Integrating constructed wetlands, water supply reservoirs, and subirrigation into a high yield potential corn and soybean production system

Three constructed wetlands have been designed, constructed, and linked with water supply reservoirs for corn and soybean production systems using subirrigation. The overall purpose is to demonstrate how construction and management of wetlands coupled with subirrigation can be economically profitable for farmers, thus stimulating the adoption of wetlands and reducing adverse impacts of agricultural runoff in the Ohio portion of the Maumee River Basin. These wetlands have been constructed on prior-converted cropland (soils are dominantly silty clay and clay) to receive drainage from adjacent cropland, resulting potentially in zero-discharge fi om those fields directly to streams, except during extreme precipitation events. Agricultural runoff and subsurface drainage recharge the wetland seasonally, and the reservoir serves as a supplemental water supply source for subirrigating corn and soybean. At each site (Defiance, Fulton and Van Wert counties, Ohio), subirrigation systems were designed and retrofitted on existing subsurface drained cropland. A conventional subsurface drained comparison is also located at each site. The Defiance County and Van Wert County sites are managed by agricultural organizations. the Fulton County site is managed by a private farmer.. Non-replicated yield data, averaged over four varieties of both corn and soybean, for 1996 (first year of study) from the Fulton County site indicated a yield increase for both corn and soybean of approximately 50% for subirrigated versus conventionally drained cropland. A comprehensive monitoring system is being designed for the Defiance County site to collect a large variety of data useful for hydrologists, biologists, wetland ecologists, modelers and decision support system designers, engineers, and natural resources conservationists. A monitoring system will be installed at the Fulton and Van Wert county sites in late 1998 or 1999. The US Army Corp. Engineers have funded the construction of a four site, which will be located in Henry County, Ohio.