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 ρ b , 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).Key words: Soil use change, edaphic apparent density, soil fertility, soil organic matter, edaphic C/N relationship. ResumenEl objetivo de esta investigación fue evaluar el impacto del cambio de uso de suelo del Sistema Agroforestal de Cacao (SAFC) sobre los niveles de Carbono Orgánico del Suelo (COS) y otras propiedades indicadoras de la fertilidad edáfica (densidad aparente ρ b , capacidad de intercambio catiónico CIC, N total del suelo NTS), cuando se produce un cambio de uso de suelo de SAFC a pastizal (PZ). Para ello, se seleccionaron sitios donde se registró este cambio de uso del suelo, considerando diferentes intervalos de tiempo (1-5, 6-10 y 11-20 años). Como referencia se consideró un SAFC de 20-35 años. Adicionalmente, se tomaron muestras de suelo a -30 cm de profundidad para determinar los contenidos de COS, NTS, CIC, ρ b , materia orgánica del suelo (MOS) y la relación C/N edáfica. Consecuentemente, se evaluó la resistencia a la penetración del suelo in situ. Los resultados indicaron que el cambio de uso de suelo SAFC a PZ, no ocasionó una disminución significativa de la cantidad de COS almacenado (0-30 cm) durante el tiempo considerado respecto al SAFC. Sin embargo, si sólo se muestrean los -10 cm primeros del suelo, se observa una significativa compactación edáfica, junto con una caída del valor de la CIC a largo plazo (20 años).Palabras clave: Cambio de uso de suelo, densidad aparente edáfica, fertilidad del suelo, materia orgánica del suelo, relación C/N edáfica.

Impact on the soil and the infiltration as a consequence of oil palm cultivation (Elaeis guineensis jacq) in Tabasco

“…In some soil use changes -for example, agroforestry systems deforested to set up grasslands-, SOM increases during the first years after the change; afterwards, the effect fades away. Salvador-Morales et al (2017) point out that the low carbon-to-nitrogen ratio of the waste that becomes part of the soil is responsible for this situation: at a 12-15 ratio, waste decomposes at a fast pace, releasing nutrients and non-mineralized remainders. This remainder accumulates low SOM quantities which become part of the soil; however, waste with high carbon-to-nitrogen ratios (18-24) causes decomposition to take place at a slower pace and higher MOS content tends to accumulate.…”