A French farmer’s ‘weed harvester’, designed to minimise seed return from survivors of mechanical or herbicide treatments by trimming off the seed heads, has been developed into a commercial product.
The device can be used wherever weeds grow above the height of the ‘host’ crop and is said to have a particular role to play in organic crops grown without pesticides, and in situations where populations of grass weeds such as blackgrass have become resistant to chemicals.
Wild oats and ‘volunteers’ from seed dropped by previous crops could also be a target for this mechanical control process.
The Top Cut Collect from Zürn Harvesting, the German manufacturer of cutting tables for combine harvesters, uses a double reciprocating knife cutterbar to trim the unwanted plants, with the seed heads then conveyed to a 4cu m tipping container for disposal.
Designing a folding mechanism for the two cutting and conveying booms has been among the challenges faced when developing the machine, which in prototype form was built as an 18m-wide machine.
Providing sufficient holding capacity to complete runs in long fields before the hopper needs emptying has been another issue. For the commercial models, Zürn has settled on a choice of 4.5m and 6m wing sections for working widths of 9m and 12m.
“The Top Cut Collect is an intelligent combination of two tasks – cutting the weed tops above the crop and collecting this material, which contains the weed seeds,” says Rolf Zürn, managing director at Zürn Harvesting.
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“Different scientific studies in France show that up to 40% of grass weed seeds are shed on to the ground before harvest, so it is effective to cut off and collect the tops of these weeds before harvesting. By doing this, the cycle of weeds adding to the seed bank is interrupted and hygiene in the field is improved sustainably by reducing the weed seed bank in the soil.”
An added benefit, he says, is that removing grass weed and wild oat seed heads in this way kills the plant, making it easier to cut and thresh badly infested crops without resorting to a pre-harvest chemical treatment.
Cutting height is adjustable between 350mm and 1500mm to cater for different crops and 5-8kph is a typical working speed. Each wing section, which folds like a gull wing to within a 3m transport width, has a helix-shaped reel with flexible rubber strips that sweep prominent weeds against the cutterbar.
The conveying belt behind the knife feeds an elevating conveyor at the centre to fill the covered hopper of approximately 4cu m or 1 tonne capacity.The hopper projects back from an axle that runs on row-crop wheels with 210/95 R44 tyres and is emptied by hydraulic cylinders tilting it rearwards.
The tractor needs load sensing hydraulics with a delivery rate of at least 80-litre/min at 180 bar pressure to supply the cutterbar and conveyor hydraulic drive motors.
Company: Zürn Harvesting
Name: Top Cut Collect
Type: Mechanical weed control
Key feature: Removes the seed heads of prominent weeds (eg blackgrass, wild oats) to reduce seed return