The overall objective of the Wensum Demonstration Test Catchment project has been to assess the effectiveness of a variety of land management measures aimed at reducing diffuse pollution from agricultural activities across the whole river catchment.

Farming is not the sole cause of diffuse pollution but it does contribute approximately 60 per cent of nitrate, 25 per cent of phosphorus and 70 per cent of sediments entering our waters, amongst other pollutants.  Defra’s England Catchment Sensitive Farming Delivery Initiative programme operates in the Wensum catchment and is encouraging land managers to undertake measures funded under Defra’s agri-environmental stewardship schemes that will help to reduce diffuse pollution.

sedimentation of water course

The extensive monitoring work undertaken in the Wensum Demonstration Test Catchment will help provide the ‘evidence base’ to assess how well these measures are working and develop recommendations that will help refine future agri-environmental policy to reduce pollution further.

 

There are a number of different land management measures that can be used as appropriate, to help reduce diffuse pollution. These can be grouped into a number of different categories:

  • Land use measures– e.g. converting vulnerable areas of land to uses with lower fertiliser/pesticide requirements
  • Soil management measures– e.g. to reduce compaction, maintain ditches and drainage; adopt minimal cultivation systems; retain stubble; plant cover crops
  • Farm infrastructure measures– e.g. fence off waterways from livestock; establish sediment traps; improve/cover slurry and manure storage; control waste water
  • Livestock management measures– e.g. avoid poaching; reduce stocking rates on wet fields; improve livestock housing; modify grazing regime; modify livestock feed
  • Fertiliser/nutrient management measures e.g. use precision technology to minimise excess applications; analyse soils regularly; use clover in place of grass
  • Manure management– e.g. modify manure application; site heaps away from watercourses; improve effluent/manure storage
  • Crop protection measures– e.g. adopt recognised crop protection management plan

With the close cooperation of Salle Farms Co.NIAB-TAG and Frontier Agriculture, nine fields were selected for experimentation with cover crops and strip tillage to reduce the impact of autumn runoff of residual nutrients following the harvest. These measures also help mitigate soil sediment loss from bare field surfaces especially where there is a risk of runoff from compacted soils.

In the first year, 2013-14, seven of the nine fields at Salle occupying 102 ha were sown with oilseed radish as a cover crop. This cover crop was followed by spring beans established using strip tillage. In subsequent years until 2017, strip tillage was used in the establishment of autumn-sown crops in rotation. The remaining two fields of 41 ha acted as a control and were managed under conventional farm practices (no cover crop and with variable depth cultivation, including complete inversion ploughing).

Soil mineral nitrogen, field drainage and stream water quality were monitored in response to the introduction of these mitigation measures in order to assess the environmental benefits in comparison to other important factors such as farm workability of the measures and crop yields.

The map below shows the nine fields included in the testing of mitigation measures using cover crops and strip tillage. Potash and Far Hempsky are control fields under conventional cultivation methods.

Map of study area

The photos below show the harvesting of spring barley at Salle in August 2013; straw incorporation post-harvest using the Lemken drill cultivator, and oilseed radish cover crop at the 5- to 6-leaf stage on 30 September 2013.

farming operations in preparation for oilseed radish crop

 

Upgrades to field monitoring installations

Over time upgrades were made to a number of the bankside monitoring sites. Suction lines to the peristaltic pumps and the corrugated protection hoses on the suction lines were replaced. All internal delivery pipes at the two high-specification kiosks at Stinton Hall Farm and Park Farm were replaced and easier access to these sites and the kiosks at Swanhills enabled with bridges and channel bank steps. The bridges include brackets for holding gauging rods to assist vertical water depth measurements for bed profiling, as well as for current metering during high-flows. The in-stream stilling wells housing pressure transducers for stage measurements were replaced with a 4-inch diameter stainless steel outer cover and an inner stake with adjustment slots. All work, including the design and installation of the bridges, was carried out by AT Engineering.

The photos below show the access bridge at Swanhills bankside monitoring site, and a view of the bridge platform showing brackets for holding gauging rods to assist bed profiling and flow measurements.

Swanhills bankside monitoring station

Salle Farms Co

Salle Farms Co. provides much information on farm machinery, crop rotation, environmental farming and grain stores. There’s also a tab ‘Working with Science’ to explain the farm’s involvement with the Wensum Demonstration Test Catchment project. A gallery of photographs is added for interest, including photos from Visitor Days that feature the DTC water quality monitoring stations. ​​​​​

 

  • Farming industry: The data generated by the project will be accessible to farmers and will help inform the farming industry on methods to mitigate diffuse water pollution whilst maintaining productivity.
  • Water industry: The evidence provided by the project will help inform the water industry and OFWAT about the effectiveness of catchment scale schemes to protect drinking water sources.
  • Environment Agency: The project will develop novel practices in water quality monitoring and provide the opportunity to evaluate these approaches on a large spatial scale.
  • Government: The research will provide an improved evidence-base for Defra and its partners to deliver policies that help to meet EU Water Framework Directive objectives.