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Don’t feed the weed
Grass weed control to prevent competition with crops for valuable nutrients is likely to prove even more crucial this autumn.
Even a moderate grass weed population could rob over 25% of the nutrients applied to, and intended for, the crop. Competition for nutrients, light and available soil moisture can all seriously impact on crop yields.
With some growers seeking to make savings on the high cost of fertiliser inputs this season, every unit needs to be focussed on delivering crop yield, advocates Syngenta grass weed specialist, Pete Hawkins.
Pete Hawkins © Syngenta
Residual cornerstone
“A robust residual pre-em strategy is now recognised as the cornerstone of an effective autumn grass weed control strategy, especially given that there’s fewer opportunities for good contact control on established weeds later in the season and wider issues of herbicide resistance,” he advised.
Pete Hawkins autumn strategy to tackle grass weeds this season includes:
- Manage stale seedbeds for specific target weed species
- Delay drilling for as long as practically possible
- Grow more competitive hybrid varieties
- Use a robust multi-active pre-em stack including DEFY®
- Higher rates of DEFY will enhance overall grass weed control
- Apply a peri-em sequence to boost residual activity where conditions allow
- Focus efforts on worst affected fields
Mr Hawkins reported last season’s Syngenta trials and field-scale work in Staffordshire had demonstrated that DEFY-based pre and peri-em combinations performed better than newer grass weed chemistry actives in reducing the populations of weeds. It also proved more cost effective to give better margins.
© Syngenta
Integrated strategies
“Newer chemistry is valuable to add another tool for growers in the most difficult grass weed situations and when facing very high populations,” he advised.
“But, as has been repeatedly proven over recent seasons, the existing options can work very effectively as part of an integrated control strategy in the majority of situations.”
Results in predominantly ryegrass control situations show that increasing the rate of DEFY in a pre-em stack from 2.0 l/ha to 4.0 l/ha would give a higher marginal increase in overall weed control and at significantly lower extra cost, compared to switching to using newer grass weed chemistry.
Field trial protocols in autumn 2021 included a cinmethylin 750g EC formulation applied at 0.67 l/ha to deliver an equivalent of 500g of active per hectare.
“Growers and agronomists have made significant strides in grass weed control with strategies to reduce both ryegrass and blackgrass. That knowledge and experience can continue to deliver gains in sustainable control, against a potential backdrop of tighter arable margins for the coming season.”
Cultivation tools
Crop establishment techniques will dictate where grass weed seeds end up buried in the field’s seed bank this season – and have a major impact on competitive weed emergence over the autumn and spring.
The new Syngenta website Cultivation Insight tool draws on multiple years of in-depth grass weed studies and different establishment techniques, to provide an interactive guide of what could happen to the seed bank in different field scenarios.
Understanding where seeds have moved in different years, along with their biology of natural decline, gives a valuable picture of potential risks and selecting cultivation options to better manage grass weeds in any situation.
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Syngenta is one of the world’s leading agricultural companies, comprising of crop protection and seeds. Our ambition is to safely help feed the world while taking care of the planet.