Tile Drains Remediation and Best Management Practices Group Members: Kelly Davis, Krista Hoffsis, Nic Lucore, Sam Wallace.
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Tile Drains
Remediation and Best Management Practices Group Members: Kelly Davis, Krista Hoffsis, Nic Lucore, Sam Wallace
Remediation Techniques
• Riparian buffers • Bio-reactant filtration • Constructed wetlands
Riparian Buffers
• Construction • Function • Lasting effects
Construction
• Plant composition • Size and shape • Cost of construction
Function
• Surface and subsurface flow o erosion mitigation • Sedimentation o phosphorus • Denitrification
Bio-reactant Filtration
• Functional properties • Construction • Long term maintenance
Function of bio-reactors
• • • Contained biological processes o removal targets Aerobic and Anaerobic Simple example o Denitrification o Sedimentation
Construction
• Two stage containment system o First stage prevents overflow o Second stage filters drainage • Inputs o Sand o o Carbon source woodchips compost Bacteria obtained from river sediment
Blowes et al., 1994
Maintenance
• • • Very cost effective o Minimal upkeep after construction Inputs are cheap and readily available Scale can be augmented for the agricultural area
Constructed Wetlands
Construction
• • Location Design o Size o o o o Shape Embankments & sealing Inlet & outlet structures Sediment traps
Plant Selection
Maintenance
• • • • Assess plant health, identify pest damage Manage water level o Adequate inflow and even dispersal Check for blockages in inlet & outlet systems Inspect embankments for weeds and erosion
Best Management Practices
• • • • • • Controlled drainage Subirrigation Winter crop cover Optimal spacing Optimal depth Fertilizer application rates
Controlled Drainage
• • Keeps water table high during the off-season Increased rate of denitrification
Subirrigation
• • Irrigations back through subsurface drain tiles used during dry periods
Management of Controlled Drainage/Subirrigation
2.
1.
Farmer needs to know: when to raise/lower the control structure at what height to maintain the weir in the control structure 3.
when to add water to the system Depends on: specific site, crops, soil type, drain depth, etc.
Seeding of Crop Fields for Winter Months
• Maintains root integrity year round • Plants are able to take up phosphorus when storm events • occur especially useful in clay and silt • dominant soils Can produce additional crop • yields Improves soil condition for next growing season
Legumes such as Hairy Vetch and Subterranean
*** Cost effective compared to fallow
Clover improve soil quality by fixing Nitrogen
field maintenance (http://www.mccc.msu.edu/images/covercrops/kura_clover.jpg)
Cover Crops for Vermont
• • •
Winter Rye
Can germinate at 33 degrees F Scavenges residual N from previous crops Can be grown with Hairy Vetch
Field Pea (Legume)
● Winter kill-crop ● Planted in August/September ○ reaches maturity before first frost ● Dead plant material shieds soil and roots remain underground
Optimal Spacing
•
Prior to Installation
The less dense the drains, the lower the amount of leached nitrogen • Closest distance → 20 meters • Closer than that and crop yield decreases and nitrogen runoff increases
Optimal Drain Depth Prior to Installation
• A decrease in drain depth from 1.5 to 0.9m decreased Nitrogen losses by 14% o o Little change when deeper than 1.2 meters Water has drained • Shallower drains not examined o Could impede root growth and water absorption
Fertilizer Application
• • Reducing Nitrogen inputs from: 200 kg ha −1 to 125 kg ha −1 reduced Nitrogen losses by 57% ** NO reduction in crop yields This application rate aligns with recommendations put forth by Waseca, Minnesota, where the study was performed o also aligns with other regional recommendations (http://www.novum-nl.com/webtheek/dscf1714.gif)
At Risk Soil Types
1. Clay soils that easily slake 1. Silty soil with low Organic content o Prone to erosion 3.
Sandy soil profiles with low P sorption capacity o Iron and Aluminum in subsoil raise P sorption cap.
Best Management Practices ** NOTE:
Often times soils are a mix of sand, silt, and clay The most important objective is to promote a healthy soil profile
Best Management Practices: Flow Chart