Journal Article

Global metaanalysis of the nonlinear response of soil nitrous oxide (N2O) emissions to fertilizer nitrogen

Shcherbak, Iurii, Robertson, G. Philip, Millar, Neville

2014

Overview

Nitrous oxide (N 2 O) is a potent greenhouse gas (GHG) that also depletes stratospheric ozone. Nitrogen (N) fertilizer rate is the best single predictor of N 2 O emissions from agricultural soils, which are responsible for ∼50% of the total global anthropogenic flux, but it is a relatively imprecise estimator. Accumulating evidence suggests that the emission response to increasing N input is exponential rather than linear, as assumed by Intergovernmental Panel on Climate Change methodologies. We performed a metaanalysis to test the generalizability of this pattern. From 78 published studies (233 site-years) with at least three N-input levels, we calculated N 2 O emission factors (EFs) for each nonzero input level as a percentage of N input converted to N 2 O emissions. We found that the N 2 O response to N inputs grew significantly faster than linear for synthetic fertilizers and for most crop types. N-fixing crops had a higher rate of change in EF (ΔEF) than others. A higher ΔEF was also evident in soils with carbon >1.5% and soils with pH <7, and where fertilizer was applied only once annually. Our results suggest a general trend of exponentially increasing N 2 O emissions as N inputs increase to exceed crop needs. Use of this knowledge in GHG inventories should improve assessments of fertilizer-derived N 2 O emissions, help address disparities in the global N 2 O budget, and refine the accuracy of N 2 O mitigation protocols. In low-input systems typical of sub-Saharan Africa, for example, modest N additions will have little impact on estimated N 2 O emissions, whereas equivalent additions (or reductions) in excessively fertilized systems will have a disproportionately major impact.

• Publisher: National Academy of Sciences
• Subject: Africa South of the Sahara / Agricultural land / Agricultural site preparation / agricultural soils / Agrochemicals / Anthropogenic factors / Atmosphere / Biological Sciences / carbon / Carbon - chemistry / Carbon - metabolism / Carbon footprint / Climate change / Crops / Crops, Agricultural - growth & development / Crops, Agricultural - metabolism / Emission inventories / Emissions / emissions factor / Emissions reduction / Environmental Sciences / Farm buildings / fertilizer rates / Fertilizers / Grains / Greenhouse Effect / greenhouse gas emissions / Greenhouse gases / Highlands / Intergovernmental Panel on Climate Change / International environmental cooperation / Meta-analysis / Nitrogen / Nitrogen - chemistry / Nitrogen - metabolism / Nitrogen fertilizers / Nitrogen Fixation / Nitrous oxide / Nitrous Oxide - chemistry / Nitrous Oxide - metabolism / ozone / Ozone depletion / Physical Sciences / Pollutant emissions / Soil - chemistry / stratosphere / Sub-Saharan Africa / Sustainability Science