drainage management for water quality and crop production benefits
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Drainage Management for Water Quality and Crop Production Benefits
Don Pitts
Agricultural Engineer
NRCS USDA
Champaign, IL
Midwest Subsurface Drained Farmland
State Acres Percent ofCropland
U.S.Rank
Illinois 9.8 million 35 1
Indiana 8.1 50 2
Iowa 7.8 25 3
Ohio 7.4 50 4
Minnesota 6.4 20 7
Michigan 5.5 30 11
Missouri 4.2 25 113
Midwest total > 50 million acres
Benefits of Drainage• Many of the most agriculturally productive
soils in Illinois require subsurface drainage for economic crop production
• Subsurface drainage allows for improved soil aeration and increased crop production
• Subsurface drainage allows for field access with equipment cultivation, planting, harvesting, etc.
Distribution of Subsurface Tile Drainage in Illinois
3-4 million ha (6-10 millionacres) drained with subsurface tile inIllinois
This comprises some of the most productive agricultural land in theUS.
Graphic based on soils that would benefit from drainage
Nitrate Concentrations from Tile Drains (McLean Co, IL. 1997-1998)
0
5
10
15
20
25
30
35
40
45
16-Nov 5-Jan 24-Feb 15-Apr 4-Jun 24-Jul
NO
3-N
mg/
l
O # N125 # N Spring140# N Sidedress175 # N Fall AA175 # N N-Serve
Unpublished Data: K. Smiciklas, ISU (Lake Bloomington Project)
MCL
Corn followingSoybeans
* new tile system
Distribution of tile-drained soils and nitrate in surface water in Illinois
Problem Statement
• Tile drainage is needed for economical crop production
• Tile drainage water is a primary source of nitrate to surface water
Possible Solutions• Reduce the amount of N applied
(source reduction)– follow U of I nitrogen fertilizer
guidelines
• Practice drainage management (affect the transport process)
– only release tile water when it is necessary to release it
Why is drainage needed?
• Due to high water tables, many soils in Illinois need drainage for economical crop production:
– to insure trafficable field conditions
– to minimize crop stress from excess water
Role of Drainage
4 ft
Soil Surface
Tile
Water Table Tile
In humid regions subsurface drainage is needed to lower the water table
2 ft
When is drainage not needed?
• During the fallow season
• During growing season – in dry periods
– after planting when the plant root system is small
What is Drainage Management?
• Allows for changing the elevation of drainage outlet
• Raising the water table can reduce the amount of nitrate discharged from the field through the tile lines
• Raising the water table after planting can keep water and nutrients available for plant use during the growing season
Fallow Season Drainage Management
4 ft
Soil Surface
Tile
Water Table with Drainage Management
Tile
Water table is raised above tile lines
0.5 ft
Tile Flow and Surface Runoff vs Tile Spacing Relationship
0
10
20
30
40
50
0 20 40 60 80 100 120 140
Tile Spacing (m)
Fie
ld W
ater
Los
s (c
m/y
r)
tile flowrunoff
DRAINMOD Simulations: Gilford soil, tile depth 1 m .
Typically Highin NO3
RelativelyLower in NO3
Tile Flow vs Runoff at Different Water Table Depths
(with drainage management from Nov - Mar)
0
10
20
30
40
1 meter M@ 60 cm M@ 30 cm M@ 15 cm
Drainage Treatment
(cm
)
Tile WaterRun off
DRAINMOD Simulation: Soil - Drummer, 30 m drain spacing, 1 m drain depth, Urbanarainfall and temperature data, and controlled-drainage (Nov 1st-Mar 15st).
