Temperature,Mg and Al Interaction Effects on Grass Tetany Potential of Ryegrass Forage1

Two annual ryegrass (Lolium multiflorum Lam.) cultivars differing in Al sensitivity were grown in nutrient solution at pH 4.2 to assess the effects of temperature (10/6 and 22/18 °C day/night), Mg (0.1 and 1 mM) and Al solution concentrations (0, 3.7 and 74 μ M) on several factors influencing grass tetany potential of forage. Added Al depressed Mg and Ca shoot concentrations and increased shoot K/(Ca + Mg) equivalent ratio especially after prolonged treatment at higher temperature and lower Mg solution concentrations. These effects were more pronounced in the relatively Al-sensitive cultivar Wilo which appeared to be less Mg-efficient as well. Grass tetany potential will therefore be higher following a temperature rise if Al-sensitive ryegrass is grown in a medium containing low Mg and high Al levels.