Data from: Quantifying soil gaseous nitrogen losses from nitrification and denitrification based on nitrogen isotope model

Gaseous nitrogen (N) losses from nitrification and denitrification
(NO+N2O+N2) pathways contribute a significant fraction of the total N
losses from cropland ecosystems. However, a large uncertainty exists in
estimating the NO+N2O+N2 losses, hindering effective management of the
global N budget. Here we proposed a novel isotope model, which considers N
fertilizer, ammonia (NH3) volatilization and crop harvest after testing
the steady state assumption of soil δ15N and N pool for croplands, and
justified if it could be successfully applied to constrain NO+N2O+N2
losses from cropland ecosystems. We compiled the first bulk-soil δ15N
dataset of 0-30cm soils (n=738) from croplands and produced a global map
of cropland soil δ15N, which is crucial input data for N isotope model to
quantify NO+N2O+N2 losses. The results show that the cropland soil δ15N
ranges from 3.5 to 9.0‰, with a mean value of 6.6±0.8‰ (mean ± standard
deviation). The estimated NO+N2O+N2 losses accounted for an average of
17±9% of N outputs and were 35.86±24.17 kg N ha-1 yr−1 in China’s rice
paddies, with an increasing trend from Central China to South or North
China. The estimations were comparable with the results from
observation-constrained Denitrification-Decomposition modelling (38.9±4.8
kg N ha−1 yr-1) and in good agreement with experimental observations at
site scale (R2=0.58). Our results suggest that soil N isotopes, as a
quantitative tracer, provide a valuable alternative approach to constrain
the NO+N2O+N2 losses in croplands at large geographic scales.