Conservation Drainage: Drainage
for the 21st Century
Diversion
Structure
Length dependent on
treatment area
5’ Soil
Backfill
Capacity
Control
Structure
20’ section
of tile
Trench bottom 1’
Below tile invert
Woodchips
The Nitrate Saga
1890s
Scientists sound alarm about
need for new source of nitrates
Fritz Haber
Carl Bosch
Nutrient contributions to the Gulf, by State
Distribution of Subsurface Tile
Drainage in Illinois
3-4 million ha (6-10 million
acres) drained with
subsurface tile in
Illinois
This comprises some
of the most productive
agricultural land in the
US.
HYDROLOGIC CYCLE (with tiles)
7.2
km/km2
Mutabaruka
The solutions that
you seek
will not be found
in the streak
of a pen,
or even one
thousand words of
mine.
Nitrate Reduction Techniques
Altering Nitrogen Application
Amounts
Altering Nitrogen Application
Timing
Edge-of-Field Treatment
Optimizing Drainage System
Conservation Drainage
The incorporation of
environmentally friendly
practices and structures into
existing drainage infrastructure
Minnesota Department of Agriculture
Conservation
Drainage
The optimization of drainage
systems for crop
production, water quality
and water harvesting
benefits
Drainage
Water
Management
Conservation
Drainage
Subsurface
Bioreactors
Depth/Spacing Modifications
Convenient and Cost-Effective
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
Drainage Water Management
Manual
Gate Structure
Automated
Gate Structure
Float Structure
Drainage Water Management Guidelines
Period
Production Activity
Control
Setting*
(inches)
Nov.1-Mar.15
Fallow
6-18
Minimize drainage outflow and
encourage denitrification
Mar. 15 – Apr.15
Tillage, corn seedbed
preparation, planting
36-48
Just deep enough to provide
trafficability and good conditions for
seedbed preparation.
Corn establishment, early
growth
24 – 30
Deep enough to promote good root
development.
Comments**
Apr. 15 – May 15
Nitrogen sidedressing
Just low enough to allow trafficability
24-36
May 15 - Aug. 15
Corn development and
maturity
18-24
Temporary adjusting during wet
periods
Aug.15 - Oct. 31
Harvesting, tillage
36-48
Lower enough to provide trafficabilty
– in an unusually dry season, control can be 3 to 6 inches higher;
– in an unusually wet season, control should be 3 to 6 inches lower;
– in coarse-textured soils, trafficability can be provided with the water table approximately 6 inches higher.
Managed Drainage - Winter
Conservation Mode for Fallow Season
Managed Drainage - Spring
Full Drainage Mode for Planting Season
Managed Drainage -Summer
Shallow Drainage Mode for Growing Season
Managed Drainage - Fall
Full Drainage Mode for Harvest Season
Drained Volume (inches) .
Potential Water Available from Drainage
Management
3
Sable
2.5
2
~ 1.5 inches
1.5
1
0.5
0
0
12
24
36
48
Depth to Water Table (inches) .
Source: Based on DRAINMOD Simulations
60
Water Deficit Stress
DWM Benefits
• Reduces Nitrate Concentrations in Effluent
– 30-95% reductions annually
• Increased Yield
– 76% higher yield in a dry year
• Lower Concentrations of Other Pollutants
Required Information for Economic
Analysis of DWM System
•Drainage Costs
•Added Revenue
•Capital Costs
•Timeliness Benefits
Drainage Water
Management
Hume 2004
Flow Depths (cm) From a Paired Drainage Site
14
13.4
12
10
FreeDrainage
Drainage
8 Free
Managed
ManagedDrainage
Drainage
6
10
4
2
3.9
3.4 3.6
0.3
0
Mar.-Oct .
Nov.-Feb.
Annual
Hume 2006
1.4
20
18
1.2
1.0
14
12
Flow (cm/day)
0.8
10
0.6
8
6
0.4
4
0.2
2
0.0
11/19/05
0
1/8/06
Free Drainage
2/27/06
4/18/06
Managed Drainage
6/7/06
Cumulative Flow (cm)
16
Long Term Nitrate Trends: 2005
2005 T ile Nitrate C onc entrations at Hume
Nitrate-N C onc entration (ppm)
25
20
15
10
5
0
11/9
12/29
2/17
F ree Drainage
4/8
Managed Drainage
5/28
7/17
Long Term Nitrate Trends: 2008
2008 T ile Nitrate C onc entrations at Hume
Nitrate-N C onc entration (ppm)
16
15
14
13
12
11
10
9
8
7
6
2/2
2/22
3/13
4/2
F ree Drainage
4/22
5/12
Managed Drainage
6/1
6/21
7/11
Free Drainage
11.3 acres
50-70 ft Spacing
Managed Drainage
13.1 acres
50-70 ft Spacing
Nitrate-N (mg/L)
Kinderhook Site
System Layout for
Drainage Water
Management
Layout Costs
Cost Differential: $50/acre