This presentation will review the issues involved with nitrate nitrogen export from agricultural subsurface drainage (tile).

1. Subsurface Drainage & Water Quality
Bruce Atherton, P.E.
Agribusiness Showcase & Conference Agricultural Engineer
February 7, 2012 NRCS, Ankeny, Iowa

2. Subsurface Drainage and Water Quality
 Review effects of agricultural subsurface drainage
 Review nutrient levels in streams, especially nitrates
 Review strategies to reduce nitrate export from field to
stream and the effectiveness of each
 Look at NRCS cost-share and payment rates
 Reminder of Conservation Compliance

3. BENEFITS OF CROPLAND
DRAINAGE
 Remove excess water
 Improve crop rooting environment
 Enhanced soil warming
 Improved trafficabilty
 More timely field operations
 Earlier planting date
 Reduce soil compaction
 Increase nitrogen availability and
efficiency
 Save energy
 Reduce runoff and erosion
 Reduce flooding potential
 Increase yields and income

4. Background
Bars Indicate Shading
Relative Crop Indicates
Yield Reduction in
Increase with Year-to-Year
Drainage Variability in
Improvement Crop Yields

5. Subsurface Drainage in Iowa
 Estimates for Iowa
 36 million acres of land
 23 million acres of row crops
 9 million acres with artificial subsurface drainage
(742,500 miles at 100 foot spacing)
 6 million acres in 3000+ organized drainage districts
Source: Baker, et al. 2004. Subsurface Drainage in Iowa and the Water Quality Benefits and Problem

6. Environmental Effects of Subsurface Drainage
• Compared to undrained agricultural land, improved
subsurface drainage can (at the field level)
• Reduce the peak runoff rate 15 to 30%
• Reduce the total surface runoff that leaves the site 29 to 65%
• Reduce sediment losses by 16-65%
• Reduce the loss of phosphorus up to 45%
• Reduce the loss of soil-bound nutrients 30 to 50%
• Increase NO3-N losses
Source: Zucker, L.A. and L.C. Brown (Eds.). 1998. Agricultural Drainage: Water Quality Impacts and Subsurface
Drainage Studies in the Midwest. Ohio State University Extension Bulletin 871. The Ohio State University.

7. Change in Nitrate Concentrations
in Midwest Rivers
In the 20th century there
were changes in:
• land use / cropping
• fertilizer use
• improved drainage
Source: Goolsby, D.A. and W.A. Battaglin. 2000. Nitrogen in the Mississippi Basin-Estimating Sources and Predicting Flux to the Gulf of Mexico

8. River Nitrate Levels
(Concentration is important for drinking water suppliers)
Iowa River at Gifford
16
14
12
Nitrate + Nitrite (mg/L)
10
8
6
4
2
0
EPA Drinking Water Standard Trendline
Source: Mary Skopec, Ph.D., IOWATER & Stream Monitoring Coordinator, Iowa DNR. Personal Communicatoin, December 2011.

9. Gulf Hypoxia
(Load is also important)
2002 estimated
nitrate/nitrite loading:
960,000 metric tons
(12th highest in 22 yrs)

10. Gulf Hypoxia Action Plan
Nutrient Reduction Goals
 Current (2003-2007) average hypoxic zone is
14,644 km2
 Goal is 5,000 km2 hypoxic zone (5-yr average)
 Strategy is a target nutrient reduction of:
 45% reduction in total nitrogen flux
 45% reduction in total phosphorus flux
(Measured against average 1980 - 1996 levels)
Source: Draft Hypoxia 2008 Action Plan, November 9, 2007

11. Gulf Hypoxia
Changes in Nutrient Loading
 Annual loads from 2001-2005 time period
(Measured against average 1980 - 1996 levels)
 21% reduction in total nitrogen flux
 12% increase in total phosphorus flux
 Current load estimates by source
 Point sources - 22% of N loads, 34% of P loads
 Point sources - higher share than earlier estimates
Source: Draft Hypoxia 2008 Action Plan, November 9, 2007

