Spatial variability analysis of physical attributes of subsurface soil in an area of no-till system with crop rotation

Brazil has been actively involved in promoting cooperation in food production, keeping up with advances in new technologies. However, the compaction of subsurface soil layers, caused by the "harrow foot" or "plow foot" phenomenon, negatively affects the development of plant roots and their ability to absorb nutrients. To evaluate this effect, a study was conducted in an area under a no-tillage system, at the São Paulo State University (FEPE) Farm. For this purpose, geostatistical tools and Principal Components Analysis (CPA) were used. Soil samples were collected from 60 points and the following attributes were analyzed: macroporosity (Ma m3 m-3), microporosity (Mi m3 m-3), determined total porosity (PTd m3 m-3), soil penetration resistance density (DS kg dm-3), soil penetration resistance with impact penetrometer (RPi MPa), soil penetration resistance with bench penetrometer (RPpb MPa), gravimetric moisture (UG kg kg-1), particle density (DP kg dm-3), calculated total porosity (PTc m3 m-3) at depth (0.20-0.40 m). For each attribute, a descriptive analysis was performed, aided by classical statistics and an analysis of the frequency distribution, using the Shapiro and Wilk test with 1 and 5% probability of error. Subsequently, the Pearson correlation matrix was performed to analyze the strongest correlations between the attributes and, subsequently, the CPA statistical analysis that took into account the influence of the physical attributes among themselves. The objective of this study was to analyze the spatial variability of physical attributes at subsurface depths and evaluate the impact of the "plow foot" in a dystrophic RED LATOSOL, under the no-tillage system (NTS).