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Get more from on-farm trials

Remember the old saying “garbage in, garbage out?” It applies to on-farm testing. That’s the conclusion reached by Shaun Casteel and Bob Nielsen, Purdue University Extension agronomists. Casteel specializes in soybean production. Nielsen works with issues related to corn production.

Key Points

Farmers interested in on-farm trials should let an Extension educator know.

The extra time taken for a trial is worth the investment.

Learn more at www.agry.purdue.edu/ext/ofr.


In “Soy Basics” the focus is on learning the basics to raise soybean yield levels. One basic is how many plants per acre you need to maximize profitability, Casteel notes. He’s seeking the answer in on-farm trials to test various soybean plant populations on Purdue Ag Centers and on farmer fields throughout Indiana. These on-farm trials are field-scale using commercial equipment and technologies.

Results so far

In the past two years Casteel worked with farmers on a handful of on-farm trials. Soybean yield was correlated to plant populations in half of the on-farm trials (see “Test your knowledge”).

“What we need are more trials over more seasons,” he says. “Our goal is to build a data base with on-farm trial results that use proper procedures. Nielsen tests nitrogen rates and populations on corn. Kiersten Wise looks at foliar fungicides in soybeans and corn with on-farm trials.”

Casteel will continue determining ideal plant populations based on region or field conditions. He will also establish a new on-farm row spacing trial in 2012.

Good plots

Farmers sometimes balk once they learn Casteel and Nielsen require that they replicate plots. While it may add a little time, Casteel contends it’s the only way to get good results.

This includes laying the plot out properly. The different treatments, which in this case would be seeding rates for soybeans, are randomized within each replication of the experiment.

For example, if you’re testing five rates, A to E, and repeating it four times across the field, in one replication rate A might be the first planted. In another it might be in the fourth slot. Purdue researchers work with farmers to design and lay out the on-farm trials.

All this attention to detail is necessary to take out the background noise, such as differences in soil type or soil fertility, Casteel says. If plots are conducted correctly and results can be statistically analyzed, then you have a much better chance of knowing whether a yield difference occurred because of the factor you were evaluating, or just due to scientific error.

Test your knowledge

So do plant harvest populations affect yield? Shaun Casteel believes they do, and that many people plant thicker than necessary. Two years of limited on-farm trials have produced conflicting results.

Half of the on-farm trials in 2010 and 2011 showed a yield response to harvest stands with the maximum yield near 110,000 plants per acre. The other half did not show yield differences from 45,000 to 225,000 plants per acre.

Casteel believes the fact that some trials were in very low-yielding environments due to limited moisture or too much moisture may help explain results.

“Right now we’re recommending 100,000 to 120,000 plants per acre to maximize yields and profitability,” Casteel concludes. “We need more on-farm trials to answer past questions and predict future results.”


This article published in the February, 2012 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.