Nitrogen in California agriculture: quantities and impacts

1. 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

2. 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 Investigator
Randy 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 Investigator
Kate Scow, co-Principal Investigator
With special acknowledgement to co-authors Daniel Liptzin and Todd Rosenstock

3. 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

4. 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

5. 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
Nflow(GgN)
Food Waste Pet Waste
Irrigation Food
Feed Manure
Synthetic Fixation Cropland Fixation
Natural Lands Fixation Deposition

6. 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

8. N outflows from cropland and
livestock in CA
8
0
200
400
600
800
1000
1200
Cropland Livestock Urban Land People & Pets Natural Land
Nflow(GgN)
Biosolids Food Waste
Pet Waste Food
Fiber Feed
Manure Sewage
Other Storage Groundwater
Surface Water Fire
N2 N2O
NH3 NOx

9. 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

10. 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.

11. 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

12. Selected values for N impacts in California
Ecosystem
service
Estimated economic benefits and costs
Source 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 mitigation
projects 2005-09 (CDPH):
• $150 million for 100 proposed projects
• $21 million for 16 funded projects
Moore &
Matalon
(2011)

13. 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??

14. 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

15. 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