Conifer growth on residual organic soils: A greenhouse study

Abstract

Legislation is being considered in Minnesota to broaden existing strip-mine reclamation laws to include the expanding peat harvesting industry, but the lack of information on plant-residual organic soil relationships will make compliance with such guidelines difficult. A greenhouse study was established to provide basic information on three representative residual organic soils and their capacity to support Scotch pine, black spruce, Norway spruce, and white spruce seedlings under different fertilizer regimes. The nature of the residual soil, the species grown upon it, the amount and type of fertilizer added, and the interactions between these factors significantly affected seedling growth, emphasizing the importance of treating each mined site as an individual case. Poor growth on a Fibrist was attributed to soil acidity, with added fertilizer further reducing growth. Seedling performance was excellent on a Hemist, particularly when fertilized with micronutrients and a high rate of NPK. A strong relationship was identified between spruce growth and foliar Cu levels, and a critical value of 3.7 μg g−1 was estimated for spruce on this Cu-deficient soil. Seedling performance was satisfactory on a Saprist, with all species responding to low rates of NPK and some to high rates of NPK plus micronutrients. The non-factorial arrangement of the fertilizer treatments made it difficult to determine which element or elements were limiting on this soil. The results of soil chemical analyses could be used to make general statements on the relative fertility of the residual soils. However, they could not be used to make statements on the availability of specific nutrients.