The variable yield of field beans is generally more due to pod set issues than weed competition.
However, weeds can be a nuisance at harvest and as beans are sown at quite a low plant population, early weed control is essential. There are very limited herbicide options for broad-leaved weeds once the crop has emerged.
Cultivations such as with a comb harrow are an option, but most crops will be treated with a pre-emergence herbicide. It is worthwhile taking care over the spray application, particularly as beans are often sown into a less worked seedbed. It makes sense to follow current advice for residuals which is to keep the boom low, use low drift nozzles, keep forward speed down and use adequate water volume. Angled nozzles might also be worth considering to achieve the best possible spray coverage of any clods that may be present. Selectivity with residual herbicides depends on the seed being covered by adequate settled soil – check the label. Avoid the use of residual herbicides in sands and gravels as there is a risk of crop damage.
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