An Assessment of Controlled Drainage Efficiency in Sandy Loam Soils

Field studies on the effectiveness of controlled drainage in sandy loam soil were carried out in the Lowland of Middle Lithuania. The plot, which has existing subsurface water removal systems operated as conventional drainage was readjusted for groundwater table management. A water level control structure was installed and two separate systems - free drainage (FD) and controlled drainage (CD) were arranged. The groundwater table level was allowed to rise to a maximum of 68 cm above the drains. Measurements to record groundwater table depth, drain outflow quantity and quality were performed through the period 2000-2007. It was determined that in the CD system annual drainage outflow lasted shorter by 40-62%, at the same time it was reduced by 25% and nitrate leaching – by 20-28% lower in comparison with drainage operating in an ordinary regime. These quantities varied depending on weather conditions