Cotton Gin Compost as a Substrate Component in Container Production of Ornamental Plants

Abstract

Brian E. Jackson, Amy N. Wright, and Jeff L. SibleyAuburn University, Dept. of Horticulture, Auburn, AL 36849awright@auburn.eduIndex Words: Buxus, Nandina, Rhododendron, Pine Bark Substitute, Organic MediaSignificance to Industry: Growth of ‘Winter Gem’ boxwood and ‘Atropurpurea Nana’ nandina were higher in substrates containing higher ratios of CGC that when grown in PB:S only, while no differences in growth were observed for azalea. Additionally, root growth in substrates amended with CGC was similar to that occurring in PB:S suggesting that composted cotton gin by-products can provide a viable alternative substrate for production of containerized ornamental crops.Nature of Work: Availability and cost of materials used as substrate blends for horticultural crop production are of frequent concern. Pine bark (PB) is one of the most widely used substrate components, yet the supply and cost of PB may be inconsistent or unpredictable (5). Alternative substrates for container production of ornamental plants are therefore important. Use of composted agricultural wastes as a replacement for PB 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 (2). Cotton is a major agronomic crop grown in the southeast United States. As a result of the cotton ginning process a large amount of by-product waste is generated. Cotton gin waste (CGW) is a term used to describe the byproducts of the cotton ginning process that includes leaves, stems, burrs, and some fiber (3). Composted cotton gin waste (CGC) has been shown to be a useful substrate component for production of bedding plants, poinsettias, and floral crops (4, 6). Further evaluation of the potential of this material for use as a substrate component for container production of woody ornamental plants is needed. The objective of this study was to evaluate the effect of substrates containing CGC on the growth of shoots and roots of three commonly produced woody ornamental cultivars.Treatments were four substrate blends that included by volume 6:1 PB:Sand (S), 4.5:1.5:1 PB:CGC:S, 1:1:1 PB:CGC:S, and 1.5:4.5:1 PB:CGC:S. The percent CGC in each substrate was 0, 21, 33, and 64% respectively. The nursery standard 6:1 P:S substrate blend was used as the control substrate for comparison to CGC amended treatments. Substrates were amended with 8.2 kg•m

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