Carbon dioxide flush as a soil health indicator in contrasting edaphoclimatic conditions

Developing a reliable soil health indicator (SHI) is essential for accurately assessing soil condition in the context of sustainable agriculture. However, current SHIs are often labor-intensive or insufficiently sensitive to management practices. We evaluated a 3-day aerobic incubation at 40 °C of re-wetted soil samples [i.e., carbon dioxide flush (F CO2 )] and its stratification ratio (SR FCO2 ) as potential SHIs. Under a wide range of edaphoclimatic conditions, we assessed: (i) their capacity to discriminate contrasting cropping systems (soybean monoculture, soybean–cover crop, and a complex rotation), and (ii) their association with edaphic variables. All differences and correlations were considered statistically significant at a p-value below 0.05. The F CO2 effectively differentiated soybean monoculture from more diverse cropping systems, particularly in the 0–5 cm soil layer. A stronger association of F CO2 with cropping intensity was observed (R 2 = 0.60 at 0–5 cm; R 2 = 0.42 at 0–20 cm) than for SR FCO2 (R 2 = 0.18). Unlike SR FCO2 , F CO2 correlated strongly with most of the evaluated biochemical (r = 0.43–0.80) and biological (r = 0.28–0.57) properties across all sampled layers; with some physical properties such as aggregate stability (r = 0.67–0.78), clay content (r = 0.19 at 0–5 cm), and bulk density (r = –0.37 to –0.33); and with selected chemical properties, including inorganic phosphorus (r = –0.40) and extractable phosphorus (r = –0.46). Overall, F CO2 at 0–5 cm is a sensitive, low-cost indicator that responds to management intensity and is linked to key soil functions. We recommend its use as a robust SHI for monitoring soil degradation and guiding sustainable agricultural practices across contrasting edaphoclimatic conditions.