Figure - available from: Frontiers in Environmental Science
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Conceptual figure of an open ditch showing all potential nitrogen and phosphorus sources (point and diffuse), pathways, and discharge connections [modified from Teagasc (2022) and Simpson et al. (2011)].
Source publication
Introduction: On dairy farms with poorly drained soils and high rainfall, open ditches receive nutrients from different sources along different pathways which are delivered to surface water. Recently, open ditches were ranked in terms of their hydrologic connectivity risk for phosphorus (P) along the open ditch network. However, the connectivity ri...
Citations
... Understanding the influence of landscape position and connectivity enables mitigation strategies to be implemented at optimal locations on nursery sites where contaminants can be reduced (e.g., vegetative buffer strips to intercept the flow path or filter the water) to minimize on-site and off-site impacts (Opoku et al., 2024). This paper (1) presents a framework characterising the effects of waterborne contaminants at plant production nurseries; (2) assesses the role that landscape position and connectivity plays in waterborne contaminant transfer both on-and off nursery production sites; (3) reviews published literature to identify types of waterborne contaminants that pose a risk to plant production nurseries and aquatic ecosystems; and (4) provides a conceptual diagram and systems approach strategy that outlines best management practices that growers can implement to reduce contaminant risks. ...
Introduction
On intensive grassland dairy farms in high rainfall areas with poorly drained soils, networks of open drainage channels linked to in-field drainage systems are needed to enable farm operations. Nitrogen and phosphorus point and diffuse sources may be connected to this open drainage channel network along surface and subsurface pathways, with negative impacts upon delivery to the downstream aquatic system.
Methods
This study developed a semi-quantitative risk assessment model by: (1) selecting parameters (categorical or continuous) representing the nutrient transfer continuum and (2) scoring (relative magnitude and impact) the risk of nutrient source connectivity and delivery for every open drainage channel section across seven dairy farms.
Results and Discussion
A Risk Index Classification System consisting of low, medium, high, or very high-risk class was developed, with high or above requiring a mitigation plan. Results showed that 23%, 68%, 9% and 0% of all open drainage channels on study farms were identified as low, moderate, high and very high-risk, respectively. A range from 2% to 25% per farm of the open drainage channels was classified as high-risk that potentially needed mitigation, although none was identified as very high-risk. Two-thirds of the high-risk open drainage channels were connected to the farmyards, with potential for high nutrient loss from point sources. A combined approach of source management and targeted breaking of the pathway (e.g., in-channel filters, water diversion bars) may help minimise nutrient losses from high risk open drainage channels on poorly draining soils.
