CONTAINER PRODUCTION OF UNDERUTILIZED URBAN TREES USING KENAF AND COCONUT COIR PITH

Abstract

Growth responses during nursery production in 2.2- and 11.4-liter plastic containers to conventional and alternative media of four species of small trees of limited availability for potential use in urban sites in the southwest United States (Acacia wrightii, Chilopsis linearis, × Chitalpa tashkentensis, and Rhus lanceolata) were compared to that of a commercially available small tree (Fraxinus velutina). Four media combinations, at 3:1 (v/v) of bark: sand (conventional), bark: coconut coir pith, kenaf stalk core: peatmoss, and kenaf: coir, with three fertilizer concentrations (3.6, 7.2, and 10.7 kg·m–3 of 18N–2.6P–10K Osmocote) were tested with each species. All species exhibited commercially acceptable growth (80 to 167 cm mean heights in 11.4-liter containers in 240 days) with near 100% survival in most media and fertilizer combinations with the following exceptions: shoot extension of Rhus lanceolata was reduced by 20 to 30 cm and survival by 20% to 50% in kenaf media with high fertility rates; and Acacia wrightii had acceptable shoot extension but exhibited poor trunk diameter growth across media relative to the other species. Slightreductions in growth of some species were noted with kenaf media and slight increases with coconut coir, but differences were not likely of commercial significance. Kenaf media was significantly lighter (20% to 80%) than bark media, but had elevated initial electrical conductivity (EC) and shrank to 60% to 70% of its initial volume after 240 days. Kenaf: peatmoss media had a slightly lower mean pH (6.34) compared to the other media (pH 6.41–6.49).