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Pre-Seed Burn-Off Adds Three Bushels An Acre

I’m one of the dinosaurs that has been at this agricultural researcher and extension specialist gig for over 20 years now. I was very lucky when I started back in May, 1990, as a humble soil-conservation technician in Manning, Alta., that my work coincided with the effort to get farmers to adopt zero-till and direct-seeding strategies. I am proud of the number of farmers that I worked with first hand over the years who made the switch as a result of the work that we did together, and the subsequent impact that this had on their neighbours in getting them to see the light.

The road early on was not an easy one. There were (wrongly) perceived issues with the seed drills we had available to us at the time, the red herring of “which opener/boot should I use?,” hoe versus disc opener debates, questions for fertility placement and pest-issues.

The machinery issues for me were always a bit of a fool’s errand. My simple take on this was that in any area where I worked you had farmers using a bunch of different machines, the common Concord, Flexi-Coil, Morris and John Deeres along with the fringe types like me using Haybusters. But we were, all in all, successful. The truth, perhaps ugly truth to some, is that is was not a case of the machine we were seeding with, it was a case of the management we were using with the machine.

Over the years I’ve done somewhere in the area of 85 conservation seeding trials, all field scale, replicated, taken to yield, subsamples processed, etc. In other words, I am as confident of the results of this body of work as anyone could ever be. The results were clear — zero till is a superior production system. My caveat on this statement is “when the proper management is used.”


I have often been asked by skeptics, “Does zero till ever fail?” My answer to that is yes, it can, when the basic management practices are not utilized. It has been my experience in looking at zero-till wrecks that the common source of failure has been the farmer failing to apply the pre-seeding burnoff herbicide for weed control.

Next to zero-till trials and perhaps fertility work, the next largest body of my work dealt with burnoff herbicide and its associated management. I’ve done countless trials looking at the impact of applying or skipping the burnoff herbicide and when it should be applied (timing). I’ve tinkered with different nozzles, water volumes and herbicide rates, too. Anything you can do to achieve better weed control is going to help, but the one conclusion was that NOT applying the burn-off was going to result in a wreck. The sad fact of the matter is that in the early days there was just no in-crop herbicide available for any crop that would allow you to make up for this.

Part of the compounding problem with this is that I have documented that if we do skip the burnoff, it is still possible to end up with a clean-looking field at harvest time. However, this practice masks the cost to the crop during seeding to in-crop herbicide application. The issue for some farmers appeared to be one of perception — if you can’t see weeds, then it’s not worth the time to spray. Well, sadly that it not the case.

From the research I’ve done, burn-off was ALWAYS a profitable activity to be engaging in when glyphosate was $18 an acre and it’s become an even better investment now that it’s $8 an acre. Yes, farmers always want to seed as early as possible and I would agree that the crop insurance data that I have seen does certainly show a rock solid correlation between seeding date and yield. But my fellow farmers, you are hurting your crop yield by not dealing with weed control prior to the crop going in.

After speaking on this issue until I was (light) blue in the face, the message started to sink in. I started to get calls from farmers and invitations out to fields where I was told about and saw burn-off misses in fields and how astounded the farmer was at how effective the weed control was when they sprayed and the weed pressure they saw in the misses. I felt good, almost a text-book job of doing good field trials and having an affective extension program to get the word out.


So you’d think that I’d be able to rest on my laurels and recline in my chair and put my feet up on my desk confident that farmers were now on the straight and narrow. And it almost happened. Life was actually good for a while. Then something unforeseen happened. The advent of Roundup Ready (RR) canola. Suddenly, the playing field had shifted. While I have no doubt that RR canola gave farmers the opportunity to have unprecedented weed control power in their canola crop, it led to two somewhat unexpected consequences:

1)The impact of RR canola volunteers in the subsequently seeded crop and how farmers were failing at first to address this issue. Just how much on an issue this can be was covered in the March 22, 2010 issue ofGrainewswhere I looked at the requirement for including a broadleaf tank-mix partner for controlling volunteer RR canola in cereal crops (and thank God for florasulam and PrePass!). The easiest money a farmer will ever make, I thought.

2)Farmers who were seeding RR canola thought that they could skip the burn-off once again because, as they told me, “with two in-crop glyphosate applications my canola was clean as a whistle at harvest time.”

Well as with the burn-off trial with wheat, skipping a pre-seed burn-off in favour of more in-crop control with herbicide-tolerant canola resulted in clean fields, but hid losses. Everything is a matter of your “sphere of reference,” as I like to call it. Did they know what the consequence of skipping the burn-off was? The answer was always sort of a muted, “Uh, no I don’t. But my field is clean so how can there be a problem?”

Well, it’s like this. Farmers tend to operate very much on a “out of sight, out of mind” belief. If they can’t see a problem, there isn’t one. This particular burn-off problem thus illustrates why it is a bit if a bug-a-boo for producers. It is not that the in-crop glyphosate didn’t take out all the weeds, it was a case of not being able to see what the impact was on the crop at harvest time that was caused by allowing those weeds to compete with your crop for that critical two to three week period between seeding and when the first in-crop herbicide went down. Thus starts a run-down of the work I’ve done on the topic.


The commonly used burn-off herbicide in direct seeding systems consists of herbicides containing the active ingredient glyphosate. With the advent and wide-spread use of Roundup Ready canola this leads to the requirement of a different strategy — obviously using glyphosate alone would not have any impact on RR volunteer canola plants. Thus farmers must utilize a burn-off herbicide tank mix that includes an additional broadleaf herbicide to specifically control volunteer RR canola plants.

