Weed control strategy is crucial to quality silage

A mixed silage season this year has left many producers considering the options for second- and third-cut and agronomists are advising a careful weed management strategy to achieve maximum quality in the clamp.

Weather in April and early May allowed some to cut silage earlier than most years, but rain since has meant many growers have had a protracted season overall, according to Dow AgroSciences grassland agronomist Vaughn Stansfield. “Some are still making first-cut, while others have had record early cuts and are now on to second crops.”

Weed control after cutting is crucial to maximising both yields and crop quality, he adds. “Key weeds, such as docks and nettles, should be targeted in their regrowth period, which is predominantly post-first- and second-cut.”

Herbicides use growth function to kill weeds, so peak growth periods, particularly at this time of year, should be used for key herbicide application. “There needs to be sufficient growth before herbicides are effective and vegetative growth is the key time to apply, as the chemical then gets drawn down into roots.”

Once plants have progressed to the reproductive stage and have thrown a stem or started to seed, herbicides have less of a success rate, as treatment only results in foliar control and not root penetration.

“When this stage is achieved, plants should be mown or topped and allowed to regrow again, with herbicide applied again at a period of fresh young growth.”

Although the temptation is to reduce water volumes – don’t, he warns. “To optimise efficacy of any herbicide, recommended water volumes should be observed, even when it means more time spent spraying. For a broad-spectrum herbicide, like Forefront, this should be 200 litres/ha and for a targeted product such as Dockstar, 300 litres/ha minimum.”

Forefront has set a new standard for grassland weed control, according to Mark Palmer, technical manager for independent agronomist company, AgroVista. Trialled independently four years previous to it’s launch last year, the product has shown limited or no re-emergence up to 18 months after initial dose.

Weed control strategy in April was limited, due to dry conditions, so post-first- and second-cut are the key times for herbicide application, says Dr Palmer. “However, September is one of the most underused months for weeds control,” he says.

“Typically, there is less grass growth and hence less crop competition, meaning weeds are more vigorous. This allows herbicides to penetrate the root structure more effectively.”

After undertaking Forefront trials two years ago, Cheshire dairy producer Steve Rosten has continued a vigorous weed control programme, something he believes is resulting in him saving 1kg a cow in concentrates.

“We took on an extra 50 acres of land last year, which was infested with docks and buttercups. After our success with Forefront the previous year on 30 acres, we decided to apply this before ripping the whole field up and applied at 2 litres/ha herbicide in 250 litres of water to ensure weeds got a complete covering.

“This was so successful that we overseeded the area in spring, resulting in a mix that has come through strongly thanks to lack of competition from weeds.”