Mechanical weeding: Weeding out control choices
Mechanical weeding is an effective technique for non-chemical weed control but equipment needs careful selection and operation to be cost effective while maintaining crop yields. The Soil Association has investigated several options and runs field labs and other demonstrations, discussing the needs of both organic and conventional farming systems. Arable and soils adviser, Jerry Alford explains: “The choice of weeder depends on the crop and also the type of weed that you are targeting, which will also affect how and when you will use it.”
Spring tine cultivators have been used for weeding for many years, and are best for cereals with their strong roots, rather than for more delicate peas or beans, he points out. “The harrow acts like a rake, with the continual movement of the tines flicking the weeds out of the soil, while weaker weeds are also pulled out by their roots,” says Mr Alford. “Due to the close spacing of the tines across the width of the implement, it also pulls some weeds out from in the row as well as between rows.”
He adds that the effects of this type of weeding can be quite dramatic and advises operators to do it on a Friday and not return to the field until Monday by which time the crop will have recovered! “The action of the tines releases nitrogen which stimulates growth so the crop can actually recover quite quickly.”
Inter-row cultivators have become especially popular recently, many developed in countries where the threat to glyphosate is more pressing. “Using a rigid tine to work between the rows, this type of implement is ideal for row crops such as cereals, sugar beet and fodder beet. A range of tools and tines can be specified to suit the row width and weed being tackled.”
Mr Alford suggests that hot and dry conditions are ideal for inter-row cultivators, as weeds pulled up will dehydrate and die, rather than being ‘transplanted’ to grow on somewhere else. “There’s lots of new technology emerging on these cultivators, expanding their use to in-row weeding and offering greater accuracy,” he says.
Choice of weeding tools extends to rotary weeders which can work aggressively to shallow depth, taking out annual weeds in-row as well as between the rows. The ultimate in mechanical control, he suggests, could be the System Cameleon, a combined drill/cultivator with rigid tines which can be used to undersow a following crop.
For all weeding operations, timing is key, say Mr Alford, with the final pass usually made
