Controlled Drainage As Measure to Reduce Nitrate Leaching in a Wheat Cropping System.

Controlled Drainage As Measure to Reduce Nitrate Leaching in a Wheat Cropping System.

Subsurface drainage of soil to avoid water logging is a prerequisite for crop cultivation for a large proportion of the agricultural land, and approximately 50% of the Danish agricultural area is artificially drained. Multifunctional drain systems can be effective measures to reduce losses of nutrients, such as Controlled Drainage (CD). With CD the water table of drained fields is raised or lowered by adjusting the drain pipe outlet elevation. By restricting drain flow at times when drainage is not needed, the overall volume of water flow is reduced, more soil moisture is available for the growing crop, and nutrient exports are reduced. CD has been shown to diminish leaching losses of soluble nutrients. So far CD has only been tested for spring sown crops but widespread implementation on drained clayey soils would rely on its adaption to winter cereal production systems. A new project on CD applied at four winter cropped fields in Denmark investigates how effects of anaerobic conditions created by CD will affect chemical/biological processes in the submerged soil, root growth, crop production, and nutrient losses. Nitrification is expected to be retarded by wet soils during winter, preserving ammonium for crop uptake in the following cropping season. Installed equipment, soil survey results and measurement results from the first winter season will be presented.