12. Gulf Hypoxia
Nutrient Reduction Strategies
 USDA will place additional emphasis on
conservation practices with high potential for
reducing nutrient loadings, such as
 nutrient management
 cover crops
 siting of wetlands
 on-farm drainage water management
Source: Draft Hypoxia 2008 Action Plan, November 9, 2007

13. Variability in Drainage, Nitrate
Concentration and Nitrate Loss
Nitrate-nitrogen Concentration (ppm)
30 Drainage 30 80
Nitrate-nitrogen Loss (lb-N/ac)
Nitrate-N Concentration
25 Nitrate-N Loss 25
60
Drainage (in)
20 20
15 15 40
10 10
20
5 5
0 0 0
19 0
19 1
19 2
19 3
19 4
19 5
19 6
19 7
19 8
20 9
20 0
20 1
20 2
20 3
er 4
e
9
9
9
9
9
9
9
9
9
9
0
0
0
0
Av 0
ag
19
Corn-Soybean Rotation 150/160 lb-N/acre Application Rate
Source: Slide courtesy of Matt Helmers, Ph. D., ISU Extension Agricultural Engineer
Data based on a research study at Gilmore City, Iowa

14. Nutrient Reduction Strategies
• Nutrient management
• Cropping changes
• Cover crops
Photo by Lynn Betts, USDA-NRCS
Photo by Lynn Betts, USDA-NRCS
• Constructed Wetlands
• Bioreactors
Photo Courtesy of IDALS • Drainage design
• Drainage water management Photo courtesy The Ohio State University
Photo by Bruce Voights, Wright SWCD

15. Agronomic Strategies
 Nutrient management
 Reduced tillage
 Cropping changes
 Cover crops

16. Nutrient management effects
 Some NO3-N loss will occur even with no N application
 Increased soil NO3-N resulting from large N applications appears
to be buffered by large amount of NO3-N naturally present in soil
 In one Iowa study, NO3-N concentrations were not higher for fall
applied N
 Split N applications during the growing season have not shown
large or consistent reduction in NO3-N concentrations in
drainage water
Source: Baker, et al. 2004. Subsurface Drainage in Iowa and the Water Quality Benefits and Problem.
In: Proceedings of the Eighth International Drainage Symposium, March 21-24, 2004.

17. Impact of Nitrogen Application Rate
Source: Slide courtesy of Matt Helmers, Ph. D., ISU Extension Agricultural Engineer
Data based on a research study at Gilmore City, Iowa

18. Nitrate-N Concentration as a
Function of Nitrogen Application
Source: Slide courtesy of Matt Helmers, Ph. D., ISU Extension Agricultural Engineer
Data based on a research study at Gilmore City, Iowa

19. Impact of Nitrogen Application Rate
~15% Reduction
Source: Slide courtesy of Matt Helmers, Ph. D., ISU Extension Agricultural Engineer
Data based on a research study at Gilmore City, Iowa

20. Tillage Effects
 Study of four tillage systems in NW Iowa
• NO3-N concentrations in moldboard- and chisel-plowed fields
averaged 30-50% higher than for flat and ridged no-till fields.
(C-Sb rotation)
• In continuous corn, losses from no-till fields were about the
same as for plowed field because of increased flow.
 Differences may be due to:
• Change in volume and route of infiltration
• Difference of N mineralization
Source: Baker, et al. 2004. Subsurface Drainage in Iowa and the Water Quality Benefits and Problem.
In: Proceedings of the Eighth International Drainage Symposium, March 21-24, 2004.

21. Crop Effects
 NO3-N concentration in shallow saturated soils
• 0.2 mg/L – native grass in RR right-of-way
• >10 mg/L – row crop field < 20’ away
 Studies in Iowa showed much reduced NO3-N concentrations
for alfalfa, CRP, and small grains
 A Minnesota study showed an 90% reduction in NO3-N
leaching losses with CRP
 Another study of alfalfa or alfalfa/grass vs. C-Sb rotation
showed 96% reduction in NO3 lost in subsurface drains
Source: Baker, et al. 2004. Subsurface Drainage in Iowa and the Water Quality Benefits and Problem.
In: Proceedings of the Eighth International Drainage Symposium, March 21-24, 2004.

