For more: http://www.extension.org/67691 Water management in the crop root-zone is crucial to successful crop growth and production. Irrigation, surface, and subsurface drainage—and other practices—are routinely implemented throughout the world to improve crop productivity and working conditions of the soil. Water management practices also impact the environmental footprint of agricultural systems by affecting the flow of water, nutrients, sediment, and other constituents through field, farms, and watersheds. Water management practices for agriculture in the Midwestern US should be designed with both profitability and the environment in mind. The design of subsurface (tile) drainage systems has traditionally been more a matter of how much drainage one can afford, rather than the aforementioned objectives. The relationship among subsurface drainage design characteristics (depth, spacing, layout), farm profitability, and environmental impact are not well known at the farm scale. Thus, drainage system design may fail to meet one or more of these important objectives. This presentation will examine the effects of subsurface drainage system design criteria on productivity, profitability, and the environment, using the soils and climatic conditions of the northern corn-belt (southern Minnesota). Water management in the crop root-zone is crucial to successful crop growth and production. Irrigation, surface, and subsurface drainage—and other practices—are routinely implemented throughout the world to improve crop productivity and working conditions of the soil. Water management practices also impact the environmental footprint of agricultural systems by affecting the flow of water, nutrients, sediment, and other constituents through field, farms, and watersheds. Water management practices for agriculture in the Midwestern US should be designed with both profitability and the environment in mind. The design of subsurface (tile) drainage systems has traditionally been more a matter of how much drainage one can afford, rather than the aforementioned objectives. The relationship among subsurface drainage design characteristics (depth, spacing, layout), farm profitability, and environmental impact are not well known at the farm scale. Thus, drainage system design may fail to meet one or more of these important objectives. This presentation will examine the effects of subsurface drainage system design criteria on productivity, profitability, and the environment, using the soils and climatic conditions of the northern corn-belt (southern Minnesota).

1. Designing Subsurface Drainage Systems
to Meet Both Profitability &
Environmental Goals
Gary R. Sands
Professor & Extension Engineer

2. Drainage pipes
or “tile”
Flow to main
or ditch

5. Hypoxia & WQ Flooding & Hydrology
Habitat Loss & Alteration

6. Golden Rule of Drainage
Drain only what is necessary for good soil conditions and
crop growth – and not a drop more
Production Environment
R. Wayne Skaggs

7. Benefits
Capital Cost
Net Return
Annual Nitrate Loss or
Drainage Volume

8. Drainage Depth is Important

10. Drainage Design Support Tool
• Illustrate effects of
drainage design
choices
• Facilitate compromise
between profitability
& environment

11. Simulation Approach
• DRAINMOD 6.0
• 100-yr Simulations
• “Benchmark” soils
• Multiple locations (S and NW Mn)
• Use outputs for spreadsheet decision
support tool

12. Drainage Design Matrix
(every soil x location)
Drain Spacing (cm)
Drain
Depth
(cm)
4500 4050 3450 2850 2250
90
6.3
mm/day
105
120
135 12.7
mm/day

13. DRAINMOD Outputs
148 133 113 94 74
90 12.4 12.7 13.2 13.8 14.1
105 12.9 13.2 13.6 14.1 14.6
120 13.5 13.7 14.0 14.3 14.8
135 13.9 14.0 14.4 14.7 15.1
Drained Volume (cm)
Drain Spacing (ft)
Drainage Depth (cm)
Drain Spacing (ft) Undrained 148 133 113 94 74
Drainage Depth (cm)
90 15.0 3.6 3.4 3.1 2.8 2.8
105 15.0 3.0 2.9 2.6 2.4 2.1
120 15.0 2.5 2.3 2.2 2.0 1.8
135 15.0 2.0 1.9 1.7 1.6 1.5
Runoff Volume (cm)
Undrained 148 133 113 94 74
90 42.6 83.2 86.1 89.7 93.1 95.9
105 42.6 89.8 92.0 94.5 96.5 97.9
120 42.6 93.4 94.9 96.6 97.9 98.8
135 42.6 95.8 96.9 98.1 98.8 99.2
Relative Crop yield (%)
Drain Spacing (ft)
Drainage Depth (cm)

