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Control Canola Volunteers At Burn-Off

After about a six-year hiatus, my first new article in Grainews discussed the idea that zero till crop management is more a factor of success than the drill you select. In a nutshell, the most expensive, fancy, fully automated zero-till drill will fail without proper management. At the same time, the average beater, Haybuster 8000 zero-till drill will work just fine — if proper management is used.

I’m often quizzed by producers about the work that I have done since 1990 with seeding-system comparisons and the management that they need to be using.

One of the questions I often get from producers is “have you ever seen zero till fail and why?” Assessing this question is difficult. It takes us to a concept that I refer to as the “sphere of reference.” For example, if you were to apply 75 pounds per acre of nitrogen (N) on a quarter section of land, would your crop yield any more or less than if you had used 100 or 50 pounds per acre? Well the sad reality is that if you put 75 pounds per acre of N on the whole field you can’t really say for sure. You simply have nothing to compare it to, no sphere of reference.

If you had a few strips in the field where you did use 50 or 100 pounds per acer of N we can start to get some idea of the differences. Of course, we’re all aware now that visual assessments of crop yields are impossible to do with any accuracy. A weigh wagon and sub-samples are necessary to get a more accurate idea. But if you lack having done something different in the field and you treated it all uniformly, sorry, but no way can you reach any accurate conclusions.

It is the crux of good agricultural research work that as a researcher you do comparisons of one type or another, for this is what allows us to alter or modify our future management strategies with confidence and reduced risk. So have I ever seen zero till fail? Of course! Nothing is foolproof. As soon as you claim that, the fool will come along and prove you wrong! There is a common thread, however, to the problems that I have seen in some zero till fields. It has to do with weed control.

The successful adoption of a zero-till seeding system requires more than simply purchasing new equipment. There are a number of factors the producer will have to consider in order to achieve the maximum results from their new seeding system. The producer has to make decisions on issues including:

1) Seed placement 2) Fertilizer placement

3) What kind of fertilizer to use 4) The degree of soil disturbance (sweep or knife)

5) Packing (type, location and width of packers, packing pressure)

6) Tank or box capacities (for seed and fertilizer)

7) Weed control — burn-off and in-crop

Of the above considerations, weed control may have the greatest impact of the performance of any zero-till program. Between weed control problems with the burn-off and in-crop applications, it is always poor burnoff weed control that kills what would have otherwise been a successful zero till crop. Let me be clear — mess with the burnoff herbicide and you are asking for a heap of trouble.

There have been a number of new technologies that have come along throughout my career but probably one of the greatest in agriculture today was the advent of Roundup Ready canola. The first of the herbicide-tolerant canolas hit the market and the performance was breathtaking. I always have held the opinion that there is no single operation you can do for ANY crop that is as cost or weed control effective as there is when you apply two in-crop applications of glyphosate, bar none. I have seen some pretty frightening, filthy weedy fields that have undergone a transformation after one year that you would have to see to believe.

P

Treatment

Check

Vantage Plus

Pre-Pass

CV

Yield

Bu./ac.*

35.4a

39.1 b

41.7 c

0.006

2.9%

%

Moisture*

24.2a

25.5a

25.5a

0.23

3.7%

%

Dockage*

1.3a

1.8a

1.5a

0.08

6.4%

Bushel

Weight lb./bu.*

52.5a

52.1a

53.0a

0.71

2.3%

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

**Vantage Plus @ $3.50/ac. PrePass @ $6.88/ac. Spraying costs @ $3.50/ac.

***using feed wheat at $5.50/bu.

%

Protein*

11.8a

12.1a

12.0a

0.73

4.1%

Treatment

Costs $/ac.**

0

7

10.38

Contribution

Margin $/ac.***

194.70

208.05

218.97

For direct seeders, embracing Roundup Ready canola meant one thing they likely didn’t anticipate — a more complicated spring burn-off. Straight Roundup in the spring has no impact on the volunteer RR canola that either blew out the back of the combine or was lost to crop shattering. For some reason, it seems that producers were slow to realize they needed to re-think their burn-off herbicide management. But why?

