Cutting frequency and nitrogen fertilization effects on yield and nitrogenconcentration of switchgrass in a short season area

Adapted warm season grasses have potential for both summer forage and bioma ss production in eastern Canada, A field study was conducted in 1995 and 19 96 to determine the response of switchgrass (Panicum virgatum L.) cv, Cave- in-Rock, Pathfinder, and Sunburst to nitrogen (N) fertilization at 0, 75, o r 150 kg ha(-1) and three harvest schedules in a short season area. The gra ss was harvested at 4- or 6-wk intervals or left uncut until the end of the season, These treatments were combined in a split-plot design in each of t hree blocks on a St. Bernard sandy clay loam (Typic Hapludalf). Herbage yie ld and herbage N concentration were determined at each harvest for the cutt ing schedules. Herbage yields revealed a cultivar x N x harvest schedule in teraction in 1996, while in 1995 only the two-way interactions beta een cul tivar x harvest schedule and N x harvest schedule were evident (P < 0.05), Total yield ranking for the harvest regimes was uncut > 6-wk > 4-wk with th eir respective mean yields being 11, 10, and 8 Mg ha(-1) for Cave-in-Rock; 10, 8, and 6 Mg ha(-1) fur Pathfinder and 11, 8, and 7 Mg ha(-1) for Sunbur st. Nitrogen concentrations increased with fertilization and varied with ha rvest and year but not with cultivar, Mean N concentrations were 12.41 13.9 , and 15.4 g kg(-1) dry matter (DM) for the 0, 75, and 150 kg ha(-1) N leve ls, respectively, under the 4-wk system. Corresponding values were 10.1, 11 .6, and 12.9 g kg(-1) for the 6-wk system, End of season N concentrations f or the uncut regime averaged 5.4, 6.0, and 7.6 g kg(-1) DM In increasing or der of N fertilization, The results indicate that switchgrass has potential in both grazed or hay Forage systems in eastern Canada.