Pine bark (PB) and peatmoss are the two most common substrate components currently used for horticultural crop production in the southeastern United States. The availability and cost of PB remain unpredictable due to reduced forestry production and its increased use as fuel and landscape mulch (Lu et al., 2006). The cost of peat substrates continues to rise due to transportation costs and growing environmental concerns over the mining of peat bogs in Canada and Europe. Therefore, alternative substrates for container production of horticultural crops are important. The use of agricultural waste and other composted materials as a replacement for PB and peat is not a new concept; however, factors such as transportation costs, consistency and reproducibility of product, disease and insect infestation, and availability of composted materials represent concerns for growers (Gouin, 1989; Jackson et al., 2005).
Alternative substrates grown from wood and wood-based products have been investigated as suitable substrates or substrate components in nursery and greenhouse crop production. European research in this area has resulted in numerous successful commercialized wood substrates (Gerber et al., 1999; Grantzau, 1991; Gruda and Schnitzler, 2003; Muro et al., 2005; Penningsfeld, 1992). In addition, Prasad and Fietje (1989) and Worrall (1981) reported successful growth of foliage plants grown in substrates containing wood when compared with plants grown in peat and PB substrates. Annual and herbaceous plants including geranium (Pelargonium ×hortorum), petunia (Petunia grandiflora), impatiens, carnation (Dianthus caryophyllus), and chrysanthemum (Dendranthema ×grandiflorum) have been grown in wood-based substrates (Bragg et al., 1993; Hicklenton, 1983; Starck and Lukaszuk, 1991). More recently, a pine tree substrate has been developed (WoodGro™; WoodGro, Blacksburg, VA) from ground whole loblolly pine logs to successfully produce a wide range of nursery and greenhouse crops (Jackson et al., 2008; Wright and Browder, 2005; Wright et al., 2006, 2008). Pine tree substrate (PTS) derived from entire ground trees (bark, wood, branches, and needles) has also been evaluated as a container substrate or substrate component to produce vinca (Fain et al., 2008).
Understanding the survival and landscape performance of plants grown in PTS is important before PTS can be used for landscape bedding plant production. Previous research describing the post-transplant survival and performance of annual plants grown in a wood-based substrate has not, to our knowledge, been reported. It is well established that wood particles incorporated into the soil (Bollen and Lu, 1957; Lunt and Clark, 1959) or as part of a container substrate (Gruda and Schnitzler, 1999; Jackson et al., 2008; Maas and Adamson, 1972; Wright et al., 2008) may cause N immobilization and require extra N applications for growth comparable to a fully composted organic material such as PB or peatmoss. The N deficiency caused by the incorporation of wood into soil could present a problem regarding planting PTS-grown plants into the landscape. However, this deficiency can likely be overcome with appropriate fertilizer applications. Therefore, the objective of this study was to evaluate the landscape performance of annual bedding plants grown in PTS or PB when transplanted into the landscape and grown at different fertilized rates.
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