Cocoa Rehabilitation Improves Soil Carbon and Nutrient Cycling

Cocoa production is essential to the economy of many countries but is confronted with key challenges, including soil degradation through long-term fertility decline and viral disease severity. Mostly, these issues are addressed through removal of diseased trees and replanting of improved cocoa varieties, accompanied by minimal soil management. However, the impact of the rehabilitation on soil organic carbon (SOC) and nutrient cycling remains poorly understood. This study evaluated partitioning of bulk soil carbon into the persistent mineral associated organic carbon pool (MAOC) and particulate organic carbon (POC) in rehabilitated and non-rehabilitated cocoa farms in tropical climate. It also assessed the extent to which rehabilitation influence soil nutrient stocks.  Soil sampling was stratified up to a depth of 45 cm in four sub-plots each measuring 20 ´ 20 m per farm type. Notably, at 15–30 cm depth, rehabilitated farms exhibited a 14% increase in the stable MAOC pool and a 31% reduction in the labile POC pool, indicating a shift toward long-term carbon sequestration in the subsoil. At 0–15 cm depth, bulk SOC and nitrogen stocks increased by 18% (42.37 Mg ha⁻¹) and 15% respectively in rehabilitated farms relative to non-rehabilitated farms. Topsoil of rehabilitated farms increased significantly in available phosphorus concentration (p=0.03) and effective cation exchange capacity (p=0.001). Correlation analyses revealed stronger relationships between SOC pools and nutrient availability in rehabilitated farms, indicative of soil improvement. The study provides valuable insights into carbon and nutrient cycling in cocoa rehabilitation scheme with implications for long-term productivity and ecosystem sustainability.