Nitrogen fertilization for hay and seed from endophyte‐free and endophyte‐infected tall fescue

Abstract

AbstractTall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] is an important forage, but a fungal endophyte often found in the aboveground biomass can negatively affect animal production. Nitrogen also affects production, but data are limited regarding N fertilization effects on hay and seed yields from endophyte‐free (EF) compared with endophyte‐infected (EI) tall fescue grown on claypan soil in the eastern Great Plains. This study's objective was to determine the effects of N fertilizer timing and rate on EF and EI tall fescue yield of R4 (anthesis) hay, seed, and hay residual after seed harvest (stubble hay, SH). Endophyte infection did not affect R4 hay, seed, or SH yields and did not interact with N timing, N rate, or year for any measured parameters. Across the 3‐yr study, N fertilizer applied in late fall resulted in 18% greater seed production than late winter, with split late fall/late winter applications being intermediate. The effect of N timing on R4 and SH varied by year. Annual fescue seed yield response to N rate varied, but required 112 kg N ha−1 or more to achieve near 300 kg ha−1 in better‐yielding years. Hay measured at R4 or SH responded to N up to at least 168 kg ha−1. Hay N concentration was diluted with initial increments of N fertilizer but increased as yield response diminished with greater N rates. Simple return functions suggest that the N rate to achieve maximum economic return is reduced when N fertilizer costs are high and when seed/hay selling prices are low.