Haoming Yu, Wenxin Ba, Peter Dörsch, Wulahati Adalibieke, Yunting Fang, Longfei Yu, Chao Wang, Yihang Duan, Huayan Zhang, Benjamin Z. Houlton, Yan Bo, Yi Wei Jian, Xiao Qing Cui, Edith Bai, Feng Zhou
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引用次数: 0
Abstract
Gaseous nitrogen (N) losses from nitrification and denitrification (NO + N2O + N2) pathways contribute a significant fraction of the total N losses from cropland ecosystems. The N mass balance and process-based models are commonly applied to estimate the NO + N2O + N2 losses but have suffered from systematic error accumulations or model over-parameterization, leading to a large uncertainty in estimation, hindering effective management of the global N budget. Here, we proposed a novel N isotope model, which considers fertilizer, ammonia volatilization and harvest after testing 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 data set of 0–30 cm soils (n = 738) from croplands and produced a global map of cropland soil δ15N, which is crucial input data for an 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 modeling (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.
期刊介绍:
Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.