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Title: SOIL MICROBIAL ACTIVITY AND DIVERSITY UNDER FESTUCA ARUNDINACEA INFECTED WITH NEOTYPHODIUM COENOPHIALUM

Author
item Franzluebbers, Alan
item NAZIH, N - AL AKHAWAYN UNIVERSITY
item HARTEL, P - UNIVERSITY OF GEORGIA
item Schomberg, Harry
item Stuedemann, John

Submitted to: World Congress of Soil Science
Publication Type: Proceedings
Publication Acceptance Date: 8/24/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Tall fescue (Festuca arundinacea) is an important cool-season perennial forage for many cattle producers in the humid regions of the USA and throughout the world. It persists with grazing better than other cool-season species in the southeastern USA, partly because of the endophytic association with Neotyphodium coenophialum, which offers several lbiochemical deterrents to overgrazing and insect pressure. Endophyte infection of tall fescue results in accumulation of toxic alkaloids in leaf tissue known to cause animal health disorders upon ingestion. We hypothesized that accumulation of these same alkaloids in plant litter, dung, urine, and soil may alter soil organic matter dynamics and microbial diversity. Soil biochemical concentrations decreased logarithmically with increasing soil depth. Basal soil respiration was greater, but particulate organic matter was lower under endophyte-free fescue than under endophyte-infected fescue. We conclude that at the end of eight years of grazing, removal of N. coenophialum from tall fescue resulted in more labile C pools and a somewhat less diverse soil microbial community that could have long-term implications for nutrient cycling and physical properties of soil.

Technical Abstract: Endophyte infection of tall fescue results in accumulation of toxic alkaloids in leaf tissue known to cause animal health disorders upon ingestion. We hypothesized that accumulation of these same alkaloids in soil could alter organic matter dynamics and microbial diversity. Two replicate paddocks (0.7 ha) were planted to endophyte-infected tall fescue in autumn 1988. Soil was collected in January 1997 at depths of 0-2.5, 2.5-7.5, 7.5-15, and 15-30 cm at distances of 1, 10, 30, 50, and 80 m from permanent shade and water. Eight cores (4.1-cm diam) were composited for each depth and distance. Soil biochemical concentrations decreased logarithmically with increasing soil depth. Basal soil respiration was greater, but particulate organic carbon and nitrogen was lower under endophyte-free fescue (E-) than under endophyte-infected fescue (E+) to a depth of 30 cm. There were lower concentrations of 25 fatty-acid peaks under E-, but higher concentraions of 10 other peaks compared with E+. More labile C pools and a somewhat less diverse soil microbial community under E- could have long-term implications for nutrient cycling and soil physical properties.