Soil Slotting to ameliorate subsoil limitations to crop production (first presented in 1991)

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Soil Slotting to ameliorate subsoil limitations
to crop production(first presented in 1991)

• N. S. Jayawardane, ex CSIRO, Division of Land and
  Water, GPO Box 1666, Canberra, ACT 2601,
  Australia.
• G. Kirchhof, ex NSW Agriculture, PMB 944,
  Tamworth 2340, Australia. gk_at_mpx.com.au
• J. Blackwell, ex CSIRO, Division of Land and
  Water, PMB 3, Griffith, NSW 2380, Australia.
  Currently ILWS Charles Sturt University, Wagga

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What is slotting

• Segmental deep loosening technique to reduce
  recompaction
• Deep mixing and placement of ameliorants

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Potential uses of soil slotting
Problem Ameliorant
Sodic soil Gypsum, sludge
Acid Soil Lime, Gypsum, sludge
Sandy, heavy clay Organic residues, sludge, (micro) nutrients
Nutrient deficiency (micro) nutrients
Dense layers No ameliorant
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Slot formation
after Jayawardane et al. 1995
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Commercial slotter
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Slot configuration
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Water logging
Not slotted
Slotted
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Air filled porosity
after Jayawardane and Chan, 1994
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Ameliorant mixing
after Jayawardane et al., 1995
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Recompaction
after Blackwell et al. 1989.
(cm)
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Root growth in acid soils
Undisturbed subsoil
Fully ameliorated slot
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Sludge incorporation
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Yield responses to slotting
Crop Increase over control
Wheat (sodic soils) 30-60
Maize (sodic soil) 40-65
Barley (acid soil) 300
Sugar cane (hard pan) 10
Pasture (degraded) 370
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Slotting vs deep ripping
Slotting Deep ripping
High cost Moderate cost
Thorough ameliorant mixing to depth Poor ameliorant mixing
Recompaction control Re-consolidation
Less restrictive to soil water content at operation Soil water content restrictive
Sub-soil obstacles could restrict operation Sub-soil obstacles less restrictive
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Is there a future in soil slotting?

• Rehabilitation of severely degraded soils
• Sludge slotting on forestry lands for sludge
  disposal
• Potential uses currently restricted to high value
  crops
• Adoption of slotting hampered by cost
• Potential use for installing a lime-slot around
  acid-sulphate lands, to neutralise discharge

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Stress fissures along slot wall
undisturbed
Slot