14. Undrained 148 133 113 94 74
90 42.6 83.2 86.1 89.7 93.1 95.9
105 42.6 89.8 92.0 94.5 96.5 97.9
120 42.6 93.4 94.9 96.6 97.9 98.8
135 42.6 95.8 96.9 98.1 98.8 99.2
Relative Crop yield (%)
Drain Spacing (ft)
Drainage Depth (cm)
148 133 113 94 74
90 12.4 12.7 13.2 13.8 14.1
105 12.9 13.2 13.6 14.1 14.6
120 13.5 13.7 14.0 14.3 14.8
135 13.9 14.0 14.4 14.7 15.1
Drained Volume (cm)
Drain Spacing (ft)
Drainage Depth (cm)
Drain Spacing (ft) Undrained 148 133 113 94 74
Drainage Depth (cm)
90 15.0 3.6 3.4 3.1 2.8 2.8
105 15.0 3.0 2.9 2.6 2.4 2.1
120 15.0 2.5 2.3 2.2 2.0 1.8
135 15.0 2.0 1.9 1.7 1.6 1.5
Runoff Volume (cm)

15. Design Objectives
• Maximize profitability (P)
• Minimize environmental (E)
response (e.g., drained vol, runoff
vol, N-loss)
• Look for opps to reduce E w/o
compromising P, or
• Look for opps to increase P w/o
compromising E

16. Spreadsheet Design Tool
Location 3
Soil 6
Installation cost per acre ($) $650
Acres Drained 160
Yield Potential (well drained) (bu) 210
Corn Price: ($/bu) $6.40
User Inputs
Acknowledgement
This project was supported by a
grant from the MinnesotaCorn
Research & Promotion Council
• User provides general
inputs
• Profitability based on
IRR
• DRAINMOD output
embedded

17. Standardized Model Outputs
(Profitability)

18. Standardized Model Outputs
(Drainage Volume—or Nitrate)

19. Standardized Model Outputs
(Surface Runoff)

20. Drainage Design Indices
• Index 1 =
P∗
D∗ • Index 2 =
P∗
D∗× R∗

21. Index 1 =
P∗
D∗

22. Index 2=
P∗
D∗× R∗

23. HYDRO EFFECTS
Other DRAINMOD Approaches

24. Mean Daily Runoff w/90% CL – No Drainage
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 31 61 91 121 151 181 211 241 271 301 331 361
MeanDailyUndrdainedRunoffVol(cm)
Bearden Soil – Crookston (99 yr)

25. Mean Daily Drainage at 0.5 in/day w/90% CL
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 31 61 91 121 151 181 211 241 271 301 331 361
MeanDailyDrainageVolume(cm)
Bearden Soil – Crookston (99 yr)

26. 0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 31 61 91 121 151 181 211 241 271 301 331 361
MeanDailyDrainedRunoffVol(cm)
Bearden Soil – Crookston (99 yr)
Mean Daily Runoff Post-Drainage w/90% CL

27. Mean Daily Drainage & Post-drainage Runoff
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 31 61 91 121 151 181 211 241 271 301 331 361
WeeklyDrainage&RunoffVols(cm)
Bearden Soil – Crookston (99 yr)

28. Mean Daily Water Yield: Pre- and Post-Drainage
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 31 61 91 121 151 181 211 241 271 301 331 361
WeeklyDrainage&RunoffVols(cm)
Bearden Soil – Crookston (99 yr)

29. 0%
20%
40%
60%
80%
100%
0
2
4
6
8
10
12
1 31 61 91 121 151 181 211 241 271 301 331 361
CumDailyWaterYield&Runoff(UD)(cm)
Post-Drainage Water Yield (D + RO)
Pre-Drainage Water Yield (RO)
Bearden Soil – Crookston (99 yr)

30. Mean Daily Water Yield: Pre- and Post-Drainage
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
1 31 61 91 121 151 181 211 241 271 301 331 361
WeeklyDrainage&RunoffVols(cm)
Fargo Soil – Fergus Falls (99 yr)

31. Post-Drainage Water Yield (D + RO)
Fargo Soil – Fergus Falls (99 yr)
0%
20%
40%
60%
80%
100%
0
2
4
6
8
10
12
14
16
1 31 61 91 121 151 181 211 241 271 301 331 361
CumDailyWaterYield&Runoff(UD)(cm)
Pre-Drainage Water Yield (RO)

32. OUTPUTS ON A WEEKLY BASIS

33. Bearden Soil – Crookston (99 yr)

34. Bearden Soil – Crookston (99 yr)

35. Bearden Soil – Crookston (99 yr)

36. 0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51
WeeklyDrainage&RunoffVols(cm)
Bearden Soil – Crookston (99 yr)

37. Fargo Soil – Fergus Falls (99 yr)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51
WeeklyDrainage&RunoffVols(cm)

38. In Summary …
• Investments in agricultural drainage will
likely continue.
• Opportunities likely exist to balance
profitability and environmental goals
through design.
• Achieving these goals requires making
prudent choices among drainage rate,
drainage spacing, and drainage depth.
• More work is required to better predict
crop yield & ET responses from
subsurface drainage.

39. Thank You!
Gary R. Sands
grsands@umn.edu
www.DrainageOutlet.umn.edu