assessing and repairing structural damage · assessing and repairing structural damage ian...

Assessing and repairing structural damage

Ian Beecher-Jones

Soil and Water Management Centre

Outline• Background

• Costs• Causes

• Effects of structural damage• Yield• Tillage• Runoff / Erosion/ flooding

• Assessing structural damage

• Preventing damage

• Repairing damage

• Drainage

• Summary

Cost of the problem

The assessment explored the total costs of

soil degradation:

• The total quantified costs of soil

degradation are estimated at between

£0.9 bn and £1.2 bn per year.

• Compaction and loss of soil organic

content account for 39% and 45%

respectively of annual costs.

• Silts and sands account 67% of total

estimated erosion costs, and clays and

sands for 91% of compaction costs.

• Almost 80% of total quantified costs occur

offsite.

• In terms of soilscapes, arable farming

accounts for over 70% of erosion and

compaction related costs.

Cost of compaction

Relationship between maize silage yield and soil bulk density (Quebec)

Traffic control effects on energy/costs requirements (kWh/ha) (£/ha)

*After: Nix 43rd Edition (2013) c.25p/kWh

at 65% Tractive efficiency (Innes and Kilgour, 1980)

Causes of structural damage

• Machinery

• Weather

• Livestock

• Nature

• Farming practices

Good soil structure

Good soil structure

• Large pores and small aggregates

• Plant roots need to push aggregates away from them as they growo They need somewhere to push the soil

that they displace

• Therefore, aggregates should be smaller than the diameter of the plant roots

• Lots of small (<1 cm diameter) aggregates are better than a few large aggregates/clods

Aggregate Stability

Grassland Arable (60 years)

3% SOC 1.5% SOC

Highfield Arable/Grass Rotation Experiment

Rothamsted (Established 1949)

Visual soil assessment

After: Shepherd (2000), Visual Soil Assessment, Volume 1, Landcare

Research, New Zealand

Visual soil assessment

After: Vaderstad, TARGET on establishment

Assessing soil structure

Penetrometer

Conductivity scanning

Profile pits

EMI Scanning

(After: Smith, 2001)

Random Traffic

Controlled Traffic


Google Earth

Traffic management

Visual indicators

Soil structure

Impaired capillary movement

of water

Visual assessment

Investigate

What others are saying

What can we do

• Don’t put it in the first place

• Can we use nature to help us?

• Mechanical solutions

• Combination of both?

Protect the soil

• Re-site gateways away from high risk areas• Reduce stocking densities when soils are wet

Protect the soil

• Move feeders to clean areas – if you can

• Place livestock drinkers and feeders on hard bases

(e.g. option CSF007 in the UK's Capital Grants

Scheme in CSF areas)

Feeding areas & Walkways

Protect the soil

• Fence waterways

• Construct bridges for livestock crossing streams

Protect the soil

• Provide alternative drinking systems for livestock

that rely on surface water; for example, pasture

nose pumps which use the cattle's own energy to

pump water

Keep some cover on the soil

Depth of compaction

>30cm

0 – 15cm

Earthworms

• Improve soil structure

• Release nutrients

• Most active spring and autumn

• Improve drainage

• Mix soil

• Spread mycorrhizal spores

• Lose C – emit N2O

• Generate humus

• Support other wildlife

Quick solutions

Loosening devices

• Aerators

• Sward lifters

• Subsoilers

Aerators

• Working depth – upto 10cm• Surface spikers or slitters

Sward lifters

Working depth – 20 – 35cm

The result

Subsoilers

Twin leg subsoiler Conventional subsoiler High Winged subsoiler

Hydrograph of mole drain discharge

with leg fissures

Hydrograph of mole drain discharge

without leg fissures

Time, hAfter: Leeds Harrison, Spoor & Godwin, 1982

Tine critical depth

After: Spoor, et al, 2003

Wearing parts

Tines for the job

Wide point, high wing lift

Narrow point, low wing lift

Plain tine

After: Spoor and Godwin, 1978

Soil disturbance

After: Spoor & Godwin 1978

Plus shallow leading tines

Wings only

Draught

Force

(tonnes)

Area of

disturbance

(m2)

Specific

resistance

(tonnes/m2)

2.39 0.24 9.6

2.35 0.42 5.4

Similar: Almost double: 45% reduction

Draught 20.43 kN 26.58 kN

Disturbed area 0.098 m2 0.184 m2

Specific resistance 208 kN/m2 144 kN/m2

After: Spoor and Godwin, 1978

Leading tines

After: Spoor & Godwin, 1978

Soil disturbance

• Simple tines = 1.5 x depth of work

• Winged tines = 2.0 x depth of work

• Winged tines + = 2. 5 x depth of work (of

shallow leading tines deeper tine)

After: Spoor & Godwin, 1978

Cultivate at the right time

Correct seedbed

• Timing

• Correct equipment

• Drainage

• Fine, but firm

Infiltration / soil wetting

0 mins

Coarse/Fine Fine/Coarse


0 mins3 mins

5 mins 8 mins



8 mins


Topsoil loosening guidelines

• Check what compaction is in the profile

• Don’t loosen on poorly drained soils

• Loosen soils in the Autumn

• Choose equipment carefully

• Set equipment correctly

Topsoil loosening guidelines

• Beware of re-compaction• Cut or graze the site immediately before treatment

• Avoid grazing after loosening and conserve rather than graze in the first spring after treatment

• If late growth needs utilising, use sheep rather than cattle to minimise re-compaction damage

• Do not spread slurry on recently loosened fields.

Reseeding

Reseeding

• Pick fields for reseeding carefully.

• Reseeding decisions should be based on ryegrass content,

quality, productivity and weed infestation, rather than age.

• Reseed in the autumn (August or early September) if

possible.

• Autumn seeding may encourage rapid establishment given

sufficient moisture, warm autumn soils

• Autumn sowing allows the new sward to be far more

productive in its first season.

• Old sward can be used up to July or early August

• A summer grazed brassica can be used as a short term

break crop

Timing

• Not too late

Reseeding

• Destroy old swards effectively and efficiently• Ensure the best soil condition before sowing• Correct nutrient indicies

• pH of at least 6 • P & K indices of more than 2

• Lime before seeding• Inspect the profile for compaction, pans and heavy poaching

too• Sub Soil wet areas to improve drainage• Select the correct mixture

Reseeding

• A fine firm seedbed

• Moisture matters

• Plough to bury sward residues

• Shallow drill with calibrated drill

• Don’t drill if too wet or dry

• Roll afterwards to retain moisture

• Keep an eye on slugs, leatherjackets and weeds

Compaction

Don’t create damage in the first place

• Costly to repair• Root of many growth issues• How can drainage help?• Infiltration rates

Livestock opportunities• Stock rotations• Housing• Fencing off areas near water courses

Compaction management

• Dual wheels on the tractor• Timeliness of operation• Method of working the field• Sward lifter

Drianage

Completion plans

• Existing infrastructure, make sure it works

• Can anything be added?

What can I do?

• Walk ditches – keep them clean

• Subsoil & mole drain in drier conditions, if correct soil type

• Clean current drains

Cleaning drains

Ditching

• £300 / day

• Move water

• Talk to drainage contractor

Drainage does it pay?

12 months later

Cost: €2800/acre

Conclusions

• Look after the soil

• Keep weight off at inappropriate times

• Choose remedial action carefully

• Timeliness is key

Conclusions

• Get the balance right

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