Submitted to: Animal Feed Science And Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/11/2003
Publication Date: 2/20/2004
Citation: Robinson, P.H., Grattan, S.R., Getachew, G., Grieve, C.M., Poss, J.A., Suarez, D.L., Benes, S.E. 2004. Biomass accumulation and potential nutritive value of some forages irrigated with saline-sodic drainage water. Animal Feed Science And Technology. 111:175-189. Interpretive Summary: Reuse of saline drainage water for irrigation is a necessary management option on the west side of the San Joaquin Valley in California to reduce the volume of drainage water requiring disposal, without sacrificing the potential productivity of the land. Several methods of utilizing saline water have been tested experimentally or are being demonstrated under field conditions. High quality forages for dairy cattle, beef cattle, and sheep are in short supply in the Central Valley of California. Identifying salt-tolerant forage crops that grow well under irrigation with saline drainage water would not only increase forage supplies, but would play a key role in drainage water management. The overall objective of this study is to evaluate a number of promising forage crops in terms of their biomass and nutritional quality when irrigated with saline-sodic drainage water dominated by sodium sulfate. The forage species performed differently in terms of biomass accumulation and forage quality. Bermudagrass, `Jose' tall wheatgrass and `Duncan' paspalum emerged as favorites based on combined attributes related to salt tolerance, biomass accumulation at high salinity and overall forage quality. Alfalfa cultivars were found to be the most sensitive to the higher level of salinity of irrigation water relative to biomass accumulation.
Technical Abstract: A controlled study using a sand-tank system was conducted to evaluate ten forage species (bermudagrass, `Salado' and `SW9720' alfalfa, `Duncan' and `Polo' paspalum, `Big' and `Narrow leaf' trefoil, Kikuyugrass, Jose Tall wheatgrass, and Alkali sacaton). Forages were irrigated with sodium-sulfate dominated synthetic drainage waters with an electrical conductivity of either 15 or 25 dS/m. Forage yield was significantly reduced by the higher (25 dS/m) salinity level of irrigation water compared to the lower (15 dS/m) level. There was wide variation in the sensitivity of forage species to levels of salinity in irrigation water as reflected by biomass accumulation. With the exception of bermudagrass, with increased accumulation at the higher level of salinity, and Big trefoil, which failed to establish at the higher level of salinity, ranking of forages according to the percent reduction in biomass accumulation due to the higher level of salinity of irrigation water was: salado alfalfa (54%) = `SW9720' alfalfa (52%) > Duncan paspalum (41%) > Narrow leaf trefoil (30%) > alkali sacaton (24%) > polo paspalum (16%) > Jose tall wheat (11%) = Kikuyugrass (11%). Bermudagrass and Duncan paspalum were judged to be the best species in terms of forage yield and nutritive quality. Kikuyugrass, which had the third highest biomass accumulation, was judged to be unacceptable due to its poor nutritional quality. Although narrow leaf trefoil had a relatively high nutritional quality, its biomass accumulation potential was judged to be unacceptably low. Alfalfa cultivar biomass accumulations were the most sensitive to the higher level of salinity, among forages that survived at the higher salinity level, although actual accumulations at the higher salinity were high relative to other forages. Increased salinity influenced several forage quality parameters, including organic matter, crude protein, neutral detergent fibre, and in vitro gas production, generally leading to higher nutritional quality at the higher salinity level, although their significance varied amongst species and cuttings.