Rotary currycomb
The rotary currycomb is a mechanical weeding tool used in full-field cultivation, a hybrid between the harrow currycomb and the rotary hoe.
Operating principle
The rotary currycomb is a recent mechanical weeding tool halfway between the currycomb and the rotary hoe. It consists of discs with round teeth of a diameter equivalent to that of a harrow currycomb. However, each disc has an attack angle similar to the discs of a stubble cultivator. The entire width of the tool is worked because the discs slightly overlap.
A sturdy frame equipped with 2 gauge wheels allows the machine to roll smoothly in the field. The success of the work is ensured by steel spring rods. The rotors are individually suspended and adapt to uneven ground. The pressure and inclination of the rings are adjusted according to needs.
Mode of action
Closer to the currycomb than to the rotary hoe, it differs by its brushing effect; the action of the teeth and the angle of the discs lift a thin layer of soil and thus destroy weeds by uprooting or covering. It allows working fully on the entire soil surface and is used on bare soil or on all types of crops: wheat, corn, soybean… Its design allows greater penetration capacity than the currycomb on compacted soils and less sensitivity to clogging by plant debris.
Under good conditions, up to 90-95% of the weeds are destroyed, including 1/3 by uprooting and 2/3 by covering.
Use
On the youngest possible weeds: from germination to the 2-3 leaf stage. A well-prepared soil: fine preparation, well-leveled ground. A dry soil, dry weather: the pass must be followed by at least one day of sun and/or wind to prevent weed regrowth.
If the working speed is too low (<4 km/h), large elements (stones, clods, and large plant debris) get stuck between the teeth.
Intervention stages depending on crops[1]
Corn
Pre-emergence then from 2 to 5 leaves:
- Forward speed: 8 to 10 km/h blindly, 5 km/h from 2 leaves, then 1 km/h per additional leaf.
- Working depth: 3 to 4 cm.
- Pressure on elements: Depending on grass cover and selectivity. This is the last adjustment to make.
Cereals
From 2 leaves until the end of tillering-beginning of stem elongation stage:
Be careful at the 2-3 leaf stage of the cereal not to cover young shoots. Limit speed accordingly.
- Forward speed: 3 to 10 km/h.
- Working depth: 2 to 3 cm depending on crop rooting.
- Pressure on elements: depending on crusting, grass cover, and selectivity.
Protein crops
It is possible to work at the pre-emergence stage, however it is necessary to have sown at 3-4 cm depth. Avoid interventions between the pointing/cross and 2 leaf stages. Passes can then be made up to the 8 leaf stage for faba bean and tendril formation for pea.
Rapeseed
From the cotyledon stage. But be careful about covering for early interventions.
Settings and aggressiveness
The rotary currycomb must be adjusted according to soil type, crop type and its development stage, and also the development stage of the weeds. The goal is to find a compromise between weeding effectiveness and aggressiveness on the crop.
There are 4 settings in order of priority:
- tool horizontality: managed by the three-point hitch,
- working depth: adjusted by the gauge wheel,
- tooth aggressiveness: by adjusting the spring pressure on the elements,
- forward speed: the higher the speed, the greater the soil displacement.
Strengths and weaknesses
Strengths
- Effectiveness adjustable with precision thanks to the inclination adjustment of the rings.
- More versatile than the currycomb (soil type).
- Wider intervention window (crop stage, weed stage).
- Early interventions on the youngest possible weeds are to be prioritized, but the rotary currycomb, more aggressive than the hoe or currycomb, will also be more effective on more developed weeds. It is useful up to the 6 leaf stage of dicotyledons and partially effective on grasses.
- Full-field work on the row.
- Ideal in simplified systems (in straw residues) with little risk of clogging.
- Less wearing equipment compared to others.
- Individual arm lifting by quick lift (ideal for row crops like corn).
- Inverted rotor arrangement preventing lateral traction forces.
- The machine is exclusively equipped with rings across its entire working width (no additional currycomb teeth).
- Higher work rate than with the currycomb of equivalent width.
- Aerates the soil, improving water and air circulation in the soil, promoting biological activity and thus improving mineralization.
- Limits soil water evaporation by breaking capillarity (mulching effect on the first cm of soil).
Weaknesses
- Longer and more delicate adjustments compared to a currycomb (pressure and individual orientation of about twenty toothed wheels). Higher damage potential than the hoe or currycomb if poorly adjusted.
- Even though each arm is independent, seedbed leveling is essential for good effectiveness and ease of adjustment.
- Not suitable for sensitive crops before an advanced stage (e.g., beets).
- Less crust-breaking than the rotary hoe.
- Quite expensive (double the price of a currycomb).
- Less effective in stony soils.
Indicative costs[2]
- Purchase price: €2500 to €3400 excl. VAT / linear meter
- 6 m: €18,400 excl. VAT
- 12 m: €30,000 excl. VAT
- Price of a star: about €120
- Annual use: 25 ha/linear meter
- Cost price (harrow only):
- 6 m: €7.90/ha
- 12 m: €10.4/ha
- Average cultural operation cost (fuel and labor included): about €20/ha. Up to €30/ha for very low work rates.
Selection criteria
| Points of attention | Comments |
|---|---|
| Adjustment of the aggressiveness of the wheels | Manual or hydraulic |
| Individual pressure adjustment of each wheel | Allows a more precise adjustment of the tool on the row |
| Adjustment of the wheel angle | Little or no interest |
Different models
| Manufacturer | Model | Minimum width | Maximum length | Aggressiveness adjustment | Reference price (for a 6 m rotary currycomb) | Details |
|---|---|---|---|---|---|---|
| APV | Rotary Weeder (RW600) | 6.15 m | 12.2 m | Manual | €29,020 | Details |
| Leroch Distribution | E-roto | 3 m | 18 m | Hydraulic | €16,000 | Details |
Sources
- Rotary currycomb - APV
- Weeding: The rotary currycomb put to the test - Paysan Breton
- Rotary currycomb - Chamber of Agriculture Centre Val de Loire
- Rotary currycomb - Technical sheets from the GAB/FRAB network
- Opti'mat: https://optimat.org/outil/roto-etrille/
- The rotary currycomb, a complementary tool to the currycomb - CAB
