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Defining Critical Capillary Rise Properties for Growing Media in Nurseries

^a Département des Sols et Génie Agroalimentaire, Centre de Recherche en Horticulture, Université Laval, Sainte-Foy, Québec, Canada, G1K 7P4
^b Land Resource Science Department, University of Guelph, Guelph, Ontario, Canada N1G 2W1
^c Assoc. Professor, Mid Florida Research and Education Center, IFAS, University of Florida, Apopka, FL 32703
^d Hortau inc, 840 Ste-Thérèse, Suite 300, Québec, Canada G1N 1S7

View larger version (25K): [in a new window]   Fig. 1. Physical representation of capillary rise in a subirrigation system with free water at the bottom of the pot.

View larger version (17K): [in a new window]   Fig. 2. Experimental set-up used to maintain a constant upward capillary movement in the laboratory experiment.

View larger version (13K): [in a new window]   Fig. 3. Water desorption curves of the different substrates at the beginning, before potting. Each point is the mean of three replicates and the error bar is the standard deviation of the data.

View larger version (23K): [in a new window]   Fig. 4. Observed K()– relationship in all three repitions for each individual substrate. The lines were fitted by segmented regression, using all the values for a given substrates, after a preliminary estimation of b, later recalculated from the intersection of the fitted curves. They represents the modeled K()– relationship used later for the (a) Se30B60 and (b) Sp60B30 treatments.

View larger version (22K): [in a new window]   Fig. 5. Matric head measured at mid container height within the three substrates at the beginning of the experiment and before harvest of the Sp60B30 treatment. Each value is the mean of three replicates. The star indicates significant differences in matric head between the Sp30B60 substrate and the other two substrates and the error bars are the standard deviation of the raw data, for the first and the last measurements, to provide an idea of the minimum and maximum variability observed between measurements.

View larger version (21K): [in a new window]   Fig. 6. Observed and predicted depth distribution of water potentials within the cylinder in the laboratory experiment for the Se30B60 and the Sp60B30 substrates. All matric head values above the horizontal asymptote were far below –250 cm for the Se30B60 substrate. The Sp60B30 curve is identical to the hydrostatic profile. The top Se30B60 predicted curve used the average value of the Se30B60 K()– data (see Fig. 4 above) while the bottom one used the data from the one replicate with the largest 1 value in the K()–.

View larger version (21K): [in a new window]   Fig. 7. Simulated values of the matric potential in the Sp60B30 and the Se30B60 substrates, using the lowest and highest measured evapotranspirative demand during the course of the experiment.

View larger version (22K): [in a new window]   Fig. 8. Simulated values of the matric potential in the Sp60B30 substrate, using the fitted K()– relationship of Fig. 4b and the average measured evapotranspirative demand during the course of the experiment. The (a) 1, 2, (b) b and Ks value were varied from 0.5 to 1.5 of their fitted value.