Edge-of-Field Research Focuses on Controlled Drainage and Saturated Buffers for Reducing Nutrient Runoff

Article by Lois Wolfson and Ehsan Ghane.

Agriculture in Michigan is one of the three biggest industries in the state and it is essential to the state’s economy. An important component of agriculture is subsurface (tile) drainage, since it improves infiltration and moves water off the field quickly for crop production. However, subsurface drainage can increase nutrient transport to surface water. A study of Ohio’s watersheds demonstrated that 48% of dissolved phosphorus losses from the field were from subsurface drainage. This nutrient delivery to streams and lakes can have a detrimental impact on the water quality and the environment due, in part, to algal blooms and toxin production from some algal species.

A new outlet pipe and anti-seep collar being installed at a saturated buffer monitoring site.

To help combat this issue, a 5-year project at Michigan State University is looking to determine if controlled drainage and saturated buffers can improve surface water quality by reducing the loss of both dissolved phosphorus and nitrogen in subsurface drainage water.

A saturated buffer is a practice where drainage water from the outlet is diverted into the soil through perforated pipes along the drainage ditch.

Controlled drainage is a practice where the outlet level of the drainage system can be raised or lowered, resulting in a lower or higher discharge based on the time of the year. The benefit of raising the outlet level during the non-growing season is to reduce nitrogen and phosphorus delivery by reducing subsurface discharge. Lowering the outlet level drains the field, so farmers can get their equipment in the field before planting and harvest. The outlet level can also be raised prior to applying manure to reduce the chance of nutrient loss through subsurface drainage. In addition to reducing nutrient loss from the farm, controlled drainage can also increase crop yield. Research regarding the phosphorus reduction of controlled drainage, however, is limited.

Dr. Ghane assessing a drainage control structure.

Principal investigator Dr. Ehsan Ghane, Assistant Professor in Biosystems and Agricultural Engineering and MSU Extension, is leading the research team.The $1.5  million project funded by the Michigan Departments of Agriculture and Rural Development and  Environmental Quality is the first on-farm research project in the state involving controlled drainage and saturated buffer conservation practices. The project aims to determine the effectiveness of controlled drainage for reducing nutrient transport of phosphorus and nitrogen and the impact the drainage has on crop yield. The team is also evaluating the performance of a saturated buffer in reducing nutrient delivery in drainage water.

The project will take place in the River Raisin Watershed, a tributary to Lake Erie. Lake Erie has experienced severe harmful algal blooms in 8 out of the last 10 years, and dissolved reactive phosphorus has been identified as one of the leading causes. Ghane’s research at three different on-farm sites within the watershed will explore the amount of water, nutrients and E.coli resulting from controlled drainage and saturated buffer practices.

“We will quantify the effectiveness of these practices for reducing nutrient transport in drainage water, and we expect to gain a better understanding of phosphorus dynamics in drainage water,” Ghane emphasized.

The team will measure drainage discharge and nutrient concentration, and calculate nutrient load in drainage water. Their findings will be used to develop a local management guideline and provide more information on potential benefits and effects of controlled drainage.