US agricultural nitrous oxide emissions: context, status, and trends

Abstract

The use of commercial nitrogen (N) fertilizers has led to enormous increases in US agricultural productivity. However, N losses from agricultural systems have resulted in numerous deleterious environmental impacts, including a continuing increase in atmospheric nitrous oxide (N2O), a greenhouse gas (GHG) and an important catalyst of stratospheric ozone depletion. Although associated with about 7% of total US GHG emissions, agricultural systems account for 75% of total US N2O emissions. Increased productivity in the crop and livestock sectors during the past 30 to 70 years has resulted in decreased N2O emissions per unit of production, but N2O emissions from US agriculture continue to increase at a rate of approximately 0.46 teragrams of carbon dioxide equivalents per year (2002–2009). This rate is lower than that during the late 20th century. Improvements in agricultural productivity alone may be insufficient to lead to reduced emissions; implementing strategies specifically targeted at reducing N2O emissions may therefore be necessary.

Nitrous oxide fluxes and dissolved N gases (N2 and N2O) within riparian zones along the agriculturally impacted San Joaquin River

“…High organic carbon in benthic sediments can sustain high denitrification rates with reduction of water column nitrate through hyporheic exchange. Restoration of organic matter in agricultural soils and fertilization management have been found to be key practices for reducing N 2 O fluxes (Cavigelli et al 2012). As the future climate changes, management of in-stream processes and nitrate reduction is equally as important as riparian zone management.…”

Do cover crops increase or decrease nitrous oxide emissions? A meta-analysis

“…Emissions of N 2 O from terrestrial ecosystems are a function of available mineral N, soil water content, the availability of electron donors (such as labile carbon [C]), and soil physical properties (Davidson et al 2000;Firestone and Davidson 1989;Venterea et al 2012). Cover crops may impact aspects of all these processes in ways that could potentially increase or decrease N 2 O emissions as is outlined in table 1.…”

“…Therefore, small reductions in N 2 O emissions from agricultural soils can have an overall large impact on global warming potential. The challenge is to find agricultural management practices with consistent reductions in N 2 O emissions across locations, cropping systems, and years given the high spatial and temporal variability of emissions (Venterea et al 2012).Emissions of N 2 O from terrestrial ecosystems are a function of available mineral N, soil water content, the availability of electron donors (such as labile carbon [C]), and soil physical properties (Davidson et al 2000;Firestone and Davidson 1989;Venterea et al 2012). Cover crops may impact aspects of all these processes in ways that could potentially increase or decrease N 2 O emissions as is outlined in table 1.…”

“…Therefore, small reductions in N 2 O emissions from agricultural soils can have an overall large impact on global warming potential. The challenge is to find agricultural management practices with consistent reductions in N 2 O emissions across locations, cropping systems, and years given the high spatial and temporal variability of emissions (Venterea et al 2012).…”

Measuring and mitigating agricultural greenhouse gas production in the US Great Plains, 1870–2000

“…Although some methods estimate future GHG fluxes under projected scenarios (14,15) and others compare the GHG production of current and past agricultural production systems (10,13), no previous study has estimated cumulative GHG emissions from all agricultural sources from initial plow-out to the present.…”