Greenhouse and Nursery Growing Substrates
Geranium grown in Sphagnum peat-based substrate with 30% perlite (L) or 30% fresh rice hull
The greenhouse and containerized nursery industries utilize artificial substrates composed of materials such as Sphagnum peat, perlite, vermiculite, composted barks and other organic and inorganic components. In addition to the basic physical components, artificial substrates are often amended with materials designed to increase water absorption (i.e. surfactants), adjust pH (i.e. lime), or increase mineral element content (i.e. micronutrients).
Impatiens grown in Sphagnum peat-base substrate with 30% perlite (L) or 30% fresh rice hull (R)
Our research is focused on the development of alternative substrate components or amendments that are derived primarily from agricultural, industrial, or municipal waste products. Among the components that we have worked with are coconut coir, shredded rubber, ground bone, ground corncob, cotton gin trash, and composted manures. Two of the most exciting components on which we are currently working are parboiled fresh rice hulls and processed poultry feather fiber.
Parboiled fresh rice hulls
Fresh rice hulls have typically not been used as a horticultural substrate component because of weed seed and the potential for nitrogen tie-up in the substrate. However, we have demonstrated that parboiled fresh rice hulls are free of viable weed seed and do not cause nitrogen tie-up in the substrate. Parboiled fresh rice hulls have a higher total pore space and a higher air-filled pore space than horticultural perlite (8mm), and we have demonstrated that parboiled fresh rice hulls can be effectively used as a lower-cost alternative to perlite in horticultural substrates. We are currently conducting research to develop a replacement for Sphagnum peat from waste rice hulls.
Feather fiber is produced by washing, grinding, and disinfecting waste poultry feathers. The resulting fiber is blended with Sphagnum peat. Feather fiber holds significant amounts of water (similar to peat depending upon grind size), has an alkaline pH and contains 15% nitrogen by weight. We have demonstrated that feather fiber can be used in horticultural substrates at rates of up to 25% (v/v). This provides a value-added use for waste poultry feathers and a reduction in the use of peat.
Geranium grown in Sphagnum peat-based substrate containing 0%, 10%, 20%, 30%, or 40% feather fiber. All substrates contained 20% perlite.
Tomatoes grown in processed rice hull product as a replacement for peat or rockwool.