C.S. Snyder, T.W. Bruulsema, T.L. Jensen, and P. E. Fixen

Greenhouse Gas Emissions from Crop Production Systems and Fertilizer Management Effects

Background• N is essential to the survival of all life• Over 40% of the people on Earth owe their

existence to the food production made possible by N fertilizers

• “Human alterations of the N cycle have caused a variety of environmental and human health problems ranging from too little to too much reactive N in the environment.” (Woods Hole Research Center)

• half the synthetic N fertilizer ever used has been utilized since 1985 (Howarth, 2005).

http://www.whrc.org/policy/global_nitrogen.htm

United Nations Educational, Scientific, and Cultural Organization & Scientific Committee on Problems of the Environmenthttp://www.icsu-scope.org/unesco/070424%20(w)%20USPB04%20En.pdf

IPNIDedicated to improved nutrient use effectiveness and reductions in environmental footprints: including GHG emissions

Billions

0

1

2

3

4

5

6

7

8

9

10

1950 1970 1990 2010 2030 2050

Less Developed Regions

More Developed Regions

Source: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005.

World Population Growth in More and Less Developed Countries

http://www.prb.org/Publications/GraphicsBank/PopulationTrends.aspx

20% more people in ~ 20 years

Food, fiber, and fuel demands will continue to increase

…… what will the environmental impacts be?

http://www.ipni.net/ppiweb/bcrops.nsf/$webindex/6F2F57CBF1C5209685257394001B2DD0/$file/07-4p16.pdf

IPNI Better Crops article, Issue 4 of 2007

Best Management Practices to Minimize Greenhouse Gas Emissions

Associated with Fertilizer UseIPNI Review Paper

Greenhouse Gas Emissions from Cropping Systems and the Influence of Fertilizer Management

Greenhouse Gases (GHGs)and their sources

• Carbon Dioxide (CO2): fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement).

• Methane (CH4): production and transport of coal, natural gas, and oil; livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

• Nitrous Oxide (N2O): agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.

• Fluorinated Gases: (Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride): synthetic, powerful greenhouse gases from a variety of industrial processes. – Sometimes used as substitutes for ozone-depleting substances (i.e.,

CFCs, HCFCs, and halons). Typically emitted in smaller quantities, but because they are potent GHGs, they are sometimes referred to as High Global Warming Potential gases (“High GWP gases”).

GWP = Global Warming PotentialN2O x 296 = CO2 equivalentCH4 x 21 = CO2 equivalent

Sources: U.S. EPA, IPCC 3rd assessment

Agriculture’s Share of GHG Emissions is Not Increasing

Agriculture< 10% of total U.S. GHG

Distribution of GHG Emissions

Estimates of N2O Emissions from Cropland in 1995 (adapted from IFA/FAO, 2001)

Region Area

(million ha)

Fertilizer N Applied

Animal Manure N Applied

N2O-N emitted

total Fertilizer-induced 1

million tonnes % of total

Canada 46 1.58 0.21 0.067 0.016 24

U.S. 190 11.15 1.58 0.316 0.112 35World 1,436 73.48 20.66 3.150 0.735 231 Estimated using IPCC emission factor of 1%Recently published reports suggest terrestrial and aquatic N2O-N emissions may range from 3 to 5% of “new N” (Crutzen et al., 2008. Atmos. Chem. Phys. 8:389-395)

Data source: IFA, AAPFCO & TFI

Consumption of N Sources

Range of N2O Emission Among N Sources can Vary Greatly

• Report 1 (Stehfest & Bouwman, 2006)

– 0 to 46% of applied N• Report 2 (Granli &

Bockman, 1994)

– 0 to 7% of applied N• Report 3 (Eichner, 1990)

– 0 to 7% of applied N

• Report 1– Median among N

sources ranged from: 0.26 to 1.56 kg of N/ha

N Rates Above Agronomic Optimum Can Increase Risk of N2O

Emission

Nitrogen Use Efficiency

• “…… estimated NUE for cereal production ranges from 30 to 35%.” 

