Long-term research at The Ohio State University has shown a 6% yield increase for corn and 3.5% yield increase for soybeans within the elevation zone influenced by controlled drainage, compared to a free draining outlet. Naturally, one is inclined to manage the structures actively only during the growing season. However, if managed properly during the non-growing season, controlled drainage has tremendous benefits to water quality downstream. The non-growing season management becomes a requirement if you are enrolled into an incentive program. Simply raising the outlet elevation by stacking boards in the control structure after harvest in the fall and leaving the structure in “controlled drainage” mode throughout the winter and spring, can help reduce up to 50% of the drainage discharge from the tile outlet. This reduction in discharge translates into net reduction in nutrient export from the field. Transitioning of seasons calls for some adjustments to the board heights in the control structures, as will be explained below.

I wrote a detailed article recently in Ohio’s Country Journal that provides some guidelines for managing control structures during growing and non-growing seasons. The article can be accessed at: