Disc seeding in conservation agriculture

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  • 1. Disc openers & Disc coulters
    Jack McHugh
    Contributions from Dr Jack Desbiolles (Ashworth et al., 2010) and Baker et al., (2007)
    and from Jeff Tullberg (Murray et al., (2006)
  • 2. Component Groups
  • 3. Summary of furrow opener attributes
  • 4.
  • 5. Disc vs tine openers
    Not simply a matter of saying “disc planters do this or tine planters do that”. The variability in performance and characteristics is as diverse amongst disc opener planters as it is with tine opener planters
    Discs require greater unit weight when compared to tine planters – can be an issue in wet soils
    Tine opener power requirements are dependent on soil condition, depth of operation, speed and rake angle of the point.
    Disc opener power requirements are related to soil condition, disc attributes, module settings and soil residue condition
    The seed firmer has been rated the best no-till technology in USA for the past 2 years
    Pressing/covering devices have a greater impact on crop yield than opener type
    Tine sweep openers perform well in wet years, whereas disc and chisel tine openers perform best in dry years with low plant available water. (Disturbance)
    This data also shows that disc openers can be very variable if not used in the right conditions
  • 6. Disc opener classifications
    Zero till openers generally classified into four design categories
    Disc coulter
    Double discs (including triple disc)
    Single discs vertical and undercut styles
    Disc/tine and disc blade hybrids
  • 7. Disc coulter
    Swivelling disc modules - wide range of blade designs
    Flat, fluted, continuous or scalloped cutting edge (dbl bevel)
    Commonly 430 - 510mm DIA
    Function – pre loosening, residue cutting and/or fertiliser banding
    Coupled with tines – small angle to sharpen, increase drive and speed ratio.
    Self align and parallel to direction of travel
    Soil disturbance – design, depth and speed
    Combined with double discs to become triple disc
    Can be combined with single discs
  • 8. Double discs & triples
    Paired discs with sweep and tilt – contacting at a pinch point
    Enough to drive the other & glide when driven independently (relative blade rotation)
    Excessive: bearing failure and blade wear
    Gap; residue cutting, furrow opening, seed placement
    Provide accuracy for best seed placement
    Suited for light soft soils
    Compact walls and base on wet clay soils
    Leading and trailing, differential DIA, smooth or notched
    Pinch point in the shadow reduces soil build up
    Self cleaning & increased residue cutting
    Accelerated wear
    Requires large vertical down force – increases smearing and reopening
    Best behind leading coulter – Triple disc
    Suited for soft to firm compactable soils
    Leading discs – sweep angle for residue cutting & fertiliser
  • 9. Terrain following
    Depth wheels
    Single or both faces
    Cleaning
    Press wheels
    Precision (always separated)
    Hair pinning (Clamping)
  • 10. Single discs
    Either fixed or contour following
    Vertical discs with sweep to maximise speed (430 – 660mm) Some at 760mm (Daybreak)
    5-70 to dir of travel
    Tilt angles to maximise penetration
    Up to 200 Sweep 3-80
    Reduces forward rotation and lowers sliding cut of residue
    Sweep + tilt (undercut) seed boot increases throw, draft, wear and smearing
    Sweep + pinch wheels
    Sweep + tilt (undercut) + tyre to close
  • 11. Soil disturbance – function of:
    Sweep and tilt angle
    Disc blade DIA
    Depth and Speed
    Other influences
    Gauge wheels
    Muffler wheels
    Seed boot guards
    Press wheels
    Side guards
  • 12. Single discs – other features
    Sweep angle not adjustable – seed/fertiliser boot in shadow
    Boots are typically shielded close to bottom
    Greater sweep or large diameter is required to avoid seed guard interference
    Guard soil throw for herbicide mixing = less from disc,
    Wear, smearing, compaction and draft
    Disc Blades
    Flat, smooth, with a single bevel – active side to reduce smearing or shadow side to increase rotational speed
    Left and right units to balance out forces
    Fitted with steering discs to maintain tracking
  • 13. Disc/tine and disc blade hybrids
    Any combination of disc rolling blade and fixed blade tine openers:
    Fertiliser coulters with banding knife (Yetter)
    Notched coulter with side blades (Cross-slot & BioBlade)
    Seeding tine associations (NDF Ag-design)
    Features:
    Coulters with banding knife – reliable independent seed and fertiliser separation. Increases soil throw.(x3 – x4)
    Cross-slot/Bio-blade - independent seed and fertiliser separation (V or H). Penetration, drive, residue cutting, seeds avoid hair pinning.
    Tine associations – moisture seeking, increased depth + accuracy, additional flexibility in placement
  • 14. Disc coulters blade technology
    Rolling coulter is defined as a circular disc, operates vertically in the dir of travel & swivel mounted. Often integrated with tine based no till seeders, equally with disc seeders.
    Increase draft, mass and cost – cutting and spreading residues at harvest and CTF/guidance can reduce the need/requirement
    Function
    Cut crop or weed residue – high levels without blockage or hair pinning
    Loosen shallow soil layers – assist optimum planting & reduce planter down pressure req.
    Generate suitable soil throw – incorporate herbicides
    Provide in row tilth – below the seed, for pressing (soil contact),for closing, covering & firming
    Classifications
  • 15. Flat coulter blades
    Smooth blade:
    Dbl bevel edge - Associated with residue manager modules similar to but thinner than single disc seeders. Good penetration, in heavy residue & hard soils tends to stop rotating and “bulldoze’
    Notched scalloped blade:
    Spaced sharpened notches – used in hard sols and heavy residue. Notch size and depth related to diameter and working depth.
    Toothed blade:
    Evolution of notched – used in heavy sugar cane residue using sharpened pointed teeth. Directional with tangential teeth – inclined teeth penetrate and cut as individual tools. Improved drive and superior cutting ability
  • 16. Coulter blades with offsets
    Rippled blade:
    Narrow alternating flutes. Sinusoidal cutting edge. Soil engaging width 8-10mm. 50 – 60 ripples. Good penetration and cutting, low disturbance.
    Bubbled/dimpled blade:
    Fewer & more pronounced – recessed from circumference, smooth straight cutting edge. Soil engaging width 16-24mm. Positive disc drive in soft soils + low soil throw. In slot compaction, reduced penetration, more throw than rippled.
    Fluted blade:
    Coarser version of rippled design. Sinusoidal cutting edge. Soil engaging width 14-16mm. 20 – 25 ripples (offsets). Trap soil and increase throw. Characteristics midway between rippled and wavy.
    Wavy blade:
    Larger coarser version of fluted. Sinusoidal cutting edge. Soil engaging width 20 - 50mm. 7 – 15 ripples (offsets). More furrow loosening and less soil catching – less soil throw at low speed. Less penetration and cutting.
  • 17. Tangential flute & toothed blades:
    Increased residue slicing, minimum hair-pinning. Offsets are not radial – tangential giving rotational direction.
    Turbo style - enter the soil vertically and leave horizontal = increased penetration, residue cutting on entry, additional tilth and soil throw on exit.
    In reverse - lose rotational speed ratio. Reduced cutting but decreased soil throw.
    As a herbicide or fertiliser coulter
    Anti hair-pinning and soil throw reducing attachment.