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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. [email protected]
J. Blackwell, ex CSIRO, Division of Land and Water, PMB 3, Griffith, NSW 2380, Australia. Currently ILWS Charles Sturt University, Wagga
18/04/23 1
What is slotting• Segmental deep loosening technique to
reduce recompaction• Deep mixing and placement of ameliorants
2
Potential uses of soil slotting
ProblemProblem AmeliorantAmeliorantSodic soilSodic soil Gypsum, sludgeGypsum, sludge
Acid SoilAcid Soil Lime, Gypsum, sludgeLime, Gypsum, sludge
Sandy, heavy claySandy, heavy clay Organic residues, sludge, Organic residues, sludge, (micro) nutrients(micro) nutrients
Nutrient deficiencyNutrient deficiency (micro) nutrients(micro) nutrients
Dense layersDense layers No ameliorantNo ameliorant
3
Yield responses to slotting
CropCrop Increase over controlIncrease over controlWheat (sodic soils)Wheat (sodic soils) 30-60%30-60%
Maize (sodic soil)Maize (sodic soil) 40-65%40-65%
Barley (acid soil)Barley (acid soil) 300%300%
Sugar cane (hard pan)Sugar cane (hard pan) 10%10%
Pasture (degraded)Pasture (degraded) 370%370%
13
Slotting vs deep ripping
14
SlottingSlotting Deep rippingDeep rippingHigh costHigh cost Moderate costModerate cost
Thorough ameliorant mixing Thorough ameliorant mixing to depthto depth
Poor ameliorant mixingPoor ameliorant mixing
Recompaction controlRecompaction control Re-consolidationRe-consolidation
Less restrictive to soil water Less restrictive to soil water content at operationcontent at operation
Soil water content restrictiveSoil water content restrictive
Sub-soil obstacles could Sub-soil obstacles could restrict operationrestrict operation
Sub-soil obstacles less Sub-soil obstacles less restrictiverestrictive
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 discharge15