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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
Assessing soil structure
Assessing soil structure
Assessing soil structure
Google Earth
Traffic management
Visual indicators
Visual indicators
Soil structure
Impaired capillary movement
of water
Visual assessment
Investigate
Investigate
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
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
Infiltration / soil wetting
0 mins3 mins
5 mins 8 mins
Coarse/Fine Fine/Coarse
Infiltration / soil wetting
8 mins
Coarse/Fine Fine/Coarse
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
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