The benefits and the environmental costs of anthropogenic reactive nitrogen 刘玲莉 中国科学院植物研究所 植被与环境变化国家重点实验室 The 7 th ISOME & the 4 th IYEF, GuangZhou, 06/12/2013

Outline Non-reactive nitrogen (N 2 ) VS. Reactive Nitrogen (NOx, NHx, organic N) The good and the bad of reactive nitrogen Can N cycle be better managed? – An assessment on the potential of nitrification inhibitors for better N fertilizer management

Humans have more than doubled the amount of natural N fixation Erisman et al. 2011, Current opinion in environmental sustainability Fertilizer Fossil fuel Legume crop natural biological N fixation on land: 110 Tg N/yr in ocean: 140 Tg N/yr

The good of anthropogenic Nr: Food Productivity Almost half of the food consumed by mankind is based on the increased production by use of nitrogen fertilizers Erisman et al 2008, Nature Geoscience Carl Bosch ( ): Nobel Prize in Chemistry, 1931, -”chemical high pressure methods” Fritz Haber : Nobel Prize in Chemistry, 1918, -”for the synthesis of ammonia from its elements”

Nitrogen’s carbon benefit Liu and Greaver, Ecology Letters

Anthropogenic Nr stimulates vegetation growth 6 Xia and Wan, 2008, New Phytologist

Anthropogenic Nr input may increase soil C sequestration 7 Liu and Greaver, Ecology Letters

Organic layer (↑) Mineral soil (n.s.) microbial activity C input (↑)C output (n.s.) Why ? Liu and Greaver, Ecology Letters

Nitrogen saturation 9 Chapin et al. 2011, Principles of Terrestrial Ecosystem Ecology Gruber and Galloway 2008, Nature NH 3 Closed N cycle Open and leaky N cycle

Increases biogenic N 2 O and CH 4 emission 10 C substrate supply (+/-) CO 2 C allocation C:N (-) DOC root uptake Photosynthesis (+) N cycle C cycle N input ANPP (+) BNPP(+/-) DIN/DON C supply (+/-) SOC N toxicity (+) + positive feedback - negative feedback heterotrophic respiration (+/-) autotrophic respiration (+) CO 2 CH 4 N2ON2O Liu and Greaver, 2009, Ecology Letters

Nitrogen’s carbon benefit is largely offset by N 2 O an CH 4 emission 11 CO 2 uptake CH 4 emission CH 4 uptake N 2 O emission 53-76% Liu and Greaver, 2009, Ecology letters

Impacts of reactive N on climate change 12 Process altered by reactive N Climate forcerdirectiondescription N2ON2ON 2 O emissionwarmingecological and atmospheric processes N deposition  CH 4 CH 4 emissionwarmingecological processes N deposition  CO 2 CO 2 uptakecoolingecological processes NOx  ozone  CO 2 CO 2 emissionwarmingecological processes NOx  ozone  CH 4 ozone, CH 4 coolingAtmospheric processes Nox  aerosolsulfate, nitrate, ammonium aerosol coolingAtmospheric processes NH 3  aerosolsulfate, nitrate, ammonium aerosol coolingAtmospheric processes

Estimates of net changes in US GHG fluxes 13 CO 2, CH 4 and N 2 O emission/ uptake factors +

Climate change impact of US Nr emissions for 20 yrs and 100 yrs 14 Pinder et al PNAS Ecological processes Atmospheric processes Atmospheric & ecological processes cooling warming

Nr’s other environmental costs Clark and Tilman 2008 Nature

Could N cycle be better managed? Low nitrogen fertilizer use efficiency Tilman et al. 2002, Nature

% of the applied N fertilizer Nitrification inhibitor Synchronize N release to that plant growth uptake

The potential of nitrification inhibitors for better N fertilizer management Qiao et al. In preparation

N NO (- 20%) N 2 O (- 56%) NH 3 (+ 11%) N fertilizer +NI NH 4 + (+ 53%) NO 3 - (- 41%) AMO DIN (n.s) DIN leaching (- 35%) NH 4 + leaching (+78%) NO 3 - leaching (- 57%) SOM CH 4 CO 2 Mineralization CH 4 (n.s) CO 2 (n.s) Litter Atmosphere Soil Surface and ground water Denitrification Nitrification N decomposition Immobilization Photosynthesis N uptake (+ 17%) N2ON2O Yield (+ 12%) N concentration (+ 10%) C cycleN cycle + increased - Decreased n.s no significant changes Qiao et al. In preparation

Cost/benefit analysis of NI in agriculture ecosystem Variable Response kg N/ha $/kg N Monetary value $/ha Cost/benefit $/ha Environmental impact N2ON2O NH NO DIN leaching Fertilizer input N fertilizer save Nitrification inhibitor Crop yield Wheat productivity 0.7 t/ha249 $/t Total monetary value Qiao et al. In preparation

Conclusion The use of Nr fertilizers makes remarkable contribution to alleviate global food shortage. The anthropogenic Nr loading also enhances ecosystem carbon sequestration The massive release of the excess N creates severe environmental problems: GHG emission, biodiversity loss, eutrophication, soil acidification… NI is an applicable approach to improve N managements.

22 Thank you!

How many kg C can be fixed with 1kg N/ha N deposition? kg C per Kg N (Magnani et al. 2008, Nature) kg C per Kg N (de Vries et al. 2008, Nature) 65 kg C per Kg N (Thomas et al. 2010, Nature Geoscience) 24.5 kg C per Kg N (Liu and Greaver 2009, Ecology letters) 23 Critical C:N ratio Wood 200+ Leaves Legume leaves 10 Fungi 8-15 Bacteria 5-10 Surface soil 14 Magnani et al. 2007, Nature