Scaled Semivariogram in the Sample Planning of Soils Cultivated With Sugarcane

Sugarcane cultivation has expanded in areas previously occupied by degraded pastures. In the first years of cultivation, besides the physical and chemical restrictions of the soils, other factors can make impossible the maximum productive expression of the crop, like the climatic and edaphic factors. The objective of this work was to evaluate the ideal sampling density and spatial variability of the physical and chemical attributes of soils cultivated with sugarcane. Georeferenced data provided by the Sugarcane Technology Center (STC) of an area of approximately 19,000 hectares located in the northwest region of São Paulo were evaluated. The granulometric fractions of the soils and organic matter contents and base saturation were determined at depths of 0.00-0.25 and 0.25-0.50 m. An index named edaphic environment (ENV) was calculated based on the records of rainfall of the areas and the productivity of the sugarcane, being represented with aptitude scores ranging from 0 (worst condition) to 10 (best condition). The results showed a strong correlation between clay and organic matter attributes with ENV index. Regions with aptitude ≥ 6.65 of ENV index corresponded to sites with clay (CL) and organic matter (OM) content above 335 g kg-1 and 30 g kg-3, respectively. Only 10.86% of the area presented base saturation (V%) concentration ≥ 68%, correlating positively with CL and ENV. Through the scaled semivariogram it was possible to verify that a density of sampling of a sample to each 18 ha can be used for a mapping in macroscale of the evaluated attributes in the northwest region of the state of São Paulo.