Search Results

You are looking at 1 - 10 of 15 items for

  • Author or Editor: A. Gosselin x
Clear All Modify Search
Authors: and

The behavior of turfgrass grown on paper-sludge-amended soils was evaluated over 2 years. Two experiments were performed, one with deinked sludge and another with primary sludge. Four paper sludge, sand, and organic soil substrate mixtures with proportions ranging from 0% to 50% paper sludge were incorporated into existing soils. Two fertilization levels were applied in strip plots across sludge treatments and three turfgrasses of seeded Kentucky bluegrass (Poa pratensis L. `Georgetown'), Kentucky bluegrass sod, and an 80 Kentucky bluegrass: 20 perennial ryegrass (Lolium perenne L. `Prelude') seed mix were arranged within split plots. Effects of deinked and primary sludge experiments were similar. Supplemental N and, to a lesser degree, P and K fertilization with N at ≈4.5 to 5.5 t·ha–1, P at 1.18 to 1.26 t·ha–1, and K at 1.34 to 1.46 t·ha–1 improved ground cover, turf color, and stand quality. Despite differences in visual evaluations, leaf mineral nutrition was only slightly affected by fertilization treatments. Soil in nonfertilized plots was several times lower in N-NO3 when compared to fertilized plots, regardless of sludge rate. Soil in fertilized plots had higher concentrations of inorganic N regardless of sludge amendment. The soil C: N ratio was ≈13:1 in nonamended plots and more than 15:1 under the highest sludge rate. Deinked and primary paper sludges can be used effectively as soil amendments if turfgrass receives adequate supplemental N, P, and K.

Free access
Authors: , , and

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.

Free access

Tomato plants (Lycopersicon esculentum Mill. cv. Capello) were grown in the three most promising and used hydroponic cultivation systems using rockwool and peatmoss substrates and nutrient film technique (NFT), either with or without recovery and recycling of the drainage solutions. Prolonged recycling of nutrient solutions in NFT caused a reduction in fresh weight, dry weight, and yield compared to plants grown in NFT with regular renewal of the nutrient solution. There were no differences in growth, productivity, and leaf mineral composition between plants grown in rockwool and peatmoss systems, with or without recycling, and in the NFT system without recycling. These results suggest that recycling drainage solutions is an economically and environmentally sound horticultural practice that when used correctly does not cause a reduction in yield of tomatoes cultivated in rockwool or peatmoss. However, prolonged use of the same solution in the NFT cultivation system can negatively affect growth and yield. This is most likely due to an accumulation of sulfate ions in the fertigation solutions.

Free access
Authors: , , and

Daily and seasonal variations of photosynthetic activity, chlorophyll a (Chl-a) fluorescence and foliar carbohydrate content were studied in situ on greenhouse tomato (Lycopersicon esculentum Mill. `Trust') plants grown under CO2 enrichment and supplemental lighting. The objective of this study was to assess the effect of seasonal variation of the photosynthetic photon flux (PPF) on photosynthetic efficiency of tomato plants and to determine the presence or absence of photosynthetic down-regulation under greenhouse growing conditions prevailing in northern latitudes. During winter, the fifth and the tenth leaves of tomato plants showed low, constant daily photosynthetic activity suggesting a source limitation under low PPF. In winter, the ratio of variable to maximum Chl-a fluorescence in dark adapted state (Fv/Fm) remained constant during the day indicating no photoinhibition occurred. In February, an increase in photosynthetic activity was followed by a decline during March, April, and May accompanied by an increase in sucrose and daily starch concentrations and constant but high hexose level. This accumulation was a long-term response to high PPF and CO2 enrichment which would be caused by a sink limitation. Thus, in spring we observed an in situ downregulation of photosynthesis. The ratio Fv/Fm decreased in spring compared to winter in response to increasing PPF. The daily decline of Fv/Fm was observed particularly as a midday depression followed by a recovery towards the end of the day. This indicated that tomato leaves were subject to a reversible inhibition in spring. Fv/Fm was lower in March than in April and May even though PPF was higher in April and May than in March. These results suggest that tomato plants develop an adaptive and protective strategy as PPF increases in spring.

Free access

Abstract

Celery transplants (Apium graveolens L. cv. Florida 683) were fertilized with complete nutrient solutions at three N concentrations and three concentrations of P in a factorial combination, both with or without atmospheric CO2 enrichment. They then were planted on a muck soil and harvested at the end of July. Carbon dioxide enrichment increased the transplant leaf area as well as shoot and root dry weight and decreased the leaf area ratio (LAR), but had no significant effect on growth parameters at harvest. Nitrogen affected leaf area, dry weight, leaf area ratio, and dry matter content of transplant shoots together with root: shoot dry weight ratio. Total, marketable, and side shoot weights at harvest were significantly increased by the intermediate N concentration (400 ppm N) provided during transplant raising. Phosphorus had no effect on transplant growth but interacted with N on the weight of marketable shoots harvested.

