Physical fractionation of organic carbon in areas under different land uses in the Cerrado

Adilson A Costa,Charles C Santana,Thalita F Sampaio,Núbia Da Silva,Bruno De O Dias,Vânia Da S Fraga

doi:10.1590/1807-1929/agriambi.v24n8p534-540

Abstract

ABSTRACT With the expansion of agricultural production, native Cerrado areas are replaced with other forms of land use. Thus, the objective of this study was to evaluate changes in the physical fractionation of organic carbon (C) in areas under different forms of land use in the Cerrado. The treatments, with five repetitions, corresponded to the following forms of use: area under conventional tillage, area under pasture plantation, area under eucalyptus plantation and area under native Cerrado vegetation, at the depths of 0-5, 5-10, 10-15 and 15-20 cm in the municipality of Luis Eduardo Magalhães, BA, Brazil. The highest C contents and stocks were found in the eucalyptus area, which were equal to those of the area under native Cerrado vegetation, while particulate C stocks were higher in the area under pasture at the depth up to 10 cm, not differing from the area under native Cerrado. Pasture and eucalyptus had positive effect on C management index, regardless of depth.

Highlights

With the opening of new agricultural frontiers in the Cerrado, an area with great agricultural potential, the adoption of agroecosystems with crops, replacing natural ecosystems, has caused reduction in the content of soil organic carbon (OC), as a result of the decrease in the supply of organic matter (Frazão et al, 2010; Hickmann & Costa, 2012)
The highest C contents and stocks were found in the eucalyptus area, which were equal to those of the area under native Cerrado vegetation, while particulate C stocks were higher in the area under pasture at the depth up to 10 cm, not differing from the area under native Cerrado
The eucalyptus has been planted for nine years, and in this period there has been a production of biomass that is deposited on the soil, which increases the soil organic matter content and, leads to greater storage of total organic C (TOC)

Summary

Introduction

With the opening of new agricultural frontiers in the Cerrado, an area with great agricultural potential, the adoption of agroecosystems with crops, replacing natural ecosystems, has caused reduction in the content of soil organic carbon (OC), as a result of the decrease in the supply of organic matter (Frazão et al, 2010; Hickmann & Costa, 2012). The objective of this study was to evaluate the changes in the physical fractionation of organic C in areas under different soil uses in the Cerrado. In each mini profile, disturbed samples were collected using an auger at depths of 0-5, 5-10, 10-15 and 15-20 cm, air dried, pounded to break up clods and passed through a 2-mm-mesh sieve to obtain ADFE for the determination of physical fractionation. All the material retained on the sieve was transferred to a Petri dish and dried in an oven (50 oC) for 24 h After this step, the material was ground in porcelain mortar and the organic C content was determined according to the methodology of EMBRAPA (2017). Where: CSI - carbon stock index, calculated through the ratio between the C stocks of the areas with different forms of land

Results and Discussion

Conclusions

Literature Cited