A clean start for winter beans – CPM – Mike Thompson
Winter beans are an attractive alternative break crop to OSR in terms of gross margin output, weed control and as an entry to first wheat, especially on heavier soils ...
Growers disillusioned by years of poor oilseed rape establishment, due mainly to flea beetle damage, could look to include break crops such as winter beans and peas in their arable rotation, while keeping a level of OSR too, says Hutchinsons’ agronomist Mike Thompson.
Winter beans drilled in October allow growers more time for stubble management for grassweed control, have lower growing costs and currently offer attractive forward prices of over £220/t.
“Winter beans are good for heavier soils and the later drilling, starting around mid-Oct, helps with stale seedbed management, and allows nature and the weathering process to break the soils,” he says. “They can tolerate some weeds but any that aren’t taken out in the winter and survive through to spring are much harder to control with the limited post-emergence herbicide options available, primarily bentazone,” says Mike.
“Growers either like growing beans or they hate them. But they aren’t difficult to grow and provided weed programmes start early so competition is removed, they can produce a gross margin potential equal to a second wheat. Where beans have been grown as an entry to first wheat, we regularly see yields of over 10t/ha.
“Poor yield in beans is often a result of forced drilling conditions,” he explains. “They need to be drilled in good conditions and not just muddled in. The pre-emergence application is critical because a clean crop going into the winter has a better chance of reaching full potential. Weeds that have been allowed to establish can knock yields by as much as 1.5t/ha.”
In previous seasons a pre-em contact herbicide application of diquat has been applied, but with diquat now gone and only glyphosate left, timing of the application becomes more critical. “The effects of diquat were felt within a week of application, whereas glyphosate can take up to 12 days to remove weed pressure,” he says.
“It’s so important to get the crop clear of weeds in the early stages of crop establishment and pre-em application of the residual herbicide Centium (clomazone) gives beans the best chance of establishing well. Once the winter weed burden is under control on medium to heavy land, there’s a reduced chance of a spring weed flush.
“The most cost-effective pre-em herbicide programme is based on Centium in tank mix with pendimethalin, imazamox, carbetamide and propyzamide, ideally sprayed within 3-4 days of drilling,” he says.
“But the window is before emergence. This should give excellent control of cleavers, chickweed, shepherds purse, red dead nettle and activity on groundsel, speedwell and sow thistle.”
Because Centium is an encapsulated suspension it makes the active very stable on the soil surface, which leads to a controlled rate of release –– remaining active for up to three months –– weed control is enhanced, he adds. In-field observations have also shown that when clomazone is mixed with carbetamide and propyzamide, it can sensitise and enhance blackgrass control.
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