Enhanced efficiency nitrogen formulations on stockpiled tall fescue production

Late summer application of nitrogen (N) fertilizer on stockpiled tall fescue [Schedonorus arundinaceus (Schreb.)] can improve forage yields. Using enhanced efficiency N fertilizers may be of benefit by reducing ammonia volatilization losses and promoting forage growth later in the growing season. This study evaluated the effect of different enhanced efficiency N formulations (Agrotain-treated urea, SuperU, and Environmentally Smart Nitrogen) and untreated urea on the yield and nutritive value of stockpiled ‘KY-31’ tall fescue over two stockpiling periods (2015–2016 and 2016–2017). Nitrogen was applied at four rates (0, 45, 90, and 134 kg N ha⁻¹) in one application in late August prior to the beginning of the stockpiling period in Lexington, KY. During the 2015–2016 stockpiling period, forage yields increased with increasing N rates; forage yields ranged from 2,913 kg dry matter (DM) ha⁻¹ when no N was applied up to 4,132 kg DM ha⁻¹ when 134 kg N ha⁻¹ was applied. Although forage yield was lower during the 2016–2017 stockpiling period, yield increased 75% even with the lowest N rate. Forage nutritive value was improved with increasing N rate. There were no differences in forage yield or nutritive value among enhanced efficiency N sources and standard urea. In summary, N applied in August improved stockpiled forage yield and nutritive value, regardless of N source.