Managing Agricultural Nitrogen in the Critical Zone along the … Huertos... · 2012-11-14 ·...
Transcript of Managing Agricultural Nitrogen in the Critical Zone along the … Huertos... · 2012-11-14 ·...
Managing Agricultural Nitrogen in the Critical Zone
along the Central Coast
Marc Los Huertos
Associate Professor
Science & Environmental Policy
The Critical Zone
Row Crops in California
• Highly intensified
– High cost of land
– Narrow margins
– Perishable products
– Market volatility
– High quality standards
• Innovative Growers
Organic Strawberry Production along Central Coast
Surface Water Contamination Groundwater Contamination
Pajaro River Surface Water Nitrate
1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001
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May September
Pajaro River (Los Huertos, et al, in preparation)
Surface Waters (Pajaro)
Surface Waters (Elkhorn Slough)
Surface Waters (Salinas)
Surface Waters (San Luis Obispo)
Surface Waters (Santa Maria)
Pajaro River Surface Water Nitrate
1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001
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May September
Pajaro River (Los Huertos, et al, in preparation)
Environmental Science: Increasing Capacity to Detect Stressors
Algal Indicators of Low TN: Epithemia turgida
Epithemia turgida contain nitrogen-fixing endosymbiotic cyanobacteria which
enable this taxon to become abundant in microhabitats with a low TN. Often
grows on an epiphyte on Cladophora and other coarse filamentous algae in
western rivers.
Reference Condition – exemplify true “naturalness”
Minimally Disturbed Condition – best approximation of “naturalness”
Least Disturbed Condition – best available conditions
Best Attainable Condition – potential for biological conditions
(Adapted from Stoddard et al. 2006)
Reference Streams and Change Point Analysis
Total Nitrogen (sum of ammonium, nitrate, and organic N)
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CHANGE POINT ANALYSIS
0.01 0.1 1 10 100
Irrigation and Nitrogen Management
Biases and Assumptions :
Efficiency:
Drip > Sprinkler > Flood
Nutrient Evaluations:
Plant Tissue > In-season Quick Tests > Annual soil tests
Fertility:
N and P control productivity
Irrigation Timing: Decision Tools to Link Irrigation
to Crop Demand
The danger of using a guideline in a regulatory approach
What does uniformity depend on? 1. Well designed system 2. Soil type 3. High quality drip tape 4. Correct Pressure 5. Growers/irrigator skill
It’s the management
Irrigation Evaluations: Distribution Uniformity Evaluations
• Why evaluate?
– Numerous factors limit irrigation efficiency
• Wind & nozzle size (sprinklers)
• Wrong pressures or pressure changes (drip)
• Clogging/Leaks
• If you are not at 80% or better, chances are that $$ and nitrogen is being lost.
Nutrient Management
• Soil Fertility – Productivity responses to N/P
– Location and Timing • Root zone/surface
• Align with plant demand – Soil sampling is the best way.
– In-season quick test: Proven and effective practice.
– Petiole sampling, not a good measure to predict future N/P applications
– Tracking amounts • w/Farm Plan!
Role of Academia: Quantifying Patterns and Processes in the Critical Zone
Off-Farm Practices
Vegetative Buffer Strips
• Sediment and nutrient trapping – 90% of the coarse textured sediment are captured within the
first 2 meters of a buffer strip.
– Infiltrating water prevents fine particle sediments from moving into adjacent surface waters.
• Pathogen and virus reduction (Entry, J. 2000. Journal of
Environmental Quality 29: 1215-1224.)
– Time(10-fold decrease/week)
– Temperature
– Moisture
Are Practices Effective at Protecting Water Quality?
Stream Channel Perched Water Table
Buffer Area
Nitrate
Groundwater wells
Surface and ground water benefits
Are Practices Effective at Protecting Water Quality?
Soil Nitrate in Vegetative Buffer Strips
Fall 95
Winter 96
Spring 96
Sum
mer 96
Fall 96
Winter 96
Spring 97
Sum
mer 97
Fall 97
Winter 98
Nitra
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Perennial
Weedy
Soil Nitrogen Dynamics Are Practices Effective at Protecting Water Quality?
