Drainage Management to Improve Water Quality and Enhanced

  • Slides: 16
Download presentation
Drainage Management to Improve Water Quality and Enhanced Agricultural Production by Don Pitts Agricultural

Drainage Management to Improve Water Quality and Enhanced Agricultural Production by Don Pitts Agricultural Engineer NRCS USDA Champaign, IL

Why is drainage needed? • Due to high water tables, many soils in Illinois

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

Tile Drainage is Water Table Management Soil Surface Water Table without Tile Drainage Tile

Tile Drainage is Water Table Management Soil Surface Water Table without Tile Drainage Tile Water Table with Tile Drainage

What is Drainage Management? • Allows for changing the elevation of drainage outlet •

What is Drainage Management? • Allows for changing the elevation of drainage outlet • Raising the water table can reduce nitrate discharges to surface water • Raising the water table after planting can keep water and nutrients available for plant use during the growing season

Water Level Control Device Raised Water Table Di tc h Solid Pipe Drain Water

Water Level Control Device Raised Water Table Di tc h Solid Pipe Drain Water Riser Boards (Adjustable) The water level control device is installed in the tile drain near the outlet and at various locations within the field depending on topography

Drainage Management Soil Surface Root Zone Ditch Water Table with Drainage Management Tile Water

Drainage Management Soil Surface Root Zone Ditch Water Table with Drainage Management Tile Water Level Control Device Ditch

Drainage Management (Parallel System and Flat Topography) main laterals Field Boundary main Water level

Drainage Management (Parallel System and Flat Topography) main laterals Field Boundary main Water level control structure

Drainage Management System (gentle sloping topography) Field Boundary 2 60 Zone of influence >

Drainage Management System (gentle sloping topography) Field Boundary 2 60 Zone of influence > 20 ac 0 60 Water Level Control Device Solid Pipe

Managed Drainage Crop Water Uptake Drain down Raised Water Table Lower Water Table as

Managed Drainage Crop Water Uptake Drain down Raised Water Table Lower Water Table as Roots Table Develop Fallow Season Jan 1 After Planting Allow Water Table to Rise Planting Fallow Season Harvest Dec 31

Water Available from Drainage Management Potential ~ 1. 5 inches Based on DRAINMOD Simulations

Water Available from Drainage Management Potential ~ 1. 5 inches Based on DRAINMOD Simulations

Production Season Drainage Management Considerations • Principle 1. Only release water sufficient to allow

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

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.

Potential Benefits of Drainage Management • Reduced Nitrate to Surface Water – inhibits nitrification

Potential Benefits of Drainage Management • Reduced Nitrate to Surface Water – inhibits nitrification – reduces the rate of mineralization – increases denitrification – altered hydrology results in less nitrate loss • Increased Crop Production – more Water available for ET – more N available for crop uptake

Fate of Nitrogen in Tile Drained Agriculture Source: Zucker and Brown (1997)

Fate of Nitrogen in Tile Drained Agriculture Source: Zucker and Brown (1997)

Site Conditions for USDA Funding • Nitrate is a water quality concern in the

Site Conditions for USDA Funding • Nitrate is a water quality concern in the watershed • Flat topography (slopes < 0. 2%) • Intensive subsurface drainage system (pattern system) • No (minimal) impact to neighbors • Field size should be greater than 20 acres

Golden Rule of Drainage • Only release the amount water necessary to insure trafficable

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