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Achilles Heel of Farm Trials: Make Conclusions First!

Achilles Heel of Farm Trials: Make Conclusions First!
Sometimes data says something different than what you expect.

From third grade on, students who participate in science fairs and learn and use the scientific method are taught that an inquisitive person begins with a hypothesis- it's what he or she thinks will happen if you do a certain experiment. Think of it as a good guess. The more knowledge you have about the subject and the more homework you've done, the better the guess should be- but it's still a guess.

Then you do the experiment. If you were 100% sure your guess was right, there wouldn't be any need to test it. Extension specialists and other experts urge farmers to run test plots for hybrids, varieties and new practices on their farms each year to see if their guesses are right. Is hybrid A better than hybrid B like you think, or not? Does corn really do better planted at 34,000 seeds per acre, as common sense says it should, or not?

The problem comes when you do the test, get results, and they don't match what you expect. Then you look for explanations, but you certainly don't try to twist results to match what you hoped to find.


"We've got a perfect example of that in our Indiana Prairie Farmer / Precision Planting study that we did at the Throckmorton Purdue University farm this year," says Jeff Phillips, Extension ad educator in Tippecanoe County. "At least one of the results didn't come out as we thought it would."

One of the variables in the study was driving speed- four, five and six miles per hour. While the data is preliminary, it appears that the corn planted at four miles per hour yielded significantly less, at an LSD or 0.10 level, than corn planted at 5 and 6 miles per hour. The yield difference was still relatively small, with all three averaging in the 190's, and the 4 mile per hour plots being about 6 bushels per acre less. There was no difference in yields between the five and six mile per hour speeds."

"You would expect that if you go slower and do a better job, you would get more yield," Phillips says. "We have an indication that we did a better job spacing plants at 4 miles per hour. The spacing between plants, which we convert into something called standard deviation, was significantly lower, a good thing, for 4 miles per hour vs. the other two. However, all three levels of standard deviation were relatively low, meaning that even at six miles per hour, the planter still did a relatively good job of placing seeds."

Now Phillips will go back and look for an explanation. Did one or more plots end up with more plants per acre because of how the planter functioned at different speeds? Is there another explanation?

"Sometimes you can't always find an explanation," he says. "Sometimes you must just accept that even though you had a strong suspicion one thing should happen, something else happened, and you really can't explain why."

The solution is to run the test again, or run it at multiple locations, and see if the results are always the same. Phillips hopes to run this test again next year, only plant earlier this time.

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