Assessing the impacts of subsurface drainage in northwest Minnesota

Water table, soil moisture, cold climate, experimental study Results of field observations of soil water table depth and soil moisture content in two soils of Northwest Minnesota are presented herein. The results showed that drainage is effective in reducing water table and soil moisture content in field to avoid waterlogging. The reduction mainly took place between April and June when snowmelt increased the antecedent soil moisture and when the ET was smaller. The effectiveness of drainage depends on the drainage spacings and soil properties. Poorly drained soils require narrower drainage spacing while relatively good drained soils need wider drainage spacing. Taking 60 cm as the depth of water table above which crop yield would be affected, undrained soil had 32 days in Brooks and 20 days in Crookston that affected the crop yield in 2002. In the drained soils of Brooks the days reduced to 12 and 6 for plots with drainage spacings 24 and 12 m, respectively. In the drained soils of Crookston the days reduced to 9 and 1 for plots with drainage spacings 18 and 5 m, respectively. The soil moisture content in the drained soil was significantly lower than that in the un-drained soil, particularly between depths 2 to 30 cm.