ARS | Publication request: Forage Quality of Irrigated Pasture Species as Affected by Irrigation Rate

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 14, 2007
Publication Date: August 19, 2007
Citation: Jensen, K.B., Waldron, B.L., Peel, M., Robins, J.G., Monaco, T.A. 2007. Forage Quality of Irrigated Pasture Species as Affected by Irrigation Rate. Symposium Proceedings.

Interpretive Summary: The USDA-ARS Forage and Range Research Lab has initiated a breeding program to improve tall fescue, orchardgrass, and meadow bromegrass in semiarid pasturelands, which are characterized by extreme temperature fluctuations and limited water resources. This proceeding summarizes a series of line-source sprinkler design studies to look at the effects of different irrigation levels and forage quality. Quality traits of interest included crude protein (CP), fiber (NDF), and digestibility (IVTD). As irrigation levels decreased, CP concentration values increased in all three species. Different irrigation rates did not significantly affect fiber and digestibility values in tall fescue and perennial ryegrass. Perennial ryegrass forage had higher CP and digestibility values than tall fescue and orchardgrass. However, it yielded 61% less than tall fescue at the lowest irrigation level.

Technical Abstract: The USDA-ARS Forage and Range Research Lab has initiated a breeding program to improve tall fescue (Festuca arundinaceae Screb.), orchardgrass (Dactylis glomerata L.) and meadow bromegrass (Bromus riparius Rehm.) in semiarid pasturelands, which are characterized by extreme temperature fluctuations and limited water resources. An understanding of how irrigation level affects concentrations of crude protein (CP), neutral detergent fiber (NDF), digestible NDF (dNDF), and in vitro true digestibility (IVTD) is critical in pasture forage management. Cultivars of tall fescue, orchardgrass, and perennial ryegrass (Lolium perenne L.) were established under a line-source irrigation system to evaluate the effect of five water levels (WLs) and multiple harvest dates on CP, NDF, dNDF, and IVTD. Within all species, the most notable trend across WLs was a near linear increase in CP going from the wettest to the driest WL. Orchardgrass maturity (early vs. late) had little effect on forage quality across WLs. Tetraploid perennial ryegrass cultivars averaged higher concentrations of CP,IVTD, and dNDF and lower NDF values compared with diploid cultivars. Endophtye-free cultivars of tall fescue had lower NDF and higher IVTD concentrations than their endophyte-infected counterparts at the higher WLs.