Efeitos da sistematização nos atributos físico-hídricos em solo de Terras Baixas, avaliados por meio de ferramentas de estatística clássica e de geoestatística

Abstract

The irrigated rice has been cultivated in lowland soils of Southern Brazil under land levelling and flood irrigation conditions. Few studies have focused on the effect of land levelling operations on retention characteristics and water availability of lowland soils, mainly under anaerobic conditions. The objective of this work was to evaluate the effect of land levelling on the magnitude of the hydro-physical lowland soil properties related to retention characteristics and water availability in the 0-0.20 m layer and on their spatial variability structure as well. The work was carried out in a 1.0 ha experimental area, belonging to Embrapa Temperate Climate, Capão do Leão, Rio Grande do Sul state, Brazil. A regular grid of 100 points, spaced 10 m apart from each other at both directions, was established. At each point, preserved and no-preserved soil samples were collected in the 0-0.20 m layer, before and after three months of land levelling operations, to determine contents of clay and sand, macro and microporosity, soil density and the experimental soil water retention curve. Each experimental soil water retention curve was adjusted to the van Genuchten's model (1980), obtaining s, r,  and n parameters. In order to evaluate the effects of land levelling on soil hydro-physical properties, all datasets were submitted to descriptive statistics and geostatistics tools. The Spearman correlation coefficient was used to evaluate the effects of land levelling on the linear correlation between s, r,  and n parameters and each soil physical property. Land levelling operations altered the statistical descriptive measures of position, dispersion and format of each data set as well as the spatial variability structure of all studied soil hydro-physical properties. Spearman correlation coefficient values and signals were affected by land levelling operations in the topsoil properties of the experimental area.