During my career as an independent crop consultant, I have witnessed the progression of university soil fertility guidelines becoming firm recommendations. Then, those have morphed into de facto law as the NRCS 590 standard has been codified in my state of Wisconsin.

All of us understand that this is driven by the need to limit environmental side effects of nutrient movement into surface water and groundwater. Nitrogen and phosphorus fertilization rates are regulation targets for good reason. Algae blooms, dead zones and elevated nitrate levels in drinking water are direct consequences of nitrogen and phosphorus movement from agricultural land and other sources.

I am not confident that all agricultural stakeholders understand the full implications of turning a guideline into law. The most obvious implication is that the recommendation needs to be correct virtually 100% of the time. This is a difficult standard to meet with nitrogen management. Excessive rainfall events and the difficulty of predicting seasonal weather patterns make soil nitrogen management more of an art than a science at times. There needs to be room for an agronomist to use professional judgment when circumstances call for an informed action. With certification programs such as CPCC from the National Alliance of Independent Crop Consultants and CCA/CPAg from the American Society of Agronomy, there should be latitude for professional judgment when it is justified and defensible.



Currently, our Wisconsin 590 standard allows a little latitude for professional judgment in some circumstances but not nearly enough for common situations. One of the provisions that allows a farmer to exceed university “guidelines” requires that the farmer/agronomist conduct on-farm research with a design similar to what the university uses. This is an impractical solution when one realizes the width of equipment available on farms to install research plots. It would not be good enough to just prove that the university recommendation is inadequate by comparing the recommended rate to the proposed rate.

 The current proposal reads:  “When documenting that a different rate of nutrients is more appropriate for farm conditions, a field trial must contain the following:

a. At least five (5) nutrient application rates including a zero rate where the nutrient of concern is not applied or is applied in starter fertilizer at rates not to exceed 20 lbs N/a, 10 lbs P2O5/a, or 10 lbs K2O/a.

(1) The total amount of nutrient applied (starter + preplant + sidedress + late season +  fertigation) is recorded as the nutrient application rate.

b. Each treatment must be replicated at least three (3) times in the same field.

c. Treatments be randomly placed within each replicate.

d. The study should be collected on at least one (1) field each year.

(1) Field conditions should be similar for comparison purposes. This includes at a minimum tillage, previous crop, and fertilizer/manure application history.

e. The study should be conducted a minimum of three (3) years.”

Is this level of on-farm research really necessary?

My goal in criticizing this path is to avoid a point in time where the farmer decides that selected university recommendations are no longer seriously considered as an option for his or her operation. It is critical that farmers have confidence in the soil fertility recommendations developed by their land-grant institutions. This requires that universities will engage and respond when farmers and agronomists demonstrate that a recommendation is not quite hitting the mark. 

We are all on the same team. If we work together as a team, then we can get this right.