36% Reduction
Tile NO3-N Discharge(DRAINMOD- N Simulation)
0
5
10
15
20
25
(lb/
ac/y
r)
200 lb N-(NM) 200 lb N-(DM) 140 lb N-(NM) 140 lb N-(DM)
Soybean-Corn Rotation, Tile Spacing= 100 ft, Soil=Drummer, Ks = 1 inch/hr, Climate Data=UrbanaNM = No Drainage Management, DM = Drainage Management (period of raised water table Oct 15 to Mar 15)
Production Season Drainage Management(when plants are young)
Soil Surface
Tile
Water Table with Drainage Management
Tile
Water table is lowered as root system develops
4 ft
1 ft
Production Season Drainage Management(when plants are older)
4 ft
Soil Surface
Tile
Water Table with Drainage Management
Tile
Water table lowered as root system develops
2 ft
Potential Water Available from Drainage Management
0
0.5
1
1.5
2
2.5
3
0 12 24 36 48 60
Depth to Water Table (inches) .
Dra
ined
Vol
um
e (i
nch
es)
.
Sable
Source: Based on DRAINMOD Simulations
~ 1.5 inches
Water Table Level with Drainage Management
Jan 1 Dec 31
Drain downRaised Water Table
After Planting AllowWater Table to Rise
Crop WaterUptake
Fallow Season
Fallow Season
Planting Harvest
Lower WaterTable as RootsDevelop
Dep
th b
elow
su
rfac
e
Time line
Drainage Management Control Structure is Placed in Tile Line
The water level control device is installed in the tile drain near the outlet and at various locations within the field depending on topography
Ditc
h
Raised Water Table
Riser Boards (Adjustable)
Drain Water
Solid Pipe
Water Level Control Structure Soil Surface
Drainage Management(Parallel System and Flat Topography)
Field Boundary
main main
late
rals
late
rals
Water level control structure
Drainage Management System
(gentle sloping topography) Field Boundary
602602
600
600
Water Level Control Device
Zone of influence > 20 ac
Solid Pipe
Site Conditions for the Practice of
Drainage Management *
• Nitrate is a water quality concern in the watershed
• Flat topography (slopes < 0.3%)
• Intensive subsurface drainage system (pattern system)
• No (minimal) impact to neighbors
• Field size should be greater than 20 acres
* Illinois NRCS Drainage Management Demonstration Project
Structures Installed
Structures Planned
Structures Proposed
Drainage Management Pilot Status Report (March2000)
Water Level Control Device
Cost => $200 to $1000depending on sizeplus installation
Simple to operate
Installation of Water Level Control Device
Water LevelControl Box
Excavate Drain Line
Installation of Water Level Control Device
20 ft of SolidPipe
Anti-seepCollar
Installation of Water Level Control Device
Key Anti-Seep Collar
Installation of Water Level Control Device
Hand back fillaround Box
Installation of Water Level Control Device
Installation Complete
Production Season Drainage Management Considerations
• Principle 1. Only release water sufficient to allow for the soil to dry for field access with equipment and to keep the water table out of the root zone. – Any water released in excess of these two
requirement is water and nutrients lost from production.
Production Season Drainage Management Considerations
• Principle 2. Know the depth of the effective root zone. – If the water table is allowed to rise into the root zone
for a prolonged (this depends on temperature) period, oxygen will be depleted and plant stress will soon follow.
– This is the greatest risk in practicing drainage management.
Soil Redox Potential (Days after Initiation of a Raised Water Table)
-150
-100
-50
0
50
100
150
0 1 2 3 4 5 6 7 8 9
Days after Initiation of Raised Water Table
mV
6-inch12-inch
Pitts, et al. 1991
Soil Temperature Effects on Oxygen Depletion
0
0.2
0.4
0.6
0 5 10 15 20 25 30
Temperature Co
Rel
ativ
e R
eact
ion
Rat
es
Arrhenius Rule (Gilmore, 1984)
Potential Benefits of Drainage Management
• Reduced Nitrate to Surface Water
– by inhibiting nitrification
– by reducing the rate of mineralization
– by increasing denitrification
– by altering the hydrology
• Increased Crop Production– because more water is available for ET
– because more N available for crop uptake
Subsurface tile line
Flow monitor
Control Structure
Weather Station
Monitoring well
40-acre 40-acre control fieldcontrol field40-acre 40-acre control fieldcontrol field
40-acre 40-acre experimental experimental fieldfield
40-acre 40-acre experimental experimental fieldfield
Monitoring Equipment at a Demonstration Site
Golden Rule of Drainage
• Only release the amount 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
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