Is mechanical site-specific weed control a fallow management option?
with Andrew Guzzomi, Senior Lecturer, School of Engineering, The University of Western Australia
There’s nothing more old school than a chipping hoe when it comes to weed control. Chipping has so many practical benefits – simple, low tech, no survivors, cheap, environmentally friendly, non-chemical, works on all weed species and sizes and keeps the kids out of the house for hours.
The downside of course is that it is slow, hot, boring work and requires teams of people to make any difference to weed numbers. So, how good would it be to have multiple chipping hoes mounted on a bar travelling at 10 km/h and poised at the ready to chip out any weeds?
UWA Agricultural engineer, Dr Andrew Guzzomi led the engineering component of a project to develop a tactical tillage machine, that can help manage herbicide resistance risk in conservation cropping fallow management. (Photo: Ryan Early, Anvil Media)
To see if this was feasible, GRDC funded a project for an expert team* of agricultural engineers and weeds researchers, along with grower and industry advisors, to build and test prototypes in various cropping areas around Australia. Their efforts have culminated in the development of the ‘Weed Chipper’, a cultivator fitted with hydraulic response tynes and commercially-available optical sensors that is ready for commercial trials and validation.
Agricultural engineer and senior lecturer at the School of Engineering at The University of Western Australia, Dr Andrew Guzzomi led the engineering development of the rapid response tyne, which was based on the Shearer Trashworker hydraulic breakout system.
“Like the optical sprayers, the ‘Weed Chipper’ is fitted with commercially-available optical sensors that can detect weeds and trigger individual tynes to rapidly chip out the weeds,” says Dr Guzzomi. “Its best fit is in fallow situations where the weed density is low – around 1 weed per 10 square metres.”
“Being well-suited to the control of larger weeds, this machine provides a fantastic non-chemical option to clean up survivors in a double-knock operation within a conservation cropping system.”
This machine has the potential to revolutionise herbicide resistant weed management and help farmers keep weed numbers low. Field trials showed the implement is a highly effective way to manage key summer weed species, such as windmill grass, feathertop Rhodes grass and awnless barnyard grass, even when these weeds are up to 70 cm in diameter.
Any tactic that can consistently achieve 90 to 100 per cent weed control needs to be taken seriously. See Table 1 below.
How much damage does the chipping do to the soil in a no-till system?
Short answer: Very little at low weed densities.
Longer answer: Targeted tillage is suitable for use at low weed densities, i.e. 1 plant per 10 m2 or less. At low weed densities the ‘Weed Chipper’ disturbs only a very small portion of the paddock’s surface during weed control. The response tyne is designed so that the amount of soil disturbance can be altered as required to control the target weeds. The cultivation depth and duration can be increased to target large tap-rooted and fibrous weed species, or reduced for smaller, shallow-rooted species.
Photos: Michael Walsh
How fast does it operate?
Short answer: The ‘Weed Chipper’ has been developed to operate at a ground speed of around 10 km/h.
Longer answer: The response tyne system was designed to operate at a nominal 10 km/h where weed densities are 1 plant per 10 m2 or less. Although higher operational speeds are possible, this would increase system loads and the potential for misses of targeted weeds. With less environmental limitations impacting on safe operation, the ‘Weed Chipper’ can be operated 24/7 if necessary.
What is the best-fit for an optical chipper in an integrated weed control program?
Short answer: As a non-herbicide fallow weed treatment option in low weed density situations.
Longer answer: The best-fit for the ‘Weed Chipper’ is to target low density (1 plant per 10 m2) weed populations in fallow paddocks – the same situation where optical sprayers are currently being used. This will remove survivors and reduce weed seed-set, to potentially prevent or delay resistance evolution. The Weed Chipper also has the benefit of being able to be used across a range of environmental conditions that prevent the application of herbicide treatments. This facilitates more timely and effective weed control.
* The Weed Chipper team led by Dr Michael Walsh (University of Sydney) is comprised of agricultural engineers Dr Andrew Guzzomi (UWA) and Dr Carlo Peressini (formerly UWA) and weed researchers Dr Michael Widderick (QDAF), Dr Adam McKiernan (QDAF) and Dr Bhagirath Chauhan (UQ).
More resources
Table 1. Response tyne efficacy on three summer weed species at three growth stages, Gatton and Hermitage, Qld 2017
| Trial site location, summer 2016/2017 |
Weed size |
Barnyard grass |
Feathertop Rhodes grass |
Windmill |
|
Control (%) |
||||
| Gatton |
Medium |
100 | 94 | 100 |
| Large (40-70cm) |
96 | 91 | 100 | |
| X-Large (>70cm) |
99 | 87 | 96 | |
| Hermitage | Medium (40cm) |
98 | 78 | 100 |
| Large (40-70cm) |
92 | 33 | 100 | |
| X-Large (>70cm) |
83 | 8 | – | |
The dash (–) indicates that established weeds were either missed by the tyne (alignment issue) or the tyne did not activate.
This table is reproduced from the Weed chipper site-specific tillage for fallow weed control GRDC Update Paper.