Sonja Brodt - Nitrogen

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  • Nitrogen in California Agriculture:

    Quantities and Impacts

    Sonja Brodt


    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:


    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









    Cropland Livestock Urban Land People & Pets Natural Land

    N f



    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)



    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


  • N outflows from cropland and

    livestock in CA









    Cropland Livestock Urban Land People & Pets Natural Land

    N f



    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


  • 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


    Examples of key practices:

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

  • Possible Reduction in N Flows to


    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


    Policy Assessment

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