YOAKUM — There are at least 70 million reasons for studying the potential impacts of using poultry litter as fertilizer, according to James Grichar of Texas Agricultural Experiment Station in Yoakum.
“It’s estimated that there are 70 million birds in the Gonzales and Lavaca County poultry business, mostly in Gonzales County,” said Grichar, a research scientist. “If managed properly, poultry litter has potential as a soil amendment, but we need to know both what its production impacts and environmental impacts are.”
Previous research has examined the impacts of chicken litter use in East Texas, but because the rainfall is heavier in East Texas, Grichar said, researchers felt they needed data on what happens in drier circumstances.
“We felt we needed to see what’s happening to the litter under these drier conditions. We have some sandy soils and some heavier clay-type soils, and we needed to have a better idea of what happens in this area,” Grichar said.
The research, funded with a $150,000 Environmental Protection Agency grant over three years, is being conducted in two different locations with coastal bermudagrass pastures — one with a sandy soil texture and one with a clay loam texture.
Each site will be cut for hay on a regular basis during the growing season, and the hay will be analyzed for nitrogen, phosphorus, potassium, calcium and magnesium content. Poultry litter may contain equal amounts of nitrogen and a form of phosphorus, but warm-season perennial grasses usually take only about a third as much of that phosphorus as nitrogen. As a result, managing litter application to avoid excess phosphorus content becomes critical.
Excess accumulations of phosphorus can contaminate both surface and groundwater during leaching or water runoff during heavy rains.
There is some history of high phosphorus content in soil profiles in Lavaca and Gonzales counties because of poultry populations or applications of poultry litter, Grichar said.
In addition to analyzing hay crops, researchers have placed several lysimeters at each site to collect water percolating through the soil after each significant rainfall.
Soil samples from various depths up to three feet were taken at each site before the tests began to determine mineral and nutrient composition of the soil, and they will be taken annually during the project to determine changes.
Each site has eight different treatments: no fertilizer treatment, one using recommended rates of commercial fertilizer, or one of six different applications of poultry litter that provide nitrogen at rates ranging from 90 pounds per acre to 650 pounds per acre per year.
The project got underway in the fall of 1998 and is slated to run through the late summer of 2001.
A very important element of the project, Grichar said, is extending the knowledge gained about poultry litter management to area producers. Local Texas Agricultural Extension Service field days will feature updates on the project, other field tours and an educational program are being developed, and Grichar is alerting news media about the project.
“We’ll show poultry producers the benefits of sustainable poultry litter management and the negative effects of excessive phosphorus accumulation in the soil,” Grichar said. “Our project is unique because of its broad-based approach, and it should help the poultry industry see the value of this as a best management practice.”
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