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Submitted to: Grassland Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/13/2016 Publication Date: 7/19/2016 Citation: Robins, J.G. 2016. Evaluation of warm-season grass nutritive value as an alternative to cool-season grass under limited irrigation in the semi-arid western United States. Grassland Science. 62:144-150. Interpretive Summary: Evaluation of the summer nutritive value of 21 warm-season grass varieties under limited irrigation found potential of several warm-season grasses as alternative summer forage sources. While the cool-season grasses possessed the highest nutritive value several warm-season varieties, they possessed very low biomass potential during the hot summer months when the study was conducted. Several warm-season varieties, including Bison big bluestem and Trailblazer switchgrass, combined high summer biomass with higher nutritive value. Thus, these are potential summer forage alternatives. Technical Abstract: The production of cool-season grasses is limited by their photosynthetic inefficiency during the hot summer months. Therefore, a study was conducted during 2006 and 2007 at a Logan, UT, USA field site to determine the potential of various warm-season grasses as alternatives to cool-season grass during summer under limited irrigation. The study included 20 environments, which corresponded to combinations of the two years, two harvest dates (June and July), and five irrigation levels. There were differences among the 27 varieties (21 warm-season and 6 cool-season) for crude protein (CP), in vitro true digestibility (IVTD), neutral detergent fiber (NDF), neutral detergent fiber digestibility (NDFD), water soluble carbohydrates (WSC), and biomass (BM) across the 20 environments. However, the overall variety effects were ameliorated by the presence of genotype by environment interaction for crude protein, water soluble carbohydrates, biomass, and to a lesser extent IVTD. The cool-season grasses generally possessed higher trait values in each environment, yet there were several warm-season grasses, such as Bison big bluestem and Trailblazer switchgrass that possessed higher values for the nutritive value traits. Additionally, these warm-season grass varieties possessed substantially higher BM than any cool-season grass variety. Thus, there are warm-season grass varieties that combine high BM and higher nutritive value in the summer months under limited irrigation. These may prove to be viable forage alternatives to the cool-season grasses during the summer slump period. |
