Spatial variation of chemical attributes in archaeological dark earth under cocoa cultivation in Western Amazon

Abstract

Archeological Dark Earths (ADEs) are fertility soils that are notoriously superior to the vast majority of soils typical of the Amazon region. The study on ADEs has intensified due to the good characteristics presented by these soils, such as high concentration of nutrients (phosphorus, calcium, magnesium). In this sense, the aim of this study was to evaluate the spatial distribution of soil chemical attributes in an area of black archeological earth soil under cocoa cultivation in the municipality of Apuí (AM). The mapping of a 42 x 88 m mesh, with irregular spacing of 6 x 8 m, totaling 88 points, was carried out, and then soil samples were collected at depths of 0.0-0.05; 0.05-0.10; (pH, O.C, Sto C, (H+Al), P, K, Ca, Mg, SB, CEC and V%). Data were analyzed using descriptive and geostatistical statistics techniques. The mean and median values were adjusted to the near values, indicating normal distribution, while the soil chemical attributes were adjusted to the spherical and exponential semivariograms models. The majority of the attributes presented coefficient of variation (CV) between 12.1 and 60%, characterized as average variability, the variables in the study presented different ranges and most of them had a strong spatial dependence. The geostatistical techniques used allowed the adjustments of the theoretical models that best represented the experimental semivariance, thus enabling the construction of thematic maps of the spatial distribution of the values of the attributes of the studied area.