Greenhouse gas emissions from cocoa production systems in the Atlantic Forest, southern Bahia, Brazil

Abstract

This study aimed to characterize greenhouse gas (GHG) fluxes in different cocoa production systems and correlate them with soil quality attributes in the Atlantic Forest biome. The research was conducted in the experimental area of the Executive Commission of the Cocoa Farming Plan (CEPLAC) in Ilhéus, Bahia, Brazil. The land-use systems analyzed were full-sun cocoa with Fabaceae cover crops (CFs); full-sun cocoa with Urochloa decumbens cover crops (CBs); full-sun cocoa with spontaneous vegetation cover (CVE); an agroforestry cocoa system of the cabruca type (SAFCAB); an agroforestry cocoa system with rubber trees (SAFSE); and a natural forest (FOREST). GHG flux monitoring was carried out twice in 2022 using the static chamber method. The chambers were constructed from plastic buckets, and the internal volume of each chamber was previously measured to enable the calculation of gas fluxes. Soil samples were collected at 0–0.10 m depth for the analysis of ammonium (NH 4 + ), nitrate (NO 3 − ), soil bulk density, soil moisture, and water-filled pore space (WFPS). Gas samples were collected using a manual vacuum sampling pump, and the gas was transferred to storage vials and subsequently transported to the laboratory, where GHG concentrations were determined by gas chromatography. Negative CH 4 fluxes were recorded in the CF, CVE, and SAFCAB systems during the high-rainfall period, with mean values of − 4.08, − 0.98, and − 5.98 mg m −2 h −1 , respectively. The forest showed a positive flux of 6.50 mg m −2 h −1 . Regarding CO 2 , SAFCAB and the forest presented the highest mean fluxes, 1.13 and 0.70 g m −2 h −1 . CVE showed the lowest value, 0.49 g m −2 h −1 . All cultivated systems emitted N 2 . O into the atmosphere, with no evidence of gas uptake. Among the agroforestry systems, SAFSE presented the lowest GHG fluxes, while SAFCAB showed unexpectedly elevated CO 2 emissions attributed to litter accumulation and microclimatic conditions favorable to organic matter decomposition. These findings provide new insights into how cocoa management systems influence soil GHG dynamics and highlight the contrasting environmental profiles of different agroforestry arrangements in tropical cocoa landscapes.

Bibliographic Information