Wednesday, November 15, 2006 - 9:00 AM

Nitrogen Rate and Source Effects on the Yield and Nutritive Value of Tall Fescue Stockpiled for Winter Grazing.

Christopher Teutsch1, John Fike2, G.E. Groover2, S. Aref2, and Mac Tilson1. (1) Southern Piedmont AREC, 2375 Darvills Rd., Blackstone, VA 23824, (2) Dept of CSES, Virginia Tech, Virginia Tech, 365 Smyth Hall, Blacksburg, VA 24061-0404

Late summer nitrogen (N) fertilization is a primary factor affecting yield of cool-season pastures allowed to accumulate herbage for deferred grazing.  Attention has been given to the quantity of N applied, but the source of N has not been investigated.  This study evaluated the effects of N rate and source on yield and nutritive value of stockpiled tall fescue.  Trials were conducted on two farms located near Amelia, VA in 2002 and 2003 and Blackstone, VA in 2004.  Six N sources (ammonium nitrate, ammonium sulfate, broiler litter, complete fertilizer, urea, and urea-ammonium nitrate) were applied at 0, 45, 90, and 135 kg plant available N ha-1 in mid-August.  Forage was allowed to accumulate until mid-December.  Yield increased linearly with N rate for each N source, but the rate of increase varied from 5 to 13 kg DM kg-1 N.  Compared to the unfertilized control, yield at the highest N rate was increased 25 to 61% depending on nitrogen source.  Ammonium nitrate and ammonium sulfate were the most effective N sources for stockpiling tall fescue.  Urea-ammonium nitrate produced the lowest yield and would not be a suitable replacement for ammonium nitrate, even when applied at higher rates.