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Title: BIOMASS YIELD AND NUTRITIONAL QUALITY OF FORAGE SPECIES UNDER LONG-TERM IRRIGATION WITH SALINE-SODIC DRAINAGE WATER: FIELD EVALUATION

Author
item SUYAMA, H - DEP PLANT SCI,CSU,FRESNO
item BENES, SHARON - DEP PLANT SCI, CSU,FRESNO
item ROBINSON, P - D ANIMAL SCI, UC DAVIS,
item GETACHEW, G - D ANIMAL SCI, UC DAVIS,CA
item GRATTAN, S - D LAWR, UC DAVIS,CA
item Grieve, Catherine

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2006
Publication Date: 4/15/2007
Citation: Suyama, H., Benes, S.E., Robinson, P.H., Getachew, G., Grattan, S.R., Grieve, C.M. 2007. Biomass yield and nutritional quality of forage species under long-term irrigation with saline-sodic drainage water: field evaluation. Animal Feed Science And Technology. Vol. 135: 329-345

Interpretive Summary: In semiarid regions with irrigated agriculture, such as the San Joaquin Valley (SJV) of California, drainage of the farmland is necessary for sustaining long term productivity. Drainage effluents in the Valley contain dissolved salts and other constituents such the potentially toxic trace elements, selenium (Se), boron (B), and molybdenum (Mo). Unfortunately, the Valley has very few drainage outlets to manage the disposal of these waters. One of the few on-farm options available to growers in the Valley is the reuse of drainage waters for irrigation, a management practice which would reduce the volumes of drainage water requiring disposal and increase productivity of these lands. Another problem that exists in the SJV is the shortage of high quality forages for dairy and beef cattle. Salt-tolerant forage crops that could grow well under saline irrigation would not only increase forage supplies but could play a key role in drainage water management. Objectives of the study were to identify and characterize forages for long term sustainability using saline-sodic waters for irrigation and to assess their productivity, nutritional value and safety for animal consumption In this five-year study, six forages (tall wheatgrass, alfalfa, creeping wildrye, alkali sacaton, tall fescue, and puccinellia) grown under field conditions in Fresno County, CA. Based on biomass production, tall wheatgrass and creeping wildrye were the most successful candidates. Forage quality of tall wheatgrass, tall fescue and alfalfa were acceptable for animals requiring high energy diets, such as lactating cows. Selenium concentrations in a few harvests of tall fescue and creeping wildrye exceeded the maximum tolerable limit for livestock..Therefore, cattle grazing on these forages should be carefully monitored for Se toxicity disorders.

Technical Abstract: On the Westside of California’s San Joaquin Valley (SJV), the discharge of subsurface agricultural drainage water (DW) is subject to strict environmental regulations due to its high selenium (Se) content and potential risks to wildlife. Reuse of saline-sodic DW to irrigate salt-tolerant forage crops is attractive because it reduces the volume of DW requiring disposal, and the land area affected by salinity, while producing forages that satisfy the regional demand due to increased numbers of animal feeding operations in that area. Biomass production and nutritional quality of 6 forages (i.e., ‘Jose’ tall wheatgrass, creeping wildrye, alkali sacaton, ‘Alta’ tall fescue, puccinellia, and ‘Salado/801S’ alfalfa) were evaluated under DW irrigation on a commercial farm near Five Points in Fresno County, California. The DW irrigated fields were in their second to fifth year of DW application and most field had soil salinities higher than 12 dS/m Ece (electrical conductivity of the saturated soil paste). In addition, to bring very saline, the fields had high levels of B, Se and sodicity [i.e., high sodium (Na) relative to calcium (Ca) and magnesium (Mg)]. ‘Jose’ tall wheatgrass and creeping wildrye had acceptable dry matter (DW) production (~ 10 t/ha/yr) under highly saline conditions of 13 to 19 dS/m Ece. Alfalfa produced 16 to 20 t/ha/yr of DM under low salinity conditions of <7.0 dS/m Ece. The forages had estimated metabolizable energy (ME) contents of 7.9 to 9.9 MJ/kg DM - with the exception of alkali sacaton (6.7 MJ/Kg DM) - which would make them acceptable as feeds for beef cattle, sheep, and some classes of dairy cattle. Se levels varied from 4.4 to 10.7 mg/kg DM in forages that had received 5 years of DW application. Forages at the high end of this range could cause Se toxicity in ruminants when used as a sole source of forage; but they could also be used as a Se supplement fed at a rate of 20 to 40 g/kg in the Se-deficient areas found along the eastern SJV. Saline-sodic DW can be used as a water resources to produce forage suitable for many classes of ruminants, although drainage waters with high levels of Se may present both problems and opportunities.