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Nicolas Tremblay

Processing plants requires that cultivars be categorized as either small, medium, or large peas to meet the different markets. A reliable nutrient diagnosis system based on sweet pea leaf analysis should be robust to the type of cultivar. The objective of this study was to determine whether the type of cultivar should be taken into account in producing the nutrient diagnosis. Proportions of peas in categories 1 (small) to 5 (large) were determined for 18 cultivars produced under commercial conditions over 3 years. Cluster analysis was conducted with the constraint of revealing three groups, as homogeneous as possible with regard to their proportions in the different categories. Three cultivars were identified as belonging to the small, nine to the medium, and six to the large group. The archetype of each group was characterized. The function discriminated among the cultivars perfectly along the canonical axes. However, no classification was possible when the nutrient composition variables (N, P, K, Ca, Mg, B, Fe, Mn, Zn) were used for discriminating cultivars' types. Hence, sweet pea cultivars of different types do not differ substantially in leaf composition.

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Nicolas Tremblay and André Gosselin

Since they grow nearly exponentially, plants in their juvenile phase can benefit more than mature ones of optimal growing conditions. Transplant production in greenhouses offers the opportunity to optimize growing factors in order to reduce production time and improve transplant quality. Carbon dioxide and light are the two driving forces of photosynthesis. Carbon dioxide concentration can be enriched in the greenhouse atmosphere, leading to heavier transplants with thicker leaves and reduced transpiration rates. Supplementary lighting is often considered as more effective than CO2 enrichment for transplant production. It can be used not only to speed up growth and produce higher quality plants, but also to help in production planning. However, residual effects on transplant field yield of CO2 enrichment or supplementary lighting are absent or, at the best, inconsistent.

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Nicolas Tremblay and Carl Bélec

Weather is the primary driver of both plant growth and soil conditions. As a consequence of unpredictable weather effects on crop requirements, more inputs are being applied as an insurance policy. Best management practices (BMPs) are therefore about using minimal input for maximal return in a context of unpredictable weather events. This paper proposes a set of complementary actions and tools as BMP for nitrogen (N) fertilization of vegetable crops: 1) planning from an N budget, 2) reference plot establishment, and 3) crop sensing prior to in-season N application based on a saturation index related to N requirement.

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Nicolas Tremblay and Yvon Perron

As plant color is often modified by nutrient status, the use of spectoradiometric properties of leaf tissues appears to be a promising tool for quick and inexpensive diagnosis of crop fertility problems. This study was conducted to examine spectral variability associated with celery cultivars. Seedlings of Florida 683, Matador, Utah 5270, and Ventura were grown in a growth chamber for 10 weeks (transplant stage; TS). Reflectance and transmittance measurements were taken on the tallest leaf with a LI-COR LI-1800 spectroradiometer. Remaining seedlings were potted and transferred to a greenhouse for another 8 weeks (mid-growth stage; MS). Transmittance was established as the parameter most suitable to distinguish cultivars. Maximum F ratio was obtained at λ = 630 mn at TS, while there were two peeks (λ = 470 and 60 mn) at MS. A discriminant function was based on λ = 470; 630 and 670 mn correctly classified cultivars more than 8 times out of 10 at TS, and more than 7 times out of 10 at MS. Further studies should focus on the induction of nutrient deficiencies and the potential interferences of cultivars with their diagnosis.

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Nicolas Tremblay and Léon-Étienne Parent

Celery (Apium graveolens var. Dulce) is a species particularly sensitive to nutritional balance. Seedlings in multicellular trays sometimes present problems that can be traced to nutritional causes. DRIS (Diagnosis and Recommendation Integrated System) and CND (Compositional Nutrient Diagnosis) are two recent concepts that can be implemented to diagnose nutritional imbalances from tissue analyses of any plant species. A data bank of 215 observations was used to elaborate DRIS and CND norms for celery transplants. The threshold yield for high yielders was set at 1600 g/plant (27% of the population). Both DRIS and CND systems were implemented and a validation process was undertaken. Nutrient deficiencies (N, P, K, Ca, Mg, Fe, B and Zn) were induced on celery seedlings in growing chambers. Tissues samples were given a balanced fertilization. The diagnosing methods (DRIS and CND) were compared on the basis of their ability to identify correctly the induced nutrient deficiencies.

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Alejandro Fierro, André Gosselin and Nicolas Tremblay

The experiment was conducted to determine the effects of CO, enrichment (900 μl·liter-1, 8 hours/day) in combination with supplementary lighting of 100 μmol·s-1·m-2(16-h photoperiod) on tomato (Lycopersicon esculentum Mill.) and sweet pepper (Capsicum annuum L.) seedling growth in the greenhouse and subsequent yield in the field. Enrichment with CO2 and supplementary lighting for ≈ 3 weeks before transplanting increased accumulation of dry matter in shoots by ≈ 50% compared with the control, while root dry weight increased 49% for tomato and 6270 for pepper. Early yields increased by =1570 and 11% for tomato and pepper, respectively.