Open Access

Micropropagated plantlets of Gerbera jamesonii H. Bolus ex Hook. F. `Terra Mix', Nephrolepis exaltata (L.) Schott `Florida Ruffles', and Syngonium podophyllum Schott `White Butterfly' were inoculated with two vesicular-arbuscular mycorrhizal (VAM) fungi, Glomus intraradices Schenck and Smith and G. vesiculiferum Gerderman and Trappe. They were potted in three peat-based media to determine the effects of mycorrhizal peat substrate on acclimatization and subsequent growth of micropropagated plantlets under greenhouse conditions. Symbiosis was established between the three ornamental species and VAM fungi within 4 to 8 weeks of culture in the greenhouse, but not during acclimatization. Mortality of Gerbera and Nephrolepis mycorrhizal plantlets was reduced at week 8 compared to the noninoculated control. A peat-based substrate low in P and with good aeration improved VAM fungi spread and efficiency. Mycorrhizal substrates had a long-term benefit of increasing leaf and root dry weight of Gerbera and Nephrolepis. Mycorrhizal Gerbera plants flowered significantly faster than non-mycorrhizal plants.

Free access

Most experiments on the effects of cover materials on greenhouse crops have provided no real statistical replication for the cover materials. This study was conducted in Winter 1996 at the Harrow Research Centre (Ontario) in nine minihouses covered with glass (single-glass), D-poly (double inflated polyethylene film), and acrylic (rigid twin acrylic panel) offering a 3 × 3 latin square experimental design. Tomato plants (Lycopersicon esculentum L.) were grown in CO2-enriched atmosphere (1000 ppm) under three covering materials, and two light treatments (natural light, and supplemental light at 65 μmol·m–2·s–1) in order to determine the effects of supplemental light on growth, photosynthesis, reproductive carbon allocation, and evolution of carbohydrates synthesis in the diurnal cycles. Overall, the application of supplemental light increased photosynthesis rate, yields, harvest index, total chlorophyll content, and starch accumulation in all treatments, regardless of the type of cover materials. Early marketable yield in acrylic and D-poly houses was higher than in glasshouses. Plants grown under enhanced light intensity flowered earlier and produced 12% more marketable fruits than those grown under natural light. The photosynthetic rate of plants grown in acrylic houses was higher than that of plants grown in glasshouses and those grown in D-poly. The leaves of plants grown in acrylic and D-poly houses had higher dry mass contents and much higher specific leaf weight (>10%) than plants in glasshouses. The net photosynthesis dropped after 3 months of treatment, accompanied by a high accumulation of carbohydrates in the leaves. These results indicate that a photosynthetic acclimation occurs earlier during the growth period suggesting a limitations in carbon metabolism.

Free access

Paper recycling generates large quantities of de-inking sludge, which is disposed of mainly by landfilling. More ecological disposal alternatives include land application and use as a container nursery medium. In this study, raw de-inking sludge was evaluated as a medium component supplemented with applications of four N fertilization regimes for the growth of three grass species (Festuca ovina duriuscula, Agropyron elongatum, Alopecurus pratensis), and four regimes of P fertilization for the growth of three Rhizobium-inoculated legumes (Medicago lupulina, Galega orientalis, Melillotus officinalis). Fertilizer was applied on the basis of sludge rate to maintain a uniform C: N ratio across sludge treatments. In one experiment, sand was mixed with 0, 10%, 20%, and 30% sludge by volume and 20% perlite, while in a second experiment, mineral soil was mixed with 0, 27%, 53%, and 80 % sludge and 20% perlite. Results indicate that shoot dry weight of all species increased with the amount of sludge in the mixture in tests with sand. In the soil mixture experiment, grasses showed the best response to treatments of 53% sludge mixture at the two highest N treatments. In general, shoot dry weight was more directly related to the total amount of N applied than to the C: N ratio of the substrate. The nutritional status (foliar N and P) also was investigated for one grass and one legume species.

Free access

The objective of the experiments was to compare the performance of metal halide (MH) and high-pressure sodium (HPS) lamps on growth and yield of vegetables. Four experiments with lettuce were carried out. The lettuce grown under HPS lamps had a head firmness higher than under MH lamps. The difference between the type of lamps on fresh weight was not very constant with the period of production. There was no interaction between lamp and cultivar. Two experiments were carried out with tomato in Spring and Fall 1991. For a tomato crop, the yield and quality of the fruit were not affected by the type of lamps. Photosynthesis and transpiration of tomato and pepper plants were measured under MH and HPS lamps. No significant differences were found between both lamps under two humidity conditions and four PPFs. Under high humidity conditions, transpiration under MH was higher than under HPS.

Free access

The main objective of this research was to produce a simulated model that permitted the evaluation of operating costs of commercial greenhouse tomato growers with respect to heating methods (hot air, hot water, radiant and heat pumps) and the use of artificial lighting for 1991 and 1992. This research showed that the main factors that negatively influence profitability were energy consumption during cold periods and the price of tomatoes during the summer season. The conventional hot water system consumed less energy than the heat pump system and produced marketable fruit yields similar to those from the heat pump system. The hot water system was generally more profitable in regards to energy consumption and productivity. Moreover, investment costs were less; therefore, this system gives best overall financial savings. As for radiant and hot air systems, their overall financial status falls between that of the hot water system and the heat pump. The radiant system proved to be more energy efficient that the hot air system, but the latter produced a higher marketable fruit yield over the 2-year study.

Free access