Performance of drainage water management systems in Illinois, United States

Abstract

Drainage water management (DWM) is the practice of varying the drainage intensity of a subsurface drainage system to ensure that no more water is transported from a field than is necessary for optimizing crop growth and for facilitating seedbed preparation and other agrotechnical practices. This variation is achieved by using stop logs in a control structure to adjust the outlet elevation of the drainage system. An experiment was set up to test the hypothesis that the implementation of this practice will reduce nitrate (NO₃) loads from subsurface drainage systems in Illinois, United States, without adversely affecting yields. This experiment consisted of instrumenting and collecting precipitation, flow, and water quality data from four pairs of fields on different soils in Illinois. Each pair consisted of one field with a conventional (free) drainage system and one field with a drainage system whose outlet was managed in accordance with the Illinois Practice Standard for DWM. Annual NO₃ load reductions from the managed fields ranged from 37% to 79%, with an average load reduction of 61%. However, because of difficulties in measuring flow under submerged outlet conditions and because water left the managed fields by pathways other than through the outlets of the drainage systems, the efficacy of the practice is likely less than these numbers would indicate. There were no consistent patterns to the relationship between DWM and yields. In some instances, yields increased on the managed fields, and in others, yields decreased. Because of confounding factors, such as weather and topography, studies of longer duration are required to determine the effect of DWM on yield.