Spatio-temporal variability of soil water tension in a tropical soil in Brazil

Soil water tension was measured 22 times through a 50 day period, in a transect with 48 sets of tensiometers at five depths. General variability and temporal stability of this property as well as the spatio-temporal dependence of its variability were evaluated. The whole data set was divided into subsets according to location and time of measurement. The variability of soil water tension could be explained by a temporal trend (macro variation) and a random-like micro-variation. The tension values increased similarly for all locations along the measured period, and exhibited strong temporal stability, which was higher at the top layers. It was possible to identify and model spatio-temporal dependence of the variability. The spatial variograms for the sub-sets presented higher uncertainties, but were very similar to each other. Temporal dependence was clearly identified for transformed data, although larger differences were found between sub-sets. Very good agreement was found between the actual and the estimated data using the product–sum model for the spatio-temporal dependence. The procedure seems suitable for combining the spatial and temporal scales to expand the description of the variability dependence of soil hydraulic properties.