22. Cover Crops Effects
 Iowa study, C-Sb rotation, rye planted each year
 Canisteo and Nicollet soils in Boone Co.
• Significantly reduced subsurface drainage water NO3
concentrations and NO3 loads in all 4 years
• 4-year average reduction in NO3 concentration was 59%
• 4-year average reduction in NO3 load was 61%
• Corn yield reduction in 2002 but not 2004
• No Soybean yield reduction
Source: Kaspar et al. 2007. Rye Cover Crop and Gamagrass Strip Effects on NO 3
Concentration and Load in Tile Drainage. J. Environ. Qual. 36:1503-1511.

23. Nutrient Reduction Strategies
• Nutrient management
• Cropping changes
• Cover crops
Photo by Lynn Betts, USDA-NRCS
Photo by Lynn Betts, USDA-NRCS
• Constructed Wetlands
• Bioreactors
Photo Courtesy of IDALS • Drainage design
• Drainage water management Photo courtesy The Ohio State University
Photo by Bruce Voights, Wright SWCD

24. Constructed Wetlands
 Remove nitrogen through denitrification
• Studies show average total nitrogen removal ranges
from 37% to 65%
Photo by Bruce Atherton, Iowa NRCS
Source: Appleboom, T.W., and J.L. Fouss. 2004. Methods for removing Nitrate Nitrogen from Agricutlural
Draiange Waters: A Review and Assessment. ASABE Paper No. 062328. St. Joseph, MI: ASABE.

25. Constructed Wetlands
 Iowa Conservation Reserve Enhancement Program (CREP)
 Research at Iowa State University has shown that wetlands
meeting CREP requirements will remove 40-90% of the nitrate
received
 The area of these wetlands is 0.5 % to 2% of the contributing
watershed area
Photo by Bruce Atherton, Iowa NRCS

26. Drainage Water Treatment
Woodchip Bioreactor
Nitrate-nitrogen is
removed from the
drainage water by
denitrification in
which nitrate is
converted to mostly
nitrogen gas
Design by Richard Cooke, University of Illinois
Source: Christianson, Laura and Matthew Helmers. 2011. Woodchip bioreactors for nitrate in agricultural
drainage. Iowa State University Extension Publication. PMR 1008.
Available at: https://store.extension.iastate.edu/ItemDetail.aspx?ProductID=13691.

27. Bioreactors
 Several Bioreactors
have been installed in
Iowa, many with financial
assistance from the Iowa
Soybean Association
 Bioreactors are eligible
for NRCS funding
assistance (EQIP)
 Nitrate reduction varies
from 10% to
90+%, averages ~35-
40%
 Still in research & Photo by Bruce Voights, Wright SWCD
demonstration stage

28. Nutrient Reduction Strategies
• Nutrient management
• Cropping changes
• Cover crops
Photo by Lynn Betts, USDA-NRCS
Photo by Lynn Betts, USDA-NRCS
• Constructed Wetlands
• Bioreactors
Photo Courtesy of IDALS • Drainage design
• Drainage water management Photo courtesy The Ohio State University
Photo by Bruce Voights, Wright SWCD

29. Golden Rule of Drainage
Only release the amount of water necessary to
insure trafficable conditions for field operations and
to provide an aerated crop root zone
any drainage in excess of this rule likely carries
away nitrate and water that is no longer available
for crop uptake - Attributed to Wayne Skaggs
Precision drainage?

30. Drain Design Modifications
 Decrease drainage intensity
• Wider spacing
• Shallower depths
 Drainage Water Management
Source: Appleboom, T.W., and J.L. Fouss. 2004. Methods for removing Nitrate Nitrogen from Agricutlural
Draiange Waters: A Review and Assessment. ASABE Paper No. 062328. St. Joseph, MI: ASABE.

