Mineral composition of lucerne (Medicago sativa) and white melilot (Melilotus albus) is affected by NaCl salinity of the irrigation water

Most glycophytic forage legumes exhibit large reductions in biomass in response to saline growing conditions, although differences among species in salt tolerance exist. As several plant metabolic processes are affected by salinity, the nutritive value of these species to animals may be altered. Mineral concentration is an important component of plant nutritive value, and was evaluated in lucerne and white melilot under salt concentrations of 0, 55 and 110 mM NaCl in a glasshouse. Lucerne consistently accumulated higher concentrations of Na and Cl than white melilot. Calculated NaCl concentrations per unit DM reached 125 g/kg in lucerne and 39 g/kg in white melilot when irrigated with water containing 110 mM NaCl. In leaves of both species the Ca and Mg concentration decreased (P < 0.0001) with increasing salinity level, and there was an interaction (P < 0.0001) for these elements in which lucerne stems had decreases. The P concentration increased (P < 0.0001) in both species and the K concentration was affected only in lucerne stems. Among trace elements, Zn and Fe had marked decreases. Leaf and stem Zn concentration decreased in both species and Fe decreased more in leaves than in stems, but most analyzed microelements remained at acceptable levels for animal production. Detrimental changes in the mineral composition of forage species in response to salinity can be minimized by selecting appropriate species, such as white melilot. This may lead to improved animal production if biomass production, voluntary animal intake and digestibility can be maintained.