The purpose of the 2008 burn-off trial was to evaluate the need and a possible control method for removing volunteer Roundup Ready canola plants.

A field scale, replicated trial was located just east of the BrettYoung Seed Facility at Rycroft. This site was located on a brown sedge peat to black silt loam (Prestville/ Rycroft complex). A randomized complete block-plot design with three replicates was used. The previous crop was RR canola. (Central Peace Conservation Society (CPCS) would like to thank BrettYoung for providing the site for this trial).

There were three treatments compared:

1.Check. No burn-off.

2.Roundup Alone at 0.33 l/ac., Roundup Transorb High Concentrate using a water volume of 5 gal./ac.

3. Roundup with 2,4-D at 0.33 l/ac. Roundup Transorb High Concentrate and 200 ml/ac. 2,4-D using a water volume of 5 gal./ac.

It should be clearly noted that the Roundup with 2,4-D treatment is not a registered tank mix to use as a burn-off when seeding canola.

The zero to six-inch soil test revealed the following information:

Nitrogen: 32 lb./ac., deficient

Phosphorus: 48 lb./ac., marginal

Potassium: 598 lb./ac., optimum

Sulphur: 64 lb./ac., optimum

pH: 5.8, acidic

Organic Matter: 8.7 per cent

EC: 0.30, good

The previous crop was canola. The target yield of 40 bu./ac. of canola called for 84 lbs. N, 21 lbs. P205, 0 lb. K2O and 19 lbs. S per acre.

The burn-off herbicide treatments were applied on May 6. The major weed noticed was volunteer canola.

Seeding occurred on May 21, using a Haybuster 8000 zero till hoe drill equipped with 10-inch shank spacing and a three-inch paired seed row. Five lb./ac. of BY 4414 RR canola was seeded 0.5 inches deep.

The fertility program consisted of a blend that provided 77-0-0-13 total fertilizer. The fertilizer was deep-banded at the time of seeding 1.5-inches below the middle of each paired seed row. The first in-crop herbicide application consisted of the 0.33 l/ac. of Roundup Transorb High Concentrate in a water volume of five gal./ac. applied on June

1. The major weed at this time was volunteer canola. The canola crop was at the cotyledon stage.

The second in-crop herbicide application consisted of the 0.33 l/ac. of Roundup Transorb High Concentrate in a water volume of five gal./ac. applied on July 3. The major weed at this time was Canada thistle. The canola crop was at the four-to six-leaf stage.

Observations made shortly after seeding found that the burnoff herbicide treatment consisting of Roundup Transorb High Concentrate and 200 ml/ac. of 2,4-D exhibited some activity on the volunteer RR canola.

While it was also very easy to distinguish the two burn-off treatments (#2 and #3) from the Check treatment (#1), this was no longer possible after the two in-crop herbicide applications had been made. This was not unexpected but still left us with a burning question — would there be an impact on the yield from either not using a burn-off or not using a broadleaf in the burn-off tank-mix to control the volunteer RR canola plants?

The centre strip of each plot was swathed on September 15. Combining occurred in the spring of 2009 due to unfavourable weather in October 2008. The strips were weighed with a weigh wagon and samples were retained to determine dockage, moisture and grade

The results are given in Table 1.


2009 results indicated that there were highly significant differences in yield of the treatments. Both burn-off treatments out-yielded the check/no burn-off treatment. There were no significant differences in moisture levels, dockage, bushel weight or green seed counts of the three treatments. All treatments graded as No. 1 canola.

The 2009 trial resulted in two lessons:

1)If you do not apply the burnoff when you are seeding RR canola you will be losing money.

2)There may be merit to including a broadleaf herbicide in the burn-off tank mix for control of volunteer RR canola. This does not occur when using glyphosate alone.

The challenge for farmers is to realize that there are economic consequences to foregoing the burnoff herbicide application. CPCS has documented this over many years of field trials with cereal crops and canola crops in general. The use of RR canola does not mean that early weed removal is any less important. While you may still think that you achieved excellent weed control by growing RR canola (which you did get) there is an economic cost to NOT controlling weeds during the most critical time period, from a few days prior to seeding to the date of the first in-crop application of herbicide.

Don’t be fooled by your eyes come harvest time simply because your RR canola field is clean, be aware that there was still a price that you paid by not performing the pre-seed burn-off herbicide application.

Farmers will often bring up the issue and concern of time, they don’t have time to be applying herbicides on all their fields and so the RR canola field doesn’t get sprayed. Well my friends, simply call your custom sprayer! The economics for using a burn-off herbicide even with RR canola are good enough that even with custom spraying costs you are going to make three to four times the return on your investment over not using a burnoff. This is good science, good sense and most of all good business!

GarryRopchanisresearchco-ordinatorfor theCentralPeaceConservationSocietyand alongwithhissonAidan,operatesagrain farmnearGrimshaw,Alta.Contacthimat [email protected]

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Costs $/ Margin $/ ac.** ac.*** 0 183.00




Roundup Transorb HC

Roundup Transorb HC and 2,4-D

Bu./ac.* Moisture* Dockage*


21.5 b

22.9 b










Weight lb./ bu.*









*means within the column followed by different letters were significantly different at P=0.05

**Roundup Transorb HC @ $5.33/ac. 200 ml of 2,4-D @ $0.80/ac. spraying costs @$4.50/ac.

***#1 canola at $10/bu.

Treatment Contribution







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