Vegetative Buffer Strips
• Vegetative Buffer Strips
Construction of experimental
Denitrification Bioreactors
Chipped construction wood waste used as the carbon source
Continuous water flow through the bed, with a residence time of approximately 2 days
Tile drain sump Surface runoff pond
Bioreactors for treating tile drain effluent: Activated May 1 (site 1) or June 1, 2011
Mean NO3-N reduction per day of residence time:
- approximately 8 PPM / day in summer
- approximately 5 PPM / day in winter
Site 1: Site 2:
Courtesy of T. Hartz, R. Smith, M. Cahn
Bioreactor for treating surface runoff: Activated June 1, 2012
Mean NO3-N reduction approximately 13 PPM / day during the summer
Courtesy of T. Hartz, R. Smith, M. Cahn
For denitrification bioreactors to be practical, management practices
have to be in place to minimize the nitrate concentration of the
incoming water !
Manage Aquifer Recharge: Harkins Slough
Nitrate removal and increasing recharge to limit seawater intrusion
Nitrate Load Reductions
Rapid Infiltration
Reduce Infiltration Rate, Lower Nitrate Concentrations
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Groundwater Nitrate: Regional, State-wide, and International Issue
High level of spatial variability
Some trends exists…in some place, in some wells
Spatial Heterogeneity
• Limited Opportunity for Problem Definition Consensus
– Scientific conclusions become contested
– Selective use of data
• Inequality for stakeholders
– Public health protection is perceived to be unevenly applied
– “Market Distortions” for regulated industries
Ground Water Flow Paths: Time Lags
Temporal Heterogeneity
• Contamination in the Present Tense – Contemporary public health concerns
– Unidentified funding sources
• Liabilities for past actions – Lessons from Superfund Program
– Regulated community “digs in”
• Liabilities for future actions – “unintended” consequences (threats or realities?)
• Exporting Industry?
• Landscape change for industry
Idealized Steps Toward Ground Water Protection
Background:
• Environmental regulation has largely failed (pollution displacement, reification of scientific knowledge, etc.)
• Environmental regulators have limited tools available (and creativity is not rewarded by stakeholders)
• Few stakeholders are willing to reach toward consensus (fears of being isolated, “sell-outs”, etc), potential to become “radicalized”/marginalized, selective science, generate pendulum swings.
• Cultural lag with (heterogeneous) stakeholders
Where are we in the process?
Contaminated Drinking Water Stakeholders
Regulated Community, On-Farm Solutions, UCCE, RCD, etc.
Regulators
Academic Researchers
Harter, et al 2012
Data Collection and Analysis
Idealized Steps…
• Environmental Stakeholders – Hold regulators to the public benefit goals, avoid being
entrenched in the legal arguments.
• Regulated Stakeholders – Develop a “Strong-Sword” self-regulation structure – Promote market incentives to promote ground water
protection – Avoid scapegoating
• Regulators – Develop “deep” commitments to provide flexible and
creative approaches the empower stakeholders to improve ground water protection.
Regulatory Tools: Flexibility to address critical zone complexities
Addressing Groundwater Contamination
• Short Term – Develop cost effective
safe drinking water supplies
• Medium Term – Provide decision support
tools for stakeholders to manage groundwater protection effectively.
– Spatially focused research on “Critical Zone”
• Long-term – Create incentives to
remediate contamination (market based?)
– Capitalize (nurture?) on appropriate sustainability initiatives
Long-Term
• Market incentives to prevent future contamination and remediation.
– Public willingness to pay
– Criteria to evaluate success
– External Legitimization
Role of Academia: Quantifying Patterns and Processes in the Critical Zone
Medium-Term Strategies
Managed Aquifer Recharge
Nitrate Remediation and Ground Water Supply Banking
High Infiltration Rates are spatially and temporally
variable
Nitrate Load Reductions
Rapid Infiltration
Reduce Infiltration Rate, Lower Nitrate Concentrations
Resources (?) to Stakeholders
Decision Tools: Capture Economic Realities
Independent Audit (20% of
the participants per year)
3PG Ranks Impairment
Priorities and selects top 10%
for Practice Evaluation
High priority farms are
evaluated for practice
effectiveness
Enrolled Growers Complete or
Update Farm Water Quality Assessment
and Action Plans
Enrolled Growers Implement and Maintain
Effective Practices to Improve Water Quality documented with Farm Assessment and Action
Plan
Annual Water Quality
Improvement Cycle
Highest value for on-farm monitoring
Grower fees to build capacity to address
WQ