Data‐driven estimates of fertilizer‐induced soil NH₃, NO and N₂O emissions from croplands in China and their climate change impacts

Abstract

Gaseous reactive nitrogen (Nr) emissions from agricultural soils to the atmosphere constitute an integral part of global N cycle, directly or indirectly causing climate change impacts. The extensive use of N fertilizer in crop production will compromise our efforts to reduce agricultural Nr emissions in China. A national inventory of fertilizer N-induced gaseous Nr emissions from croplands in China remains to be developed to reveal its role in shaping climate change. Here we present a data-driven estimate of fertilizer N-induced soil Nr emissions based on regional and crop-specific emission factors (EFs) compiled from 379 manipulative studies. In China, agricultural soil Nr emissions from the use of synthetic N fertilizer and manure in 2018 are estimated to be 3.81 and 0.73 Tg N yr −1 , with a combined contribution of 23%, 20% and 15% to the global agricultural emission total of ammonia (NH 3 ), nitrous oxide (N 2 O) and nitric oxide (NO), respectively. Over the past three decades, NH 3 volatilization from croplands has experienced a shift from a rapid increase to a decline trend, whereas N 2 O and NO emissions always maintain a strong growth momentum due to a robust and continuous rise of EFs. Regionally, croplands in Central south (1.51 Tg N yr −1 ) and East (0.99 Tg N yr −1 ) of China exhibit as hotspots of soil Nr emissions. In terms of crop-specific emissions, rice, maize and vegetable show as three leading Nr emitters, together accounting for 61% of synthetic N fertilizer-induced Nr emissions from croplands. The global warming effect derived from cropland N 2 O emissions in China was found to dominate over the local cooling effects of NH 3 and NO emissions. Our established regional and crop-specific EFs for gaseous Nr forms provide a new benchmark for constraining the IPCC Tier 1 default EF values. The spatio-temporal insight into soil Nr emission data from N fertilizer application in our estimate is expected to advance our efforts towards more accurate global or regional cropland Nr emission inventories and effective mitigation strategies. K E Y W O R D S climate change, emission factor, fertilizer, nitrogen use efficiency, reactive nitrogen 1 | INTRODUC TI ON Reactive nitrogen (Nr) into and out of terrestrial ecosystems plays a critical role in global N cycle (Sutton et al., 2013). In general, gaseous Nr emissions have long-lived warming effects from the production of nitrous oxide (N 2 O) and tropospheric ozone (O 3 ), along with short-lived cooling effects by changing tropospheric aerosol, methane (CH 4 ) and O 3 (Galloway et al., 2008). Worldwide rapid growth | 1009 MA et Al.

Biochar Mitigated Yield-Scaled N2O and NO Emissions and Ensured Vegetable Quality and Soil Fertility: A 3-Year Greenhouse Field Observation

“…In our study, N 2 O-N and NO-N emission factors ranged from 0.21% to 0.57% and 0.09% to 0.21%, which was much lower than the latest results reported by Ma et al [8]. We speculated that this may be due to the lower production of N 2 O and the higher reduction ratio, resulting in a net reduction in N 2 O and NO emissions.…”

“…Previous studies indicated that excessive N input disrupted nutritional balance, and lowered soil pH, microbial activity, and diversity [5][6][7]. Furthermore, N fertilizer-induced soil nitrous oxide (N 2 O, a long-lived and potent greenhouse gas) and nitric oxide (NO, atmospheric photochemical pollutant) emissions have received widespread attention owing to the robust and steady rise of emission factors [8]. Therefore, the integrated improvement of N 2 O and NO mitigation while enhancing crop production and soil fertility should be implemented to promote sustainable agricultural development.…”

Gaseous Reactive Nitrogen Losses From Orchards, Vegetables and Tea Plantations

“…NO background emissions from tea plantations were significantly higher than those from vegetables (P < 0.01) but not different from those from orchards. Overall, we found that the magnitude of background emissions of gaseous reactive N was generally greater in Chinese OVT systems than in upland cereals [35] .…”

“…The mean EF of N2O emission in Chinese orchards was 1.2% (range: 0.7%-1.72%), which was slightly lower than the world average of 1.4% (0.84%-1.86%) [20,25,37] . The mean EF of N2O emission from Chinese vegetable fields was 0.85% (0.55%-1.7%), and notably lower than the world average of 1.4% (0.93%-2.4%) [17,35,[38][39][40][41][42]44,45] . The EF of N2O in orchards and vegetables and its variability were comparable with the global mean (1%, range: 0.1%-1.8%) [48] .…”

A synthesis of nitric oxide emissions across global fertilized croplands from crop‐specific emission factors

“…Such EF d approaches are widely used to quantify not only N 2 O and NH 3 emissions from croplands across national and global scales (e.g., Cayuela et al, 2017; Aliyu et al, 2019; Yue et al, 2019; Ma et al, 2021a, b; Hergoualc’h et al, 2021), but also from cropland NO emissions at regional scale (e.g. Ma et al, 2021b; Yan et al, 2003). According to the Intergovernmental Panel on Climate Change (IPCC) Tier 1 guidelines, the EF d default value for NO is 0.70% for synthetic N fertilizer and manure (IPCC, 2006), though recently updated to 1.1% for synthetic N fertilizer (IPCC, 2019).…”