Nitrogen Management for Seed and Residual Forage from Low- and High-endophyte Tall Fescue.

Tall fescue (Festuca arundinacea Schreb.), a major cool-season grass in the US, is attributed with good stress tolerance in part because of its association with a fungal endophyte, Neotyphodium cenophialum.  However, the endophyte produces alkaloids that impair animal performance and, thus, many pastures have been planted with low-endophyte seed.  Nitrogen management is important for seed production and utilization of hay left after seed harvest, but data are limited regarding differences in N management, if any, for low- compared with high-endophyte tall fescue.  The objective of this study was to determine the effect of fertilizer N rate and timing on seed and residual forage production from low- and high-endophyte fescue during 2004 to 2006.  Endophyte infection level did not affect clean seed yield or residual forage production.  Nitrogen applied in late fall resulted in 17% greater clean seed yield than when applied in late winter.  Clean seed yield was maximized with 112 kg N/ha in 2004 at around 280 kg/ha.  In 2005, seed yields were lower, especially at N rates from 56 to 168 kg/ha, but linearly increased to 260 kg/ha with 224 kg N/ha.  Seed yields in 2006 were greatly reduced by dry conditions and were less than 50 kg/ha with any N rate.  Residual forage cut after seed harvest was increased by late winter compared with late fall fertilizer N applications in 2004 and 2005, with no effect due to timing in 2006.  In all three years, forage increased with increasing N rate, but in 2004 the overall production level was greater than in 2005 or 2006.