Seeking Hybrid Selection Information
Greg Stewart, OMAFRA Corn Specialist

Corn hybrid selection, faster than any other decision, can make or break your corn yield. Growers must be able to draw upon a wide range of information in order to make the best decision. It really does boil down to numbers. You simply can’t select corn hybrids without the numbers that support a hybrid’s claim to be high yielding, and without some understanding of where those numbers are coming from. Here are some scenarios to illustrate a few points.

1. Precision versus Power
Joe is determined that a trial consisting of single strips running the length of the field to compare 7 or 8 hybrids is full of potential errors. He likes the idea that the OCC Hybrid Performance Trials are replicated several times across a site, but there isn’t one very close to his farm, so he decides to take the matter into his own hands. Joe splits his planter into two hybrids and plants side-by-side strips across an entire 80-acre field and weighs off 20 comparisons from each hybrid. Hybrid A outyielded Hybrid B by an average of 12 bushels, and the twelve-bushel difference was pretty consistent across the entire field. Joe decides, with great confidence in his numbers, that Hybrid A will be the replacement for his Old Faithful, Hybrid B.

Joe is correct in figuring that if the 12-bushel trend was consistent across 20 side-by-sides, he should be very confident in the number. The flaw that is most likely to come back to haunt Joe is that his precise measurements probably capture only one environment, especially if the soil type is uniform across the field. Joe probably cannot have much confidence that the environment he tested under this year will be similar to the one he grows Hybrid A under next year on his farm.

There may very well be some errors associated with single strip hybrid evaluation trials, so you would never want to put too much confidence in any single location. But their real value is that they expose the hybrids to more environments than is possible under performance testing. Seek out numerous test locations to see if your hybrid is a consistent performer over a range of environments. That usually means you will need trials over two years and across some 30 locations to build real confidence that a hybrid deserves a significant portion of your acreage.

2. When are two hybrids really different?
In poring over the Performance Trials, you continue to run into the term LSD. LSD, Least Significant Difference, is a statistical term used to determine whether two hybrids are really different from each other, or whether there is too much variability or ‘noise’ in the data to draw that conclusion. So if the LSD (0.10) value is 8 index points, as listed at the bottom of the table, you can be confident that two hybrids which are greater than 8 index points apart are really yielding differently. Hybrids that are less than the 8 index points apart should be considered as yielding roughly the same within that trial.

If you are looking at strip trial data, there will usually be no such LSD values. If, however, there is a single hybrid that has been entered several times across the trial, it can be used as the same sort of guide. If the same hybrid ranges in yield across the site by 10 bushels, then you probably should have very little confidence in saying that Hybrid A is really different than Hybrid B within this trial unless it outyields Hybrid B by considerably more than 10 bushels.

3. Performance Trial Strength
One of the real strengths of performance trial data is the fact that nearly all available hybrids for a given heat unit rating, including many new ones, are entered in the trial. This allows for some effective screening regarding which new hybrids should be considered for small on-farm trials and will indicate hybrids for which you should actively seek out more information.

4. Workhorses vs Racehorses
Corn hybrids are often classified as ‘workhorses’ or ‘racehorses’. Those hybrids that yield above average under good conditions, but below average under poor conditions are considered racehorses, while those that have relatively consistent yields in both low and high yielding conditions are considered workhorses. Most hybrids that are considered to be more variable performers (racehorses) have specific defects which cause them to yield lower than average when exposed to certain conditions. Growers can avoid some of the risk associated with hybrid selection by taking time to find out as much as possible about a hybrid’s past performance. Select hybrids that complement each other because they have different specific weaknesses. For example, when selecting two full-season hybrids with high yield potential for earliest planting, ensure that they don’t both score low for stalk strength.

Finding out as much as possible about a hybrid’s specific weaknesses will allow you to fine-tune your management of that hybrid. Some questions that need answering are: Will this hybrid hold its yield potential if weather conditions force later planting than expected? Do high densities compromise stalk strength? Does this hybrid have a soil-type preference or drought tolerance that has been demonstrated?

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