Title: Purple threeawn in vitro fermentation and gas production response to nitrogen fertilization and fire Authors
Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 14, 2012
Publication Date: February 3, 2013
Citation: Dufek, N., Vermeire, L.T., Waterman, R.C., Ganguli, A. 2013. Purple threeawn in vitro fermentation and gas production response to nitrogen fertilization and fire. Society for Range Management Meeting Abstracts. Oklahoma City, OK. February 3-7, 2013. Abstract #0218. Technical Abstract: Purple threeawn (Aristida purpurea) is a native perennial bunchgrass with poor forage quality. It often dominates sites with disturbed soils and persists with continued severe grazing. Nitrogen fertilization and fire have each been used to reduce threeawn, however, greater utilization of threeawn by livestock is required to extend treatment longevity. We evaluated the effects of fire (summer, fall, no fire) and spring urea nitrogen fertilization (0 kg/ha, 40 kg/ha, 80 kg/ha) on threeawn forage quality in southeastern Montana during the 2011 and 2012 growing seasons with a completely randomized design in a 3X3 factorial arrangement. Forage quality was assessed using a 96-h in vitro gas production. First-year treatments were followed by the wettest spring in 76 years and second-year treatments were followed by the second driest. Fire effects varied by year. Following a wet spring, in vitro organic matter disappearance (IVOMD) was greater for burned (70%) than non-burned (62 ± 2.1%) threeawn. Similarly, average fermentation rates of threeawn were greater for burned (2.3 mL/h) than non-burned sites (1.3 ± 0.06 mL/h). During drought, fire had no effect on IVOMD (61%) or average fermentation rate (1.6 mL/h). Fertilization did not affect IVOMD either year (64 ± 1.5%). Average fermentation rate was not affected by fertilization under wet conditions (2.0 mL/h), but was reduced by urea addition during drought (1.5 versus 1.8 ± 0.06 mL/h). Results indicate that fire may enhance the rumen digestibility of purple threeawn during wet conditions. However, drought overshadowed fire effects and led to reduced fermentation on fertilized plots.