Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 21, 2009
Publication Date: February 10, 2010
Citation: Jensen, K.B., Waldron, B.L., Peel, M., Robins, J.G. 2010. Nutritive Valve of Herbage of Five Semi-Irrigated Pasture Species Across an Irrigation Gradient. Grass and Forage Science. 65:92-101. Interpretive Summary: For most forage-producing areas, reduction in available irrigation water is a critical concern as the potential for even greater drought events occur in the future. Limited information is available concerning how different amounts of irrigation affect the forage nutritional characteristics, crude protein (CP), in-vitro true digestibility (IVTD), and neutral detergent fiber (NDF) in forage grasses smooth bromegrass, Matua bromegrass, hybrid-brome, creeping foxtail, and RS-hybrid wheatgrass during the growing season. This study used a line-source sprinkler plot irrigation system that produces a nearly linear water application pattern the further the distance from the sprinkler line. Smooth brome forage had higher CP, IVTD, and lower NDF concentrations than hybrid-brome, Matua brome, creeping foxtail, and RS-hybrid at all levels of irrigation. There was a general increase in CP concentration of the forage as irrigation amounts decreased. The amount of irrigation did not affect IVTD and NDF concentrations. Our results indicate that CP values of smooth brome, hybrid-brome, Matua brome, creeping foxtail, and RS-hybrid can be increased if grown under limited irrigation. However, the increase in nutritional value associated with water stress is in most cases negated by the associated negative trend in dry matter yield with increased water stress.
Technical Abstract: As water resources become limiting, the need to produce stable amounts of highly nutritional forage increases. An understanding of how levels of irrigation affect crude protein (CP), in vitro true digestibility (IVTD), and neutral detergent fiber (NDF) is critical in pasture forage management. Smooth brome (Bromus inermis Leyss.), Matua brome (Bromus willdenowii Kunth), hybrid-brome [meadow (Bromus riparius Rehm.) x smooth bromegrass cross], creeping foxtail (Alopecurus arundinaceus Poir.), and RS-hybrid wheatgrass (Elymus hoffmannii Jensen & Asay) were established under a line-source irrigation system to evaluate the effect of five water levels (WLs) and three harvest dates on concentrations of CP, IVTD, and NDF. Mean CP rankings across WLs and harvest dates were smooth brome > RS-hybrid > hybrid-brome > creeping foxtail > Matua brome. Positive linear trends in CP concentration across WLs were significant for all species with decreasing water applied. No consistent trends in IVTD across WLs were detected among the species. Averaged across WLs, harvests, and years smooth brome, hybrid-brome, and creeping foxtail had significantly higher IVTD levels than RS-hybrid and Matua brome. Mean NDF concentration rankings across WLs and harvests combined over years were Matua brome > RS-hybrid > hybrid-brome > creeping foxtail > smooth brome. Smooth brome forage had higher CP, IVTD, and lower NDF concentrations than hybrid-brome, Matua brome, creeping foxtail, and RS-hybrid at all WLs. The increase in nutritional value associated with water stress is in most cases negated by the associated reduction in dry matter yield with increased water stress.