Yield and Crude Protein Responses of Eastern Gamagrass to Nitrogen Under Two Harvest Systems.

Eastern gamagrass [Tripsacum dactyloides (L.) L.] is a native, warm-season perennial grass with potentially high forage quality and productivity.  More intensive management of nitrogen (N) application and harvest frequency may help realize its potential.  This study was to determine the responses of eastern gamagrass forage yield and crude protein concentration (CP) to three annual rates (0, 50, or 100 kg ha^-1) of N fertilizer solution applied by broadcast or subsurface band (knife) placement for five of 10 years, and harvested using 1-cut or 2-cut systems.  Nitrogen increased average total forage yield in years of N treatment by 44% with the first 50 kg ha^-1 increment, and an additional 15% with the next 50-kg increment.  CP was increased by an average 15% with 100 kg N ha^-1 compared with no N fertilizer.  Residual from the previous year’s N application increased forage yield, but did not affect CP.  The 1-cut system yielded more than the 2-cut system only when no N was applied.  However, CP was reduced in the 1-cut system compared with either cut of the 2-cut system at all N rates.  Knife placement of N increased total seasonal yield only at the 100 kg ha^-1 rate, and CP response was inconsistent.  The application of N improved forage production, even in post-treatment years.