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Title: SOIL C AND N POOLS IN RESPONSE TO TALL FESCUE ENDOPHYTE INFECTION, FERTILIZATION, AND CULTIVAR

Author
item Franzluebbers, Alan
item Stuedemann, John

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2004
Publication Date: 3/1/2005
Citation: Franzluebbers, A.J., Stuedemann, J.A. 2005. Soil c and n pools in response to tall fescue endophyte infection, fertilization, and cultivar. Soil Science Society of America Journal. 69:396-403.

Interpretive Summary: Tall fescue is an important cool-season perennial forage in the southeastern USA. Endophyte infection of tall fescue is known to cause a variety of health disorders in grazing animals. However the presence of the endophyte may be necessary for adequate plant survival under drought- and heat-stressed conditions. Scientists at the USDA-Agricultural Research Service in Watkinsville Georgia measured the cumulative effects of 20 years of tall fescue management on soil organic carbon and nitrogen. With 300 lb N/acre/year, soil under tall fescue with a high percentage of plants infected with the endophyte stored more soil organic carbon and nitrogen than soil under tall fescue with a low percentage of plants infected with the endophyte. This extra carbon and nitrogen in soil due to the presence of the endophyte was further found to be located in intermediately sized soil aggregates, which are important for reducing water runoff and improving water quality. These results suggest that well-fertilized tall fescue pastures with a high percentage of plants infected with the endophyte have the potential to help offset the rising carbon dioxide in the atmosphere.

Technical Abstract: Tall fescue is an important cool-season perennial forage used for grazing animals in the humid regions of the USA and throughout the world. The endophyte, Neotyphodium coenophialum, naturally inhabits the majority of tall fescue stands. This study was conducted to determine whether fertilization (134-15-56 vs 336-37-139 kg N-P-K/ha/yr) and tall fescue cultivar ('Kentucky-31', 'AU-Triumph', and 'Johnstone') would modify soil C and N responses to endophyte infection. Soil organic C and total N at a depth of 0-20 cm under Kentucky-31 with high fertilization were greater with high (42 Mg C/ha and 2.7 Mg N/ha) than with low (39 Mg C/ha and 2.4 Mg N/ha) endophyte infection. Under low fertilization, soil organic C and total N were not different between low and high endophyte infection. Carbon and N concentrations of small macroaggregates (0.25-1.0 mm) were the only soil properties that were related (r=0.70, p=0.001) to endophyte infection frequency (range of 1 to 79%) across all treatments. Soil C and N pools can be modified by endophyte infection, but these results narrowed this phenomenon more dominantly to (1) conditions of high fertility and (2) isolation in small macroaggregates.