Fed up with high fertilizer prices, more and more U.S. farmers are looking at poultry litter to feed their crops.

But before deciding on any source of fertilizer, poultry litter or commercial, it’s important to know your fertility costs in cents per pound of nutrient or nutrients instead of cost per ton. Many producers figure this cost based on nitrogen, but phosphate and potash are important components too.

First determine the analysis of the fertilizer you intend to purchase — the numbers expressed as N, P2O5 (phosphate) and K2O (potash). These numbers represent the percent by weight by of each nutrient.

To convert dollars per ton into cents per pound for N, multiply the percentage of N by 2,000 to get the number of pounds. Anhydrous ammonia at 82 percent N would provide 1,640 pounds of N per ton. Then divide the current price per ton by the number of pounds to get cents or dollars per pound.

For example, current prices for nitrogen are a moving target, but $575 per ton divided by 1,640 pounds, gives you around 35 cents per pound of N. Thirty-two percent N would provide 640 pounds of total N. If the cost were $320 per ton, your cost would be 50 cents per pound of N.

“So even though the liquid UAN 32 percent will cost less per ton when you look at it side-by-side with anhydrous, per pound of N, you’re actually paying more,” said Jac Varco, professor, plant and soil sciences, Mississippi State University.

With complete fertilizers, it’s more difficult to separate out the cost of one nutrient. With poultry litter, try combining the analysis numbers together to get cents per pound for all three — N, P2O5 and K2O. For example, in poultry litter with an analysis of 3-2-2, add the numbers of the analysis together, multiply each by 2,000 to get pounds, then add up the total amount of nutrients and divide into the price/ton (say it’s $30 a ton). The 140 pounds of N, P and K would cost you about 21 cents a pound for the three nutrients.

Varco says “The best option is to figure out what your total needs for nitrogen, phosphate and potash are for a field, then figure out what it would cost to partially offset some of that with poultry litter at a set price, which hopefully would reduce total costs somewhat.”

You could create some problems by depending too much on poultry litter for your nitrogen according to Varco, “The primary element in poultry litter is phosphate, at almost a 1:2 ratio of N to P2O5 in some of the poultry litters I’ve been seeing. The problem with that is that most producers are really going after nitrogen. So you could meet your phosphate demand with litter, then calculate how much nitrogen came along with it, then use your traditional fertilizer to make up the difference in need for nitrogen.”

Varco doesn’t have figures on an exact cost benefit for poultry litter over commercial fertilizer, “but it could be pretty close right now because producers are using it more and asking more questions about it. Or it could be that producers are just so irritated with the high fertilizer prices they’re just buying the poultry litter. But I do know that the farther you get away from poultry country, the more it’s going to cost you, because of transportation costs.”

According to Charles C. Mitchell, Extension soils agronomist at Auburn University, poultry litter-based fertilizer “has the most fertilizer value the day it comes out of the chicken house. Whatever you do to it is adding costs. So if you pelletize it, it makes it easier to handle, but you haven’t added any fertilizer value to it.”

Researchers also stress that the analysis in raw poultry litter can be highly variable while processed or pelletized litter is more stable. Some states may have regulations on the use of raw poultry litter.

According to Bill Evans, assistant research professor, Mississippi State University, processed poultry litter has some advantages over fresh chicken litter. “With fresh chicken litter, you have to move some water (in transporting), and the total analysis is lower, but with their product most of the water is removed, so you’re not moving water. But there is a cost of pelletizing the litter.”

Evans says the processed poultry litter is not any more difficult to handle and apply than a commercial fertilizer. “There is a little bit of dust with the application, but I don’t think it’s any more dusty than a dry, granular fertilizer. The pellets are a little bigger than a standard fertilizer though. So it’s possible that certain kinds of equipment might not handle it as well. For example, I’ve never tried to run it through a Gandy applicator. I wouldn’t think you would have any problem with a sling spreader.”

John Strickland, who runs Organic Growing Systems, an organic fertilizer processor in Monticello, Miss., says interest in his product has also spiked. “Last year, commercial fertilizers jumped 68 percent. The predictions were that in 2008 they would rise another 102 percent, but they’ve jumped so far since January that the people we were talking to in October who were not interested in our product are now asking us to bring our product to them.”

Organic fertilizer has largely been perceived as a boutique product for dedicated organic farmers, noted Strickland. “You pay more money for it, but you could feel good because it was better for the environment because it doesn’t leach and we have no atmospheric volatilization. With the current price curve, people are finding that it’s not only good for the earth, but it’s saving money too.”

But the cost, which averages around $400 per ton, is still considered cost-prohibitive for most commercial operations desperately looking to slash costs. With an analysis of 4-2-2, if you’re counting N, P and K, that comes to $2.50 per pound of fertilizer nutrients.