Abstract
The characterization of substrate properties supports the correct choice of components and directs management decisions in container cultivation. There are several systems of analysis, however, the routine procedures to determine the water retention curve (WRC) are time consuming and inaccurate. This study proposed a reproducible, less time-consuming, and easy to perform method for physical characterization of substrates. We used Sphagnum peat, coconut powder, carbonized rice husk, expanded vermiculite, and expanded clay in isolation. The WRC was obtained at tensions 0, 10, 50, and 100 hPa using the method of Büchner funnel, the European standard (CEN-EN13041), and by the centrifugation method of samples. In centrifugation, tensions were simulated by combining the angular velocity, sample height, and radius measured from the sample outermost point to the central point of the centrifuge. Three rotations were applied (230; 520 and 730 rpm), testing the centrifugation time for each tension and then the volumetric water content was compared between the methods. The results showed a positive correlation (p < 0.001) between the centrifugation and standard methods, considering that the centrifugation time required for moisture stabilization varied according to the material analyzed and the tension applied. However, the time required to obtain a report was reduced by half. Sample centrifugation is a promising method, ensuring that the tensile force actually acts on the entire sample to determine the water retention curve of the substrate also reducing the duration of the analyses.
Highlights
Substrates are important in seedling production; experiments using new components and studies of analysis methods have been carried out for decades
Sample centrifugation is a promising method, ensuring that the tensile force acts on the entire sample to determine the water retention curve of the substrate reducing the duration of the analyses
According to the Brazilian legislation (Normative Instruction No 17 of May 21, 2007), the water retention curve (WRC) is determined by the Tension Table Method in which the volumetric humidity is obtained through the percentage of water retained at 10 hPa
Summary
Substrates are important in seedling production; experiments using new components and studies of analysis methods have been carried out for decades Many of these experiments provide information on physical characteristics (Verdonck et al, 1978; Fonteno et al, 1981; Bunt, 1983; Wallach et al, 1992; Wever and van Winkel, 2004; Caron et al, 2005; Fermino and Kämpf, 2005; Vence, 2012; Zorzeto et al, 2014). According to the Brazilian legislation (Normative Instruction No 17 of May 21, 2007), the water retention curve (WRC) is determined by the Tension Table Method in which the volumetric humidity is obtained through the percentage of water retained at 10 hPa. choosing substrates based on other characteristics that are not provided in this Normative Instruction is essential to support the choice for each demand, such as available and remaining water. This study proposed a method for physical characterization of substrates that is reproducible and easy to perform, allowing to determine the WRC in less time, improving routine procedures of laboratory analyses and reducing the time to obtain reports
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