Preplant lime and micronutrient amendments to pine bark affect growth of seedlings of nine container-grown tree species

The objective of this study was to determine the effects of lime and micron utrient amendments on growth of seedlings of nine container-grown landscape tree species in two pine bark substrates with different pHs. Acer palmatum Thunb, (Japanese maple), Acer saccharum Marsh, (sugar maple), Cel-cis cana densis L, (redbud), Comas florida L, (flowering dogwood), Cornus kousa Hanc e. (kousa dogwood), Koelreuteria paniculata Laxm. (golden-rain tree), Magno lia xsoulangiana Soul.-Bod. 'Lennei' (magnolia), Nyssa sylvatica Marsh. (bl ackgum), and Quercus palustris Muenchh. (pin oak) were grown from seed in t wo pine bark substrates with different pHs (pH 4.7 and 5.1) (Expt. 1), Prep lant amendment treatments for each of two pine (Pinus taeda L,) bark source s mere: with and without dolomitic limestone (3.6 kg.m(-3)) and with and wi thout micronutrients (0.9 kg.m(-3), and with and without micronutrients (0. 9 kg.m(-3)), supplied as Micromax. Seedlings were harvested 12 and 19 weeks after seeds were planted, and shoot dry weight and tree height were determ ined. The same experiment was repeated using two of the nine species from E xpt. 1 and pine bark substrates at pH 5.1 and 5.8 (Expt. 2). Seedling shoot dry weight and height were measured 11 weeks after planting. For both expe riments, pine bark solutions were extracted using the pour-through method a nd analyzed for Ca, Mg, Fe, Mn, Cu, and Zn. Growth of all species in both e xperiments was greater in micronutrient-amended than in lime-amended bark. In general, adding micronutrients increased nuaient concentrations in the p ine bark solution, while adding lime decreased them. Effect of bark type on growth in Expt. 1 was variable; however, in Expt. 2, growth was greater in the low pH bark than in the high pH bark. In general, nutrient concentrati ons in bark solutions were higher in low pH bark than in high pH bark for b oth experiments. Under the pH conditions of this experinent, micronutrient additions stimulated growth whereas a lime amendment did not.