the role of drainage depth and intensity on hydrology and nutrient loss in the cornbelt
DESCRIPTION
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).TRANSCRIPT
Designing Subsurface Drainage Systems to Meet Both Profitability &
Environmental Goals
Gary R. Sands Professor & Extension Engineer
Drainage pipes
or “tile”
Flow to main
or ditch
Hypoxia & WQ Flooding & Hydrology
Habitat Loss & Alteration
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
Benefits
Capital Cost
Net Return
Annual Nitrate Loss or
Drainage Volume
Drainage Depth is Important
Drainage Design Support Tool
• Illustrate effects of drainage design choices
• Facilitate compromise between profitability & environment
Simulation Approach
• DRAINMOD 6.0
• 100-yr Simulations
• “Benchmark” soils
• Multiple locations (S and NW Mn)
• Use outputs for spreadsheet decision support tool
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
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)
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)
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
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
AcknowledgementThis project was supported by a grant from the Minnesota Corn Research & Promotion Council
• User provides general inputs
• Profitability based on IRR
• DRAINMOD output embedded
Standardized Model Outputs (Profitability)
Standardized Model Outputs (Drainage Volume—or Nitrate)
Standardized Model Outputs (Surface Runoff)
Drainage Design Indices
• Index 1 =P∗
D∗ • Index 2 =
P∗
D∗× R∗
Index 1 =P∗
D∗
Index 2= P∗
D∗× R∗
HYDRO EFFECTS Other DRAINMOD Approaches
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
Mea
n D
aily
Un
drd
ain
ed
Ru
no
ff V
ol (
cm)
Bearden Soil – Crookston (99 yr)
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
Mea
n D
aily
Dra
inag
e V
olu
me
(cm
)
Bearden Soil – Crookston (99 yr)
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
Mea
n D
aily
Dra
ine
d R
un
off
Vo
l (cm
)
Bearden Soil – Crookston (99 yr)
Mean Daily Runoff Post-Drainage w/90% CL
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
Wee
kly
Dra
inag
e &
Ru
no
ff V
ols
(cm
)
Bearden Soil – Crookston (99 yr)
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
Wee
kly
Dra
inag
e &
Ru
no
ff V
ols
(cm
)
Bearden Soil – Crookston (99 yr)
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
Cu
m D
aily
Wat
er Y
ield
& R
un
off
(U
D)
(cm
)
Post-Drainage Water Yield (D + RO)
Pre-Drainage Water Yield (RO)
Bearden Soil – Crookston (99 yr)
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
Wee
kly
Dra
inag
e &
Ru
no
ff V
ols
(cm
)
Fargo Soil – Fergus Falls (99 yr)
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
Cu
m D
aily
Wat
er Y
ield
& R
un
off
(U
D)
(cm
)
Pre-Drainage Water Yield (RO)
OUTPUTS ON A WEEKLY BASIS
Bearden Soil – Crookston (99 yr)
Bearden Soil – Crookston (99 yr)
Bearden Soil – Crookston (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
Wee
kly
Dra
inag
e &
Ru
no
ff V
ols
(cm
)
Bearden Soil – Crookston (99 yr)
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
Wee
kly
Dra
inag
e &
Ru
no
ff V
ols
(cm
)
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.
