This document discusses different types of disc openers and coulters used in no-till planters. It describes disc openers as being more variable than tine openers depending on soil conditions and settings. The main types of disc openers discussed are disc coulters, double discs, single discs, and disc/tine hybrids. For each type, the document provides details on their design characteristics and how they interact with soil and residue to perform functions like furrow opening, seed placement, and soil loosening.

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

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.