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S. Côté, C.J. Beauchamp, and S. Yelle

In 1991, a project was initiated in collaboration with the Daishowa paper company to characterize de-inking residues resulting from paper recycling in detail and to determine the value of this organic residue as an amendment to agricultural soils. Our objective was to determine the effects of field applications of de-inking residues on potato crop culture. In 1992, 1993, and 1994, experimental plots were established and maintained at the Horticultural Experimental Farm of Laval Univ. A factorial design was composed of four replications of four doses of de-inking residues (0, 15, 30, and 45 t·ha–1) combined with four doses of N (0, 45, 90, and 135 kg·ha–1). Treatments were applied to a total of 64 plots. The results indicate the importance of adjusting the fertilization to prevent the immobilization of N by the residues. In 1992, as a result of adding de-inking residues, potato yields were increased significantly when sufficient N fertilizer was added. However, significant decreases in yield were noted when a high level of de-inking residues was applied without any adjustment of the C:N ratio. In 1993, potato yields were reduced in treatments having a second application of residue at the highest doses (30 and 45 t·ha–1), even when additional N was provide. Interestingly, harvested tubers gave no indication of toxicity effects due to heavy metals or other contaminants. Results also will be discussed in terms of overall potato quality and the incidence of disease.

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A. Gagnon, S. Yelle, and A. Gosselin

The objective of this experiment was to examine the influence of continuous and intermittent carbon dioxide enrichment on the growth of greenhouse tomato plants. Tomato plants were grown under four CO2 regimes: Control at 330 ppm, continuous supply at 1000 ppm, and intermittent supply (1h supply/2 hours) at 1000 ppm and 2000 ppm. Carbon enrichment produced an increase in photosynthetic rate and plant dry weight, a decrease in leaf nitrate level, and leaf accumulation of reducing sugars and starch. A loss in efficiency was observed over time in plants grown under high atmospheric C02 concentration. However, intermittent carbon enrichment reduced the plant acclimation. Even with 32% less C02, intermittent enrichment at 1000 ppm produced yields 6% greater than continuous enrichment. The superior yield may be explained by preferential allocation of photosynthates to the fruit under intermittent supply.

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Mohamed Badrane Erhioui, A. Karam, and S. Yelle

The large amount of organic carbon content present in de-inking residues makes them attractive for use in agricultural soils as an organic soil amendment. Greenhouse bioessays were undertaken to evaluate the agronomic value of de-inking sludge (DS). It was incorporated in a sandy soil to study the effects of different rates of de-inking residue amendments and N fertilizer combinations on soil properties and growth of corn. Particular attention was given to trace element concentrations. In a split factorial design, three variables were investigated: harvest time (after 20, 40, and 60 days), application rates of DS (0, 35, 70, and 105 t·ha–1), and four N rates (0, 140, 280, and 420 kg·ha–1). Chemical analyses of the fresh residues did not indicate the presence of heavy metals at levels potentially toxic to the environment. Soil chemical properties were clearly improved following the incorporation of DS. For example, adding different amounts of DS had a significant impact on the pH, the cation exchange capacity, and soil moisture. In addition, salinity was not affected with DS application. Seed germination was high in all the treatments and was not significantly influenced by DS application. Moreover, results on vegetative growth indicated a good relationship between the C:N ratio and biomass production. The DS combined with supplemental fertilizer seems to have a positive effect on plant growth. Overall, these results suggest that the limiting factor in de-inking paper sludge valorization is the amount of N available to the plant. Also, no other toxic products were found that could be harmful to the environment.

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S. Overney, V.Q. Le, S. Visal, and S. Yelle

Bioengineering economically important plants with proteinase inhibitors (PIs) is a promising method for the control of insect pests. In the case of the Colorado potato beetle (CPB; Leptinotarsa decemlineata Say), the major insect pest of potato fields, 80% of the digestive proteases are of cysteine type. We showed that 60% of these cysteine proteases are inhibited by oryzacystatins (OCs). The use of these cysteine protease inhibitor genes therefore appears of great interest for the production of Coleoptera-resistant transgenic plants of potato. Complementary studies of biochemical in vitro assays showed an apparent absence of direct interference between OCs and potato proteases. The high regeneration efficiency of the genetically transformed plants with OC gene and the “normal” phenotypical growth of the resulting transgenic potato plants suggested that these foreign genes do not interact with important physiological processes in the potato plants. In vivo assays of PIs against CPB at various developmental stages suggest the significant potential of OCs as an effective way to control CPB populations and crop damage.

