Damon E. Abdi

As peat (P) demand increases throughout the horticultural industry, alternative fibers must be evaluated. Sugarcane bagasse (B), wood fiber (W), and coconut coir (C) have received interest as domestically available alternatives to P, with demonstrated success in producing greenhouse crops. However, there is limited research comparing these materials to peat. This research evaluated the substrate properties and productivity of Petunia Supertunia Mini Vista ‘Indigo’ in pine bark substrates amended with C, W, B, or P and fertigated weekly at 100, 200, or 300 parts per million (ppm) nitrogen (N) to account for possible N immobilization. The container capacity was lowest and air-filled porosity was highest in W and B substrates. Substrate pH increased in W and B substrates, and C substrates were fertigated at 100 ppm N. Increasing the N rate increased the growth index in all substrates, especially B and W substrates later in the production period. Higher fertilization increased shoot mass, chlorophyll content, and blooms across all substrates, demonstrating that fertilizer supplementation may offset possible N immobilization. While plant growth and quality parameters were greatest in the P blend, increasing N applications produced similar-quality plants using alternative substrates, demonstrating that modifying fertilizer management practices can make alternative fibers a viable horticultural substrate.