Sources of nitrous oxide emissions from agriculturally managed peatlands
Yuqiao Wang, Pierluigi Calanca, Jens Leifeld
Abstract
Abstract The draining and fertilization of peatlands for agriculture is globally an important source of the greenhouse gas nitrous oxide (N 2 O). Hitherto, the contribution of major sources to the N 2 O emission—that is, fertilization and nitrogen (N) release from peat decomposition—has not yet been deciphered. This hampers the development of smart mitigation strategies, considering that rewetting to halt peat decomposition and reducing N fertilization are promising N 2 O emission‐reduction strategies. Here, we used machine learning techniques and global N 2 O observational data to generalize the distribution of N 2 O emissions from agriculturally managed peatlands, to distinguish the sources of N 2 O emissions, and to compare mitigation options. N 2 O emissions from agriculturally managed croplands were 401.0 (344.5–470.9) kt N year −1 , with 121.6 (88.6–163.3) kt N year −1 contributed by fertilizer N. On grasslands, 64.0 (54.6–74.7) kt N 2 O‐N year −1 were emitted, with 4.6 (3.7–5.7) kt N 2 O‐N year −1 stemming from fertilizer N. The fertilizer‐induced N 2 O emission factor ranged from 1.5% to 3.2%. Reducing the current fertilizer input by 20% could achieve a 10% N 2 O emission reduction for croplands but only 3% for grasslands. Rewetting 1.9 Mha cropland and 0.26 Mha grassland would achieve the same N 2 O emission reductions. Our results suggest that N 2 O mitigation strategies for managed peatlands should be considered separately across land‐use types and climatic zones. For croplands, particularly in the tropics, relevant N 2 O mitigation potentials are achievable through both fertilizer N reduction and peatland rewetting. For grasslands, management schemes to halt peat degradation (e.g. rewetting) should be considered preferentially for mitigating N 2 O and contributing to meeting climate goals.