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) were removed from the effluent. At Laval University, artificial wetlands with Typha latifolia were more efficient than wetlands with Phragmites australis or without plants. Addition of sucrose increased wetlands' microbial population and consequently reduced the mineral content of the wastewater, but increased significantly the emission of greenhouse gases. Results will further be discussed in terms of the best wetland design to treat greenhouse effluents, but also in terms of the environmental impact.

Allaire, S. E., Caron, J., Ménard, C. and Dorais, M. 2005. Potential replacements for rockwool as growing substrate for greenhouse tomato. Can. J. Soil Sci. 85: 67-74. The greenhouse industry needs renewable, cheap, and available substitutes for rockwool. The physical properties and performance of rockwool substitutes such as low grade peat, composted bark white spruce and fir, shavings, sawdust, and peat-bark mixtures were compared during two greenhouse experiments with tomato grown in plastic bags. Air and water filled porosities greatly differed between substrates, particularly for sawdust and shavings. Relative gas diffusivity (D s /D o ) and the hydraulic conductivity were less different between substrates. The physical properties of the substrates changed over a production cycle but the changes were small compared to treatment differences. Yields in peat-bark substrates were similar to rockwool substrates during both the short and long experiments but were lower in sawdust and shavings during the long experiment. The yield differences expected between media were less than the differences between some substrate physical properties of the various media. Yields were positively related to easily available water (EAW) and negatively related to D s /D o and airfilled porosity (AFP). This indicated excessive drainage for the low-yielding substrates. In plastic bags, media properties related to aeration were not good indicators of production because the plants adapted to the lack of aeration by modifying their root distribution. White spruce and fir bark alone or mixed with low-grade peat showed high potential for greenhouse tomato production and represent an environmental sound alternative to rockwool. Aucune différence entre les rendements de la laine de roche et les mélanges tourbe-écorces n'a été mesurée, alors que ceux des sciures et des copeaux furent plus bas durant la production la plus longue. Dans la plupart des cas, les rendements n'étaient pas corrélés aux propriétés physiques des substrats. Dans un cas seulement, le rendement était positivement corrélé à EAW et négativement à D s /D o et à la porosité en air (AFP), suggérant un drainage excessif des copeaux et sciures. Pour la culture en sac, les propriétés reliées à la teneur et au mouvement de l'air n'ont pas étés de bons indicateurs de la productivité, en partie parce que les plantes ont adapté leur distribution racinaire au pourtour du substrat dans les cas asphyxiants. Les écorces seules ou avec la tourbe brune ont montré un bon potentiel de remplacement de la laine de roche et causent moins de problèmes environnementaux que la laine de roche.

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Organically grown greenhouse sweet pepper crops, as is the case with most year-around greenhouse crops, rely on pre-grown transplants. Production of adequately balanced (source and sink strength potential) healthy organic sweet pepper transplants is a challenge and is often related to early and total harvested yields. Liquid and/or solid organic fertilizers for greenhouse sweet pepper transplants were compared with a conventional liquid fertilizer. Transplants were grown under greenhouse conditions and inoculated, or not, with a beneficial microbial agent, Trichoderma harzianum Rifai, strain KRL-AG2 (Rootshield®). Medium respiration (CO2 efflux) and fluorescein diacetate (FDA) hydrolysis analysis showed a higher microbial activity in the liquid organic fertilizer treatment. Higher microbial activity was observed after 10 weeks than at 5 weeks after transplanting. Transplant development was greater in the liquid conventional fertilizer treatment compared with the two organic treatments. Transplants that received liquid organic fertilizer had greater development compared with transplants that only received water in addition to the initial solid fertilizer. Organic amendment mineralization did not completely fulfill transplant nutrient requirement compared with conventional transplants. Solid fertilization in the growing medium affected plant growth during the first 5 weeks but not after 10 weeks after transplanting. Solid and liquid organic fertilizers at a higher concentration should be provided to reach a similar transplant development because conventional seedlings or other slow-release sources of solid amendments should be added to the growing medium to keep an adequate and constant nutrient release. Providing a beneficial agent to the organic growing medium increased its biological activity but had no effect on seedling growth during this study. Solid organic fertilization (1600 mL·m−3 of shrimp meal with 50 mL·m−3 of kelp meal) combined with an organic liquid fertilization should be used in combination with inoculation with T. harzianum to obtain high-quality organic sweet pepper transplants.