CPT: Get the most out of the data

November 7, 2012 - Issue 32


The on-line Canola Variety Selection tool is now live with data from the 2012 Canola Performance Trials (CPT), giving canola growers another tool to compare variety performance. Growers also received a booklet of the results in their November Canola Digest.

CPTs provide independent variety comparison utilizing both small and large plot data with a systems approach that uses the corresponding herbicide on each variety. This is a unique service to canola growers. Canola growers provide funding for CPTs through their provincial canola grower organizations.

The online tool provides comparative data on leading varieties and newly introduced varieties. The tool includes interactive maps,  an economic calculator, and the ability to refine searches by season zone, herbicide tolerance (HT) type, yield, days to maturity, lodging and height. You can also compare data from 2011 trials. We recommend the 12 minute video tour at the top of the website as an introduction.

Here are tips to help you get the most out of the data:

1. Look at how a variety yields at every site, not just those closest to your farm and not just the overall average. The statistical significance of results increases with more sites analyzed, but digging deeper will show how the variety performed under different stresses, soil types and growing conditions. Growing conditions in your region in 2012 may not be typical and may not represent what you’ll have in 2013.

2. Variety decisions will depend on your risk management strategy. If you want to reduce risk, then choose a variety that performed consistently across all sites. If you are more of a home run hitter who can accept the odd strike out, you may choose a variety that has a wider range of results, including top yields at some sites and lower than average yields at other sites. Under good growing conditions, a home run variety will be a top yielder, but under certain stresses may be average or below. A variety with good overall yield but poor results under conditions typical on your farm — similar growing season, soil zone, etc. — perhaps should be traded for a more reliable alternative.

3. Small yield differences are less reliable to predict, so don’t overemphasize them. In most cases, if varieties are within a couple bushels of each other their yields will be statistically equivalent. LSD numbers are given for each small plot result. The definition of LSD is given on page 5 of the booklet.

4. Compare CPT data to other sources, such as registration data and crop insurance.
WCC/RRC: Seed registration trial data from the Western Canada Canola/Rapeseed Recommending Committee (WCC/RRC) is intended to compare variety more on quality than yield performance, but it does yield, maturity, lodging, height and blackleg ratings. Growers can get a summary based on first year private and second year public data. Contact Raymond Gadoua of the Canola Council of Canada at gadouar@canolacouncil.org. WCC/RRC tests use conventional herbicides across all sites, so varieties do not get their matching HT herbicide. Also, in WCC/RRC trials, rarely would any cultivars have been tested in the exact same set of head to head trials. They are tested against the same checks, but WCC/RRC has new checks (5440 and 45H29) starting in 2012.
Crop insurance: Alberta and Manitoba publish summaries of crop insurance yield reports by variety and zone. Read the latest editions online at Yield Alberta and Yield Manitoba. These are based on grower responses, are field by field, and do not include other data such as maturity, lodging and disease resistance. Click here for Saskatchewan crop insurance yield data.

5. Disease tolerance. Blackleg tolerance is becoming more important again. Most varieties are an R or MR, but if a grower is really concerned, then an R rating should be the choice. However, just because a variety has an R rating doesn’t mean it will be equally effective at suppressing incidence and severity at all locations. Blackleg strains at individual fields may be different from those at WCC/RRC sites where ratings were determined. Also note that strains present in a field can shift over time, especially in tight canola rotations.

6. Do you alternate HT systems? This can be a good strategy for long-term weed management, and will introduce other seed sources into your cropping system that may provide additional benefits for disease management. When looking at CPT results, if you find a location where varieties from one system consistently outperform varieties from another system, this may have been driven more by weed control performance than by yield potential alone.

7. Try at least one new variety every year. By doing so, when your current favorite is taken off the market or when its disease resistance starts to break down, you have an idea what varieties are best suited to take its place.

8. Yield vs. maturity. A long season variety is always assumed to yield more than a shorter season variety, but in areas where the season ends quickly due to hot/dry conditions or a frost, later maturing varieties should be grown with more caution. Growing a few different varieties with a mix of maturities can also help with harvest management. For example, seeding an early-season variety first may allow you to harvest that field early enough to seed winter wheat. These acres may also mature early enough to avoid some yield losses from late season insect or disease infestations or heat stress in years when these are major limiting factors Growing varieties with different maturities can also help to spread out the harvest period.

9. Economic margins. Gross revenue is provided for each variety in small plot results. A variety may not be the highest yielding, but differences in seed cost or premiums on price for the production may offer a financial advantage. Profitability of a variety may also depend on benefits associated with other agronomic factors such as disease resistance or harvest ease. All varieties have pretty good yield potential, and economics may be a deciding factor between two otherwise close contenders.

10. Height vs. lodging scores. A tall variety with a really good lodging score could still be a better choice than a medium height variety with a poor lodging score. When looking at height and lodging scores for a new variety, compare the ratings to a variety you’ve grown so you have a gauge for how they stack up.

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