Nitrogen in California Agriculture:

Quantities and Impacts

Sonja Brodt

1

True Cost of American Food Conference

San Francisco, CA

April 15, 2016

University of California Sustainable Agriculture Research and Education Program

The California Nitrogen Assessment

Agricultural Sustainability Institute at University of California, Davis

UC Sustainable Agriculture Research and Education Program

UC Agricultural Issues Center

Kearney Foundation for Soil Science

California Institute for Water Resources, UC ANR

Water Science and Policy Institute, UC Riverside

Thomas Tomich, Principal InvestigatorRandy Dahlgren, co-Principal Investigator

Supported by the David and Lucile Packard Foundation, UC Division of Agriculture and Natural Resources, the W.K. Kellogg Foundation, and the USDA Hatch project CA-D-XXX-7766-H

Collaborating Institutions:

2

Sonja Brodt, co-Principal InvestigatorKate Scow, co-Principal Investigator

With special acknowledgement to co-authors Daniel Liptzin and Todd Rosenstock

California Nitrogen Assessment

Based on stakeholder-driven questions generated by engaging with more than 350 stakeholders statewide

What are the big sources of nitrogen pollution in California?

What practices are most effective in mitigating nitrogen pollution?

What are the impacts of N management on society and human health?

What are the policy challenges and opportunities?3

Statewide N Inputs (circa 2005)

Total nitrogen Inputs ≈1.8 million tons per year

(1628 Gg N yr-1, roughly 1% of global human N inputs)

22% NOx

33% Fertilizer

12% Crop BNF

11% Feed

Contributions of cropland and

livestock to N imports into CA

5

0

200

400

600

800

1000

1200

Cropland Livestock Urban Land People & Pets Natural Land

N f

low

(G

g N

)

Food Waste Pet Waste

Irrigation Food

Feed Manure

Synthetic Fixation Cropland Fixation

Natural Lands Fixation Deposition

Statewide N Outputs and Storage:

Net of Groundwater Denitrification

≈1.8 million tons (1626 Gg N yr-1)

26%

20%

NOx: 270 Gg

N2: 204 Gg

NH3: 201 Gg

N2O: 38 Gg

Groundwater Storage: 257 Gg

Other Urban Storage: 122 GgNatural Land Storage: 91 Gg

Sewage Discharge: 82 Gg

Food: 79 Gg

Urban Land Storage: 76 Gg

Landfills Storage: 71 Gg

Cropland Storage: 65 Gg

River Discharge: 39 Gg

Reservoirs Storage: 30 Gg

Food

N outflows from cropland and

livestock in CA

8

0

200

400

600

800

1000

1200

Cropland Livestock Urban Land People & Pets Natural Land

N f

low

(G

g N

)

Biosolids Food Waste

Pet Waste Food

Fiber Feed

Manure Sewage

Other Storage Groundwater

Surface Water Fire

N2 N2O

NH3 NOx

Trends in Groundwater Nitrate (Salinas Valley & Tulare Lake Basin)

Five-year moving average of the % of wells with average annual NO3 levels > 9 mg / L (background), 22.5

mg / L (1/2 MCL) and 45mg / L (MCL). Prior to 1990 most wells sampled were public supply wells. In 2007,

Central Valley dairies began testing domestic and irrigation wells.Boyle et al. 2012

Human Health Effects: The Cost of

N-Related Air Pollution

• Costs > $1,600 per person per year.

• nearly $6 billion in savings if federal ozone and PM2.5 standards were met.

Hall et al. 2008

San Joaquin Valley:

South Coast Air Basin:

• Costs > $1,250 per person per year.

• nearly $22 billion in savings if federal ozone and PM2.5 standards were met.

Co-location of Air and Groundwater Pollution:

Environmental Justice Concerns

Clarisse et al. 2009

Nitrate in groundwater Ammonia in the air

San Joaquin Valley, CA

Bakersfield

Selected values for N impacts in California

Ecosystem service

Estimated economic benefits and costsSource of estimate

Food production $36.6 billion per year $28 billion in San Joaquin Valley in value added

CDFA (2009), MOCA (2009)

Air quality $100 million per year loss due to crop damage

Approximately $65 million year due to human health effects due to Ozone and PM2.5 in SJV alone

Delucchi(1986), Hall et al. (2006)

Drinking water SJV nitrate-related drinking water mitigationprojects 2005-09 (CDPH):• $150 million for 100 proposed projects• $21 million for 16 funded projects

Moore & Matalon(2011)

N use efficiency in crops is consistently higher in research trials than on-farm averages.

• California area weighted average PNB across 33 crops = 54%• Some research trials: PNB as high as 80 – 100+% (tomatoes, almonds)

Partial Nutrient Balance = N exported/N applied * 100

(Brown et al. unpub; Bottoms and Hartz 2009)

Possible Reductions in N Flows to Cropland

• Soil testing• Modify fertilizer placement

and timing• Improve irrigation system

performance

Examples of key practices:

Could (conservatively) reduce N leaching by 8% ……or more??

Possible Reduction in N Flows to

Livestock

Increase N utilization efficiency in livestock• Conservative estimate that total feed demand could decrease to 85% of

current levels (82 Gg N decrease)

Improve manure management• Estimated range in CA dairies: 25-50% of manure N volatilizes to NH3

Examples of key practices:

• Animal breeds with higher feed conversion efficiency • Feed management• More frequent manure collection• Anaerobic manure storage• Composting• Nitrification inhibitors

Envir. effectiveness

Technological feasibility

Cost effectiveness

Education Policies Poor Good/mod. Good

Standards Good Good/mod. Mod./poor

Emission standards

Economic Incentives Good/mod. Good/mod. Mod./poor

Emission charges

Tradeable emission permits

Abatement subsidies

Auction-based abatement contract

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Policy Assessment

NOTE: • Voluntary BMP adoption subsidies do not have good historical record• Flexibility and responsiveness to local conditions results in most cost-effectiveness