Microbial efficiency and seasonal sensitivity as early indicators of soil health recovery under regenerative management

Regenerative agriculture (RA) aims to restore soil health by increasing ground cover, reducing disturbance, enhancing biodiversity, maintaining living roots, and integrating livestock. This study assessed the effects of RA adoption on soil organic matter (SOM) and biological indicators in a commercial beef cattle system in Mato Grosso, Brazil. Three land uses were compared: regenerative integrated crop–livestock systems (RA), permanent pasture, and native forest as a reference. Soils were sampled at 0–5, 5–15, and 15–30 cm during the dry (August 2024) and wet (November 2024) seasons to determine soil organic carbon (SOC), total nitrogen (TN), enzyme activities, microbial biomass, and community composition. Microbial efficiency was evaluated using the microbial quotient (qMic), and stable carbon isotopes (δ¹³C) were analyzed in soils and roots up to 210 cm. Microbial biomass and qMic exhibited significant land use × season interactions (p < 0.05). During the dry season, both were lower under RA than under pasture and forest, but in the wet season, RA values matched forest and exceeded pasture up to 15 cm. Enzyme activity responses were limited; β-glucosidase showed a significant interaction only at 0–5 cm, where forest activity was 38% lower than in pasture and RA. The forest had the greatest SOM, SOC, and TN across depths, while RA showed intermediate values. Strong correlations occurred between qMic and microbial biomass (>0.70), whereas enzyme activities correlated weakly. δ¹³C revealed deeper C₄-derived carbon under RA, suggesting that microbial indicators may detect early soil health recovery before SOM increases.