Nitrogen retention in vegetation filters of short-rotation willow coppiceAronsson, Pär
Irrigation of short-rotation willow coppice (SRWC) is a potentially efficient way of treating various types of wastewaters. In this thesis the nitrogen retention capacity in such cropping systems (vegetation filters) is assessed both within season and for several years and rotations. In addition, the retention and potential leaching of viruses in such systems are assessed. The experimental work was carried out in two types of lysimeters and in experimental fields.
Nitrogen leaching loads from wastewater irrigated willow vegetation filters can be high or very high during the establishment phase (i.e. the year of planting), and thus, during establishment, neither wastewater nor commercial fertilizers should be applied to the crop. However, once established, nitrogen leaching loads from willow vegetation filters are low or very low, enabling high inputs of nitrogen-rich wastewater. Within reasonable limits, nitrogen leaching loads are independent on irrigation rates and thus dosing of wastewater should be based of nitrogen loads. The nitrogen retention in a willow vegetation filter (up to in the order of 200 kg N/ha-yr) is due to plant uptake and incorporation into woody tissue (including harvestable shoots), and to a build-up of the pool of soil organic matter. In addition, gaseous nitrogen losses (primarily due to denitrification) are probably substantial.
Preferential flow of water in cracks and fissures can facilitate a rapid transport of viruses applied to a structured clay soil, and within a few hours viruses might reach the groundwater. However, in a sandy, non-structured soil, viruses are efficiently retained in the soil mainly as a result of strong electrostatic interaction between viruses and soil colloids.
Keywordswillow; Salix viminalis; coppice; nitrate leaching; nitrogen retention; groundwater quality; lysimeter; virus; bacteriophages
Published inActa Universitatis Agriculturae Sueciae. Silvestria
2000, number: 161
Publisher: Department of Short Rotation Forestry, Swedish University of Agricultural Sciences