“When you get to harvest, most of the seed has been shed. Lolium multiflorum [Italian ryegrass] holds on to its seed much longer and goes through a combine, so something like a seed destructor could be very effective,” he says.
Being a simplified version of the iHSD, the V12 is likely to bring its purchase price point down to compete with more recent market entrants.
With the farm running two combines side by side, one with the Seed Terminator fitted and the other without, it provides a great opportunity to assess its efficacy. “We are going to see if we can put some well-designed comparisons in the field and overlay some small untreated patches so we can get a real measure of what’s going on,” Mr Cussans adds.
Counter-rotating cage mills are integrated into the rear of the harvester. Weed seeds in the chaff are pulverised after passing through the mills, rendering them unviable. Control rates of up to 98% have been noted in Australia.
SCU can be controlled through the John Deere combine monitor
“Waterhemp is awfully smart,” says Meaghan Anderson, an Iowa State University Extension field agronomist. “It could outsmart harvest weed seed control by dropping its seed before harvest.”
Similar results occurred when Redekop Manufacturing engineers tested the firm’s Seed Control Unit (SCU) in 2016 and 2017. “It was a complete disaster,” says Trevor Thiessen, Redekop president.
“This is one thing people don’t like to hear, but we need to do something else besides [rely on] herbicides,” says Gordon Vail, product biology head for Syngenta.
Resistance still lurks
After weighing various options, he chose to crush the weed seeds so they could not sprout. He used a cage mill that pulverized coal lumps into a black powder finer than talc.
Harvest weed seed control systems aren’t immune to weed resistance that’s plagued numerous herbicide sites of action.
“Ryegrass in Australian wheat is one thing, but it’s not the same as the pigweeds in soybeans in our environment,” says Bradley.
Harvest weed seed control (HWSC) systems slightly spin Keeler’s hitting logic when it comes to managing weeds.
Crop topping canola proved very effective last spring as growers took the opportunity to target weeds prior to maturity, particularly high ryegrass populations that had survived an application of clethodim in winter. Weedmaster ® DST ® is a glyphosate herbicide registered for canola crop topping, either over the top from 20% seed colour change or under the cutter bar at windrowing.
Lemerle D, et al (2004) Reliability of higher seeding rates of wheat for increased competitiveness with weeds in low rainfall environments. Journal of Agricultural Science 142.
Table 2. Impact of narrow windrow burning and chaff tramlining on the autumn emergence of annual ryegrass compared with conventional harvest (control) at two sites, North Parkes, NSW
Stack the ‘big six’
The long term impact of HWSC on annual ryegrass is driving the introduction and development of HWSC options for Australian growers. The iHSD is now commercially available following several years of field stationary mill testing that have proven its efficacy and commercial capacity (Table 1). This system has the potential to deliver 99% control of the seed of major weed species during harvest.
Table 1. Efficacy of the iHSD mill on the survival of four weed species
To upsize their weed control and kill any survivors, many growers in the region undertook the ‘canola combo’ and followed up crop topping with NWB. NWB is where chutes are attached to the back of the header to divert straw and chaff into condensed rows; the rows are then burnt prior to sowing to destroy any remaining weed seeds. Although NWB remains the dominant HWSC tool in the eastern states, chaff lining and chaff decks were used by an increasing number of growers in 2016 as part of a ‘canola combo’. The interest in these chaff collection tools (along with the integrated Harrington Seed Destructor (iHSD)) over NWB is driven primarily by time savings and not having to burn. While research is continuing to quantify their longer term weed control benefits, growers are getting on with the job and adapting machinery to suit their integrated weed management (IWM) systems.
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