Measuring soil water retention capacity by centrifugation: a reliable method that is fast and easy to set up in the laboratory

Abstract

The soil water retention capacity is used for practical applications in agriculture (irrigation), but also in research (e.g., modeling of water flow and solutes transport drought). It depends on the relationship between water content and the soil matrix pressure (or pF) which can be measured in the field or at the laboratory. Curves are established with specific points, such as the permanent wilting point (pF 4.2). The laboratory reference method is based on the use of the pressure plate method. The method described in this article is a miniaturization of an alternative method by centrifugation with equipment present in most of laboratories. We supply the calculations allowing to adapt the method according to the type of centrifuge and the height of studied soil column. We tested this alternative method on a panel of 25 soils with contrasting textures and focusing on a specific key point of soil water retention (pF 4.2). The results produced by the miniaturized centrifugation method are linearly correlated with those of the reference method. The linear model explains 94% of the variability for a range of soils with contrasting water retention capacities at the point of wilting [1.34% - 64.15%]. These results suggest that the method for determining the water retention characteristic of soils proposed by this study is reliable. We have also estimated that the optimum centrifugation time is 10 minutes. The scope of use of this method is discussed.