Impact of short-term land-use change on soil organic carbon dynamics in transitional agro-ecosystems: a case study in the Brazilian Cerrado

Agricultural expansion directly impacts the dynamics of organic carbon (C) in the soil. After land use change, agricultural systems with greater resilience of soil C stocks could be preferentially adopted. The objective of the present study was to determine the impact of short-term conversion of grassland into different agricultural systems on soil organic C stocks and their resilience in a site-specific region of Brazilian Cerrado in the State of Goias. The following systems were evaluated: pasture (PAST), no-tillage system (NT), four organic production systems (ORG) at different years of cultivation (2, 6, 8 and 10 years), and a continuous monoculture corn cropping system (CC). An area of native Cerrado ('Savanna', CE) was selected and sampled for use as a steady state reference point. Resilience of soil organic C was measured based on calculation of the C resilience index and C management index. Soil C stocks in the 0-0.40 m depth varied from 61 to 111 Mg ha(-1) and were reduced by 33% when converting from CE to cultivation regardless of management system. The labile C contents varied from 425 to 900 mg kg(-1), and increased when PAST soils were converted to ORG cultivation. The highest values of C resilience and management indexes occurred in the ORG-2 and ORG-6 soils, showing that organic systems can recover organic C levels in the soil faster than other agricultural systems. On the other hand, no-tillage system when converted from pasture presents the lowest potential of soil C resilience in short-term in the site-specific conditions of studied Cerrado of Goias State.