The potential of some soil amendments to improve tree growth on metalliferous mine wastes

Abstract

Trees are commonly planted on metalliferous mine wastes as a means of reclaiming these contaminated substrates. Other land-uses are often limited. However tree establishment is often poor owing to hostile substrate properties such as acidity, low macronutrient concentrations, high trace element concentrations, poor substrate structure and poor water retention. Soil amendments are a potentially cheap amelioration option. A factorial experiment was set-up to investigate the effects of seven amendments on the substrate chemistry and the growth and leaf chemistries of alder and sycamore. The amendments included ammonium nitrate, mineral phosphate and sulphate of potash fertilizers, calcareous sand, a superexpanding polyacrylamide gel polymer, cake sewage sludge and diatomite. The last two amendments are used here in a novel capacity. The most successful amendments with regard to their growth and leaf chemistry effects were found to be cake sludge and diatomite for alder and mineral phosphate, calcareous sand and cake sludge for sycamore. The least successful amendments were ammonium nitrate, sulphate of potash and calcareous sand for alder and ammonium nitrate for sycamore. The results differed according to the autoecological properties of the two species, with alder being easily the most productive. The implications of these results for tree-planting schemes are discussed.