Responses of forage grasses to aluminum in solution culture

Growth, nutrient uptake and nutrient uptake efficiency differences in orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb), and timothy (Phleum pratense L.) were evaluated at 0, 100, 200, and 300 .mu.M Al. In each of the species, cultivar differences were also compared. In the absence of Al stress, cultivars of orchardgrass outperformed other grasses. The presence of Al reduced shoot and root growth; however, the magnitude of the growth reduction depended upon the species and cultivars. The growth of shoots and roots showed a significant difference with respect to species, cultivars, treatment Ala and their interactions. Aluminum reduced the uptake of many essential nutrients. At 100 .mu.M Al Potomac orchardgrass had the highest and climax timothy had the lowest mineral content. The efficiency ratio (ER) assisted in classifying grass entries into efficient and inefficient utilizers of the absorbed nutrients. The ER is defined as milligrams of dry shoot weight produced per milligram of element in the shoot. The ER for P, K, Cu and Zn gave a positive correlation with shoot weight; however, in general, negative relationships were observed for shoot growth and ER for Mg, Fe, and Mn. In all the species increasing Al concentration from 0 to 100 .mu.M increased ER for Mg and decreased ER for K and Zn. With the exception of tall fescue cultivars, the ER for P was reduced by 100 .mu.M Al. The species and cultivars used in this study showed inter- and intraspecific differences in growth, uptake, and ER for nutrients in the presence or absence of Al stress. Significant reduction in growth, even at 100 .mu.M Al by all the three species of grass indicates that these grass species are far more sensitive to Al than the field crops. Therefore, experiments with levels of Al lesser than 100 .mu.M would have given a better outlook on the performances of these grass species.