Model estimates of nitrous oxide emissions from agricultural lands in the United States

Abstract

The Denitrification‐Decomposition (DNDC) model was used to elucidate the role of climate, soil properties, and farming practices in determining spatial and temporal variations in the production and emission of nitrous oxide (N2O) from agriculture in the United States. Sensitivity studies documented possible causes of annual variability in N2O flux for a simulated Iowa corn‐growing soil. The 37 scenarios tested indicated that soil tillage and nitrate pollution in rainfall may be especially significant anthropogenic factors which have increased N2O emissions from soils in the United States. Feedbacks to climate change and biogeochemical manipulation of agricultural soil reflect complex interactions between the nitrogen and carbon cycles. A 20% increase in annual average temperature in °C produced a 33% increase in N2O emissions. Manure applications to Iowa corn crops enhanced carbon storage in soils, but also increased N2O emissions. A DNDC simulation of annual N2O emissions from all crop and pasture lands in the United States indicated that the value lies in the range 0.9–1.2 TgN. Soil tillage and fertilizer use were the most important farming practices contributing to enhanced N2O emissions at the national scale. Soil organic matter and climate variables were the primary determinants of spatial variability in N2O emissions. Our results suggest that the United States Government, and possibly the Intergovernmental Panel on Climatic Change (IPCC), have underestimated the importance of agriculture as a national and global source of atmospheric N2O. The coupled nature of the nitrogen and carbon cycles in soils results in complex feedbacks which complicate the formulation of strategies to reduce the global warming potential of greenhouse gas emissions from agriculture.

Human and animal wastes: Implications for atmospheric N2O and NOx

“…have been employed to simulate the nitrogen cycle and generate yield data [Li et al, 1992;Schmid et al, 2001]. The discrepancy between the two approaches [Li et al, 1996[Li et al, , 2001Schmid et al, 2001] raises questions as to whether emission factors are known to a precision adequate to justify the level of complexity implicit in either method. Current understanding of aerobic denitrification suggests an important sensitivity of yields of N 2 O and NO to environmental conditions, specifically to levels of ambient O 2 .…”

Modeling impacts of farming management practices on greenhouse gas emissions in the oasis region of China

“…In the past 20 yr, the DNDC model has been proven to be effective in many places around the world, such as North America, Europe, Asia and Oceania (Li et al, 1996;Plant, 1999;Stange et al, 2000;Li, 2000;Zhang et al, 2002;Xu et al, 2003;Cai et al, 2003;Frolking et al, 2004;Grant et al, 2004;Smith et al, 2004;Butterbach-Bahl et al, 2004;Pathak et al, 2005;Jagadeesh Babu et al, 2005;Beheydt et al, 2007;Smith et al, 2010). Application of this model in China began in the late 1990s.…”

A process‐oriented model of N2O and NO emissions from forest soils: 2. Sensitivity analysis and validation

“…We believe the most promising strategy to overcome these problems is the development of process-oriented models, which are able to describe the processes in forest soils involved in N-trace gas production and emission (e.g., mineralization, nitrification, denitrification, plant-microbe competition for inorganic nitrogen) and their dependency on changing environmental conditions. Such models could be used to quantify N-trace gas flux rates from temperate forest soils on a regional and global scale, as has been already demonstrated for agricultural ecosystems of the United States [Li et al, 1996]. In addition, the process of model development highlights data gaps and can suggest areas where field and laboratory studies can focus.…”