Economic aspects of broadcast fertilizer use for tree seedling establishment on surface mines

While the biological effects of fertilizer on tree seelings grown on surface mines have been examined to some extent, the economic performance of this soil amendment is less well established. A study was undertaken to analyze, over four growing seasons, the economic factors involved in using diammonium phosphate (18-46-0) to enhance tree seedling survival and height growth. Virginia pine and European alder seedlings were grown under 2.5 cm of hardwood bark mulch and three fertilization rates. For both species, there is no incentive to apply fertilizer to improve survival. Applications of fertilizer either decreased survival or improved it slightly at a disproportionately higher cost. If height growth is the parameter of primary interest, however, fertilization can provide economically efficient benefits. Significant improvements in Virginia pine height growth were observed for the 560 kg/ha treatment which, by the fourth growing season, was the most economically attractive alternative. Although non-significant, increased alder height growth was also observed for this treatment. Economic trends indicate, however, that the benefits of the fertilizer on this species may soon be outweighed by the costs.