Nitrogen's influence on stockpiling of ‘Jesup’ tall fescue cultivars with diverse fungal endophyte presence

摘要

Abstract Tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] is used in the southern United States to extend the cow–calf grazing season during autumn and winter by stockpiling. However, livestock producers are reluctant to graze tall fescue because of the toxicity associated with the presence of an endophyte within the grass plant. In this study, the effects of the amount of N fertilizer rate (0, 50, and 100 acre–1), the N source (ammonium nitrate and urea), and the date of N application (September and October) were evaluated for the herbage accumulation (HA) and nutritive value on stockpiled tall fescue. The study was conducted in the autumn of 2007–2009 with six experimental ‘Jesup’ tall fescue cultivars with different endophytic fungal strains: endophyte‐infected wild‐type, endophyte‐free, and infected with the novel endophytes (NE) AR502, AR514, AR542, and AR584. Greater HA was observed with the September N application. Ammonium nitrate was more efficient at increasing HA than urea at both N application rates. Herbage accumulation increased by 56 and 98% at 50 and 100 lb N acre–1 compared with the control. The nutritive value of the stockpiled tall fescue declined as the winter season advanced, despite the source, rate, and timing of fertilizer application. Although the study reported a reduction in nutritive value from November to January, the nutritive value concentrations and estimations are considered optimum for livestock production.