How should a farmer sample for diagnostic purposes?

Robert Mullen, Ph.D.

Robert Mullen

Robert Mullen, Ph.D.


Director of Agronomy

To say Dr. Robert Mullen is passionate about agriculture would be an understatement. He holds a Bachelor of Science degree in ag business from Cameron University, along with a Master of Science degree in plant and soil science and a Ph.D. in soil science from Oklahoma State University. In addition, Dr. Mullen has been published in a variety of scientific and trade journals. But it’s not just his academic accomplishments that make him unique. It’s his unwavering ability to take complex data and — in simple terms — explain how it impacts a farmer’s bottom line. Dr. Mullen delivers the kind of insightful observations that can lead to a more profitable business. As a leading agronomy expert, Dr. Mullen has a goal to further educate farmers on best management practices that improve their yields and maximize their return on investment.

Share This:

Like most production issues, nutrient deficiencies rarely affect an entire field. When there are areas that are exhibiting suspected nutrient issues, here is the best way to go about determining what the likely issue is.

Ideally, plant tissue and soil samples should be collected for comparison. Collect around 15 samples from the affected area and 15 samples from the unaffected area near the affected area. Sample the same plant parts from both areas. If the samples are collected early in the growing season, collect the entire plant for tissue analysis. Later season sampling should focus on specific plant parts (corn – ear leaf, soybean – newest most fully expanded trifoliate, etc.). Soil samples should be collected to a traditional soil sampling depth (typically 6-8 inches).

Compare the affected area against the unaffected area and see what differences there are. Interpreting the information can be a complicated exercise. Pay close attention to the details for each area that was sampled.

Robert Mullen, Ph.D., CCA, CPAg
Nutrien | Director of Agronomy