Nutrient Management and Edge of Field Monitoring Conference December 1-3, 2015 Memphis, TN

1. Targeted Monitoring:
Can We Monitor More Strategically
to Enable Conservation Know-How,
Help Improve Models, and Inform Policy?
Mark Tomer

2. Why monitor at the field edge?
(as opposed to watershed outlet)
 Identify effectiveness of an individual
conservation practice on runoff, nutrient
and sediment losses.
 Management system can be well
documented.
 Lag effects diminished.
 Spatial variability easier to characterize.

3. Why monitor at the field edge?
 Identify effectiveness of an individual
conservation practice on runoff, nutrient and
sediment losses. (But compared to what?)
 Management system can be well documented.
(But many management actions are tactical
adjustments to weather conditions.)
 Lag effects diminished. (But not eliminated)
 Spatial variability easier to characterize.
(But temporal variability increases)

4. Why monitor at the field edge?
 Edge of field monitoring is waiting (and
waiting…) to measure and sample rapidly
changing flows.
 Long periods of monitoring are needed to help
place into context impacts of large runoff events.

5. Yet, practices are proven through
research on conservation effectiveness:
 Conservation Reserve plantings (P, sed, herbicides)
 Controlled drainage (NO3)
 Cover crops (NO3)
 Floodwater detention structures ($ flood damage)
 Livestock (whole farm) nutrient management (P)
 No tillage and strip tillage (P, sed, runoff)
 Nutrient removal wetlands (NO3)
 Perennial crops in rotation (runoff, sed, NO3)
 Riparian buffers (P, sed, herbicides)
 Split fertilizer applications (NO3)
 Two-stage drainage ditches (NO3)
 Wood chip bioreactors (NO3)
 Saturated buffers (NO3, P)

6. Effectiveness of Practices for Nitrogen Reduction-
Results of Iowa Nutrient Reduction Strategy
Literature Review
Practice
% Nitrate‐N Reduction
[Average (Std. Dev.)]
Crop Rotation
/ Land Use
Cover Crops 31 (29)
Perennial – Land retirement 85 (9)
Living Mulches 41 (16)
Extended Rotations 42 (12)
Drainage
Management
Controlled Drainage 33 (32)*
Shallow Drainage 32 (15)*
Bioreactors 43 (21)
Downstream
Wetlands 52 (flow dependent)
Buffers 91 (20)**
*Load reduction not concentration reduction
**Concentration reduction of that water interacts with active zone below the buffer

7. Where to from here?
 Can we afford paired watershed
experiments?
 Are we still looking for the silver bullet?
 Can we shift focus to experimentally
evaluate performance of stacked
practices?

8. The problems with experimental (paired
watershed) design to assess conservation effects
1. Pretreatment calibration
(2+ years)
2. Treatment evaluation
(3+ years)
• Five years duration (minimum)
• Requires two monitoring points to answer one question
• How many fields are represented by this experiment?

9. Flow
Monitor inflow Monitor outflow
Evaluation of field edge practices
(denitrifying bioreactor example)
• Three years duration (likely minimum)
• Requires two monitoring points to answer one question
• How many locations are appropriate for this practice?
• How does in-field management impact EoF practice
performance?

10. An alternative experimental design
(twice-paired watershed experiment)
1. Implement field edge practice
and calibrate two fields (replicated
experiment, 2+ years)
2. Implement field practice
evaluate two practices
(3+ years)
• Five years duration (but useful data within 2-3 years)
• Requires four monitoring points but answers three questions
• Can pair practices that represent regional opportunities

11. Distribution of Different Types of Watersheds Across the UMORB
Schilling et al, Environmental Management, 2015

16. Ho: Effectiveness
of nutrient removal
wetlands is
influenced by
cover crops

19. Ho: Effectiveness
of denitrifying
bioreactors is
influenced by
drainage water
management

22. Ho: Effectiveness
of saturated buffer
is influenced by
contour buffer
strip placed to
intercept runoff

23. An alternative experimental design
(twice-paired watershed experiment)
1. Implement field edge practice
and calibrate two fields (replicated
experiment, 2+ years)
2. Implement field practice
evaluate two practices
(3+ years)
• Five years duration (but useful data within three years)
• Requires four monitoring points but answers three questions
• Can pair practices that represent regional opportunities

24. How to best use monitoring to assess practice
performance, test models, and inform policy?
• Field-edge monitoring has improved understanding of
conservation practice effectiveness, but has often given wide-
ranging results (large error bars)
• Monitoring is both expensive, and difficult to do well. We
should be asking how to best target monitoring efforts to
better inform policy.
• Suites of practices may be suited to different types of
landforms regions /watersheds –we can utilize this information
to better target research on conservation effectiveness.
• Few studies have addressed the effectiveness of stacked
practices. We may not reach WQ goals until we can leverage
(and model) combinations of practices.
• A twice-paired watershed experimental design is proposed to
address this knowledge gap. May inform reasons for variable
performance of practices, and provide data to test models.

25. Thanks to:
Sarah Porter
David James
Dan Jaynes