Improving Nitrogen Use Efficiency for Cereal Production ( 1999 Agronomy Journal 91:357-363)

N Recovery and NUE are Affected by Other Essential Nutrients

Food Yield/Net GWP.01

.09

.02

.02

.02

.02

.01

.01

N Loss Consequences Requiring Management Attention

• Decreased crop production and profitability – Inefficient land use, reduced performance of other crop

inputs, reduced water use efficiency• Water resource contamination

– eutrophication: lakes, streams, rivers, estuaries– groundwater contamination– coastal water contamination - urea and harmful algal

blooms (neurotoxin poisoning)• Air pollution

– Ammonia and particulates, nitrous oxide and NOx (global warming, stratospheric ozone depletion, acid rain)

Loss of NO3 - N to Water Resources May Also Impact N2O Emissions

Kg/ha.01 .01- 0.10.1 to 11 to 55 to 10>10

SPARROW - Modeled Estimate of N and P Discharge in Watersheds of the Mississippi R. Basin

Alexander et al., 2008. Environ. Sci. Technol. 42: 822–830

Nutrient Use Efficiency and Effectiveness:Indices of Agronomic and Environmental Benefit

http://www.ipni.net/ipniweb/portal.nsf/0/d58a3c2deca9d7378525731e006066d5/$FILE/Revised%20NUE%20update.pdf

Encourage post-harvest evaluation of N effectiveness in cropping systems

NUE Term Calculation Reported Examples

PFP - Partial factor productivity

Y/F 40 to 80 units of cereal grain per unit of N

AE - Agronomic Efficiency

(Y-Y0)/F 10 to 30 units of cereal grain per unit of N

PNB - Partial nutrient balance (removal to use ratio)

UH/F 0 to > 1.0 - depends on native soil fertility and fertility maintenance objectives<1 in nutrient deficient systems (fertility improvement)

>1 in nutrient surplus systems (under replacement)

Slightly less than 1 to 1 (system sustainability)

RE – Recovery efficiency of applied nutrient

(U-U0)/F 0.1 to 0.3 - proportion of P input recovered first year

0.5 to 0.9 - proportion of P input recovered by crops in long-term cropping systems

0.3 to 0.5 - N recovery in cereals-typical

0.5 to 0.8 - N recovery in cereals- best management

F-amt. nutrient applied, Y- yield of harvested portion with applied nutrient, Y0- yield of harvested portion with no applied nutrient, UH –nutrient content of harvested portion of crop, U –total nutrient uptake in aboveground biomass with nutrient applied, U0 –total nutrient uptake in aboveground biomass with no nutrient applied

Increased Farmer Interest in Better N Management

• Increased N costs• Better crop prices• Calibration and

verification of newer technologies

• Improved farmer skills, and availability of professional guidance by crop advisers

“The Market” Nov.1, 2007

0.50.60.70.80.91.01.11.21.31.4

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

bu p

er lb

of N

Corn grain produced in the U.S. per unit of fertilizer N used, 1964 to 2005.

0.760.76

1.151.15

51% increase in N efficiency12% increase in N fertilizer useSince 1975:

*

*Application rate for 2004 estimated as avg of 2003 & 2005.

Data sources: USDA Ag Chem Use Survey & Annual Crop Production.

Effects of Crop Harvest N Removal on Net Anthropic Nitrogen Input (NANI)

Source: McIsaac, 2006.

Figure 1. Net anthropogenic N input (NANI) in major sub-basins of the Mississippi River Basin estimated from state level statistics.

Fertilizer N in California and GHG Emission802,682 x 0.01= 8,027 metric tons N2O–N emitted

(assuming IPCC 1% factor)N x 1.57 = 12,602 metric tons of N2O

N2O x 296 = 3.73 million metric tons GWP CO2 equivalent

Source: AAPFCO

All GHGs in CA in 2004 (CA EPA, ARB 2007) : 479.74 million metric tons CO2 equivalent

Portion of total that is “fertilizer N induced” = (3.73/479.74) x 100 = 0.78% of all GWP in California

• N source, rate, placement , and timing …. which may include– Urease inhibitors– Nitrification inhibitors– Slow-release materials– Controlled-release materials

• In combination with appropriate, site-specific cropping system and conservation practices – (e.g. conservation tillage, cover crops,

vegetative buffers, managed drainage, wetlands, bioreactors, etc.)

• Fertilizer N BMPs can help minimize potential for residual NO3-N accumulation & losses

http://www.fertilizer.org

http://www.ipni.net/bettercrops

http://www.floridaagwaterpolicy.com/BestManagementPractices.html

CONCLUSIONS• Appropriate fertilizer N helps increase crop

biomass to restore & maintain soil organic matter (SOM)

• Tillage practices with the least soil disturbance help maintain SOM

• Intensive crop management can help minimize GHG emissions, and lower GHG emission/unit of crop or food produced

• Fertilizer N contributions to agricultural GHG emissions can range widely, BUT agricultural emissions are relatively small compared to other source emissions

• We must continue to strive to improve NUE

QUESTIONS ?

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