title: Enrichment of natural15N abundance during soil N losses under 20years of continuous cereal cropping.
abstract: It is generally accepted that the enrichment of natural15N abundance in soil over time is reflective of historic N cycling and loss, but this process in cropping soils is not yet clear. In this study, we identified an enrichment gradient of natural15N abundance during 20-year chronosequence of cereal cropping on Alfisols in southwest Queensland, Australia, that have no history of fertilisation. We demonstrate that the increase in soil15N abundance is explained by isotopic fractionation of15N during organic N mineralisation and nitrification, which lead to isotopically heavier ammonium retained in the soil and isotopically lighter soil nitrate taken up and removed by seasonal crops during harvest. Here we present a framework for natural15N isotopic fractionation co-occurring with N losses during long-term cultivation.
authors.affiliation: School of Food and Agriculture Sciences, The University of Queensland, St Lucia, QLD 4072, Australia; Department of Science, Information Technology and Innovation, Dutton Park, QLD 4102, Australia; CSIRO Agriculture, PMB No. 2, Glen Osmond, SA 5064, Australia. Electronic address: Andrew.Jones2@uqconnect.edu.au.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Jones
authors.affiliation: School of Food and Agriculture Sciences, The University of Queensland, St Lucia, QLD 4072, Australia; Department of Science, Information Technology and Innovation, Dutton Park, QLD 4102, Australia.
authors.forename: Ram C
authors.initials: RC
authors.lastname: Dalal
keywords: (15)N; Ammonium; Cropping; Nitrate; Nitrification; Soil nitrogen