The two Rs, resistance and regulation, are combining to reduce the effectiveness of the chemical-based weed control farmers have used and, in most cases globally, over-relied upon for the past decades.
But up-and-coming technologies for weed control are being developed which could help fill gaps, some of which involves technology that can be fitted to kit, as well as new mechanical options.
Potentially this could see a changing of the guard where machinery firms are best placed to support weed management on-farm because of the ability to integrate this technology into their equipment.
1. Harvest weed seed control Perhaps the most well-known and well-established of the newer technologies is physical destruction of weed seed at harvest.
Counter-rotating cage mills, integrated into the back of a combine pulverise weed seed in the chaff.
A concept first developed by West Australian farmer Ray Harrington, up to 98% control of herbicide-resistant ryegrass has been achieved in Australia.
With growing problems with ryegrass in the UK, seed mills could play an important part in future control, but efficacy does rely on seed being retained on plants through harvest – which means it is less effective against black-grass.
Various milling options are available globally including the Seed Terminator from Zuhn Harvesting, Redekop’s Seed Control Unit and De Bruin’s updated version of the original Harrington Seed Destructor, the iHSD.
US company Global Neighbor is developing a variation on the theme – using blue LED light to disrupt weed seeds in its Weed Seed Destroyer, which it says is complementary to other forms of weed control.
The ‘Directed Energy’ technology was originally developed following a US Air Force small business investment research grant to destroy tumbleweed seeds.
An Iowa farmer challenged Global Neighbor to similarly prevent water hemp seed from germinating.
Lab tests found warming the weed seed to 60degC and applying blue LED for a few seconds at an intensity 20 times that of sunlight destroyed the seed’s viability.
Delivering that technology to a moving combine is a challenge, but the firm has built a tubed auger design with light sources along its length, which can replace a chaff spread er where the spreader and chopper are separate within the combine.
The chaff is blown back into the chopper waste stream after going through the Destroyer.
INTEGRATED If the combine has an integrated spreader and chopper, the Weed Seed Destroyer can fit before that unit, diverting the chaff through the Destroyer, but not the straw.
Both versions will be trialled in wheat and barley crops in the US this summer.
Stationary testing puts control at 97-99% of four common US weed species, with smaller seeds easier to disrupt.
Other forms of harvest weed seed management being used include chaff tramlining where seed-containing chaff is directed into wheelings for natural degradation of seed or where it can more easily be targeted with herbicides, and Zuhn’s Top Cut Collect which cuts off, collects seed heads for removal prior to harvest, which might make it more viable for black-grass.
2. Smart Spraying Another area which has attracted major investment from machinery companies, tech firms and herbicide manufacturers is targeted spot spraying.
These see and spray technologies involve cameras mounted onto the booms of sprayers, which use machine learning to identify weeds in a field and then signal individual nozzles to spray the weed.
This could reduce herbicide use by up to 70-90%, according to firms developing the technology.
They include Amazone, in combination with Bosch and BASF using its digital platform Xarvio; John Deere, through its acquisition of agtech firm Blue River Technology; Bilberry’s Intelligent Spot Spraying System working with Agrifac, Dammann and Berthoud; and Greeneye Technologies, backed by investment from Syngenta and AGCO.
The first phase of these systems is ‘green on brown’; identifying weeds in fallow or non-crop situations, but the technology is rapidly moving to ‘green on green’ which recognises weeds in cropped fields.
It offers the opportunity to reduce herbicide use, improve resistance management and reduce herbicide stress on crops.
Most of these emerging systems have a split spray tank design enabling residual herbicides or other products to be sprayed across the entire field, while applying contact herbicides to just target weeds.
RGB cameras mounted at around one-metre intervals on the spray boom scan the field, with operation speeds of typically 12km/hour.
Pulse width modulation enables maximum savings on nozzles spaced 25cm apart.
3. Electric weeding British startup Rootwave’s weed zapping technology is being incorporated into Small Robot Company’s non-chemical weeding robot ‘Dick’ to individually treat weeds.
Rootwave uses electricity to kill weeds by destroying chlorophyll and the water system of the plant.
The natural resistance of the weed transforms the electrical energy into heat, which boils the weed inside out from the root upwards, the firm says.
CNH has a partnership with Swiss firm Zasso to help de velop its Electroherb solution, while NuFarm is partnering German startup Crop.
Zone on Nucrop.
What differentiates Nucrop is the spraying of a light saline solution from a boom attached to the front of the tractor onto the plants before treating with electricity with a unit on the back.
The tractor’s pto shaft drives a generator that converts mechanical energy into electrical energy and then converters in a switch cabinet convert that from low voltage to high voltage electricity.
An application frame channels the energy into the plants completing the circuit, to which the VoltFuel spray makes the plants more sensitive.
ENERGY That reduces the energy requirement by 10 times and increases the width that can be treated from 12m to 24m versions this season.
The firm is targeting potato desiccation initially, with replacing glyphosate and potentially weed control in sugar beet to follow.
Latvian firm WeedBot uses cameras to identify weeds and high-power lasers to eradicate weeds using thermal energy to a 2mm accuracy.
It has been piloting its Lumina product with organic carrot growers in the UK, with the aim of expanding into other crops.
US-based Carbon Robotics has recently unveiled a similar system called LaserWeeder.
Both WeedBot and Carbon Robotics have units that attach to tractors, but are also aiming to produce autonomous versions of their weeders to join the likes of the Small Robot Company.
One drawback of the systems currently is the working speed – Carbon Robotic’s system can cover just 0.8ha/hour, which is very slow even in high value, low area crops and will limit the potential until improved.
4. Autonomous weeding Also in the autonomous weeding area is the Danish-built FarmDroid FD20, distributed in the UK by Opico.
This unit goes one step further by integrating both drilling and subsequent weeding into one.
The firm claims that by using high precision GPS-seeding it knows the position of each seed, making it possible to weed both between the rows and plants in the row and can start before the crop emerges.
Weeding between rows is by dragging three weeding wires a few mm below the soil surface, while a robotic arm connected to an electrical motor weeds between the crop plants.
It is powered by four solar panels, generating enough power to work for 18-24 hours/ day depending on weather and working conditions.
Again, working speeds are slow – up to 6ha/day.
Trials in the UK have begun in sugar beet