Micronutrient Fertilization of Woody Seedlings Essential Regardless of Pine Bark pH

The objective of this study was to determine the effect of micronutrient amendments to pine bark on seedling growth over a wide pine bark pH range. Koelreuteria paniculata (Laxm.) was container-grown from seed in pine bark amended (preplant) with 0, 1.2, 2.4 or 3.6 kg/m³ (0, 2, 4, 6 lb/yd³) dolomitic limestone and 0 or 0.9 kg/m³ (1.5 lb/yd³) Micromax^™ (micronutrient fertilizer). Initial pine bark pH for each lime rate was 4.0, 4.5, 5.0, and 5.5, respectively. Final pH (week 10) ranged from 4.7 to 6.4. Seedlings were harvested 10 weeks after planting and shoot dry mass and height determined. Pine bark solution was extracted using the pour-through method at 3, 7, and 10 weeks after planting. Solution pH was measured, and solutions were analyzed for Ca, Mg, Fe, Mn, Cu, and Zn. Shoot dry mass and height were greater in Micromax^™ amended bark than in bark without Micromax^™. Lime had no effect on shoot dry mass or height. In general, adding Micromax^™ increased pine bark solution Ca, Mg, and micronutrient concentrations. Adding lime increased pine bark solution pH and Mg concentration and either had no effect on or decreased solution Ca and micronutrient concentrations. Regardless of pine bark pH, Micromax^™ additions resulted in better growth, and adding lime was not necessary.