By Linda Geist

University of Missouri agronomists found corn and soybean yields increase by 20% or more when they use drainage control systems, says Kelly Nelson, Missouri University Extension agronomist at the Greenley Research Center in Novelty.

A combination of drainage and subirrigation boosts corn yields by 45% and soybean yields by 20% in claypan soils, Nelson says. The Greenley system allows excess water to drain and be retained as needed.

Nelson says the research shows how proper drainage protects the environment and cuts input costs. The drainage water management system reduced nitrate loss by 70% and phosphorus loss by 80%.

He describes the drainage structures as boxes buried in the ground. The boxes have slides, or gates, that allow adjustment of the water table in the soil. Water is sped up for drainage or slowed for irrigation, based on soil needs.

The structures are spaced through water management zones based on the field’s slope. Water either flows or is retained based on precipitation and the growth stage of the plant.  

The system may not be cost-effective or necessary for all sites, Nelson says, adding that “benefits must outweigh the cost.”

Also, Nelson found reduced yields result if the system is not designed and installed properly.

Proper drainage keeps nutrients in the field and sends cleaner water downstream. This reduces the amount of nitrate that flows into ditches and streams.

Properly drained fields can be planted 10-14 days earlier, often leading to increased yields, Nelson says.

University of Missouri research shows undrained, saturated fields affect crop health even after a single rainfall event, he says. Excess water flow also leads to soil compaction.

Greenley faculty and staff began work with contractors and engineers in 2001 to develop the farm’s drainage water management system.

Computer models show that the optimal distance between drainage tiles was 20 feet. 

Researchers found that wider spacing, while less expensive, was ineffective in claypan soils.

Greenley Research Center plans to upgrade its system in 2017. A large-scale drainage water management system will be installed in cooperation with the Missouri Land Improvement Contractors of America and USDA’s Natural Resources Conservation Service at the center’s 240-acre Grace Greenley Farm.

The planned installation includes a large lake and closed-loop system.

More Information

Information on drainage research in Missouri is available at

Nelson is co-author of the Purdue University Extension publication “Drainage Water Management for the Midwest,” available for free download at