Balancing nutrient costs, yields

JOHNSTON, Iowa — Making fertilizer decisions is even more challenging in this high-cost environment.

Maximizing a return on investment in fertility expenses begins with a good soil test, according to Matt Essick, Pioneer agronomy manager.

“A soil test for phosphorous and potassium that shows we’re in the high or very high category for a field can indicate that we can possibly skip a year of fertilizer application in those fields,” Essick said.

“However, if we skip a year of fertilizer application, we do need to keep in mind that the next crop is going to remove some of that fertility from the field and will eventually need to be replaced.”

Essick added that applications of P and K at higher than economically optimal rates in a particular year can offset fertilizer requirements in future years. Both P and K are relatively stable in soils and can be “banked” for later use if economically advantageous.

Growers may also adopt a nutrient sufficiency management plan. This philosophy focuses on applying the minimum amount of inputs needed to maximize profitability in the year of application, with little concern for future soil test values or requirements.

Build-and-maintain fertility programs contrast with the nutrient-sufficiency approach in that they are not intended to maximize economic returns in any given year.

Rather, they are designed to provide flexibility and consistent economic returns over the long-term by removing P and K as yield-limiting factors.

“Regardless of which method growers go with, a few general rules of thumb apply: Always fertilize when soil test levels fall below the optimal range, avoid applications on high-testing soils and, when in doubt, fertilize based on expected rates of crop removal,” Essick said.