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- Author or Editor: Léon-Étienne Parent x
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.
A 2-year experiment with Prunus ×cistena sp. was conducted in pots using seven substrates composed of various proportions of primarily peat, compost and bark. Peat substrates significantly affected root and shoot dry weight. Water desorption characteristics and saturated hydraulic conductivity were measured in situ to estimate the pore tortuosity factor and the relative gas diffusion coefficient. The pH, electrical conductivity, C/N ratio, total and hydrolyzable N, as well as NO3 --N and NH4 +-N in solution were also measured. Estimates of the physical properties suggest that a lack of aeration limited plant growth. Plant growth was significantly correlated with both the gas relative diffusivity and the pore tortuosity factor. Among the chemical factors, pH and soil nitrate level were also correlated with plant growth. No significant correlation was found between plant growth and air-filled porosity or any other measured chemical properties. This study indicates that an index of gas-exchange dynamics could be a useful complementary diagnostic tool to guide substrate manufacturing.