Response of CO₂ and H₂O fluxes to the adoption of regenerative practices in Brazilian subtropical agroecosystems monitored by Eddy Covariance

Regenerative agriculture is recognized as a promising strategy for mitigating greenhouse gas emissions through the adoption of practices that improve soil quality and modulate biogeochemical cycles. Southern Brazil is characterized by a subtropical climate and intensive agricultural systems with a high potential for carbon sequestration. However, quantifying the effects of regenerative practices on CO₂ fluxes and defining reliable emission and uptake factors remain significant scientific challenges. This study presents multiyear time series of carbon dioxide (CO₂) fluxes and evapotranspiration (ET) obtained from eddy covariance flux towers installed in representative conventional and regenerative agricultural systems of the region, including wheat–soybean–maize succession, flooded rice cultivation, and cattle grazing on native grasslands of the Pampa biome. The regenerative practices evaluated included the introduction of cover crops during fallow periods, thereby eliminating bare-soil phases in the wheat–soybean–maize system. In rice systems, winter forage crops and summer rotation with soybean were implemented. In native grasslands, winter forage species were introduced without soil disturbance. The results consistently show that regenerative systems exhibit greater net CO₂ uptake across different agricultural years compared to conventional systems. Reducing fallow periods in the wheat–soybean–maize succession and introducing winter forages in native Pampa grasslands increased carbon uptake, making agroecosystems in southern Brazil important sinks of CO₂-eq. Flooded areas used for irrigated rice cultivation, although not becoming net CO₂-eq sinks with the introduction of soybean rotation or pasture, showed a substantial reduction in CO₂-eq emissions. Interannual analyses demonstrated that the magnitude of CO₂ and H₂O fluxes is strongly modulated by climatic variability, particularly differences in precipitation regimes, temperature, and crop cycle duration. These findings highlight the importance of continuous, long-term measurements to capture the uncertainty range associated with climate variability and agricultural management, thereby enabling the development of more robust and representative emission and uptake factors. Based on strong observational evidence, this study contributes to improving the scientific basis for assessing agroecosystem sustainability, supporting public policies, and advancing carbon certification mechanisms.