Spatial variability of soil physical and hydraulic properties in the southern Brazil small watershed

摘要

In order to provide an adequate usage to agricultural soils it is crucial to comprehend the soil physical attributes and their spatial variability. The variability of soil attributes is dependent on several formation processes and interactions. To properly describe such complex variability, the statistical methods used must incorporate the spatial and temporal influences. In this context, the present study was developed with the objective of evaluating the spatial variability of physical and hydraulic soil attributes, such as sand, clay and silt contents, soil macroporosity (Ma), soil microporosity (Mi), soil total porosity (TP), soil bulk density (BD), hydraulic conductivity (K), water contents at field capacity (tension of 10 kPa) and permanent wilting point (tension of 1500 kPa) (θFc and θPWP), in a watershed, located in the Sul-Rio-Grandense Shield, in the South of Brazil, through the geoestatistics analysis based on Ordinary Kriging. It was found a better performance of exponential model for the semivariograms of most physical and hydraulic soil attribute in the 0-0.15 and 0.15 to 0.25 m layers. Spatial dependence was observed for all the soil physical and hydraulic attributes studied, classifying as high for the variables macroporosity (0 to 0.15 m) and clay (0.15 to 0.25 m), with the other variables classified as moderate spatial dependence. Besides, the variables K and macroporosity presented a high heterogeneity in relation to the average, with K in the surface layer and the variables clay, Ma, K and qPWP in the subsurface layer not presenting normality according to Shapiro and Wilk test (p ≤ 0.05).