Greenhouse gas fluxes in different yerba mate cultivation systems

Addressing climate change, which is marked by shifts in historical meteorological patterns, is one of the greatest challenges facing humanity today. In this context, yerba mate is a promising crop with significant potential to function as a decarbonizing agricultural system. The present study aimed to evaluate greenhouse gas (GHG) fluxes in yerba mate production systems. For this purpose, an agricultural property located in the municipality of Ilópolis, in the state of Rio Grande do Sul, Brazil, was selected. The fluxes of CO2, CH4, and N2O were measured in a native forest, used as a reference system, and in two yerba mate production systems: full sun and shaded. The full sun system is characterized by the production of yerba mate in monoculture, with the soil covered only by spontaneous vegetation in the space between plants. The shaded system consists of growing yerba mate among larger trees, which provide shade. In this case, the yerba mate is grown among araucaria trees. Between August 2024 and February 2025, monthly measurements of GHG fluxes were made using a portable FTIR gas analyzer Gasmet DX4015. The analyses were performed in four replicates, and the data were analyzed using repeated measures ANOVA and Tukey's multiple comparison test. Throughout the seven-month study, CO2 flux varied across treatments and seasons. The average flux was significantly higher in the native forest, with the lowest CO2 flux recorded in August 2024, showing no significant differences in the other seasons of the year. All treatments acted as CH4 sinks, with the native forest exhibiting the highest uptake. Comparing different evaluation seasons, the highest CH4 influx was recorded in August, while the lowest occurred in October 2024. On average, N2O flux showed no significant differences between treatments. The highest flux was recorded in October 2024, with no significant variations across other seasons. Based on the average fluxes recorded during the evaluation period, the estimated global warming potential (GWP) was 0.42 Mg CO2e ha⁻¹ year⁻¹ for the native forest, 0.22 Mg CO2e ha⁻¹ year⁻¹ for yerba mate in full sun, and 0.18 Mg CO2e ha⁻¹ year⁻¹ for shaded yerba mate. These results highlight the decarbonizing potential of yerba mate cultivation, particularly in shaded systems. In addition to its low GWP, the shaded system sequesters significant amounts of carbon in plant biomass, litter, and soil, aided by the presence of companion trees.