Believe it or not, there are times when a harvest of weeds is a welcome sight.
Researchers at the Prairie Agricultural Machinery Institute recently modified a Massey 200 self-propelled swather and used it to clip off weeds that had grown above the canopy of a lentil crop.
The machine was designed to control weed growth in organic crops by shearing off the plant heads before they ripen and sprinkle their seeds on the ground. And it seems to be working.
“I think it’s very worthwhile, particularly if you have a lot of tall growing weeds that get away early and get up high,” said Philip Leduc, PAMI’s senior manager of research and development.
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Other than seeding late or using summerfallow, organic growers have few tools at their disposal for controlling weed growth.
For competitive crops like wheat, that’s not as big a problem as it is for flax, peas and lentils, which the invaders can usurp.
“The weeds kind of get a start and get ahead of them and cause severe problems,” said Leduc.
Three years of PAMI field trials in Spalding, Sask., and two years of plot testing at Agriculture Canada’s Scott Research Farm showed that clipping didn’t lead to a detectable increase in crop yields, but it did significantly decrease the number of weed seedlings found in the following year’s crop.
Leduc said by the time the weeds get tall enough to trim, they have already done the damage to that year’s yields by sucking up moisture and nutrients. But shearing off their heads limits infestations in the following crop.
“It consistently reduced the weed population.”
Modifying a swather to act as a weed whacker was a fairly trivial adjustment.
“Instead of making a swath of these tops of the weeds, we had to just drop them back into the crop,” said Leduc.
That involved removing the draper canvas and as many braces and supports as possible. The reel also had to be adjusted so the knife wouldn’t gum up with wet, green material.
“Some swathers are easier to convert than others.”
The clipping technique only works on tall weeds like wild mustard and flixweed, which have to be at least five to 10 centimetres above the crop canopy before they can be swathed. Leduc suggests late June or early July as a good time to shear off the heads, before the weeds ripen.
