Subsurface drainage volume reduction with drainage water management: Case studies in Ohio, USA

Drainage water management (DWM) is promoted as an agricultural best management practice that reduces subsurface drainage volume and thereby the transport of soluble nutrients to streams. This study was conducted on private crop fields to quantify the effect of managed subsurface drainage on daily subsurface drainage volume, in poorly drained and somewhat poorly drained soils of northwest Ohio. A paired zone approach was used where a part of each field was conventional free draining and the other part was under drainage water management. At each site, comparison of median daily subsurface drainage volume from the two zones indicated that drainage water management was effective at reducing daily subsurface drainage volume. A linear mixed model procedure was applied to determine the percent reduction in daily subsurface drainage volume as a result of drainage water management. Using the paired dataset at each site, the model predicted the total daily subsurface drainage volume from the managed zone as a function of the observed total daily subsurface drainage volume from the conventional zone. The percent reduction of daily subsurface drainage volume varied from 40% to 100% depending on site. While the magnitude of the reduction of the daily subsurface drainage volume is site specific, the general expectation is that if DWM is instituted broadly and appropriately in northwest Ohio, mean daily subsurface drainage volume would lessen on an annual basis. Such reduction may eventually translate into a reduction in nutrient loads exported from farm fields.