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Title: Evaluating Performance and Stability of Polyethylene Terephthalate (PET) and Cellulose Polymer as Soilless Mix Components

Author
item PASIAN, CLAUDIO - The Ohio State University
item Frantz, Jonathan

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2008
Publication Date: 10/7/2009
Citation: Pasian, C., Frantz, J. 2009. Evaluating Performance and Stability of Polyethylene Terephthalate (PET) and Cellulose Polymer as Soilless Mix Components. Acta Horticulturae. 843:289-295.

Interpretive Summary: The objective of this work was to test the suitability of two fiberous materials as growing mix components for floriculture crops. One material was a synthetic fiber made of polyethylene terephthalate (PET), and the other was a cellulose-based fiber. A basic mix of either peat, coconut coir or blends of these with perlite were amended with the polymers up to 100% of the final volume and irrigated with water containing fertilizer as needed. Respiration of each component was also measured over time to test the long-term stability after colonization by common fungi. In addition to visual observations of plants, dry weight, leaf area, plant height and consumer preference were measured. Results indicated that plants in 100% of either material were smaller (DW), had less leaf area, and were shorter than plants grown in the commercial substrates or in mixes containing smaller proportions of the materials, with the exception of begonia, which were largest in 100% and 75% PET. The plants grown in substrates containing cellulose material were smaller than the plants grown with similar amounts of PET. The substrate containing 50% of the polymers produced plants that were equal to or larger than substrates containing less of the fiber. Respiration rates indicate the cellulose material would be suitable for short-term (<6 month) production. These results indicate that the PET fiber has potential as a soilless mix component, either as a substitute for high-porosity components such as perlite, or as a peat substitute. However, the movement of the greenhouse industry towards sustainability likely favors the adaptation of the cellulose-based component.

Technical Abstract: In the U.S., concerns over the long-term sustainability of peat, perlite, and other media components have led to searches for alternative materials. FiberFill, a synthetic fiber made of recyclable polyethylene terephthalate, and Tencel, a cellulose fiber, are new materials with potential as substrate components. FiberFill blocks have already been used for hydroponic vegetable production, but its suitability as well as the suitability of Tencel has not yet been tested as soilless mix components. The growth of several floriculture crops was tested using substrates containing different proportions of the two polymers. Furthermore, the long-term stability of the materials was tested by measuring respiration rates of the different components by themselves or as blends with peat. A peat- or coir-based mix was amended with the polymers up to 100% of the final volume and fertigated with water-soluble fertilizer as needed. Visual observations of plants, dry weight (DW), leaf area (LA), plant height, and consumer preference were measured. Plants grown in 100% FiberFill or Tencel were shorter and had smaller DW and LA than plants grown partially-amended substrates with the exception of begonia, which were largest in 100% and 75% FiberFill. Substrates containing 50% FiberFill produced plants that were equal to or larger than substrates containing less polymer. Plants grown in Tencel-containing mixes were consistently smaller than plants grown in substrates containing an equal amount of FiberFill. Initial respiration rates of Tencel were lower than those of peat or peat:perlite blends, but after only ten days, respiration rates of Tencel increased after saprophytic organisms colonized the material. These results indicate that FiberFill has potential as soilless mix component, but the high respiration rates suggest Tencel would not be suitable for long-term (>6 months) production. However, the movement of the U.S. floriculture industry towards sustainability likely favors the adaptation of the cellulose-based component, Tencel.