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

Abstract

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 0-0.40m depth varied from 61 to 111Mg ha1 and were reduced by 33% when converting from CE to cultivation regardless of management system. The labile C contents varied from 425 to 900mg kg1, 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.