Cotton Gin Compost as a Substrate Component in Container Production of Nursery Crops

Abstract

Shoot and root growth of plants grown in substrate blends containing cotton gin compost (CGC) were compared to plants grown in a traditional pine bark (PB) blend. In 2002 ‘Winter Gem’ boxwood, ‘Firepower’ dwarf nandina, and ‘Midnight Flare’ azalea were potted in four substrate blends containing by volume 6:1 PB:sand (S), 4.5:1.5:1 PB:CGC:S, 1:1 PB:CGC, or 1.5:4.5:1 PB:CGC:S. Plants were grown for nine months on a container pad in Auburn, AL. In 2003–2004 this study was repeated with ‘Renee Mitchell’ azalea as a replacement for ‘Midnight Flare’ azalea. Periodic growth measurements and a final visual root ball evaluation were conducted in each experiment. Substrates were analyzed to determine physical properties (air space, water holding capacity, total porosity, and bulk density) and chemical properties (pH and electrical conductivity). In both experiments, growth indices of all cultivars in substrates containing CGC were similar to or greater than those of the PB:S control blend. Visual quality of root systems was similar for all plants across all substrates.