Nutrient Science

Fertilization: Comparing The Maintenance Approach vs. The Sufficiency Approach

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.

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Virtually everyone in the industry agrees that fertilization is required when soils fall below the critical level for P and K. But that’s where the consensus ends. The real debate begins when determining a course of action for fields right at that critical level. Fertilize? Or not to fertilize? In this video, Dr. Robert Mullen explains the difference between the Maintenance and Sufficiency Approaches to fertilization and offers his opinion on what method he recommends to ensure farmers get the most out of their fields.

When fields reach critical levels for P and/or K, farmers are faced with two choices

The Maintenance Approach

Action: Fertilization is required.

Result: Nutrient application ensures the entire field is above the critical levels for P and K, thereby maximizing yields.

The Maintenance Approach

The Sufficiency Approach

Action: No fertilization required.

Result: Although the field has an average at or above the critical level, some areas of the field may still fall below the critical level. Therefore, the farmer risks yield loss in order to save on nutrient costs.

The Sufficiency Approach

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