Spatial Variability of Soil Properties in Archeological Dark Earth Sites under Cacao Cultivation

Abstract

ABSTRACT:Soils with an A horizon formed by human activity, an anthropogenic A horizon, are found in the Amazon Region. Few studies have examined the spatial distribution of the properties of these soils. We mapped the spatial variability of some soil properties in an area of Archaeological Dark Earth (ADE) in the Brazilian Amazon. A sampling grid was defined over an area of 42 × 88 m under cacao cultivation in which sampling points were established at a spacing of 6 × 8 m, for a total of 88 points. Samples were collected from the 0.00-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30 m depth layers. Soil texture, aggregate stability, and organic carbon (OC) analyses were performed on disturbed soil samples. Undisturbed samples were used to determine soil macroporosity (Macro), microporosity (Micro), total porosity (TP), and soil resistance to penetration (RP). The results were analyzed by descriptive statistic, Pearson correlation (p<0.01), and geostatistics. Soil bulk density, total pore volume, and geometric mean diameter are dependent on the total amount of OC in the ADE area. Increased soil bulk density and RP are proportional to a decrease in OC content and lower Micro and TP. Moreover, soil resistance to penetration is influenced by soil water and clay content with depth.

Spatial variability of aggregates and organic carbon under three different uses of indian black earth in southern Amazonas

“…At the three soil uses both Mean Weight Diameter (MWD) and aggregates class > 2.00 mm, obtained the highest values and they did not differ statistically at 0.0-0.05 m, evidencing few influence in this attributes influence. However, the decreased of MWD and aggregates > 2.00 mm at 0.10-0.20 mm was due to the smaller amount of CO, given that the magroaggregates genesis is closely associated to the CO content, mainly up to a 0.05-0.20 m depth (Garcia et al, 2010;Oliveira et al, 2015;Silva et al, 2016).…”

Spatial variability and sampling density of chemical attributes in archaeological black earths under pasture in southern Amazonas, Brazil

“…Chemical quality of ABEs has been an attraction for agricultural exploitation in the Amazon (Silva et al, 2016). However, the lack of detailed studies on these earths is a barrier to the development of precision agriculture (Gomes et al, 2017).…”

“…In the Amazonas State, some studies such as those of Campos et al (2012) have been a pioneer in characterizing the spatial variability of soil chemical and physical attributes, as well as have served as a reference for conducting other investigations on this subject. Many of these studies have revealed the potential of ABEs for agricultural purposes (Silva et al, 2016;Gomes et al, 2017;Brito et al, 2018). However, many of these researchers have warned that an adequate ABE management has altered their natural and desirable chemical properties.…”