Subsurface drainage was introduced in the Midwestern United States in the 1830s and has since become a necessity to sustain crop production in the region’s poorly drained soils. Is there any farmer in this region who does not understand the benefits of drainage? “Twenty Benefits of Drainage” was published in 1982 by OSU Drainage Extension Agricultural Engineer, Mel Palmer. The list goes beyond the improved trafficability and crop yield benefits. Most of those benefits still hold true 40 years later!
Despite its numerous benefits, some of the adverse impacts of drainage on the environment have become a major concern in recent decades. Two noteworthy water quality issues are caused by nitrogen and phosphorus, which can escape farm fields through drain tile: the formation of harmful (sometimes toxic) algal blooms in the Western Basin of Lake Erie and other lakes, and the huge hypoxic “dead zone” where the Mississippi River empties into the Gulf of Mexico. Note that agricultural drainage is not the only source of the nutrients reaching these water bodies, but it s one of the major contributors.
Conservation drainage: It is possible to minimize the negative impacts of drainage on the environment. The Golden Rule of Drainage is: “Drain only what is necessary for good crop growth and trafficability, and not one drop more.” “Conservation drainage” goes further, incorporating approaches and practices to minimize the environmental impacts on the downstream environment and ecology. Controlled drainage (drainage water management), drainage water recycling, saturated buffers, denitrifying bioreactors, phosphorus filters, and two-stage ditch design are some of the examples of conservation drainage. It is important to note that conservation drainage refers to in-field, edge-of-field, as well as ditch and stream-level conservation practices, as these are all important spatial units of agricultural drainage systems. More details on the conservation drainage practices can be found at tranformingdrainage.org and conservationdrainage.net.