Abstract
Agriculture is often responsible for the eutrophication of surface waters due to the loss of phosphorus—a normally limiting nutrient in freshwater ecosystems. Tile-drained agricultural catchments tend to increase this problem by accelerating the transport of phosphorus through subsurface drains both in dissolved (reactive and organic phosphorus) and particulate (particle-bound phosphorus) forms. The reduction of excess phosphorus loads from agricultural catchments prior to reaching downstream surface waters is therefore necessary. Edge-of-field technologies have been investigated, developed and implemented in areas with excess phosphorus losses to receive and treat the drainage discharge, when measures at the farm-scale are not able to sufficiently reduce the loads. The implementation of these technologies shall base on the phosphorus dynamics of specific catchments (e.g., phosphorus load and dominant phosphorus form) in order to ensure that local retention goals are met. Widely accepted technologies include constructed wetlands, restored wetlands, vegetated buffer strips and filter materials. These have demonstrated a large variability in the retention of phosphorus, and results from the literature can help targeting specific catchment conditions with suitable technologies. This review provides a comprehensive analysis of the currently used edge-of-field technologies for phosphorus retention in tile-drained catchments, with great focus on performance, application and limitations.
Highlights
Agriculture is generally the main source of phosphorus (P) to inland and coastal waters [1,2].Application of mineral fertilizers and manure in agricultural fields and the presence of excess manure in intensive livestock farming commonly result in the surplus of P in the soil followed by loss [1,3].This represents a problem in the long-term as P losses tend to increase as a result of P accumulation in the soil [4]
This study demonstrated that outflow loads of dissolved reactive P (DRP) and total P markedly increased with shorter hydraulic residence time (HRT)
The surface-flow constructed wetlands (SFCWs) investigated in this study presented percentage P retentions between 41 and 51% as reported in Mendes et al [73]
Summary
Agriculture is generally the main source of phosphorus (P) to inland and coastal waters [1,2].Application of mineral fertilizers and manure in agricultural fields and the presence of excess manure in intensive livestock farming commonly result in the surplus of P in the soil followed by loss [1,3].This represents a problem in the long-term as P losses tend to increase as a result of P accumulation in the soil [4]. Application of mineral fertilizers and manure in agricultural fields and the presence of excess manure in intensive livestock farming commonly result in the surplus of P in the soil followed by loss [1,3]. The P surplus can be transported during precipitation events through surface runoff, subsurface flow and/or erosion, eventually reaching downstream surface waters [4], where P loads exceeding a certain threshold may cause eutrophication [5,6]. This is the case in freshwater ecosystems, where P is generally the limiting nutrient [7,8].
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