Drainage Management to Improve Water Quality and Enhanced Agricultural Production

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

2. 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

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

4. 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

5. Raised Water Table Ditch Drain Water Riser Boards (Adjustable) 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 Solid Pipe

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

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

8. 602 Zone of influence > 20 ac 600 Water Level Control Device Solid Pipe Drainage Management System (gentle sloping topography) Field Boundary

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

10. ~ 1.5 inches Water Available from Drainage Management Potential Based on DRAINMOD Simulations

11. 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.

12. 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.

13. 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

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

15. Site Conditionsfor 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

16. 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