A winter hardy, aluminum tolerant, perennial pasture grass for reclamation of acid mine spoils

Abstract

Limpograss, Hermarthria altissima, (Poir) Stapf & C. E. Hubb (PI 364344) was tested for Al tolerance in acid, Al‐toxic Tatum subsoil (pH 4.1), in an acid mine spoil (pH 4.0) and in nutrient solutions containing 0 to 24 ppm Al added at initial pH 4.5 or 4.0. The grass was exceptionally tolerant to Al in all three media and can therefore be considered a “calcifuge”;, or perhaps more accurately, an “alumicole”;. In both Tatum soil and mine spoil, liming to pH values above 4.5 decreased growth, but the reasons for this were not determined. In our nutrient culture experiment (initial pH 4.0), the yields of plant tops were not significantly reduced by added Al concentrations up to 6 ppm but roots were injured by 4 ppm Al added. At initial pH 4.5 Al concentrations up to 4 ppm added appeared beneficial to root growth. Both tops and roots produced 50% of maximal yield with a final solution pH of 4.1 and with 17 ppm Al in the solution filtrate. Maximal growth was associated with plant‐induced pH increases to 7.0 or above, and with final Al concentrations below about 0.61 ppm in the solution filtrate.

Tops of plants injured at pH 3.‐3 on acid mine spoil had higher concentrations of Al, Zn, Fe, Mn, Na, Ca and Mg than did those of uninjured plants grown at pH 4.5. Plant tops showing reduced yields at pH 7.0 on mine spoil had lower concentrations of Zn, Mn and B than those making maximal growth at pH 4.5. The tops of plants injured by 24 ppm Al in nutrient solution had higher concentrations of Al and K and sometimes Fe, Na and Cu than those grown with no Al. Growth reductions by Al were consistently associated with higher concentrations of Al and K and lower concentrations of Ca, Mg, Mn and Zn in both tops and roots. Roots of Al‐injured plants also tended to accumulate higher concentrations of P and Fe than those of non‐injured plants. Limpograss (PI 364344) did not accumulate Al in its tops, even when yields were reduced by 50% with Al stress, but trapping of Al in roots may partially account for its Al tolerance.

Limpograss (PI 364344) has demonstrated outstanding winter hardiness, insect resistance, ability to compete with other species and tolerance to excess Al. Hence, the evidence suggests that it has a potential for use in revegetating strongly acid mine spoils at medium to high elevations in temperate climates.

Key words:

• Hemarthria altissima (Poir) Stapf and C. E. Hubb
• Al toxicity
• plant‐induced pH changes
• lime response over liming injury