||Eastern gamagrass, Tripsacum dactyloides (L.), requires two growing seasons to achieve good establishment and economic yield. This study investigates the effects of five levels of nitrogen (0 to 224 kg/ha) on forage yield and quality during the establishment period. The study
was conducted in Corning, New York, on a Unadilla silt loam soil. The “Pete” eastern gamagrass was planted on 5/21/91 after a two-month stratification period using a corn planter with a 76 cm row spacing at 3.8 kg/ha pure live seed. There were five nitrogen treatments: 0, 56, 112, 168, and 224 kg/ha nitrogen applied using ammonium nitrate. During the establishment year, the nitrogen was applied at a one-half rate on 8/1/91. The full rates were applied on 5/26/92, 5/24/93, and
5/19/94. The fertilizer treatments were applied to plots 3.0 meters (4 rows) by 3.0 meters with five replications. The dry matter yields were taken from a 1.5 meter section of a center row from each of the plots. In 1992, the average dry matter yields were relatively consistent above the 112 kg/ha nitrogen treatment. In 1992, the yields for the 0, 56, 112, 168, and 224 kg/ha nitrogen rates
were 6.0, 6.5, 9.2, 7.8, and 9.4 Mg/ha, respectively, from a single harvest on 9/18/92. In 1993, three harvests were conducted on 6/10/93, 7/27/93, and 10/1/93; there was a yield response for
the 224 kg/ha nitrogen rates. The average total yields for the 0, 56, 112, 168, and 224 kg/ha nitrogen rates were 5.5, 6.5, 6.5, 6.5, and 8.3 Mg/ha, respectively. In 1994, two harvests were conducted on 6/17/94 and 8/11/94. The average total yields for the 0, 56, 112, 168, and 224 kg/ha nitrogen rates were 5.1, 6.7, 7.4, 8.4, and 7.6 Mg/ha, respectively. The crude protein (CP), in vitro true digestibility, neutral detergent fiber (NDF), digestible NDF, acid detergent fiber (ADF), and lignin were measured for all three cuttings for all fertilizer treatments in 1993. In 1993, the 168 kg/ha nitrogen treatment had the following forage quality. First cutting values were 178, 815, 647, 714, 288, and 26 g/kg, respectively. For the second cut, they were 106, 687, 678, 537, 327, and 39 g/kg, respectively. For the third cut, they were 141, 752, 666, 628, 277, and 32 g/kg, respectively. The first cutting had the highest forage quality. There was a trend for higher digestibility and CP and lower NDF and ADF with increasing rates of nitrogen. For the first cutting, there were significantly higher CP levels at the 168 and 224 kg/ha rates than the 0 and 56 kg/ha nitrogen rate with CP means of 176 g/kg and 155 g/kg, respectively. The forage quality of the second cutting was reduced due to the later-than-optimum harvest interval. The third cutting, although harvested late, had an intermediate forage quality analysis.