DAYCENT National‐Scale Simulations of Nitrous Oxide Emissions from Cropped Soils in the United States

Abstract

Until recently, Intergovernmental Panel on Climate Change (IPCC) emission factor methodology, based on simple empirical relationships, has been used to estimate carbon (C) and nitrogen (N) fluxes for regional and national inventories. However, the 2005 USEPA greenhouse gas inventory includes estimates of N 2 O emissions from cultivated soils derived from simulations using DAYCENT, a process-based biogeochemical model. DAYCENT simulated major U.S. crops at county-level resolution and IPCC emission factor methodology was used to estimate emissions for the approximately 14% of cropped land not simulated by DAYCENT. The methodology used to combine DAYCENT simulations and IPCC methodology to estimate direct and indirect N 2 O emissions is described in detail. Nitrous oxide emissions from simulations of presettlement native vegetation were subtracted from cropped soil N 2 O to isolate anthropogenic emissions. Meteorological data required to drive DAY-CENT were acquired from DAYMET, an algorithm that uses weather station data and accounts for topography to predict daily temperature and precipitation at 1-km 2 resolution. Soils data were acquired from the State Soil Geographic Database (STATSGO). Weather data and dominant soil texture class that lie closest to the geographical center of the largest cluster of cropped land in each county were used to drive DAYCENT. Land management information was implemented at the agricultural-economic region level, as defined by the Agricultural Sector Model. Maps of model-simulated county-level crop yields were compared with yields estimated by the USDA for quality control.Combining results from DAYCENT simulations of major crops and IPCC methodology for remaining cropland yielded estimates of approximately 109 and approximately 70 Tg CO 2 equivalents for direct and indirect, respectively, mean annual anthropogenic N 2 O emissions for 1990-2003.

Nitrogen fertilizer management for nitrous oxide (N2O) mitigation in intensive corn (Maize) production: an emissions reduction protocol for US Midwest agriculture

“…However, these gradient studies provide the only detailed information of their kind, and the non-linearity of N 2 O emissions has significant consequences when comparing N 2 O emissions reductions with the very general IPCC Tier 1 approach. This approach also offers an evidence-based, less complex solution to estimating N 2 O emissions, when compared to the typically non-transparent Tier 3 approaches (e.g., Del Grosso et al 2006). In the absence of evidence to the contrary we assume that these N gradient experiments are representative of the soil and corn cropping systems throughout the Midwest.…”

The Lancet Countdown: tracking progress on health and climate change

“…Greenhouse gas emissions associated with agriculture (including livestock systems and biogeochemical processes) will be quantifi ed with the use of existing models (eg, the DAYCENT or DeNitrifi cation-DeComposition [DNDC] models). [69][70][71] An understanding is needed of the potential for multiple environmental factors to aff ect food systems, and the nuances within and between countries and cultures. Further work will be required to refi ne indicators for this area, and the scientifi c community is invited to suggest potential metrics and data sources.…”

The Community Land Model underestimates land-use CO<sub>2</sub> emissions by neglecting soil disturbance from cultivation

“…We use the models DayCent (Parton et al, 1998;Del Grosso et al, 2006) and CLM4.5bgc, the most recent version of the CLM with biogeochemistry (Oleson et al, 2013;Koven et al, 2013 Hartman et al (2011) Fig. 1 for map).…”