Farmers considering poultry litter as fertilizer this year had better go ahead and “get it done” as springtime supplies may be limited.

Commercial nitrogen fertilizer costs have increased to 40 cents per pound from about 35 cents a pound last year. Potash (potassium) has increased from 15 cents per pound to 23 cents in the last six months, said Gerald Evers, forage management expert with the Texas Agricultural Experiment Station at Overton.

Because nitrogen fertilizer production uses natural gas, its price increase is directly linked to higher fuel costs in 2004. Higher potassium prices are also connected to increased energy costs, but the link is a little more complex, according to Leon Young, Stephen F. Austin University.

“There seems to be a supply problem both in production and in transportation, both expenses are due to higher fuel costs and actual production at the mines as well as rail movement issues,” Young said.

Whatever the cause of the price increase, the bottom line is that alternative sources of fertilizer such as poultry litter have become a better deal, said Evers.

Poultry litter is a good source of nitrogen, potassium and other nutrients, but even in a normal year, supplies are often short in the spring, he said. With more producers in “fertilizer-price-ticket shock,” Evers expects poultry litter supplies to be tighter than ever.

Also, because fuel costs are a big factor in the cost of poultry litter delivery costs, producers can expect transportation and spreading fees to climb as well.

How can producers determine if the price they're quoted for poultry litter is economical? There are a number of rules-of-thumb to go by, Evers said.

For starters, each ton of poultry litter contains from $32 to $35 worth of nitrogen, phosphorus and potash.

“However, if producers use only litter and do not supplement it with extra commercial nitrogen, they will only utilize about $22 to $24 of the ingredients,” Evers said.

This disparity results because for every pound of nitrogen, poultry litter has about a pound of phosphorus. Forage crops typically use 4 pounds of nitrogen for every pound of phosphorus, so a lot of phosphorus is left over, Evers said.

“With poultry litter, nitrogen becomes the limiting nutrient for plant growth because all the nitrogen is taken up, but only about 25 percent of the phosphorus,” he said.

For some time, Evers has recommended using commercial nitrogen in conjunction with poultry litter to compensate for this imbalance. The main idea for supplemental nitrogen was to reduce the buildup of excess phosphorus in soils or its being washed off into streams and waterways.

Now, with commercial fertilizer costs increasing, it makes economic sense too, Evers said.

Ideally, the producer should base supplemental applications of fertilizer on a soil test. Evers, however, has some general recommendations.

First, he recommends overseeding with a cool-season annual forage such as ryegrass or clover. Overseeding is primarily for weed control. The decaying broiler litter releases nutrients throughout the year. In the winter, when warm season grasses such as bermudagrass are dormant, winter weeds take advantage of the released nutrients.

“Without the overseeding, it's guaranteed they'll get a great crop of winter weeds,” Evers said.

The amount and timing of supplemental commercial nitrogen depends upon whether the pasture will be used for grazing or for hay production.

For grazing only, the general recommendations are to apply 2 tons of poultry litter per acre every other year. On in-between years — when poultry litter is not used — apply 75 pounds of nitrogen per acre.

When only two hay cuttings are needed, use 2 tons of poultry litter.

Follow the first cutting with 75 pounds of nitrogen per acre.

When three or more cuttings are needed, apply 4 tons of poultry litter per acre in the spring.

With a 4-ton application, no additional nitrogen is needed until after the second harvest. Then apply 75 pounds of nitrogen per acre.

Subsequent harvests should be followed with 75 pounds of nitrogen and 75 pounds of potash. Of course, no fertilizer should be applied after the final harvest, Evers said.

These general guidelines are just that, “general.” Evers emphasized that for a number of reasons — economics, better yields and the environment — it's in the best interests of producers to base fertilizer applications on soil tests.

The producer should have samples of the poultry litter analyzed by a soils lab. On the average, a ton of poultry litter contains about 55 pounds of nitrogen, 50 pounds of phosphorus and 45 pounds of potash.