Spatial and temporal variability of soil moisture in the semiarid area of the Duero basin (Spain)

Abstract

The aim of the present work is to determine the physical and hydrodynamic properties of the soils and the factors that govern the spatial and temporal variability of soil moisture in the semiarid sector of the Duero basin (Spain). To accomplish this, we used a soil moisture-measuring network, with 20 stations, each endowed with 4 TDR (Time Domain Reflectometry) probes inserted at different depths. At each of the soil moisture sampling points we determined the texture, bulk density, organic matter content and the water retention curve. The study period lasted 21 months, during which contrasted climatic situations were recorded. The results show that the textural fraction is the main variable accounting for the patterns of spatial soil moisture distribution over time. Its effect is direct on i) the water retention capacity of the soils, with an amount of plant available water ranging between 6.5 and 8.9 % vol.; ii) the spatial variability of the soil moisture throughout the area, and iii) soil moisture distribution along the profile. Finally, an outstanding aspect is the considerable effect of the organic matter, despite its low contents, on the water retention capacity of the soils studied.