Evolution of soil organic carbon during a chronosequence of transformation from cacao (Theobroma cacao L.) plantation to grassland

Abstract

The aim of this research was to evaluate the impact of the soil use change of the Cocoa Agroforestry System (CAS) on soil organic carbon (SOC) levels and other indicating soil chemical fertility properties (edaphic density ρb, cation exchange capacity CEC, soil total nitrogen STN), when a soil use change occurs from CAS to grassland (GL). For this, in order to be selected was recorded, considering different time intervals (1-5, 6-10 y 11-20 years). However, a CAS of 20-35 years was considered as a reference. In addition, soil samples were taken at -30 cm depth to determine the contents of SOC, STN, CEC, ρb, soil organic matter (SOM) and the soil C/N ratio. Consequently, the soil penetration resistance was evaluated in situ. The results indicated the change in soil use from CAS to GL, did not cause a significant decrease in the amount of stored SOC (0-30 cm) during the considered time with respect to CAS. However, if only the first -10 cm of soil is sampled, a significant soil compaction is observed throughout a decrease in the CEC value in the long term (20 years).