importance both from an agricultural productivity and an environmental pollution perspective. Due to its prevalence as a fertilizer, mineral N is usually the only form routinely quantified in soil fertility assessments, despite significant quantities of dissolved organic N (DON) often being present. In the present study, we collected 358 topsoil samples from 89 sites under 13 different land uses. We quantified a wide range of soil N properties including pools and fluxes of organic and inorganic N to develop a better understanding of N cycling in Australian soils. Though nitrate dominated in some land uses, DON and free amino acid-N (FAA-N) were present in significant quantities in most land uses. Rates of N cycling were rapid in most soils, with only very nutrient-poor arid zone soils having particularly low N flux rates. Further research is required to better understand the availability of DON and its accessibility to plants.