Ergovaline Concentration of Tall Fescue as Affected by Limestone Application

Core Ideas Limestone application reduced ergovaline concentrations by 20 ppb compared with non‐treated control plots. This slight reduction in ergovaline concentrations is not enough to affect toxicosis, but the reduction occurred with a corresponding increase in soil pH, which can improve the growing conditions for pasture legumes and indirectly affect toxicosis. Unlike limestone, other soil amendments, such as N and poultry litter, increase ergovaline concentrations and therefore create a sort of penalty for the producer. Ergovaline is an ergot alkaloid produced by Epichloë coenophiala [(Morgan‐Jones & W. Gams) C.W. Bacon & Schardl], an endophyte in tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] that causes fescue toxicosis. Ergovaline concentrations can be affected by soil nutrients such as N and P. However, its response to limestone has not been documented. This study evaluated the effect of limestone application on ergovaline concentration in established tall fescue. Limestone was surface‐applied in December 2011 on an existing ‘Kentucky 31’ tall fescue (95% infected with E. coenophiala) pasture near Alton, MO. Soils were sampled annually in October by collecting ten 6‐inch cores per plot; cores were divided into three increments: 0 to 1, 1 to 3, and 3 to 6 inches in depth. Whole tillers were harvested spring and autumn from 2012 to 2014 and analyzed for ergovaline concentration. Limestone increased (p < 0.01) soil salt pH [pH(s)] during the 3‐year period, and the greatest increase occurred at the soil surface. The soil pH(s) was 5.6 for the limestone‐treated plots and 5.0 for the non‐treated plots. Limestone application reduced (p < 0.10) ergovaline concentration by 20 ppb compared with non‐treated control plots. An important application of this study is that limestone did not increase ergovaline concentration as other soil nutrients have done, thereby making it possible to improve soil conditions for legume growth and pasture dilution without increasing the potential for fescue toxicosis. Future studies will explore the possibility of a greater reduction in ergovaline concentration with a larger increase in soil pH.