Soil: Strength and compaction
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Transcript of Soil: Strength and compaction
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Soil:Strength & Compaction
Contributions from Dr Jack Desbiolles (Ashworth et al., 2010) and Baker et al., (2007)
Jack McHugh
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Soil Strength
Soil Strength is the soil resistance to deformation and is strongly
influenced by soil moisture and management.
Cone penetrometers can be used to quantify relative soil strength.
Soil workability and friability – Measures of soil quality.
Soil moisture thresholds – solid, semi solid, plastic, liquid
(Atterberg limits)
Small plastic index and Large friability index – best workability.
Soil at its best for planting - is also the weakest for compaction.
Soil monitoring – soil physical changes over time due to
management.
Disc seeders are highly sensitive to soil strength.
Optimal - reduce soil strength and increase soil moisture at
maximum friability.
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Cover
Maximum compactability Generally soil with a high friability
index and a low plasticity index with FC close to the plastic limit are considered most cultivation friendly.
Workability as influenced by soil moisture
Improve workability:Increase organic matterLow compaction management
Best for cultivation = Best for compactionSeparate beds from tracks
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Soil and Furrow compaction
Typical profiles of V,U and inverted T furrow profiles in a silty loam at 15, 20, & 27% moisture content. Heaving (h), cracking/loosening (l), smearing (s) and compaction (c).
Triple disc Narrow hoe opener T chisel opener
Response of contrasting zero till slot shapes to dry soilconditions
Pressing seeds into the base of V & U slots assists emergence
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Response seedling emergence and earth worm numbers to three contrasting zero till slot shapes and surface residues in a wet soil
Drilling into wet soils
Soil and Furrow compaction
Response/opener Winged Hoe Double Disc
Oxygen diffusion √√ √√ xxx
Non-hair pinning √√√ √√√ xx
Infiltration √√√ √√ xx
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Using disc drills in wet and sticky soils
Dr Jack Desbiolles. Institute for Sustainable Systems and Technologies, University of South Australia. GroundBreaker 2009 - Issue 50
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V Slots U Slots
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Developed in 2004…
Field – based
“VS – Fast”
- soil descriptors & measures- for farmers / agronomists- to measure & monitor- land condition- & monitor trend
“simple yet scientifically robust ”
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First evaluation of
“VS – Fast”FAO - LADA Pilot Study site
- Fengning Manchu County, Hebei Province
LADA
August 2004
August 2004