P Stripping of Agricultural Runoff

1. P Stripping of Agricultural Runoff Or Integrated Runoff Management Plans for Farms Paul Quinn and Sebastian Tellier

2. The Rural P Problem • Surplus P in the land bank • Saturation of P in the soil • P losses associated with sediment losses • High P in ditch and river sediments – a ‘conveyer belt’ • Enough P to keep eutrophication risk high for the next 50 years • WFD & P– has no chance unless a more proactive approach is taken

3. Addressing the problem Traditional approach • Soil management and P applications • Land use change OR a new paradigm • P is locked into soil (soil amendment?) i.e for plant consumption only • Stripped from the flow at source (in ponds and ditches) • Suppress P impacts in rivers and lakes by scavenging P.

4. Nutrient Export Risk Matrix N loss or P loss high Fertiliser applications and Soil Management clay poor low Soil Type clay rich low risk high risk Flow Connectivity and Remediation features

5. IRMP Overall Vision To create an Integrated Runoff Management Plan (IRMP) for a demonstration site at Nafferton Farm, where a series of proactive measures will be taken to control runoff flow paths and the physical and chemical properties of the water before the flow enters the Whittle Burn – thus reducing flood peaks and diffuse pollution levels.

6. IRMP Objectives • To control overland flow runoff from intensely farmed fields by using strategically placed, within-field bioreactors/ponds; • To reduce runoff from hardstandings by forcing flow back into fields containing bioreactors/ponds; • To create a series of small and un-intrusive sediment traps within the ditch network and the sediment recovered and recycled to land; • To create a phosphorus (P) stripping zone using ochre pellets (a recycled minewater treatment waste material). P saturated pellets, the trapped sediment and the ochre will be recycled back to land as fertilizer; • To create a denitrifying potential to treat the bulk of the flow leaving Nafferton farm; • To evaluate the potential of the storage and attenuation features to reduce the magnitude of flood risks as caused by UK farming systems.

7. Nafferton Farm Study

10. Pilot study 11 single bag ~ 25 kg ochre pellets Bag inserted Bag moved Major Event

11. P bag deployment • Easy to handle and deploy • Geotextile bag – 10 kg of ochre pellets

12. Pilot study 2 • 1 Ambient TP levels • 2 Disturbed TP levels Little effect on TDP (though flows were quite high)

13. P stripping issues • Sedimentation rates are very high • Ditch preparation? Lined or not lined? • Flashy hydrologic regime 10 l/s to 200 l/s. can all the flow be processed (attenuated)? • Sediment management plan • Ochre recovery plan – when, how much? • Benefits to agriculture • Perception of putting waste to land

14. Low flow level flow A P loss B Bed Sediments Scavenging P in rivers and lakes • Gabions of ochre pellets in the water column A – suspended in water column B- resting on the channel bed (at a suitable location) • In place at times of high risk • removed from the water column and returned to land

15. Proposed Runoff Plot Experiment Cockle Park Farm -10 plots • Large scale soil amendment experiments • Biomass production and buffer strip impacts • Nutrient and metal fluxes control sludge ochre Sludge/ ochre 30 m Lime 1 Lime 2 10 m

16. Conclusion • Huge potential but the waste to land issue needs to be tackled • Practical issues to be resolved. • Remediation should work as part of a multi-disciplinary plan for all pollutants, biodiversity and flood reduction • Defra funded schemes need to consider proactive measures compared to traditional passive methods. • WFD - must strip P and protect larger rivers and lakes