Agronomic success: How to evaluate yield data from trials

Written by: Robert Mullen, Ohio State University

Now that crop harvest is winding down, many companies that conduct field experimentation will be getting out and sharing their success stories, so how can you weed through the information to find the truth?

The first thing I often say as it relates to fertilizer products (but this likely extends to other agronomic products/practices) is “if it sounds too good to be true, it likely is.”

The first thing to look for when evaluating yield data from field trials is to look for some information regarding how field experimentation was done.

This does not require you to have a statistical background.

Simple questions like - “Was the study replicated?”, “How many locations were utilized?”, “Were there any locations that did not respond positively (environmental interactions)?”

To my knowledge, no agronomic practice (within reason) results in a yield increase every time it is evaluated. So if someone states, “we conducted field research on 50 fields, and we saw a yield increase every time,” be suspicious.

View split field research data cautiously. Back in 2006 we prepared a CORN Newsletter article that shared our concerns regarding the use of split field experiments to direct agronomic decisions (2006-37). Split field comparisons can reveal yield differences, but our ability to determine how confident we are that the differences are due to an actual treatment effect and not just shear random chance (or due to some other underlying factor) is negligible.

Inquire why a specific treatment resulted in a supposed yield difference. This can be critical. If the explanation does not make sound agronomic sense, then you have your answer as to whether or not it would be beneficial on your farm.

Along this line, determine if the salesperson is marketing something specific to your situation (soil test level, agronomic practice, insect pest, disease pressure, etc.) or just selling something that everyone should use. Many non-traditional approaches to nutrient supplementation can be beneficial, but they are only beneficial in specific instances. Are they telling you it works everywhere, or just under a certain set of circumstances?

Ag marketers/salespersons are important to the introduction of new products that you as a producer benefit from annually. Our goal at Ohio State Uni-versity is to provide you tools that allow you to make better decisions. Your ability to separate good information from a marketing ploy is simply another tool in your arsenal.