2007 Annual Report 1a.Objectives (from AD-416) 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. 1b.Approach (from AD-416) 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. 3.Progress Report This report serves to document research conducted under a specific cooperative agreement between the ARS and the Defiance Agricultural Research Association (DARA). Additional details of the research can be found in the report for the parent project 3604-13000-008-00D, MANAGEMENT AND TREATMENT OF DRAINAGE WATERS FOR WATER QUALITY PROTECTION AND SUSTAINABILITY OF AGRICULTURAL PRODUCTION IN THE MIDWEST U.S. The agreement covers research to be conducted at a new subsurface drainage research facility. The overall project goal for the DARA site (located near Defiance, OH) is to demonstrate the water quality, and if possible, the crop yield benefits of controlled subsurface drainage versus conventional, unrestricted subsurface drainage. The facility itself is comprised of two pairs of replicated test plots, four in total, that contain a variety of subsurface drainage infrastructure characteristics (different drainage pipe diameters, placements depths, and spacing distances). There has been a substantial amount of activity on this project over the past year. One main focus was the development of water flow rate relationships for the weirs contained in the eight hydraulic control structures placed at the site. The type of hydraulic control structure used in this study can be described simply as a PVC box containing a weir, where at one side on the bottom of the box there is a pipe inlet and at the opposite side on the bottom of the box there is a pipe outlet. Water flows into the control structure through the pipe inlet, over the weir, and is discharged offsite through the pipe outlet of the control structure. The position of the top of the weir governs the water table level in the adjacent agricultural field. The height of the water flowing over the top of the weir can be used to determine the flow rate for drainage water leaving the site through the control structure. Field tests on a control structure the same as ones installed at the DARA site were conducted to determine flow rate equations for both a rectangular and a V-notch weir. These tests indicated that the V-notch weir is the best choice for use in measuring drainage water discharge at the site. As a consequence of these field test results, V-notch weirs have been inserted within all DARA site hydraulic control structures. The second focus for the project over the past year was the installation of a weather station along with equipment to measure flow and collect samples for drainage water leaving the site. Before this equipment could be installed, electric lines were extended out to all eight of the site control structures, thereby providing the electric power needed for the water flow measurement and water sample collection equipment installed at each control structure. With the weather station and all the water flow/sampling equipment now in place, the site is fully operational with regard to monitoring the environmental benefits of controlled drainage. The ADODR, through numerous phone conversations and site visits, maintains close contact with the project’s principle investigator, thereby ensuring that project objectives are achieved.