Evaluation of salt-tolerant forages for sequential water reuse systems III. Potential implications for ruminant mineral nutrition

Reuse of drainage waters is an attractive management option that has been proposed for many irrigated agricultural areas. In California’s San Joaquin Valley (SJV), however, drainage effluents are not only saline, but may also contain potentially toxic trace elements such as selenium and molybdenum. Crop suitability for reuse systems depends on the influence the sodium sulfatedominated waters have on biomass production, plant sustainability, and mineral elements that are critically important for forage quality. Ten promising forage crops were grown in greenhouse sand cultures irrigated with synthetic drainage waters dominated by Na2SO4 with an EC of either 15 or 25 dS/m each containing 500 mg/L Se and Mo as SeO4 2 and MoO4 2 . Plant material was analyzed three times for mineral content and selected trace elements that may have a profound influence on ruminant health. Trace element concentrations indicate Se toxicity is of little concern, but that high concentrations of both Mo and S in the herbage may lead to Cu deficiency in ruminants. Similarly, high K/Mg and K/ (Ca + Mg) ratios in many of the legume and grass forages, respectively, indicate that there may be potential for development of sub-normal Mg levels (hypomagnesaemia) in ruminants. However, each of these disorders can be avoided or corrected with dietary supplements. The most concern regarding www.elsevier.com/locate/agwat Agricultural Water Management 70 (2004) 137–150 * Corresponding author. Tel.: +1 909 369 4836; fax: +1 909 342 4963. E-mail address: [email protected] (C.M. Grieve). 0378-3774/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2004.04.011 ruminant nutrition based on these data is sulfur toxicity. Sodium-sulfate dominated drainage waters will likely elevate forage S concentrations to levels that might cause excessive sulfide concentrations in the rumen and potentially lead to serious neurological disorders affecting animal health. # 2004 Elsevier B.V. All rights reserved.