Disc openers &

Disc coulters

Contributions from Dr Jack Desbiolles (Ashworth et al., 2010) and Baker et al., (2007)and from Jeff Tullberg (Murray et al., (2006)

Jack McHugh

Component Groups

Summary of furrow opener attributes

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

Disc vs tine openers

Disc opener classificationsZero 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

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

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

Terrain followingDepth wheels

Single or both facesCleaningPress wheels

Precision (always separated)Hair pinning (Clamping)

Single discsEither 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 + pinch wheels

Sweep + tilt (undercut) + tyre to close

Sweep + tilt (undercut) seed boot increases throw, draft, wear and smearing

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

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

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

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

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

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.

Coulter blades with offsets

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.

Anti hair-pinning and soil

throw reducing attachment.

As a herbicide or

fertiliser coulter