What is in this article?:
- Nitrogen peaked at about 85 cents per pound in 2008, and went from about 45 cents last year to about 60 cents this year.
- 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, 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 is that commodity prices are up, and that helps.
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 http://aesl.ces.uga.edu, 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.