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

Water policy and on-farm interventions

Parallel work streams

Fundamental empirical evidence

Evidence synthesis for national policy

support

On-farm measures for sediment control

The scale challenge for sediment mitigation

Measure scale

Farm scale

Landscape scale

control

realism

Demonstration test catchments (DTCs)

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?

Targets for guiding sediment management

Targets for guiding sediment management

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?

Defining sediment as a stressor

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

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

Conceptualising the sediment cascade

Receptor Delivery Mobilisation Source

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

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

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

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

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

Listening to farmer preferences for options

Challenges for on-farm sediment mitigation

Farm incomes – note not profit and commodity prices

Challenges for on-farm sediment mitigation

General poor management – e.g. maintaining cover

Challenges for on-farm sediment mitigation

General poor management – e.g. compaction and runoff problems

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

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

Challenges for on-farm sediment mitigation

Targeted advice – e.g. remembering treatment-trains

Challenges for on-farm sediment mitigation

Due consideration of common configurations of risk

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

Re

lati

ve f

req

ue

ncy

(%

)

Drain age

Drain age distribution Hampshire Avon

Wensum

Eden

Challenges for on-farm sediment mitigation

Current low impacts at landscape scale

Challenges for on-farm sediment mitigation

Cross sector sediment source apportionment

72

22

5

1

Agriculture

Urban

Channel banks

STWs

Challenges for on-farm sediment mitigation

Source-specific sediment impacts on aquatic ecology

Challenges for on-farm sediment mitigation

Interactions with hydromorphology

Challenges for on-farm sediment mitigation

Overriding effect of hydro-climatic patterns

The sustainable intensification agenda

SI

Environmental

Social Economic

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