31. Hydrological modifications of subsurface (tile) drainage systems to reduce
Subsurface Drainage Types
subsurface drainage from Iowa’s tile landscapes:-
Conventional Drainage
Free Outlet
Shallow Drainage Controlled Drainage

32. Subsurface (tile) Drainage System : Representation
in DRAINMOD
Evapotranspiration Evapotranspiration
Precipitation Precipitation
Surface runoff Surface runoff
Lateral Water table Lateral
seepage seepage
Drain Drain
Subsurface drainage Subsurface drainage
Vertical seepage
Impermeable layer

33. Shallow Drainage
 Minnesota Research
 15% reduction in nitrate loss
 As high as 40% on some plots
 15-40% water conserved
 No yield changes observed
Source: Gary Sands, P.E.

34. Nitrate Loss & Drain Depth
Source: Illinois Drainage Guide (online). http://www.wq.uiuc.edu/dg/

35. Hydrological modifications of subsurface (tile) drainage systems to reduce
Subsurface Drainage Types
subsurface drainage from Iowa’s tile landscapes:-
Conventional Drainage
Free Outlet
Shallow Drainage Controlled Drainage

36. Drainage Water Management
(Controlled Drainage)
 Since 1984, over 4000 water control structures affecting about
400,000 acres have been installed in North Carolina.
 Conservative estimates based on results of research indicate that
these systems, properly managed, reduced N losses to coastal
streams and estuaries by 4 million pounds annually.
 Research in North Carolina (1990-2010) showed:
 Controlled drainage plots on both sites experienced significant (10.4%) corn yield
increases compared to the free drainage plots.
 No significant change in wheat yields was observed under CD.
 Soybean yield increased in all years.
 Research in the Midwest has failed to show significant yield
increases
Source: C.A. Poole et al. 2011. The Effects of Drainage Water Management on Crop Yields in Eastern
North Carolina. ASABE Paper No. 1111599. St. Joseph, MI: ASABE.

37. Drainage Design
The Influence of Slope
Raised Water Table
Tile
Riser Boards (Adjustable)
The water level control device place in a tile line. The area impacted is a function of
the slope of the field. The flatter the field the greater the area impacted.

38. Typical layout of subsurface drainage system
Image courtesy of Agri Drain Corp.

39. Idealized drain layout for drainage water management (DWM)
Drain laterals laid on contour to maximize area in management zone
Image courtesy of Agri Drain Corp.

40. Seasonal Water Table Management
Non-growing season
Raise to near the surface
Growing season
Raise to hold water, but
manage for plant health
Drain Watertable
Planting
Harvest
Lower water
Lower water
table for
table if needed
trafficability
for trafficability
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Source: Gary Sands, P.E.

41. Seasonal Water Table Management
Source: Illinois NRCS

42. Managing the Water Table
ISU Research – Crawfordsville, Iowa
0
Depth of Drain Outlet Level
Below Ground Surface (in)
10 Outlet Setting
20
30
40
7
8
9
07
07
07
08
08
08
09
09
09
10
/0
/0
/0
1/
1/
1/
1/
1/
1/
1/
1/
1/
1/
/1
/1
/1
1/
4/
7/
1/
4/
7/
1/
4/
7/
1/
10
10
10
Source: Helmers, Matt. July 2010. Personal Communication

43. Managing the Water Table
ISU Research – Crawfordsville, Iowa
0
Outlet Level
Depth of Drain Outlet Level
Below Ground Surface (in)
Depth to water table mid-way between drains
10
20
30
40
7
8
9
07
07
07
08
08
08
09
09
09
10
/0
/0
/0
1/
1/
1/
1/
1/
1/
1/
1/
1/
1/
/1
/1
/1
1/
4/
7/
1/
4/
7/
1/
4/
7/
1/
10
10
10
Source: Helmers, Matt. July 2010. Personal Communication

44. DWM Example of Area Controlled
Water Control
structure set just
below 1128
contour.
Shaded area
includes the area
between 1128
and 1130
contours.

45. Drainage Water Management
Drainage Water Management - Drain layout at a Minnesota site
Source: Agriculture Drainage Management Drainage Coalition; http://www.admcoalition.com/

46. Drainage Water Management
Southeast Iowa Research
 Drainage water management through controlled or shallow drainage
significantly reduced overall drainage by 30 to 40%
 Nitrate load reduction closely follows the drainage reduction
 Implies the nitrate load can be reduced 30-40%
 Water table response was quick with drawdown to tile depth within 2
to 3 days after significant rain events
Source: Helmers, et al. 2010. Water Table Response to Drainage Water Management in Southeast Iowa
ASABE Paper No. IDS-CSBE100138. St. Joseph, MI: ASABE.

