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

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 Tile Water Table with Tile Drainage Water Table without Tile Drainage

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

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

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

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

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

Water Available from Drainage Management Potential Based on DRAINMOD Simulations ~ 1.5 inches

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 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 –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)

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 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