Soil:Strength & Compaction

Contributions from Dr Jack Desbiolles (Ashworth et al., 2010) and Baker et al., (2007)

Jack McHugh

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.

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

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

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

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

V Slots U Slots

Developed in 2004…

Field – based

“VS – Fast”

- soil descriptors & measures- for farmers / agronomists- to measure & monitor- land condition- & monitor trend

“simple yet scientifically robust ”

First evaluation of

“VS – Fast”FAO - LADA Pilot Study site

- Fengning Manchu County, Hebei Province

LADA

August 2004

August 2004