Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2008
Publication Date: 6/1/2008
Citation: Fain, G.B., Gilliam, C.H., Witcher, A.L., Sibley, J.L., Boyer, C.R. 2008. WholeTree Substrate and Fertilizer Rate in Production of Greenhouse Grown Petunia (Petunia*hybrida Vilm) and marigold (Tagetes patula L.). HortScience June1 2008 p. 700-705.
Interpretive Summary: Peat moss is the primary component of substrates in the production of greenhouse-grown herbaceous annual crops. Rising transportation costs of peat moss from Canada and Europe is sure to affect the profitability of many greenhouse operators in the United States. Alternative substrate components have been evaluated in the United States for use in greenhouse production. Although comparable plants have been grown in alternative substrates compared to standard substrates, results from studies utilizing wood substrates and peat-based substrates indicate a difference in nutrient availability between substrates. In our study, we evaluated supplemental starter fertilizer rate in combination with WholeTree as an alternative growth substrate and substrate component for greenhouse-grown petunia and marigold. Data from this study show that WholeTree, with the addition of an adequate starter nutrient charge, can be successfully utilized solely or as a component of substrates for greenhouse-grown petunias and marigolds. What is most promising about WholeTree is the possibility of an economically sustainable greenhouse substrate which could be available in close proximity to major horticultural production areas throughout the Southeastern United States.
Technical Abstract: A substrate component (WholeTree) made from loblolly pine (Pinus taeda L.) was evaluated along with starter fertilizer rate in the production of greenhouse-grown petunia (Petunia 'hybrida Vilm. ‘Dreams Purple’) and marigold (Tagetes patula L. ‘Hero Spry’). Loblolly pine from a 12 year old plantation were harvested at ground level, chipped and further processed through a hammer mill to pass a 0.64 cm screen. The resulting WholeTree (WT) substrate was used alone or combined with 20% (WTP2) or 50% (WTP5) (by volume) Canadian sphagnum peatmoss and compared to an industry standard peat-lite (PL) mix of 8 peatmoss : 1 vermiculite : 1 perlite (by volume). Substrates were amended with 1.78 kg•m-3 dolomitic lime, 0.59 kg•m-3 gypsum (CaSO4-2(H2O)), 0.44 kg•m-3 Micromax, 1.78 kg•m-3 16N-2.6P-9.9K (3-4 month release) and 1.78 kg•m-3 16N-2.6P-10.8K (5-6 month release). A 7N-1.3P-8.3K starter fertilizer (SF) was added to each substrate at 0.0, 1.19, 2.37, or 3.56 kg•m-3. Container capacity (CC) was greatest for PL and decreased as the percentage of peatmoss in the substrate decreased with WT having 35 % less CC than PL. Conversely air space (AS) was greatest for the WT and decreased as percentage of peatmoss increased with PL containing 33% less AS than WT. In general petunia dry weight was greatest for any substrate containing peatmoss with a SF rate of 2.37 kg•m-3 or greater. The exception was that petunia grown in WT at 3.56 kg•m-3 SF had similar dry weight to all other treatments. Marigold dry weight was similar for all substrates where at least 2.37 kg•m-3 SF was used.