Mineral composition of forage legumes as influenced by aluminum

The nutritional quality of plants is primarily controlled by concentrations of essential nutrients and potentially detrimental substances, and these a re influenced to a great extent by phytotoxic aluminum (Al). Alfalfa (Medic ago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil ( Lotus corniculatus L.), cultivars were grown in nutrient solution culture u nder controlled conditions and the effects of Al on growth and mineral comp osition of plants were evaluated. With a few exceptions, Al significantly r educed shoot and root dry weights, and generally increased the concentratio ns of elements in shoots. Further increases in Al tended to reduce mineral concentrations in each species and cultivar. This was probably related to r oot injury, reduced dry matter accumulation at higher Al, and reduced nutri ent demand at higher Al levels. In alfalfa and red clover cultivars, elemen tal equivalency ratios for K/Mg and K/(Ca + Mg) increased, and ratios for C a/P decreased in plants grown with Al. Forage with low Ca/P indicates poor quality, and high K/Mg and K/(Ca + Mg) ratios indicates higher grass tetany hazard to animals. Most of the elemental concentrations and nutrient ratio s were similar for Al-sensitive and At-tolerant cultivars of alfalfa and re d clover. The species and cultivars used in this study had inter- and intra specific differences in growth and nutrient concentrations, both in the pre sence and absence of phytotoxic levels of Al.