Volume 41, Number 13 | JULY 21, 2015
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PRACTICAL PRODUCTION TIPS FOR THE PRAIRIE FARMER
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TWO GOOD REASONS FOR PRE-HARVEST HERBICIDE Pre-harvest application can give you better weed control and simplify harvest. But know the residue rules By Angela Lovell
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1. Effective weed control There are a couple of reasons why a pre-harvest glyphosate application is effective against perennial weeds, says Brenzil. First, perennial plants at this time of year are moving sugars to the roots, which helps translocate the herbicide to the root system and prevent growth the following year. Secondly, prior to harvest there is more plant material present, which provides a larger target to maximize the uptake of the herbicide and give better control. The other economic advantage is
that it’s generally less expensive to deal with perennial weeds in-crop than the following year. “Canada thistle, as an example, is very competitive, so if a producer has a well-established stand no crop will grow underneath it,” says Brenzil. “If there are a substantial number of thistle stands within the field that’s a significant yield loss.” Dalgarno says using a pre-harvest glyphosate application is fairly economical for him as he has his own high clearance sprayer. “The herbicide cost is anywhere from $3.50 to $4.50 an acre, plus the cost to run the sprayer,” he says. “I’d say it probably costs us around $6 an acre, but it would be more if you had to hire a custom sprayer, although you’re saving the cost of swathing as well.”
2. Harvest quality For Dalgarno a pre-harvest herbicide treatment isn’t just about weed control; it’s also about ensuring a good quality crop on his farm, which is located amid rolling hills and potholes, which means maturity is all over the map. “We can’t
straight cut our wheat without pre-harvesting it because everything is a different moisture level and maturity, so the herbicide also kills the plants and makes it more even by the time we harvest,” he says. “When we used to swath our wheat, and it had lain out there for a week or two we were lucky if we got No. 2, and most of the time it was a No. 3. Now 90 per cent of the time it’s a No. 1, and if the difference is $2 a bushel, at 60 bushels an acre, we potentially could lose $120 an acre by not pre-harvesting it.” Dalgarno also knows from his own experience that timing of a pre-harvest glyphosate application is crucial. “We’ve run into a few situations where it’s turned cool for a week or two after application and the chemical doesn’t uptake as well,” he says. “So you have to look at all the factors — the weed situation in that field, the crop type and stage, and the value of the crop to determine if a pre-harvest treatment is worthwhile, whether it’s barley, oats, wheat, or any crop.” “Another challenge with having dead plants sitting out there in the weather » continued on page 4
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arming decisions always seem to come back to economics, and whether to do a pre-harvest treatment for perennial weed control or harvest management is no exception. But there are many other considerations such as crop type, geographic location, weather and even trade risks that contribute to that decision, says Clark Brenzil, provincial weed specialist with Saskatchewan Agriculture. In northern regions of the Prairies a pre-harvest herbicide application is often the only opportunity farmers have to control perennial weeds because the season is too short to allow enough re-growth for a post-harvest application to be effective. But even in the southern prairies a pre-harvest application is a better economic option, says Brenzil. “For a pre-harvest application of glyphosate the recommendation is 360 grams of active ingredient per acre,” he says. “Following harvest, weed re-growth presents a smaller target, so producers have to use about two-and-
a-half times more glyphosate to get the same amount of control.” Bruce Dalgarno, who farms near Newdale, Manitoba, started using a pre-harvest application of glyphosate on his crops around 1994, partly to try and control the Canada thistle and quack grass in his fields. “We’ve certainly seen a change in our weed spectrum in that we’re getting rid of Canada thistle and the quack grass has all but disappeared,” he says.
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In This Issue
Wheat & Chaff .................. 2 Features . ........................... 5 Crop Advisor’s Casebook . 8 Columns ............................ 10 Machinery & Shop............. 33 Cattleman’s Corner .......... 39
Winter wheat strategies
Ross McKenzie page 10
Morris’s new air cart tender scott garvey page 38
FarmLife ............................ 44