Friday, 12 December 2014

Diffuse pollution by agriculture

The UK Government has produced a briefing paper on the diffuse pollution of water by agriculture and has summarized measures that have the potential to reduce the effects on waterbodies by agricultural activities.  This can be found here:

In summary: ‘Surface, coastal and ground waters in England suffer from significant pollution problems: 78% of surface and groundwater bodies fail to meet the ‘good’ ecological status prescribed by the EU Water Frameworks Directive. Pollution increases water treatment costs and adversely affects wildlife. Compared to treatment, preventing water pollution at source can have a cost-benefit ratio as high as 1:65.

On-going trials are investigating a number of potential measures to reduce diffuse pollution from agriculture. These measures involve changes in land management, land use, riparian and buffer zone management.   Some of these changes are simple to implement and have little or no impact on the costs of farming (many actually lead to a reduction in inputs) whilst others require planning over the entire land holding over the long-term.

  • Strips of uncultivated land along the bottom edge of fields and alongside streams provide a ‘buffer strip’ that slows the runoff of water from cultivated land. It also helps reduce sediment, nutrient and pesticide load, as long as buffer strips are not bypassed by field drains.
  • Large wetlands and marshes are particularly good at retaining and slowing water, providing an efficient means of nutrient and chemical removal. Wetlands that accept a large amount of polluted water require regular maintenance to remain effective.
  •  Catch and cover crops. Temporary vegetation planted when an arable field lies unused, reducing the amount of bare soil vulnerable to erosion. These crops can also reduce nitrate leaching.
  •  Appropriate land use. Planting crops that are appropriate to the location and soil type helps reduce pollution inputs – e.g. maize planted on steep slopes is a significant source of sediment.
  • Slurry storage and application. Leaking slurry stores are a significant source of nitrogen and phosphates, and uncovered stores can overflow in heavy rain. The timing of slurry application and the application method can also significantly affect the amount of runoff from fields.
  • Appropriate drainage management. Blocking unnecessary ditches and field drains to slow down rainwater runoff and promote ‘slow water’ can aid water absorption, and reduce sediment and nutrient loads.
  • Controlled trafficking. Managing farm traffic to minimise soil compaction can help improve soil health and water absorption

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