Consider the following scenario. You seed RR canola, harvest it, but some seed is lost and falls to the ground. You apply your straight Roundup burn-off, seed your cereal crop (remember crop rotations), do your in-crop herbicide application and then in the fall you harvest a beautiful, high-yielding, clean cereal crop. But was there a cost to not having controlled the volunteer RR canola? Well, for most of us it’s impossible to tell. The reason why? The in-crop herbicide! Most in-crop herbicide tank mixes for cereals have a good broadleaf component. Even something as simple as a shot of 2,4-D, Refine or Banvel is going to eliminate volunteer canola of any type. But farmers are left with one question unanswered: what was the impact on the cereal crop yield by not taking out the volunteer canola in the spring? In most cases, since the whole field was treated in the same way, it’s impossible for the producer to know. And this is how we get to our next Central Peace Conservation Society (CPCS) test plot — evaluating the economic impact of controlling RR canola volunteers prior to seeding.

Glyphosate, under whatever proper name, is the most commonly used burn-off herbicide in direct seeding systems. 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 producers 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 2007 burn-off trial was to evaluate the need for and a possible control method for removing volunteer Roundup Ready canola plants.

A field scale, replicated trial was set up at Rycroft, Alta. This site was located on a brown sedge peat to black silt loam (Prestville/ Rycroft complex). CPCS would like to thank Brett Young for providing the site for this trial.

A randomized complete block plot design with three replicates was used. There were three treatments compared:

1) Unsprayed check

2) Vantage Plus applied as 0.5 litre per acre (giving 180 grams of glyphosate per acre) 3) PrePass applied at

recommended rates (giving 180 grams of glyphosate and two grams of florasulam per acre).

The previous crop on all plots was Roundup Ready canola. The burn-off herbicide treatments were applied on June 11 in a water volume of five gallons per acre. The major weed noticed was volunteer canola. Seeding occurred on June 12 using a Haybuster 8000 zero-till hoe drill equipped with 10″ shank spacing and a 3″ paired seed row. 149 pounds per acre of McKenzie wheat was seeded 0.5″ deep. The fertility program consisted of a blend that provided 81-17-24-0. The fertilizer was deep banded at the time of seeding 1.5″ below the middle of each paired seed row.

The in-crop weed control program consisted of the recommended rates of Horizon and Prestige applied in a water volume of five gallons per acre applied on June 27. The major weed at this time was volunteer canola. The wheat crop was at the one to two leaf stage.

Observations made shortly after seeding found that the Pre-Pass treatment (glyphosate and flurasulam) was very effective at controlling all weed species present. The Vantage Plus treatment (glyphosate alone) was very effective in controlling all weed species except the volunteer RR canola and of course the check treatment was weedy with volunteer canola, foxtail barley and dandelion.

The most interesting observation was made in early July after the in-crop herbicide application. The check treatment was suffering from noticeable weed pressure due to weeds that were not effectively controlled by the in-crop herbicide application, specifically weeds such as foxtail barley and dandelion. Between the two herbicide treatments, Vantage Plus and Pre-Pass, however there were no observable differences we could see between them at this time. Similar observations were also made later in the summer and at harvest time.

The centre strip of each plot was straight cut using a stripper header on October 10. 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.

THE BOTTOM LINE

The plot results indicated that there were highly significant differences in yield of the treatments. The check treatment yielded lower than both the Vantage Plus and PrePass treatments and the PrePass yielded higher than the Vantage Plus treatment. There were no significant differences in moisture, dockage, bushel weight or protein between the three treatments. All treatments graded as feed.

Applying glyphosate alone (Vantage Plus treatment) resulted in an increase in contribution margin of $13.35 per acre for the producer over the unsprayed check treatment (hence why you always should do a burn-off) but the kicker is when you look at the glyphosate and florasulam (PrePass treatment) which resulted in a further increase in contribution margin of $10.92 per acre for the producer. This trial clearly illustrated that there is a significant economic penalty for not controlling volunteer RR canola prior to seeding and the need for more than just glyphosate. The difference is not necessarily an obvious visual one at harvest time if a good in-crop herbicide program has been used but is economically very significant. Producers who either elect to forego the burn-off herbicide application or not include an additional broadleaf herbicide like florasulam should be prepared to face a significant economic penalty.

While there was no dockage difference between the treatments this should not be a surprise to us when we remember that the major weed problem at this site was foxtail barley which, while being a severe competitor with crops, is not a significant contributor to dockage as compared to other weeds such as cleaver and wild oat.

Garry Ropchan is research co-ordinator for the Central Peace Conservation Society and along with his son Aidan, operates a grain farm near Grimshaw, Alta. Contact him at [email protected]

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