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