Responses of tail fescue cultivars to an irrigation gradient

Seasonal availability of water is a major consideration in the management a nd selection of plant materials for irrigated pastures in the Intermountain West, USA. Objectives were to evaluate the forage field of 10 tall fescue (Festuca arundinacea Schreb.) strains and cultivars across five irrigation levels and fo elucidate the effects of the endophytic fungus Neotyphodium c oenophialum (Morgan-Jones & Gems) Glenn, Bacon & Hanlin an productivity and trends. a differ-source irrigation system was used in a 2-yr study, Signif icant differences were detected among the fan fescue entries for dry matter yield (DMY), and differences were relatively consistent across wafer level s (WL) as indicated by the nonsignificant cultivar x WL interaction and sig nificant correlations among WL. Trends in DMY across WL were largely curvil inear; however, linear bends were much more predominant during the late sum mer and fall. Stability parameters, based on regression of cultivar x WL X year means on their respective WL x gear means, differed among cultivars in analyses including all harvests but were relatively uniform (b approximate to 1.0) for most cultivars later in the season. Differentes in DMY between 'Ky 31' tall fescue infected with the Neotyphodium endophyte and its endop hyte-free counterpart confirms earlier reports of the positive effect of th is fungal organism on forage yield in fall fescue, particularly in water-li mited environments. Seasonal distribution of yield was primarily determined by water availability during the late summer and fall. The relative consis tency in DMY of the cultivars across WL indicates that annual yield average d across levels of wafer stress mould be a logical criterion for selection of germplasm for irrigated pastures in the Intermountain Region.