LAUSR

Abstract Landscapes are intrinsically related to spatial soil variability. Understanding soil chemical fertility based on topographic parameters is essential to ensuring sustainable agronomic management through the rational use of inputs. The aim of this study was to perform a comprehensive assessment of soil organic matter (OM), pH, sum of bases (SB) and cation exchange capacity (CEC) according to topographic parameters, with the goal of identifying spatial patterns and better understanding the relationship between them to capture the soil variability in sugarcane fields. A soil dataset from nine sugarcane experimental fields was evaluated. Approximately 3000 soil samples collected between 2008 and 2017 were evaluated. The topographic parameters of vertical and horizontal curvatures were related to the variability in the soil attributes. The results showed that the horizontal morphometric classes (HConv, HPlan and HDiv) associated with vertical concave areas (VConc) presented higher levels of OM, SB and CEC, which indicated that these areas have higher soil chemical fertility. The VConcHDiv showed the highest soil chemical fertility; regardless of site, topographic level and inherent soil fertility. For all vertical morphometric classes (VConc, VRet and VConv), soil pH levels were higher in horizontal divergent areas (HDiv) and lower in convergent areas (HConv), suggesting that stricter soil acidity management was needed in the HConv areas. The VConvHConv areas, where lower soil chemical fertility was observed, should be sampled with greater accuracy for adequate spatial soil characterization because it had a higher coefficient of variation (CV) than the other morphometric classes. The results showed that the detected spatial patterns were temporally stable. With high spatial and temporal stability, topographic parameters could be excellent sources of economically feasible and easily assessed information to support farmers in soil chemical fertility characterization. Finally, topographic attributes proved to be an excellent source about soil spatial variability for farmers to use in their fields aiming a site-specific management or an additional layer of data for management zones delineation.