Geostatistics and Sample Density of Chemical Attributes for Soil under Sugarcane and Agroforestry in Humaitá – AM, Brazil

Abstract

There is a lack of studies focusing on spatial variance of chemical attributes in Amazonas, Brazil. The objective of this study was to evaluate geo-statistics and sample density of chemical attributes in soils under sugarcane and agroforestry, Humaitá, Amazon state, Brazil. The research was carried out in the municipality of Humaitá, Amazon state, the areas were in meshes of 70 m x 70 m regularly spaced by 10 m, with 64 points per area, and then soil samples were collected in layers of 0.0-0.2 m and 0.4-0.6 m. We performed chemical analyses of the proprieties of soil. Then, it was applied descriptive statistics, geo-statistics and sample density techniques based on semivariogram coefficient of variation and range. As a result, we observed spatial dependence for most of the chemical proprieties in the two areas. Based on Cline, sugarcane presented a sample density of 237 (0.0-0.2 m) and 225 (0.4-0.6 m); and agroforestry had 356 (0.0-0.2 m) and 465 (0.4-0.6 m) points per hectare. Yet in the range sample density, sugarcane showed 30 (0.0-0.2 m) and 5 (0.4-0.6 m), whereas agroforestry areas had 23 (0.0-0.2 m) and 9 (0.4-0.6 m) points per ha.