By Charmain Tan Courcelle

MISSISSIPPI STATE -- Researchers believe the discovery of new uses for poultry litter will expand the market for this byproduct.

Mississippi Agricultural and Forestry Experiment Station researchers are working with the Southwest Mississippi Resource Conservation and Development Council, Inc. One new application they are considering is the use of litter as a horticulture fertilizer.

"There are several good reasons to look at using poultry litter outside of traditional land application to pastures. For one thing, the nutrient level of poultry litter -- and especially the nitrogen level -- is high, making it very useful in gardening," said Richard Harkess, MAFES horticulturist.

Harkess is interested in using poultry litter as a fertilizer for potted plants grown in commercial nurseries and in home gardens. He and his team have assessed the benefits of adding heat-processed, pelleted poultry litter as part of a potting mix and determined the best application rates for litter.

"When we first started this project, we were hoping to use poultry litter as a soil amendment because that would mean using larger quantities of litter," Harkess said. "But we found out early on that poultry litter has too much nutrients to be used as an amendment, so we looked at using poultry litter as a supplementary fertilizer."

Harkess has compared the growth of blue salvia, petunias and ornamental peppers planted with and without poultry litter added as a fertilizer.

"We chose these plants because they are very popular among consumers as potted plant varieties and bedding plants," he said. "The pepper plants also provided us a hint at how vegetables will do with poultry litter as a fertilizer, even though we grew them as ornamentals for these experiments."

Plant growth performance was used to demonstrate poultry litter's value as a fertilizer and to indicate whether there are toxicity issues in potted plants related to litter use. The nutritional status of the test plants under fertilized and unfertilized conditions was also determined.

Harkess said the study has shown promise, however some of the plant species experienced toxic effects from the addition of processed poultry litter.

"The salt levels in soil were higher than expected when litter was added to our potting media, which indicated potential toxicity," Harkess said. "At higher litter application rates, we found salt accumulation to be dangerously high, especially at early stages of plant growth."

Harkess said his group will optimize growing conditions to account for salt accumulation with poultry litter treatment. He will also look at using raw versus processed poultry litter to see if that affects the health of potted plants.

In the meantime, Harkess is also studying poultry litter use in landscape flower beds.

"Mississippi soils stay warm year-round, which causes the organic material in soil to break down a lot faster," he said. "We want to know if adding poultry litter to soil will add an organic component that can be used by plants."

Similar to the greenhouse studies, these tests will examine plant growth as a measure of how well poultry litter performs as a landscaping fertilizer. Some growth indicators that Harkess will use for the plants, which are now growing in contained field plots, include flowering earliness and the rate at which the plants fill out their plots.

If the field tests show poultry litter is suitable for landscape use, it could "go a long way in helping the poultry industry use a significant amount of byproduct from their facilities," Harkess said. In addition, it would provide the homeowner interested in using organic fertilizers a new product to try.

For more information, contact: Dr. Richard Harkess, (662) 325-4556