Presentation given by Adie Collins at the SILTFLUX workshop, UCD, Dublin, February 2016

1. Rothamsted Research
where knowledge grows
Rothamsted Research
where knowledge grows
On-farm measures for
sediment control:
options, impacts and
challenges
Adie Collins
SILTFLUX workshop, UCD, Dublin, February 2016

2. Water policy and on-farm interventions

3. Parallel work streams
Fundamental
empirical evidence
Evidence synthesis
for national policy
support
On-farm
measures for
sediment
control

4. The scale challenge for sediment mitigation
Measure scale
Farm scale
Landscape scale
control
realism

5. Demonstration test catchments (DTCs)

6. Example policy questions to the DTCs
• How can you extrapolate mitigation efficacy from
a single measure to a series of interconnected
measures?
• How much of an improvement in terms of
receptors can we attain by implementing
mitigation?
• To what extent does targeting only part of the
anthropogenic pressures on water bodies allow us
to achieve significant improvement in status?
• How long will it take for mitigation interventions
to: (i) meet a set pollutant threshold (WFD related
targets) at a given point in a catchment and (ii)
achieve an ecological response?

7. Targets for guiding sediment management

8. Targets for guiding sediment management

9. Overarching questions
• how do you best characterise
‘the problem’?
• what are the technical remedies?
• how do you best get farmers more
engaged?
• what are the challenges for
delivering positive outcomes from
targeted on-farm interventions?

10. Defining sediment as a stressor

11. Typical problems in livestock areas
1. 4. 6.
2. 5. 7.
3. 1.Poached surface soils
2.Over-full FYM store
3.Dirty yard by parlour
4.Drain connecting 3. to stream
5.Runoff from 2. to stream
6.Timing of slurry applications
7.Farm track channelisation

12. Typical problems in arable areas
1. 2.
3. 4.
5.
1. Exposed arable soils in the
winter months
2. Field drain and ditch
discharge to rivers
3. Grazing of fodder crops
4. Rill and gully formation on
steep, cultivated slopes
5. Cultivation practices:
ploughing downslope

13. Conceptualising the sediment cascade
Receptor Delivery Mobilisation Source

14. Potential source mitigation options
Method Efficacy Farm scale
costs
Mean Range Mean Range
Reduce field stocking rates when soils are
wet
25 10–50 5413 3419-
7814
Move feeder rings at regular intervals 10 2-25 1190 928-
1461
Construct troughs with a concrete base 10 2-25 394 333-
451
Do not apply manure to high risk areas 25 10-50
Do not spread slurry or poultry manure at
high risk times
50 10-95

15. Potential mobilisation mitigation options
Method Efficacy Farm scale
costs
Mean Range Mean Range
Loosen compacted soil layers in grass fields 25 10–50 1425 1104-
1745
Establish cover crops in the autumn 80 50-95 3843 3612-
4058
Cultivate compacted tillage layers 25 10-50 3276 2532-
4004
Incorporate manure into the soil 50 25-80 8417 7670-
9177
Use slurry injection application techniques 50 25-80 1151 447-
1844

16. Potential delivery mitigation options
Method Efficacy Farm scale
costs
Mean Range Mean Range
Re-site gateways away from high risk areas 10 2-25 1314 1196-
1438
Farm track management 50 10-95 190 158-
223
Cultivated and drill across the slope 25 10-50 812 628-
995
Establish new hedges 10 2-25 2025 1757-
2297

17. Potential receptor mitigation options
Method Efficacy Costs
Mean Range Mean Range
Fence off rivers and streams from livestock 50 10-95 926 801-
1050
Construct bridges for livestock crossing 80 50-95 944 732-
1154
Locate out-wintered stock away from
watercourses
2 0-10 165 150-
179
Riparian buffer strips 50 25-80 505 405-
606

18. Listening to farmer preferences for options
Mitigation measure
Establish cover crops in the autumn
Adopt reduced cultivation systems
Cultivate compacted tillage soils
Manage over-winter tramlines
Loosen compacted soil layers in grassland fields
Ditch management on arable land
Ditch management on grassland
Move feeders at regular intervals
Increase the capacity of farm slurry stores to improve timing of slurry applications
Install covers to slurry stores
Minimise the volume of dirty water produced (sent to dirty water store)
Minimise the volume of dirty water produced (sent to slurry store)
Store solid manure heaps on an impermeable base and collect effluent
Use slurry injection application techniques
Incorporate manure into the soil
Fence off rivers and streams from livestock
Construct bridges for livestock crossing rivers/streams
Re-site gateways away from high-risk areas
Farm track management
Establish new hedges

19. Listening to farmer preferences for options

20. Challenges for on-farm sediment mitigation
Farm incomes – note not profit and commodity prices

21. Challenges for on-farm sediment mitigation
General poor management – e.g. maintaining cover

22. Challenges for on-farm sediment mitigation
General poor management – e.g. compaction and runoff
problems

23. Challenges for on-farm sediment mitigation
General poor management – e.g. maintenance of buffer leading
edges
Riparian
buffer
efficacy
statistics
(0-2 m
leading
edge)
Avon Wensum Eden All DTCs
Mean 71 93 97 86
SE Mean 13 4 3 6
Median 78 92 100 92
Range 55 13 8 63
Minimum 37 87 92 37
Maximum 92 100 100 100

24. Challenges for on-farm sediment mitigation
Grass re-seeds and specific crops are high risk for soil loss during cultivation,
establishment and post harvest phases

25. Challenges for on-farm sediment mitigation
Targeted advice – e.g. remembering treatment-trains

26. Challenges for on-farm sediment mitigation
Due consideration of common configurations of risk

27. Challenges for on-farm sediment mitigation
Due consideration of the drain flow pathway
0
10
20
30
40
50
60
70
Pre-1939 1940s 1950s 1960s 1970s 1980s 1990s Unknown
Relativefrequency(%)
Drain age
Drain age distribution
Hampshire Avon
Wensum
Eden

28. Challenges for on-farm sediment mitigation
Current low impacts at landscape scale

29. Challenges for on-farm sediment mitigation
Cross sector sediment source apportionment
72
22
5
1
Agriculture
Urban
Channel banks
STWs

30. Challenges for on-farm sediment mitigation
Source-specific sediment impacts on aquatic ecology

31. Challenges for on-farm sediment mitigation
Interactions with hydromorphology

32. Challenges for on-farm sediment mitigation
Overriding effect of hydro-climatic patterns

33. The sustainable intensification agenda
SI
Environmental
SocialEconomic

34. Concluding remarks
• mitigation of agricultural
sediment losses must be part of
whole-farm, multi-pollutant
intervention planning and must
cover inorganic and organic
components of sediment
pressure
• on-farm sediment management
is only part of the solution to
cross sector catchment
sediment problems
• the current SI agenda should be
seen as an opportunity, not a
barrier, for sediment
management