Storage and physical fractionation of organic carbon in different phytophysiognomies in the cerrado in the West of Bahia, Brazil

The Western Bahia region is one of the country's agricultural frontiers with the capacity to expand without harming the environment. The aim of this work was to evaluate the total carbon stock and the physical fractions of the organic matter of the soils under different phytophysiognomies of the Cerrado of the West of Bahia. The soils of the studied vegetation types were classified, according to Embrapa (2018) as dystrophic Red-Yellow Latosol (LVAd), (Oxisols), Orthic Quartzarenic Neosol (RQo), (Quartzipsamments) and Haplic Gleysol (GX), (Entisols). In each of the areas, trenches were randomly opened at four points at depths of 0.0-0.10 and 0.10-0.20 m. The total organic carbon (TOC) content was quantified by humic oxidation of organic matter (OM) with potassium dichromate in sulfuric acid. The values ranged in the superficial layer (0.00 to 0.10 m) for the TOC from 4.42 ± 0.22, in the cerrado clean field (CCL) to 48.25 ± 0.14 g kg-1. In the footpath (VRD), for particulate carbon (OCp) the variation was from 0.54 ± 0.36 in the cerrado stricto sensu (CSS) to 20.78 ± 0.80 g kg-1 in the VRD and for carbon associated with mineral fraction (OCam) it varied from 3.07 ± 0.27 in the CCL to 24.34 ± 0.50 g kg-1 in the VRD. The soils under different phytophysiognomies in the cerrado have different levels of TOC, (OCp), OCam and differ, depending on the granulometry and density of trees.