Soilless root substrates (substrates) are commonly used in the production of containerized greenhouse and nursery crops (Nelson, 2003). Substrates are formulated from various organic and inorganic components to provide suitable physical and chemical properties as required by the specific crop and growing conditions (Bunt, 1988). One of the most common materials used in the formulation of substrates is sphagnum peat. Environmental concerns (Barkham, 1993; Buckland, 1993; Robertson, 1993) in the European Union (EU) and cost in markets such as Japan that are far from commercial sphagnum peat sources have generated significant interest in the development of new substrate components.
Most research on the development of new substrate components has been focused on agricultural, industrial, and municipal waste products. Among these products are coconut coir (Evans and Stamps, 1996), cotton gin waste (Wang, 1991), waste paper products (Chong and Cline, 1993; Raymond et al., 1998), composted rice hulls (Laiche and Nash, 1990), kenaf (Wang, 1994), municipal sewage sludge (Klock-Moore, 1999, 2001), composted yard waste (Beeson, 1996), and various composted animal manures (Tyler et al., 1993). Some of these materials were not produced in large enough quantities to affect the market, whereas others were too expensive for their intended use. Some of these materials have proved to be unsuitable because of their high degree of variability and their likelihood of containing contaminants such as metal fragments, glass, lead, and mercury, whereas others have been used successfully locally, regionally, or in niche markets.
Poultry feathers are a significant waste material produced by the meat processing industry. About 2 billion pounds of feather remained as a byproduct of poultry production in 2002 (U.S. Department of Agriculture, 2003). Depending upon location and specific environmental regulatory requirements, feathers may be dried and ground for use in fertilizers (Choi and Nelson, 1996a, b; Hadas and Kautsky, 1994) and animal feeds (Brown and Pate, 1997; Moritz and Latshaw, 2001; Palmquist et al., 1993), burned or land filled. In the EU, many poultry producers pay for the disposal of waste feathers (M.R. Evans, unpublished).
Being made almost entirely of the protein keratin, feathers are strong, fibrous, biodegradable and contain ≈15% N by weight (Hadas and Kautsky, 1994).
Feathers were reported to have more surface area and to be more absorbent than plant fiber (McGovern, 2000). Keratin is made of complex proteins that are not easily broken down and remain in a relatively stable state (Tan and Tai, 1983). The large quantity available, their low cost, and their physical characteristics might serve to make poultry feather a desirable component for greenhouse substrates.
Evans (2004) demonstrated that ground poultry feather fiber could be used to grow several annual bedding plant species successfully when used in peat or bark-based substrates containing up to 30% ground feather fiber. However, no information was reported regarding how the inclusion of the feather fiber affected the physical properties of the substrates. The objective of this study was to determine whether the incorporation of feather fiber into sphagnum peat-based substrates significantly affected the physical properties of the resulting substrates.
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