determine how much of the water present in a pine bark-based substrate is actually plant-available and to test whether this is species-dependent, as suggested by van Iersel and Dove (2005) . Materials and Methods Expt. 1: Substrate hydraulic properties
Pyrus calleryana, Decne, `Aristocrat'; Cryptomeria japonica, D. Don; Populus maximowiczii, Henry × `Androscoggin' and Koelreuteria bipinnata, Franch. trees were grown in low-profile containers. The optimum height and width of these containers was 20 to 30 cm and 84 cm, respectively. Pine bark and mixtures containing 50% or more of pine bark were preferable to mixtures containing leaf mold for filling the containers because the former weigh less. Roots penetrated pine bark mixtures better than sphagnum peat mixtures and also retained their shape better during transplanting. When grown in low-profile containers, trees grew fibrous root systems; after transplanting, roots grew downwardly radial and trees were able to withstand extremely difficult landscape conditions.
University of Florida, Gainesville, FL (29°38′N latitude and 82°21′W longitude). The growing medium consisted of Arredondo sandy soil ( Thomas et al., 1979 ) mixed with fresh pine bark at the ratio of 1:1 (v/v). Owing to the potential for fresh pine bark to
containing pine bark, peat, and sand at a ratio of 3:1:1 produced less leachate NH 4 –N than a comparable substrate when peat was replaced with composted paper ( Cole and Newell, 1996 ). However, few studies have evaluated the leaching potential of composted
of composted pine bark (B) and Canadian peatmoss (PM) in ratios (vB:vPM) of 70%:30%, 80%:20%, or 90%:10% (Renewed Earth, Kalamazoo, MI). Thirty trees of each species were potted in each substrate mix. Fertilizer treatment Controlled
. Medium was carefully rinsed off. Plantlets were transplanted individually in plastic pots (20 cm diameter × 15 cm deep) containing a mixture of peat and pine bark (1:1). All plantlets were maintained in a greenhouse and hand-watered as needed. Statistical
organic matter was applied on the top of the root ball. In the fourth treatment, plants were planted at-grade with NOM. Pine bark was fresh cut, chipped, and supplied by Pineywoods Mulch Co. (Alexander City, AL) from trees grown in Roanoke, AL, and Cassco
clay and gravel (1:1). In each variety, a mulch-free control, a synthetic mulch treatment (black PE film), and an organic mulch treatment (pine bark) were compared. Synthetic mulching used a 1-mm-thick black PE plastic film; organic mulching was covered
when the soil amendments are added to clay-textured soils, which are inherently more difficult to till than sandy- or loam-textured soils. Most of these products traditionally use pine bark (PB) and peatmoss (PM) as their major ingredients. Short
A broccoli (Brassica oleracea var. botrytis L.) seedling bioassay was used to measure paclobutrazol activity and distribution in two growing media following drench or subirrigation applications. The bioassay exhibited a saturation-type response curve for paclobutrazol concentrations up to 1000 μg·L-1 in solution and 100 μg·L-1 in the media. The concentration of paclobutrazol required to achieve one-half of the maximum observed bioassay activity was 3-fold as high in bark-based commercial potting medium as in a peat-based medium. Less than 2% of applied paclobutrazol leached out during the drench application despite the collection of up to 50 mL of leachate per 120 mL of the solution (1000 μg·L-1) that was applied per 15-cm pot. Immediately following drench application, paclobutrazol concentrations in both media were highest in the uppermost 2.5 cm and decreased downward. By 3 weeks after treatment, drench-applied paclobutrazol had moved into lower depths. Distribution of paclobutrazol was limited to the bottom 2.5 cm of media when applied as a subirrigation soak. Chemical name used: (±)-(R*,R*)-β-[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).