The most frequently asked question in farming recently is about fertilization. Farmers want to know how to limit costs. Matt Clover, Pioneer agronomy sciences manager, and Eric Miller, Pioneer field agronomist for eastern Indiana, developed a webinar to address those concerns.

“We assumed soil test readings were such that crops should still be responsive to phosphorus and potassium,” Clover says. “If you have soils testing high or very high in one or both, that is a different conversation.”

Clover addressed three strategies. Make sure you understand the implications of each strategy.

1. Hold the line on N, but cut back on P and K. If you still expect good yields, other nutrients besides nitrogen are important too, Clover says. “There is synergy between some nutrients,” he explains. “If you apply both, you see more benefit than if you apply one.

“We see that with nitrogen and potassium. Data indicates that adequate levels of potassium are needed to get maximum impact from nitrogen.”

2. Cut back on N, P and K. Clover points to biomass studies conducted by Pioneer at different yield levels and different growth stages. Achieving high yields means producing lots of biomass. That requires a sufficient amount of each nutrient.

“We found that by harvest, a 200-bushel-per-acre corn crop and a 250-bushel-per-acre corn crop contain about the same amount of potassium,” Clover explains. “However, at certain times during the season, potassium in the higher-yielding crop was much higher. More potassium is needed during the season. You don’t want potassium to be the yield-limiting factor.”

3. Apply a base amount of fertilizer; then wait and see. If you sidedress nitrogen, you can wait until sidedressing to dial in final N rate. If the crop looks good, you can apply more.

“The risk is waiting too late to apply the rest,” Clover says. “Having enough nutrients in the soil by V6 is important. That’s when the plant begins making decisions that affect yield.

“You can still make corrections if you believe a nutrient is short from V8 to tasseling. After R1, you’re into a rescue situation.”

Other situations

Suppose you already applied P and K last fall, with P at $900 per ton and K at $800 per ton.

“With corn around $6 per bushel and soybeans around $15 per bushel, you can likely rest easy that you made a good investment,” Miller says. If you didn’t apply then but are thinking about it now, and prices are now $1,000 and $1,200 respectively, you may need to evaluate it carefully, Miller adds.

“It all starts with good soil test information,” he says. “Without it, you’re just guessing. If soils are acidic, the first dollars should go to lime.”

Suppose you have high to very high levels for P and K on land you own. If you opt not to apply this year, remember that you will begin to draw down soil test levels over time, he explains. Information is available so you can calculate how quickly levels may drop.

If you don’t apply for a year or two on soils in the medium range and then want to raise the soil test to previous levels, account for both crop removal and additional fertilizer to build back test levels, Miller says.