12/21/1993

Innovative Approach Applied to Water Quality Study

AUBURN, Ala. - Science sometimes requires intense detective work, so Auburn University researchers are using a chemical spy to trace the activities of a useful, but potentially troublesome agricultural byproduct.

That product is broiler litter, a mixture of manure, bedding material, feathers, wasted feed and other debris that collects on the floor of broiler houses. Though broiler litter is a byproduct of Alabama's billion dollar poultry industry, it has many beneficial uses, including as an economical alternative to manufactured fertilizers.

However, unlike manufactured fertilizers, the amount and availability of nitrogen contained in the broiler litter can vary, and little is known about what happens to this essential plant nutrient once it is applied to agricultural land.

Billy Kingery, a former graduate research associate at Auburn, has been involved in a study, sponsored by the Alabama Agricultural Experiment Station (AAES) at Auburn, that is attempting to track the fate of nitrogen from broiler litter.

This study was spurred by an earlier AAES experiment in which Kingery surveyed areas in the Sand Mountain region of North Alabama where broiler litter had been applied to crop and pasture land for many years. Results of that study indicated that prolonged and excessive use of broiler litter on certain soil types may pose potential environmental problems because of too much nitrogen in the soil.

"It's really excess nitrates -- those that exceed plant requirements and move on down through the soil or into surface runoff -- that cause a problem," he explained.

"High nitrates in drinking water supplies have been connected with human and animal health problems," added Kingery, who is now assistant professor of agronomy and soils at Mississippi State University. "It also can cause excessive algal blooms in ponds and recreational water areas."

Knowing more about broiler litter's impact on the environment is critical to assure that broiler litter is an effective and environmentally sound fertilizer. But nitrogen can be an elusive nutrient because there are many places, or "pools," where it can go once it is in the soil.

Kingery and Auburn researcher Wes Wood enlisted a special form of nitrogen, N15, as a chemical spy to track the movements of nitrogen.

"N15 is a naturally occurring, nonradioactive isotope of nitrogen that doesn't hurt the birds but it can be concentrated in quantities higher than are normally found in common nitrogen so that they can be traced," Kingery explained.

Corn containing N15 nitrogen was fed to birds at Auburn's poultry research facility and the litter produced by these birds was used in the study.

"When you are trying to do research it is a kind of balancing act," explained Kingery. "You need to get as many natural conditions as you can, so that you know how things will work in the real world, but you need to be able to control factors so you can take a more detailed look."

Though this study was undertaken in a greenhouse, it was designed to closely approximate the natural environment. "We tried to simulate as many of the natural conditions as we could," he said.

To do this, the researchers collected columns of undisturbed soil from the Wiregrass area of Alabama. These columns were moved to a greenhouse on the Auburn campus and pearl millet was planted at the top of each column. The columns then were subjected to various treatments, including commercial fertilizer, the N15 broiler litter with added nutrients and no-fertilizer treatments.

"We wanted to find out where these nutrients, that are potential environmental problems but also are essential to successfully make a crop, wind up," he said. The study evaluated several "pools," including biological, hydrological and soil spheres.

"We wanted to know how much goes into plants, how much is stored in the soil, how much moves down in the soil with water and how much winds up in the microbial populations, because they incorporate it into their systems," he said.

"Microorganisms break down the litter and also take up some of the nutrients. They release this nitrogen to plants, but they also can release so much that rainfall or irrigation water can carry it down through the soil and move it away from the plants," explained Kingery.

Though results of the first season of the study have not yet been analyzed, Kingery said the plants grown on broiler litter appeared to perform better than plants grown on commercial fertilizer. This indicates that the broiler litter may be doing an exceptionally good job of supplying nutrients to the plants.

"This is as complete an accounting of the nitrogen as we think we can achieve," said Kingery. "We think the study will help us know how closely we need to pay attention to these spheres where nitrogen can collect," he added.

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News from:

Office of Ag Communications & Marketing

Auburn University College of Agriculture
Alabama Agricultural Experiment Station
3 Comer Hall, Auburn University
Auburn, AL 36849
334-844-4877 (PHONE) 334-844-5892 (FAX)

Contact Jamie Creamer, 334-844-2783 or jcreamer@auburn.edu
Contact Katie Jackson, 334-844-5886 or smithcl@auburn.edu

12/21/93