Project Number: 3604-13000-008-14
Project Type: Specific Cooperative Agreement

Start Date: May 23, 2005
End Date: Apr 30, 2010

Objective:
The broad objective of this cooperative research project is to compare the economic and environmental effects of managed and unmanaged subsurface drainage for the very poorly drained lakebed soils in northwest Ohio. Limited research data collected under different soil and climatic regimes indicates that managed subsurface drainage can reduce annual pollutant loads delivered to streams in the drainage water. These preliminary results have resulted in the establishment of the Agricultural Drainage Management Systems Task Force within the US Department of Agriculture to promote the adoption and further study of this drainage water management practice within the Midwest. Before this practice can be incorporated on a large scale, there is a clear need for more research sites throughout the Midwest U.S. that quantify the environmental benefits of managed subsurface drainage. The Defiance Agricultural Research Association (DARA) Test Plots #2, #3, #4, and #5, with modification, are an ideal location for comparing managed drainage versus conventional unmanaged drainage, and in addition, investigating managed drainage design criteria and operational strategies needed to achieve the dual goals of improved water quality and good crop yields. This cooperative research project will enhance and support the contributions of the USDA/ARS Soil Drainage Research Unit to the Agricultural Drainage Management Systems (ADMS) Task Force goals.

Approach:
Field scale experiments integrated with computer modeling simulations will be conducted to address the specific project goals listed above. To initiate the project, DARA Test Plots #2, #3, #4, and #5 will have to be modified. The accompanying diagram details proposed modifications to the existing subsurface drainage system at DARA Test Plots #2, #3, #4, and #5. Blue lines represent drainage pipe laterals or mains that are already in place. Red lines represent drainage pipe laterals or mains that will need to be installed. The new 2-inch diameter drainage pipe laterals to be installed in Test Plot #4 duplicate the system in Test Plot #2. As shown, new collector mains connect preexisting drainage pipe laterals in Test Plots #2, #3, and #5 and new drainage pipe laterals in Test Plot #4. The small yellow boxes indicate positions where water table management hydraulic control structures are to be installed. The hydraulic control structures contain weirs that are comprised of track-mounted flashboards. The weir height, in large part, controls the position of the water table in the adjacent field zone. When the weir is removed, unmanaged drainage conditions exist. Conversely, when the weir is in place, managed drainage conditions exist, in which the water table is kept at a higher level. The hydraulic control structures also provide a location where water flow and water quality can be monitored. The positions of the new collector mains accommodate the adjacent airport¿s future expansion of the runway and taxiway. With these alterations, the effective size of each drainage test plot is reduced to 2.75 acres (500 ft x 240 ft). With two pairs of replicated test plots, conventional unmanaged and managed drainage can be compared under the same field conditions (climate, soil type, and drainage pipe infrastructure characteristics). The two different drainage pipe diameters, two different drainage pipe depths, and three different drainage pipe spacing distances will provide insight on managed drainage design criteria. To allow maximum research flexibility with regard to operational protocols, an individual test plot will have two hydraulic control structures so that water table management practices can be employed and monitored separately based on the two drain line spacing distances present.