Australia
July 30, 2012
Trials across south eastern Australia have demonstrated the importance of targeting weed seeds at harvest to reduce the prevalence of weeds in cropping systems.
Evaluation of three harvest weed seed control systems – chaff carts, windrow burning and the Harrington Seed Destructor (HSD) – has shown that all three systems are similarly effective in reducing the emergence of annual ryegrass and the control of herbicide resistant populations.
A prototype of the HSD was involved in trials and demonstrations to growers across southern Australia late last year.
The trials in South Australia, Victoria and New South Wales during the 2011 harvest produced results consistent with those recorded during trials in Western Australia the previous year.
Supported by the Grains Research and Development Corporation (GRDC) and Rural Industries Research and Development Corporation (RIRDC), the trials in the southern and western regions were led by Australian Herbicide Resistance Initiative (AHRI) researcher Dr Michael Walsh (photo), who is based at the University of WA.
“As expected, there were no differences between harvest weed seed control systems in their effect on subsequent annual ryegrass emergence the following autumn,” Dr Walsh said.
“All three systems – chaff carts, windrow burning and the HSD – target the chaff fraction during harvest and if they are all working efficiently then they will produce the same result.”
Dr Walsh said the average impact of harvest weed seed control across all sites in south eastern Australia was 56%, remarkably similar to the 55% average from the WA trials in 2010.
“We now have a comprehensive data set on the efficacy of harvest weed seed control systems that covers the western and southern Australian crop production regions.”
Dr Walsh said targeting weed seeds at harvest was a pre-emptive action against problematic annual weed populations infesting Australian crop production systems.
“Our most damaging crop weeds are annual species capable of establishing large persistent seed-banks. Fortunately for most of these problematic annual weed species seed bank decline is rapid.
“That means, without inputs, a very large seed bank can be reduced to a very modest one in just a few years. Low weed seed bank levels allow easier and more effective weed control with a reduced risk of herbicide resistance development.
“Thus, effective weed management in productive cropping systems is reliant on preventing viable seed entering the seed-bank. For crop producers, harvest weed seed control represents an opportunity to specifically target weeds during harvest, preventing inputs to the weed seed bank.”
Dr Walsh said processing of chaff to destroy any weed seeds present during the harvest operation represented the ideal system for large-scale Australian conservation cropping systems.
“Rendering weed seeds non-viable as they exit the harvester removes the need to collect, handle and/or burn large volumes of chaff and straw residues,” he said.
Due to the importance and potential industry benefits of this process there has been substantial interest in the development of the HSD which is attached to harvesters as a trailer-mounted system incorporating a high-capacity cage mill to process chaff residue sufficiently to destroy weed seeds.
Evaluation of the HSD under commercial harvest conditions by AHRI over the last four seasons has determined the HSD will destroy at least 95% of annual weed seeds during harvest.
At 13 locations across the southern cropping region during the 2011 harvest, the HSD was evaluated alongside chaff cart and narrow windrow burning systems for its ability to reduce annual ryegrass emergence in the following growing season.
The HSD has now progressed to commercial production. The GRDC recently awarded the licensing of the innovative HSD technology to de Bruin Engineering of Mount Gambier, SA. The first HSD is expected to be commercially available in time for harvest this year.
The HSD is the brainchild of WA grain grower and inventor Ray Harrington, and its development has been funded by the GRDC and assisted by AHRI and the University of South Australia’s Agricultural Engineering department.
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