Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2000
Publication Date: N/A
Interpretive Summary: Grazing of cattle on tall fescue is a significant component of the Southern Piedmont agricultural system. The fungal endophyte associated with tall fescue produces an alkaloid that protects the plant from herbivory but also negatively affects animal performance. We investigated the effects of fescue-endophyte level and fertility regime on the vertical and horizontal distribution of P, K, and Mg, in grazed pastures after 15 and 8 years. We found that nutrient accumulation was greatest at the shade and water sources which were permanently located during the life of the study. At distances further from the shade and water sources no significant increase or decrease in P, K, or Mg was observed. The fescue-endophyte increased accumulation of P and Mg near the water and shade sources but there was no differentiation of the endophyte effect for K. These results indicate that the location of the water and shade source should be moved occasionally to eliminate significant accumulation of nutrients in one location and to reduce the potential for nutrient losses in runoff and transfer through the soil profile to ground water.
Technical Abstract: The influence of grazing animals on nutrient cycling may be significant with tall fescue (Festuca arundinacea, Schreb.) because of endophyte produced alkaloids that cause fescue toxicosis. Twelve grazed fescue pastures, established in a Typic Kanhapludults soil near Watkinsville, GA, were used to measure fertility(134-15-56 and 336-37-139 kg N-P-K per ha per ryr) and endophyte (low, 0 to 29% and high, 65 to 94%) effects on P, K and Mg distribution. Samples were collected winter 1997 at distances of 1, 10, 30, 50, and 80 m from permanently located shade and water sources at eight depth increments down to 1.5 m. Nutrients were greatest 1 m from shade and water sources where P, K, and Mg concentrations were 1.7 to 8, 2.5 to 15, and 1.1 to 1.5 times greater, than concentrations at remaining distances depending on depth and fertility. Accumulation of P, K, and Mg at 10 to 80 m from shade and water was limited. Summed for the 0 to 300 mm depths, extractable P was 64% greater in high than in low endophyte-infected pastures 1 m from shade and water sources (703 versus 428 kg ha-1 LSD=93) and averaged 252 kg/ha-for remaining distances. Endophyte did not affect K distribution and affected Mg only under low fertility. Endophyte effects accrued over a long-time period indicating altering pasture management (lime and fertilizer rates, and shade and water location)would be needed occasionally to reduce environmental risks.