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item Franzluebbers, Alan
item HILL, N

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2004
Publication Date: 3/1/2005
Citation: Franzluebbers, A.J., Hill, N.S. 2005. Soil carbon, nitrogen, and ergot alkaloids with short- and long-term exposure to endophyte-infected and free-tall fescue. Soil Science Society of America Journal. 69:404-412

Interpretive Summary: Tall fescue is an important cool-season grass in the southeastern USA. The plant is naturally infected by a fungus that produces a variety of low-level toxins. Animals that graze this grass perform less than ideal. On the other hand, the fungus in tall fescue appears essential for the plant to survive the hot, humid conditions of the southeastern USA. A consequence of having the fungus present in the plant is an accumulation of soil organic matter. Soil organic matter is an important component of soil fertility, but also plays a role as a mechanism to help reduce carbon dioxide concentration in the atmosphere. A collaboration between scientists at the USDA-Agricultural Research Service in Watkinsville Georgia and the Department of Crop and Soil Sciences at the University of Georgia investigated nutrient and toxin release from tall fescue leaves added to soil. Changes in nutrient release were observed and toxins were found in soil. Scientists will be able to use this information to better understand the ecological impacts of animals grazing tall fescue, and possibly to identify and cultivate other similar associations for improving soil organic matter storage.

Technical Abstract: Tall fescue is an important cool-season perennial forage naturally infected with an endophyte, Neotyphodium coenophialum, which produces ergot alkaloids. We conducted a controlled incubation study to determine the fate of carbon, nitrogen, and ergot akaloids in tall fescue leaf tissue added to soil. The experimental setup was a factorial combination of endophyte-free (E-) and endophyte-infected (E+) leaf tissue (short term) incubated in soil exposed to 10 years of E- and E+ tall fescue pasture (long term). Compared with soil history of E-, soil history of E+ reduced carbon mineralization per unit of soil organic carbon and the fraction of inorganic N as nitrate, but increased ergot alkaloid concentrations in the sediment, coarse, and water extract fractions of soil. Compared with short-term exposure (32 days) of soil to E- tall fescue leaves, addition of E+ leaves reduced carbon mineralization and soil microbial biomass carbon, but increased net nitrogen mineralization, soil microbial biomass nitrogen, and ergot alkaloid concentration in the coarse fraction. Both short- and long-term exposure of soil to E+ tall fescue were affecting soil organic matter dynamics.