Seed production, herbage yield, and quality of Carex filifolia. Fassett, Jeff^*,1, Stubbendieck, Dr. James², ¹ Bureau of Land Management, Socorro, NM² University of Nebraska-Lincoln, Lincoln, NE

ABSTRACT- Species diversity and ecosystem function is limited by self-reestablishment of threadleaf sedge (Carex filifolia Nutt.) in highly disturbed areas of the northern Great Plains. Livestock and wildlife are widely dependent on it as a native forage and little herbage quality has been documented. The objectives were to evaluate the influence of increased soil fertility on the seed (achene) production of threadleaf sedge and to document the herbage yield and quality as influenced by added soil fertility in grazed and exclosed areas. In the fall of 2002 and 2003, N and P were applied at 0, 34, and 67 kg ha^-1, and 0 and 45 kg ha^-1, respectively. A randomized complete block, split plot design was used to test six different fertilizer combinations on native rangeland in western Nebraska. Achene and inflorescence production was significantly improved with 45 kg ha^-1 P fertilization in exclosures during a year of average precipitation (2003), but they were not influenced during a year of below-average precipitation (2002). Herbage yield was not improved with small fertilizer additions during either year, but herbage quality was improved during the year with average precipitation. Crude protein ranged from 18 to 10% and neutral detergent fiber ranged from 62 to 70% from April to June. Herbage production may be more easily improved from a rest-rotation grazing strategy than fertilization. Improved herbage quality is not a large advantage on a native species of good quality herbage. There is potential for improved achene production of threadleaf sedge with elevated soil fertility.

KEY WORDS: threadleaf sedge, Carex filifolia, achene production, herbage quality