ISHS Acta Horticulturae 761: XXVII International Horticultural Congress - IHC2006: International Symposium on Advances in Environmental Control, Automation and Cultivation Systems for Sustainable, High-Quality Crop Production under Protected Cultivation
RISK OF PHYTOTOXICITY OF SAWDUST SUBSTRATES FOR GREENHOUSE VEGETABLES |
| Authors: | M. Dorais, C. Ménard, G. Bégin |
| Keywords: | bioassay, conifer, growing media, toxicity indicator, wood waste |
| DOI: | 10.17660/ActaHortic.2007.761.82 |
| Abstract:
The use of forestry wastes based substrates for greenhouse production constitutes a sustainable alternative to largely used inorganic or peat substrates. Our recent studies have shown benefits of using Picea glauca sawdust/composted bark based substrates compared to rockwool in terms of reducing production costs with equivalent or higher yield and root growth. However, in addition to their specific physical properties, forestry waste products can contain phytotoxic compounds such as manganese, heavy metals, terpenes and phenols. These compounds can have serious consequences owing to the direct root contact with the concentrated form. Phytotoxic molecules can be detected and quantified by complex analytic methods, while bioassays are rapid, economic and include known and unknown toxic compounds. Therefore, this study was intended to evaluate the phytotoxicity risk of fresh sawdusts and sawdust species mixture substrates on greenhouse vegetable crops (tomato, cucumber and sweet pepper) by biotests. Ten tree species have been selected according to the usual byproducts of the Canadian forest industry (Abies balsamea, Picea sp., Pinus sp., Thuja sp., Chamaecyparis nootkatensis). Plant biomass, leaf area and Chl a fluorescence parameters were measured after 3–5 weeks of growth depending on the crop. The experimental design was a complete bloc with ten replicates (3 pots of 10 cm diameter per e.u.) including positive (peat/perlite substrate) and negative controls (peat/perlite substrate + dichlobenil). Our results have shown that Thuja sp. based substrates were phytotoxic for tomato, cucumber and pepper seedlings, while other tree species did not reduce plant biomass and leaf area. The Fv/Fm ratio was not a good indicator of the plant phytotoxicity. | |
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