Phosphorus in soils, surface/ subsurface drainages and ditches from agricultural used grasslands of different landscape areas in NW-Germany

The data was collected as part of a study (“Waterbuddies”) of grassland agroecosystems of the northwest German (NWG) coastal region. The aim of the study was to identify the sources and discharge paths of nutrients like phosphorus that play an important role as contaminants for surface waters and the North Sea. The NWG coastal region is characterized by a dense network of drainage ditches that directly connect agricultural areas with surface waters. The Jade catchment area was selected to represent the different landscape areas of the NWG coastal region.

Therefore, the study differentiates between the landscape areas of the geest with mostly sandy soils (Geest), the peatlands with bogs (Hochmoor) and fens (Niedermoor) as well as the marsh (Marsch) with a predominance of clay-rich soils. In addition to these landscape areas, two transition sites were identified. Both are oragnomineral in character but are either increasingly characterized by clay in the transition to the marsh (ÜMoMa), or increasingly characterized by sand in the transition to the geest (ÜGeMo). Besides drainage ditches, grassland areas are often drained via surface drainage and drainage pipes, which mark a second discharge path for nutrients. Surface drainage mainly is used for clay soils, whereas drainage is used in sandy and organic-rich soils. Surface drainage in the marsh region is permanently installed, leading ditch run-off via end pipes into higher order waterbodies. The Geest differs in this respect, here, temporary surface drainage is installed during the runoff period without an end pipe. This way, stagnating water on the field plots are drained as needed. Within this study area Phosphate-P contents of soils and phosphate-P concentration of discharge and ditch waters were determined to get a further insight into how different factors (soil type, surface vs. subsurface drainage) are influencing the P-dynamics of the ditches as surface waters of the intensively drained coastal region of Germany.