Agronomist: Repeat Fertilizer Programs Waste Money Under Tight Margins

Growers who simply repeat last year's fertilizer program risk spending on nutrients their fields no longer need, according to Tyler Kidd, principal sales agronomist at Wilbur-Ellis, who says yield data and soil tests — not habit — should set next season's nutrient budget.

"The first step is getting an idea of where we're at before we make a plan," Kidd said. "Growers need to decide what crop they're going to plant, what kind of yield they think they can make and fertilize accordingly."

His guidance lands as growers face tight margins and unpredictable growing conditions, forcing harder scrutiny of where each fertility dollar returns value — and where it does not. The combine and the scale, Kidd notes, are the best report card a grower gets all season, but yield results alone do not reveal what nutrients remain in the field.

Why did last year's rates stop working?

Yield maps, crop removal estimates and field history anchor any fertility plan. But a high-yielding field and a drought-stressed one carry very different nutrient balances into the next season, and neither can be read from the other.

A crop that yielded below expectations removed fewer nutrients than planned. That does not mean those nutrients are still plant-available. Rainfall and soil conditions can move them out of the root zone before planting.

Kidd recommends agronomic soil testing that represents the full range of conditions across an operation. A few samples from similar fields will not capture the spread.

"Sample a field with a high-yielding crop, one that received less water and maybe didn't grow a crop that yielded as high, or some other problem areas," Kidd said. "You don't want to sample two similar fields and treat the whole farm according to those two tests."

North Dakota State University Extension advises growers to divide problem fields into zones before sampling, using visual observations and the history of plant stands or crop yields, then sample each zone separately based on its unique characteristics.

Are N, P and K the whole picture?

Nitrogen, phosphorus and potassium dominate most fertility plans. They are only part of the equation, according to University of Wisconsin Extension guidance on crop nutrients.

Secondary nutrients — sulfur, calcium and magnesium — and micronutrients such as zinc, manganese and boron all drive crop development. Soil pH also shapes nutrient availability, which means adequate nutrient levels in the soil do not guarantee adequate plant uptake.

Before raising fertilizer rates, growers should ask whether another nutrient limitation or soil condition is capping performance. Applying more of one nutrient delivers little if a different factor restricts yield potential. Kidd's point: correct the factors most likely to influence crop performance rather than applying nutrients simply because they appeared in last year's program.

How should rates track yield potential?

The most aggressive fertility program is not necessarily the most profitable. Water availability, crop selection, soil conditions and realistic yield expectations should all size the input investment. Fertilizing for a yield goal that growing conditions cannot support inflates production costs without a matching return.

In water-limited regions, Kidd says growers manage financial risk by front-loading essential nutrients and holding back nitrogen until crop potential becomes clearer.

"We'll try to get our P out early," Kidd explained. "Then a lot of the N we'll put through the pivot or through the drip. That way, you know you have the potential to make a crop before you get all your money out there."

For irrigated operations able to make in-season applications, the split approach preserves flexibility to scale nitrogen investment up or down as the season develops. The principle holds across crops and regions: match nutrient spending to achievable production, and adjust when conditions warrant.

Is the cheapest product the best buy?

A lower price does not guarantee better value, and a higher price does not guarantee better performance. Before adding any product, Kidd says growers should confirm it addresses a documented need and that trustworthy field research supports its benefits under similar growing conditions.

He cautions against products that promise results without credible supporting evidence. A trusted agronomic adviser, he adds, can help evaluate product claims, interpret soil and tissue test results, and rank investments by potential return.

What happens this fall?

Fall soil sampling answers many fertility questions, but timing matters for nitrogen. In areas where winter precipitation or other factors can significantly shift soil nutrient levels, testing closer to planting gives a better read on nitrogen availability.

A profitable fertility program is not about applying more, Kidd's framework holds. It is about knowing what each field needs and spending where the investment supports yield potential without unnecessary expense.