Dissertations and Theses

Summary

Relief forms can be used as indicators of variability of soil attributes since this variability is caused by small slope alterations that affect pedogenetic processes such as the transport and storage of water in the soil. This work was developed at Catanduva (SP) and aimed to characterize the spatial variability of soil attributes and erosion factors in different landforms where sugarcane has been cropped. Relief forms were characterized as concave and convex according to the model of Troeh. Altimetric measurements were taken and a grid with regular intervals of 50 m was projected on the area. Two hundred seventy grid points were placed in the concave landform and 353 points in the convex landform, totaling 623 points. Soil was sampled at the depth of 0.0-0.2 m in an area of 200 ha. Soil chemical attributes, particle-size distribution, soil thickness and local erosion factors, such as erosivity (R), erodibility (K), relief (LS), use and management (C), conservation practices (P), natural potential of erosion (PNE), soil erosion (A) and erosion risk (RE), were measured. The results were firstly evaluated by exploratory statistical analysis, calculating average, median, variance, variation coefficient, kurtosis coefficient, skew coefficient and normality test. Subsequently, spatial dependence was verified through semivariograms. The greatest soil loss, erosion risk and natural erosion potential and minor soil thickness occurred in the convex landform, indicating strong spatial dependence on the relief form. The concave landform presented greater spatial variability, demonstrating that the relief form conditions differentiated standards of variability. The magnitude of the variability of the soil attributes is more affected by the relief forms than by erosion. The thickness of A+E horizon integrated with relief form is an indicator of erosion processes for Argissolos (argillic-B horizon soils).