Soil water diffusivity: A simple laboratory method for its determination

Soil water diffusivity (D) is an important hydraulic property that is fundamental to characterize unsaturated water transport. Its determination is complex, time-consuming and requires expensive instruments. The objectives of this work were: to propose a simple and low-cost laboratory methodology to determine D function; and to analyze the influence of soil management systems on D and Sorptivity (S). The studied soil was classified as a vertic Paleudol. The first 10 cm of the soil under three different management systems (T1: Natural grassland, T2: direct drilling, and T3: Polyphitic Pasture) was sampled. The samples were sieved and packed into horizontal columns. The columns were analyzed under horizontal infiltration and D was determined by variations of water content as a function of time for fixed positions, obtained from low-cost soil moisture capacitance sensors. The results showed that the proposed methodology is valid in the studied soils. Soil management system significantly affected D and S. They were greater for T2 compared with T1 and T3 (D varied between 0.00033 and 0.0321 cm(2).s(-1)). This means that the soil under T2 can transmit water faster under non-saturated conditions as compared with the soil under grazing. In conclusion, the proposed methodology allowed to determine D in a simple and low-cost way, and to determine the influence of these properties on productive conditions.