EVALUATION OF PINE BARK AS A SUBSTRATE FOR ANTHURIUM PRODUCTION IN SOUTH AFRICA

Pine bark is the basis for most growing media in South Africa.
Fresh pine bark is usually composted before use but this increases the cost from R20 m^-3 to about R70 m^-3. Consequently anthurium growers use uncomposted pine bark despite inherent problems of toxin release and ongoing composting.
This experiment compared seven grades of pine bark viz., fresh, uncomposted bark (UPB), half composted bark (HPB), fine potting mix (FPM), coarse potting mix (CPM), CPM with a super-absorbent gel (0.75 kg m^-3 Synpol^R), CPM with a wetting agent (1.5 kg m^-3 Saturaid^R) and very coarse potting mix (VCPM). The trial was designed as a factorial experiment using two cultivars, ‘von Egmont’s Favourite’ and ‘Miriam’, with three replications.
In June 1993 mature anthuriums were planted at a density of nine plants m^-2. The bark was pre-enriched with 2.0 kg m^-3 calcitic lime and 0.8 kg m^-3 single superphosphate and irrigated daily with a nutrient solution.
Flower production and flower quality was recorded weekly.
The substrates were analysed for physical and chemical properties.
The two cultivars differed in their yield and disease susceptibility responses to the various grades of pine bark. ‘von Egmont’s Favourite’ produced most flowers in CPM amended with Synpol^R while ‘Miriam’ performed best in CPM amended with Saturaid^R. No significant interaction between cultivar and substrate was found.
Performance by both cultivars was reduced in FPM and VCPM. Physical properties of the media appeared to have a greater effect on yield than organic chemicals released from the bark.
UPB and HPB had superior physical properties and consequently less disease.
Further trials are planned to compare uncomposted and composted pine bark of similar physical properties.

International Symposium on Growing Media & Plant Nutrition in Horticulture

D.M. Holcroft, M.D. Laing

https://doi.org/10.17660/ActaHortic.1995.401.21