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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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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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

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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