MINERAL COMPOSITION OF FORAGE LEGUMES AS INFLUENCED BY ALUMINUM

Abstract

The nutritional quality of plants is primarily controlled by concentrations of essential nutrients and potentially detrimental substances, and these are influenced to a great extent by phytotoxic aluminum (Al). Alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.), cultivars were grown in nutrient solution culture under controlled conditions and the effects of Al on growth and mineral composition of plants were evaluated. With a few exceptions, Al significantly reduced shoot and root dry weights, and generally increased the concentrations of elements in shoots. Further increases in Al tended to reduce mineral concentrations in each species and cultivar. This was probably related to root injury, reduced dry matter accumulation at higher Al, and reduced nutrient demand at higher Al levels. In alfalfa and red clover cultivars, elemental equivalency ratios for K/Mg and K/(Ca + Mg) increased, and ratios for Ca/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 ratios were similar for Al-sensitive and Al-tolerant cultivars of alfalfa and red clover. The species and cultivars used in this study had inter- and intraspecific differences in growth and nutrient concentrations, both in the presence and absence of phytotoxic levels of Al.

ACKNOWLEDGMENTS

The excellent technical assistance of Mr. M. D. Smedley and Ms. B. K. Sweeney is appreciated. We thank Drs. Susan E. Miyasaka and Zhenli He for reviewing this manuscript.