An improved mechanistic model for ammonia volatilization in Earth system models: Flow of Agricultural Nitrogen version 2 (FANv2)

Abstract

Abstract. Volatilization of ammonia (NH3) from fertilizers and livestock wastes forms a significant pathway of nitrogen losses in agricultural ecosystems and constitutes the largest source of atmospheric emissions of NH3. This paper describes a major update to the process model FAN (Flow of Agricultural Nitrogen), which evaluates NH3 emissions interactively within an Earth system model; in this work, the Community Earth System Model (CESM) is used. The updated version (FANv2) includes a more detailed treatment of both physical and agricultural processes, which allows the model to differentiate between the volatilization losses from animal housings, manure storage, grazed pastures, and the application of manure and different types of mineral fertilizers. The modeled ammonia emissions are first evaluated at a local scale against experimental data for various types of fertilizers and manure, and they are subsequently run globally to evaluate NH3 emissions for 2010–2015 based on gridded datasets of fertilizer use and livestock populations. Comparison of regional emissions shows that FANv2 agrees with previous inventories for North America and Europe and is within the range of previous inventories for China. However, due to higher NH3 emissions in Africa, India, and Latin America, the global emissions simulated by FANv2 (48 Tg N) are 30 %–40 % higher than in the existing inventories.

Simulating Agriculture in the Community Land Model Version 5

“…Increasing manure application (e.g., Riddick et al, 2016) is also expected to increase yields prior to 1950, although changes in the aerial application rate are not represented in CLM5. More robust manure application schemes are under development (Vira et al, 2019). Corn, wheat, and rice yields increased most with fertilizer application, whereas nitrogen‐fixing soybean yields, as expected, did not change much with fertilizer application (Figure S8).…”

“…Industrial fertilizer is prescribed by crop type, year, and country based on LUH2 fertilization rates (Hurtt et al, 2011). More realistic development of manure application, including transient application rates and N fluxes, is under development (Riddick et al, 2016; Vira et al, 2019) but not included in the released version of CLM5. The application of irrigation water is limited to only the irrigated crop columns.…”

Northwestward cropland expansion and growing urea-based fertilizer use enhanced NH<sub>3</sub> emission loss in the contiguous United States

“…The records of the other seven crops are available since the 1980s. To extend the crop-specific planting date records back to 1900, we adopted the approach used in the Environmental Policy Integrated Climate (EPIC) crop model (Williams et al, 1989), which considers daily heat unit accumulation (HU, Eq. 4) and heat unit index (HUI, Eq.…”

Improved Estimates of Ammonia Emissions from Global Croplands

“…To assess the abatement potentials of NH 3 emissions, it is prerequisite to identify the volatilization rates (VRs) associated with diverse farming systems and fertilization practices. However, the quantification of VR (i.e., NH 3 -N emission per unit of N fertilizers applied) and relevant emissions remains highly uncertain, primarily attributable to the episodic nature of NH 3 volatilization and the highly spatial variability of agricultural practices 1,2,[18][19][20][21] . For example, estimates of global cropland-NH 3 volatilization from synthetic fertilizer application by various bottom-up approaches 2,18,19,21 ranged from 9 to 14 Tg N (Table S1).…”

“…For example, estimates of global cropland-NH 3 volatilization from synthetic fertilizer application by various bottom-up approaches 2,18,19,21 ranged from 9 to 14 Tg N (Table S1). Such differences were as large as almost two times within the major emitting countries (e.g., China 18,22 , Pakistan 19,23 , USA 2,21 ).…”