drain tile

What is conservation drainage?

Subsurface tile drainage is an essential agricultural water management practice on many highly productive soils in the Midwest.  However, nitrate carried in drainage water can lead to local water quality problems and contribute to hypoxia in the Gulf of Mexico, so strategies are needed to reduce the nitrate loads while maintaining adequate drainage for crop production.  The term "conservation drainage" has been coined to describe practices that can reduce nitrate loads on tile-drained soils, including modifying drainage system design and operation, woodchip bioreactors, and modifications to the drainage ditch system. This web site provides information that has been developed by university extension specialists and researchers to inform farmers, agency staff, decision makers, and others about these practices.

Practices that reduce nitrate from drainage systems

Drainage water management


Drainage water management is the practice of using a water control structure to raise the drainage outlet to various depths. This allows farmers to have more control over drainage.


Woodchip bioreactors

bioreactorBioreactors consist of a large trench filled with woodchips or other carbon sources, that allow microbes to treat drainage water through denitrification.More

Drainage system & ditch design


The drainage system can be designed to reduce nitrate losses by using shallower drains, wider spacing, and two stages within the ditch to increase nutrient trapping and processing.

USDA Natural Resources Conservation Service resources
State initiatives and opportunities



Land-grant university resources

Illinois: Richard Cooke, Agricultural & Biological Engineering, University of Illinois; Web Site: Illinois Drainage Guide

Indiana: Jane Frankenberger, Agricultural & Biological Engineering; Eileen Kladivko, Agronomy; Purdue University; Web Site:Purdue Ag Drainage

Iowa: Matt Helmers, Iowa State University; Web Site:Ag Water Management Research

Michigan: Tim Harrigan, Michigan State University

Minnesota: Gary Sands, University of Minnesota; Web Site:The Drainage Outlet

Missouri: Kelly Nelson, University of Missouri;

North Dakota: Xinhua Jia, North Dakota State University

Ohio: Larry Brown, The Ohio State University

South Dakota: Chris Hay, South Dakota State University