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 flowo erosion mitigation

• Sedimentation o phosphorus

• Denitrification

Bio-reactant Filtration

• Functional properties

• Construction

• Long term maintenance

Function of bio-reactors

• Contained biological processeso removal targets

• Aerobic and Anaerobic

• Simple exampleo Denitrification o Sedimentation

Construction

• Two stage containment system o First stage prevents

overflow o Second stage filters

drainage

• Inputs o Sando Carbon source

woodchips compost

o Bacteria obtained from

river sediment

Blowes et al., 1994

Maintenance

• Very cost effectiveo Minimal upkeep after construction

• Inputs are cheap and readily available

• Scale can be augmented for the agricultural area

Constructed Wetlands

Construction

• Location

• Designo Sizeo Shapeo Embankments & sealingo Inlet & outlet structureso Sediment traps

Plant Selection

Maintenance

• Assess plant health, identify pest damage

• Manage water levelo 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

Farmer needs to know:1. when to raise/lower the control structure2. at what height to maintain the weir in the

control structure3. when to add water to the systemDepends 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

*** Cost effective compared to fallow field maintenance

Legumes such as Hairy Vetch and Subterranean Clover improve soil quality by fixing Nitrogen

(http://boyneriver.org/wp-content/uploads/Hairy-Vetch_Web-jpg.jpg)(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 DepthPrior to Installation• A decrease in drain depth from 1.5 to 0.9m decreased Nitrogen

losses by 14%o Little change when deeper than 1.2 meterso Water has drained

• Shallower drains not examinedo 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 performedo also aligns with other regional

recommendations

(http://www.novum-nl.com/webtheek/dscf1714.gif)

At Risk Soil Types

1. Clay soils that easily slake

2. Silty soil with low Organic contento 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