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H. Desilets, S. Rochefort, J. Coulombe, S. Yelle, and J. Brodeur

The potential impact of propane flamers on the development and release of ascosporic inoculum of Venturia inaequalis (Cke.) Wint. from infected dead apple (Malus domestica Borkh.) leaves that overwintered on the soil of an experimental orchard was assessed. Thermal reduction of scab primary inoculum was first conducted under controlled conditions using an indoor testing facility. At the time of ascospore maturation, heavily infected leaves were submitted to temperature rises ranging from 150 to 200 °C with open-flame burners, thus reducing the number of ascospores subsequently released by 76% and 87%, respectively. During Spring 1995, thermal treatments of overwintered dead leaves were performed directly on the ground of an apple orchard with an experimental propane flamer design to generate uniform heat at ground level. Four thermal treatment strategies, involving two dates of flaming and two heat intensities, were tested. Flaming orchard ground, when performed in early May, before significant development of ground cover, reduced the number of ascopores released from infected dead leaves by half. A significant residual effect of the treatments on ascospore ejection was still observed 2 and 4 weeks after the treatments, thus indicating that ascospore maturation inside the leaves may be reduced by heat treatment. These results indicate potential for propane flamers to reduce apple scab primary inoculum in orchards.

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Benolt Lacasse, C. Laguë, S. Yelle, P.M. Roy, and M. Khelifi

A front-mounted prototype designed to pneumatically remove Colorado potato beetles (CPB) from potato plants was tested in the field. Effects of different combinations of airflow velocities, nozzle widths, and travel speeds were investigated. Results showed that capture and dislodging of CPBs were better for adults and big larvae (L3 & L4). On the other hand, neither the airflow width and velocity nor the travel speed affected significantly the dislodging and the collection of small larvae. Field trials on the removal of larvae under the effect of different travel speeds showed that, the slower the prototype moved, the better was the collection of L3-L4 larvae. This study demonstrates the potential of pneumatic control of adult and L3-L4 CPBs.

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J. Gill, C. Laguë, N. Lehoux, G. Péloquin, J. Coulombe, and S. Yelle

To develop new alternatives to chemical pesticides in agriculture, a research program was elaborated on the use of propane flamers for weed control. One part of this project is the evaluation of different propane burners commercially available. We measured the temperature distribution within the burner flames and the fuel consumption of three different types of burner. Flame characterization allowed for the selection of appropriate burners and settings for specific applications. We also investigated the effect of preemergence thermal weeding on crop establishment for 10 different crops. The use of flaming in preemergence of crops is an effective method for controlling weeds, especially for younger and broadleaf weeds. Depending on the crop, thermal weeding can affect the emergence rate when applied just before seedling emergence.

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Y. Zhang, L. Gauthier, D. de Halleux, B. Dansereau, S. Yelle, and A. Gosselin

qA 3-year study was undertaken to quantify the effect of four greenhouse covering materials on energy consumption, microclimate, and the growth and production of cut flowers Matthiola incana (Stocks) and Antirrhinum majalis (Snapdragons) in the greenhouse. The four materials are single glass (GL), polyethylene (PE) + anti-fog 1-year polyethylene (AF1), polyethylene + antifog 3-year polyethylene (AF3), and polyethylene + anti-fog thermal polyethylene (AFT). The effect of thermal screen and supplementary lighting (60 μmol·m–2·s–1) also are discussed. This study indicated that AFT film is the most energy efficient material and AF3 film is the most transparent to photosynthetic active radiation (PAR). For stocks, good quality can be obtained in GL and AF3 in terms of spike length, stem diameter, as well as number of buds and flowers. The stocks in GL, however, always possess the highest photosynthetic capacity, regardless light treatment. For snapdragons, the growth and flowering in PE houses were significantly improved by supplementary lighting