47. Wetland-Reservoir-Subirrigation (WRSIS)
A WRSIS is a water
management system to
collect subsurface drainage
and runoff, treat this water
in a constructed wetland,
and store the treated water
in a reservoir for
subsequent use for
subirrigation during drier
parts of the growing
season.
Source: http://www.ars.usda.gov/Research/docs.htm?docid=14999&page=9
Accessed January 18, 2008.

48. WRSIS Benefits
Potential benefits of this system inlcude:
(1) enhanced crop yields,
(2) reduced offsite release of nutrients, pesticides, and sediment,
(3) additional wetland vegetation and wildlife habitat,
(4) more carbon sequestration in soil, and possibly,
(5) decreased flooding potential downstream
Marsh Foundation WRSIS site in Van Wert Co., Ohio
Source: http://www.ars.usda.gov/Research/docs.htm?docid=14999&page=9
Accessed January 18, 2008.

49. WRSIS Yield Benefits
As of 2006, at 3 sites, 1996-
2006 WRSIS subirrigated
yield increases for corn and
soybeans, respectively,
were :
30.8% and 26.0% during
drier growing seasons
13.3% and 6.9% during near
average to wetter growing
seasons
Schematic of a WRSIS site in Fulton Co., Ohio
18.1% and 13.0% overall.
Source: http://www.ars.usda.gov/Research/docs.htm?docid=14999&page=9
Accessed January 18, 2008.

50. Schematic of nitrogen transformation and
retention in a riparian buffer.
plant uptake
denitrification
filtering
interflow leaching
Tile
Source: Slide provided by Dan B. Jaynes, USDA-ARS-National Laboratory for Agriculture and the Environment
January 2012.

51. Question:
 Could reconnecting tile flow to riparian buffers remove
substantial amounts of nitrate before it reaches surface
waters?
Source: Slide provided by Dan B. Jaynes, USDA-ARS-National Laboratory for Agriculture and the Environment
January 2012.

54. Induced interflow
a) Enhanced uptake b) Enhanced denitrification
c) Surface discharge d) Channel slumping
Source: Slide provided by Dan B. Jaynes, USDA-ARS-National Laboratory for Agriculture and the Environment
January 2012.

56. Saturated Buffer Summary
•1st year shows re-saturating riparian buffers can remove
all the nitrate that is diverted into them.
•We were able to divert about 60% of the flow from a tile
draining about 50 ac of field
•The cost of the practice is comparable to other N
removal practices
•Practice shows potential of preventing > 11 million lbs of
N from entering IA streams each year
•Currently expanding study by re-saturating 3 new sites
in each of IA, IL, and IN (CIG – ADMC).
Source: Slide provided by Dan B. Jaynes, USDA-ARS-National Laboratory for Agriculture and the Environment
January 2012.

57. Summary
Approach Nitrate Limitations
Reduction
Nutrient 0 – 15% Most reductions already
management obtained
No-till vs. 30 – 50% Acceptance
conventional (C-Sb)
No-till vs. ~ 0% No advantage
conventional (C-C)
Alfalfa/Grass/CRP ~ 90% Economics
vs. row crop
Rye cover crop > 50% Additional expense, trips
Allelopathic effects on corn
Timeliness at harvest

58. Summary (Cont)
Approach Nitrate Reduction Limitations
Constructed 37 – 65% Topography
Wetlands
Bioreactors 10 – 90% Expense
More research needed
Drain intensity ~15% up to 40% Topography
(design) New systems only
Drainage Water ~ 50% (but maybe not in Topography
Management Iowa) Seasonal flow
Saturated Buffers ~60% (one site, one year) Limited Research

59. NRCS Financial Assistance
Cover Crop
Practice Code 340
 Crops including grasses, legumes, and forbs planted for seasonal
cover and other conservation purposes.
 EQIP payment rate for 2012 is about $19.99 (oats) to $27.08 (rye)
per acre
 Rates may be higher for historically underserved persons and for
initiative projects.

