NEW research into dry seeding, seeding rates and their interaction with pre-emergent herbicide effectiveness in controlling annual ryegrass in wheat has put the spotlight on early sowing and its potential weed control benefits for Western Australian growers.
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The research was presented by Australian Herbicide Resistance Initiative (AHRI) research agronomist Mike Ashworth at the recent virtual 2022 Grains Research Update - Perth.
Dr Ashworth said while it had long been advised that delaying seeding of weedy paddocks to maximise the effectiveness of knockdown applications results in optimal weed control, with the development of more pre-emergent herbicides and greater seed dormancy in many weed populations, early seeding may now be the optimum weed control strategy.
"With the rise of dry seeding around WA, and the resultant increases in crop yields, AHRI has put a lot of effort into understanding how growers can maintain weed control within that farming system," Dr Ashworth said.
"In general, dry seeding out-yielded delayed seeding which was shown in seven of the nine trials completed.
"While delayed seeding generally resulted in lower ryegrass seed production (eight of the nine trials), the seed production of annual ryegrass at the end of the season consistently (all trials) correlated with the measured pre-emergent herbicide persistence in the soil.
"The other result we found was that increasing the crop seeding rate consistently reduced annual ryegrass seed production in all trials for all herbicides used."
When it comes to what these results might mean for future ryegrass control when growers are looking to dry seed wheat, Dr Ashworth said firstly, if they get the opportunity, growers should dry seed their cleanest paddocks first and then delay seeding in their weedier paddocks.
The reason being low soil seed banks allow growers to manage to maximise profit, so using Harvest Weed Seed Control makes sense
"Secondly, understand the key properties of your pre-emergent herbicide choice, taking into account soil type, seeding system, soil organic matter and likely rainfall after application," Dr Ashworth said.
"Thirdly, always try to increase your crop seeding rate, or your crop competitiveness - that can be in the form of cultivar selection, seeding earlier, seeding rate, row spacing and just good agronomy.
"Finally, if you're going to dry sow, understand the frost risk."
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