1. Soil:Strength & Compaction Jack McHugh Contributions from Dr Jack Desbiolles (Ashworth et al., 2010) and Baker et al., (2007)
2. 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.
3. Cover Workability as influenced by soil moisture 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. Best for cultivation = Best for compaction Separate beds from tracks Improve workability: Increase organic matter Low compaction management
4. 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 soil conditions Pressing seeds into the base of V & U slots assists emergence
5. Soil and Furrow compaction Drilling into wet soils Response seedling emergence and earth worm numbers to three contrasting zero till slot shapes and surface residues in a wet soil
6. 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
