Sustainable Growing Substrates for Potted Greenhouse Gerbera Production

Greenhouse ornamental plants in Canada make up a billion dollar industry. This large industry requires substantial amounts of growing substrates. At present, most of the substrates are composed of primarily peat moss and perlite. Current environmental concerns surrounding the over use of peat has increased the demand for more environmentally sustainable growing substrates. Four newly formulated growing substrates comprised of reduced peat and locally available, sustainable materials were tested against the commercially used product BM6 (80% peat and 20% perlite) in potted greenhouse Gerbera jasmonii production. The four substrates included: 1) peat, coir chunks, compost, aged bark, composted pine mulch; 2) peat, coir chunks, manure, aged bark, composted pine mulch; 3) peat, coir chunks, compost, aged bark nuggets, composted pine mulch; and 4) coir fines, coir chunks, compost, aged bark nuggets, composted pine mulch. After a 14 week production period plants in BM6 exhibited higher above-ground dry and fresh weights, and had larger leaf area. Plants in substrates 1 and 3 had similar leaf areas as plants in BM6 at the final harvest. No differences in specific leaf area were found at any harvest amongst the treatments. At 14 weeks there were no differences in substrates total porosity (84.2% +/- 0.85), container capacity (65.9% +/- 0.74) or air space (18.1% +/- 0.75). Bulk density of BM6 was lower than that of the four new substrates; however the four new substrates decreased in bulk density throughout the 14 week period whereas BM6 did not. The pH (6.1 +/- 0.05) and EC (1.596 dS.m(-1) +/- 0.06) of the new substrates were not within the optimal range (pH of 5.8-6.0) for gerbera production which may have contributed to the delay in growth and development of the plants. Although these initial results showed that BM6 outperformed the new substrate mixes in some aspects, at least two of the substrates indicated promise as a growing medium comprised of sustainable materials to replace excessive use of peat.