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Lucette Laflamme, Nicolas Tremblay and Marie-Hélène Michaud

Angelica is grown in Quebec (Canada) for its root-bound medicinal properties. Matol Botanique Int., a major user of Angelica extracts, decided 4 years ago to promote local production in order to secure supplies and quality. However, the crop has to be started from seed that show low and variable germination behavior. Emergence occurs after ± 12 days and most of the germination if obtained after 20 to 40 days depending on seed origin and test conditions. Maximum germination ranges from 6 to 57%. Three treatments were first compared in order to stimulate germination: seed soaking in warm water for 24 h, watering germination trays with algae extracts and placing floating row covers over the trays. Angelica germination was significantly improved only by row covers with a maximum of 24% vs 19%. Results were obtained from experiments with other techniques (stratification, seed conditioning, etc,...) to further improve germination.

2Working for the Horticultural Research Centre, Laval University, Que.

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Elizabeth Herrera, Nicolas Tremblay and André Gosselin

Transplants of angelica (Angelica archangelica L.), horehound (Marrubium vulgare L.), and thyme (Thymus vulgaris L.) were grown in multicompartment trays with five proportions of compost (0%, 15%, 30%, 45%, 60%) mixed to peatmoss and perlite. Plants were fertilized with different electrical conductivity (EC) levels of the nutrient solution (0, 1, and 2 mmho/cm). Horehound and thyme plants were transplanted in the field to measure the residual effects of treatments on dry matter yields and level of active substances. The three medicinal plants showed increased shoot and root dry weights as well as leaf mineral content (some nutrients) when proportion of compost and EC of nutrient solution were higher. The optimal combinations of compost and fertilization treatments on plants growth varied between species. Residual effects of treatments applied in greenhouse on shoot dry matter weight of horehound and thyme plants were observed until the 9th and 12th week, respectively, after transplantation. Treatments also affected active substance levels in horehound plants in field. Organic fertilization management influenced growth, yield in the field and level of certain active substances of the harvested parts of medicinal plants.

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Nicolas Tremblay, Edith Fallon and Noura Ziadi

Diagnosing nitrogen (N) sufficiency in crops is used to help insure more effective management of N fertilizer application, and several indicators have been proposed to this end. The N nutrition index (NNI) offers a reliable measurement, but it is relatively difficult to determine. This index is based on the relationship between plant tissue N concentration and the biomass of the plant's aerial parts. However, a good estimate of the NNI should be obtained by nondestructive methods that can be carried out quickly. Although dependent on sites, chlorophyll meter (CM) measurements have been correlated with the NNI in corn (Zea mays). Since chlorophyll can be estimated through remote sensing, the possibility of quickly obtaining measurements for large surface areas points to practical applications for precision agriculture. When combined with the mapping of soil properties such as apparent electrical conductivity (EC), elevation and slope, such chlorophyll measurements make it possible to derive N fertilization recommendations by taking into account natural variations in the soil. Recently, an instrument called the Dualex (FORCE-A, Orsay, France) is marketed, which uses measurement methods based on the fluorescent properties of plant tissues. It is similar to the CM in terms of its operating principle but it measures polyphenolics (Phen), compounds that accumulate in the epidermis of leaves under N stress. Epidermal transmittance to ultraviolet light is assessed by the fluorescence excitation ratio F(ultraviolet)/F(REF), where F(ultraviolet) is the fluorescence excitation detected following ultraviolet excitation, and F(REF) is the fluorescence detected on excitation at a reference wavelength, not absorbed by the epidermis. Although the Dualex generally did not identify more differences among treatments than the CM in our studies on wheat (Triticum aestivum), corn, and broccoli (Brassica oleracea ssp. italica), combining the two measurements in a chlorophyll/Phen ratio improved the relationships with crop N nutrition status appreciably. This ratio can also be estimated by remote sensing techniques. The NNI on its own does not constitute an economically optimal recommendation for N fertilizer [economically optimal N rate (EONR)]. The EONR is the N rate at which profit is greatest. Work is currently being done to use overfertilized reference plots for this purpose and to permit an improved correlation between the indicator (NNI or chlorophyll) and EONR.

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Jean Masson, Nicolas Tremblay and André Gosselin

This experiment was initiated to determine the effects of supplementary lighting of 100 μmol·s-1·m-2 (PAR) in combination with four N rates (100, 200, 300, and 400 mg N/liter) on growth of celery (Apium graveolens L.), lettuce (Luctuca sativa L.), broccoli (Brassica oleracea italica L.), and tomato (Lycopersicon esculentum Mill.) transplants in multicellular trays. Supplementary lighting, as compared with natural light alone, increased shoot dry weight of celery, lettuce, broccoli, and tomato transplants by 22%, 40%, 19%, and 24%, and root dry weight by 97%, 42%, 38%, and 21%, respectively. It also increased the percentage of shoot dry matter of broccoli and tomato, leaf area of lettuce and broccoli, and root: shoot dry weight ratio (RSDWR) of celery and broccoli. Compared with 100 mg N/liter, a N rate of 400 mg·liter-1 increased the shoot dry weight of celery, lettuce, broccoli, and tomato transplants by 37%, 38%, 61%, and 38%, respectively. High N fertilization accelerated shoot growth at the expense of root growth, except for tomato where a 16% increase of root dry weight was observed. High N also reduced percentage of shoot dry matter. Supplementary lighting appears to be a promising technique when used in combination with high N rates to improve the production of high quality transplants, particularly those sown early.