As corn planting time has approached this year, growers have had a lot of questions — just as in 2008 — about how high fertilizer prices might go.

Bracing for the inevitable, some producers booked early, while others made fall applications.

“I had a lot of calls back in November and December from growers who wanted to know if they should go ahead and put out their fertilizer or at least go ahead and buy because they were afraid prices would go up,” said Glen Harris, University of Georgia soil scientist, speaking at the Georgia Corn Short Course held recently in Tifton.

“I’m not a big fan of storing fertilizer or of fall fertilization in the South,” says Harris. “It’s a different story in the Midwest, where it’s frozen. It also depends on the nutrient. We can put out phosphorus in the fall because it’s immobile. But nitrogen is very mobile. If you put it out in November or December and don’t plant corn until February or March, with no cover crop — we don’t know how much nitrogen will be left out there.”

Growers have had some issues with potassium because it gets fairly mobile in Georgia soils, he adds.

Looking at the recent history of fertilizer prices, nitrogen peaked at about 85 cents per pound in 2008, and went from about 45 cents last year to about 60 cents this year, says Harris. Phosphorus is up from 25 cents last year to about 45 cents this year. Potassium was about 12 cents per pound for a long time, he says, peaked at around 80 cents, came down slowly, and now has leveled off at about 50 cents, but it’s likely to increase.

The good news, he says, is that commodity prices are up, and that helps.

Online program

Growers can take soil test data, either from the University of Georgia or private labs, and plug the phosphorus and potassium numbers into a program called UGFertex that is available at, says Harris.

UGFertex allows the user to interactively select from 35 agronomic crops and/or cropping systems along with various management practices. Then, based on soil test results, it uses functions for soil management group, yield goal, irrigation, plow depth, soil buildup, prior crop, and manure applications to derive lime and nutrient guidelines for that crop-soil group combination. Growers can change yield goals and adjust other factors with this program.

“When we look at P and K for irrigated corn, corn is a fairly high user of fertilizer compared to cotton, soybeans and peanuts. We do recommend you maintain medium or high levels of P and K. If your levels of these nutrients are low, you have an 80 percent chance of a yield response to added fertilizer. If you have medium levels, we say you have a 50 percent chance. “That’s a flip of the coin whether or not you’ll see a yield response at the medium level. But if you don’t get a yield response it’s not wasted because P and K will help to maintain levels in the soil. When you get too high, you have only a 10 percent chance of a yield response from added fertilizer, and at very high levels we don’t recommend adding any fertilizer.”

Harris says he gets a lot of calls from farmers about banding P and K.

“Growers want to know if they can reduce their rates by banding P and K. There are no advantages to banding P and K once your levels are medium to high. There are made-to-band fertilizers, but, hopefully, they’re not being sold within the context that you can reduce your rates. If you’re at medium to high, broadcasting should be just as good.”

Starter fertilizers, he says, are another situation when it comes to banding. Banding a starter fertilizer 2 inches to the side and 2 inches below the seed increases the chances of roots penetrating the fertilizer band and taking up needed nitrogen and phosphorus.

Deduct starter fertilizer

Growers should deduct the amount of nitrogen and phosphorus used in a starter fertilizer from the total nitrogen and phosphorus needed for the season, says Harris. However, total phosphate requirements of the corn crop often can be supplied in the starter fertilizer. Since nutrients applied in starter fertilizers are a part of the total fertilizer program, using this recommended practice is not very costly.

“We do not recommend putting anything in the furrow,” he says. “There are products that are recommended for putting in the furrow, but they make me nervous at this point. We’ll continue to look at them.”

As for poultry litter applied as fertilizer, it’s important to know the amounts of nutrients contained in the manure prior to making a decision to use it as your main source of phosphorus and potassium, says Harris.

“The majority of the nutrients contained in the manure are readily available in the season. If you are using poultry litter, in general, you should be able to use about 65 percent of the nitrogen and 80 percent of the phosphorus and potassium contained in the litter the first year.”

For example, if your analysis is 50-50-50 per ton, and you apply 2 tons per acre, then credit your fertility program 65 pounds of nitrogen, phosphorus and potassium the first year. At least 25 percent of the nitrogen should be available within the first two to three weeks after application and the remainder throughout the season.

“I like to see it put on preplant and then still side-dress with commercial nitrogen,” he says.

Other nitrogen materials are available that are known as enhanced efficiency (EE) fertilizers, says Harris, and these are being tested.

“I had this conclusion two years ago, and I still stand by it. They are not silver bullets. Some will play a role, depending on the product and how we use them. We still need to further test them. At this point, one that is working pretty well is Agrotain, which is a urease inhibitor. Where I think a urease inhibitor really comes into play is when dry urea, a 46-percent nitrogen material, is used in a dryland, strip-till situation.”