60. NRCS Financial Assistance
Bioreactor
Practice Code 747
 A structure containing a carbon source (wood chips) to treat
subsurface drainage outflow.
 EQIP payment rate for 2012 is about $4000 each
 Rates may be higher for historically underserved persons and for
initiative projects.

61. NRCS Financial Assistance
Drainage Water Management Plan
Conservation Activity Plan - 130
 Plan is completed by a certified Technical Service Provider (TSP)
who is paid by the farmer
 Each plan is for one field
 Plan includes
 A topographic survey of the field
 Location of the control structures the controlled zones
 Description of when and how to adjust the stop boards
 EQIP payment rate for 2012 is about $1400 - $1600 per plan
 Rates may be higher for historically underserved persons and for
initiative projects.

62. NRCS Financial Assistance
Structure for Water Control
Practice Code 587
 Installation of a water control structure in a drainage system (for
example, an Agridrain inline control structure)
 Payment is for each structure
 EQIP payment rate for 2012 is about $1000 for a structure 10” or
smaller
 EQIP payment rate for 2012 is about $1400 for a structure 12” or
larger
 Rates may be higher for historically underserved persons and for
initiative projects.

63. NRCS Financial Assistance
Drainage Water Management
Practice Code 554
 This is the annual management of the control structures in a field
with a drainage water management plan
 Farmer adjusts stop boards and records settings
 EQIP payment rate for 2012 is about $5.05 per acre
 Rates may be higher for historically underserved persons and for
initiative projects.

64. Mississippi River Basin
Healthy Watersheds Initiative

65. Mississippi River Basin
Healthy Watersheds Initiative
 13 state effort
 $80,000,000 per year for 4 years (authorized)
 In Iowa there are 13 projects in 6 watersheds
 Fiscal year 2010 - $1.35 million for 45 contracts
 Fiscal year 2011 - $6 million obligated for 155 contracts

66. Farm Bill Compliance
•When producing an annual agricultural commodity, USDA
program participants must apply an approved conservation
system that meets the substantial reduction or no substantial
increase definitions, (see NFSAM, Part 512, Subpart A,
Paragraph 512.01(e).)
•To maintain eligibility, participants must also certify that they have
not produced crops on converted wetlands after December 23,
1985, and did not convert a wetland after November 28, 1990, to
make agricultural production possible.
•NRCS will determine whether land contains areas that are
classified as a wetland type.
Ref: National Food Security Act Manual, Fourth Edition, January 2008. 510.02, 510.12

67. Wetland Delineation Process
(abridged)
 Producer requests wetland determination via form AD-1026
• Or, NRCS responds to a whistleblower complaint
 NRCS personnel determine if sampling units in a field , either
cropland or non-cropland, meet the definition of wetlands
• Hydrophytic vegetation, hydric soils, hydrology
 The Food Security Act wetland type is determined. If site is altered
by drainage, an exemption may be granted. Labels may include:
• W – Wetland or NW – Non-wetland
• PC – Prior converted cropland
• FW – Farmed wetland
• FWP – Farmed wetland pasture
 Farmer is notified of decision and has a right to appeal

68. Allowable Maintenance Actions
Allowable Maintenance
 (1) Maintenance or improvement of drainage systems is allowable on all
prior converted (PC) cropland as long as adjacent wetlands are not
adversely affected.
 (2) On farmed wetland (FW) and farmed wetland pasture and hayland
(FWP), manipulation that exceeds the scope and effect of the original
manipulation will result in ineligibility for USDA program benefits.
Ref: National Food Security Act Manual, Fourth Edition, January 2008. 516.12

69. Contact information:
Bruce Atherton, P.E.
Agricultural Engineer
USDA-NRCS
1513 N. Ankeny Blvd., Ste. 3
Ankeny, IA 50023-4167
Ph: 515-964-1883
Fax: 515-964-8613
Email: bruce.atherton@ia.usda.gov
USDA is an Equal Opportunity Provider
and Employer