70th SWCS International Annual Conference July 26-29, 2015 Greensboro, NC

1. SHOOTING A MOVING TARGET: A
DISSOLVED PHOSPHORUS PROBLEM
PARADIGM
Rem Confesor Jr.
Laura Johnson
Dave Baker
Ken Krieger
NCWQR, Heidelberg University
310 E. Market St., Tiffin, OH
rconfeso@heidelberg.edu
Voice: 419-448-2204

2. Acknowledgment
GLRI-CSMI Grant
4R Research Project
USDA-NRCS-CIG Grant No. 69-3A75-13-216

3. 2015 Seasonal HAB forecast

4. MOTIVATION
BMPs – Best Management Practices:
Necessary for nutrient export reduction from
agricultural lands <= desired ecological
responses.
Limited funding <= targeted implementation.
Target: Critical source areas (CSAs)

5. CRITICAL SOURCE AREAs
Areas that are most vulnerable to nutrient and
sediment loss.
Identification traditionally based from risk indices,
e.g., Phosphorus Index:
TransportPollutant
Source
CSA
Critical Source Areas (CSAs) concept
A pollutant source (e.g.,
P, N, sediment) interacts
with active hydrologic
transport mechanisms.

6. CRITICAL SOURCE AREAs
Pollutant Source - depends on land use and
management: tilled land -- sediment; elevated soil
P, excessive P application -- P loss.
Transport potential - factors that affect hydrologic
path/transport mechanism:
hydrologic soil group, drainage class.
slope/terrain.
land use/cover.
hydrologic connectivity.

7. CRITICAL SOURCE AREAs
80% of the pollution comes from 20% problem area?
Acute vs. chronic sources?
Info to consider:
In the Sandusky watershed , the median M3-P soil
test at 0-1 in is ~60ppm.
NW Ohio Ag is highly-tiled system (as close as 20ft)

8. FURTHERMORE...
The pollutant source and transport potential factors
are taken into account in agricultural watershed
models (e.g., SWAT, APEX, AGNPS, etc).

9. A word of caution:
"...all models are wrong...”

10. “… the only question of interest is:
‘Is the model illuminating and useful?’”
- George E.P. Box -

11. Terrain
Weather
Soil
Land use/
crop cover Agricultural practices & mgt.:
tillage, fertilizer, etc.
Flow,
sediment,
nutrients
(N & P),
etc.
Main SWAT Components

12. APPROACH
Implement a highly detailed Soil and Water
Assessment Tool (SWAT) model setup
OBJECTIVES
1.Identify CSAs.
2.Evaluate the characteristics of these CSAs.

13. Digital elevation model
(slope/terrain)
Land use/
crop cover
Soil type
+
+
The hydrologic response unit (HRU)- SWAT’s basic spatial
unit: unique combination of slope, landuse, & soil.

14. HRU CAVEAT

15. 2008
2009
2010
2011Soybean
Soybean
corn
corn
4-Yr (2008 to 2011) crop rotation in a selected hru:
CORN-SOYBEAN-CORN-SOYBEAN
Based from USDA Crop Data Layer

16. SWAT SETUP
Project Area/Watershed
Sandusky Watershed, northwest Ohio.
Area: 1250 mi2 = 3236 km2 at USGS gage
station in Fremont, OH
Sub-basin/HRU Delineation
373 Sub-basins
4350 (40/20/20 ha) HRUs
ArcSWAT2009; SWAT2009 rev 488

17. SWAT SETUP: Management practices
Corn
Fall Tillage Chisel Plow GE 23 ft
Fall Fertilizer 11-52-00 (115 kg/ha, 0.2 frt_sur)
Late April-Early May Fertilizer Anh. NH4 (100 kg/ha, 0.05 frt_sur)
Mid Apr-Mid May Plant Corn
1 month after plant Fertilizer Anh. NH4 (120 kg/ha, 0.05 frt_sur)
5 months after plant +/- 5 days Harvest and Kill
Corn doubled with soy
Fall Tillage Chisel Plow
Fall Fertilizer 11-52-00 (210 kg/ha, 0.2 frt_sur)
Late April-Early May Fertilizer Anh. NH4 (100 kg/ha, 0.05 frt_sur)
Mid Apr-Mid May Plant Corn
1 month after plant Fertilizer Anh. NH4 (100 kg/ha, 0.05 frt_sur)
5 months after plant +/- 5 days Harvest and Kill
Late Spring Plant SOY
5 months after plant +/- 10 days Harvest and Kill

18. SWAT SETUP: Management practices
Soybeans
Winter wheat
Late Apr to Mid-May Plant SOY
Mid Apr Fertilizer 11-52-00 (95kg/ha, 1 frt_sur)
5 months after plant +/- 10 days Harvest and Kill
Mid October Fertilizer 18-46-00 (130 kg/ha, 0.2 frt_sur)
Mid/Late October Plant WWHEAT
Late March Fertilizer 46-00-00 (210 kg/ha, 0.2 frt_sur)
Early-Late July Harvest and Kill

19. SOME RESULTS…

20. Water Year
2008 2009 2010 2011
Annualwateryield,cm
0
25
50
75
Water Yield

21. Simulated annual dissolved P exports
2008 2009

22. Simulated annual dissolved P exports
2009 2010

23. Simulated annual dissolved P exports
2010 2011

24. Simulated
annual
dissolved
P exports
2008 2009
2010 2011

25. Simulated annual dissolved P exports, kg/ha
2008 2009
2010 2011

26. Simulated
annual
sediment
yield
2008 2009
2010 2011

27. Management practices
CPBCast CPInject MPInject No_Till NTBCast NTInject
ChangeinSRPexport,kg/ha-yr
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
Several Scenarios
Baseline reference

28. SUMMARY/TAKE HOME
Critical areas are changing with time and space.
Traditional concept of CSA may not be
applicable to NW OH (Tile drain connectivity)
Targeting CSAs may not be enough to attain load
reduction goals.
Watershed-wide implementation of “cultural”
(e.g. 4R) BMPs rather than structural is needed.

29. NEXT STEPS/ONGOING
Convert to SWAT2012.
Update to include 2014 (2008-2014).
Include point sources.
Implement in the Maumee watershed.
More BMP scenarios.
Climate Change?

30. Rem Confesor Jr.
National Center for Water Quality Research
Heidelberg University
310 E. Market St., Tiffin, OH
rconfeso@heidelberg.edu
Voice: 419-448-2204
THANKS!!!