Soil health assessment using SOHMA KIT® reveals contrasting carbon responses across soil textures

Regenerative practices are strategies to improve soil health and enhance the resilience of agricultural systems to climate change. However, quantifying their effects under field conditions remains challenging. The objective of this study was to evaluate soil health using the KITSOHMA® and its relationship with soil carbon across environments with contrasting textures. The study was conducted in a subtropical region of Brazil, including one sandy-soil farm (Pinhal Grande, RS) and two clayey-soil farms (Coxilha, RS and Imbituva, PR), all under no-tillage systems. The traditional soybean/wheat succession was compared with regenerative practices, as well as with native vegetation, and the relationship between the soil health index and carbon stock was assessed using Spearman’s correlation. In the sandy soil, regenerative practices promoted a 24% increase in soil health compared to the traditional management, mainly associated with improvements in physical and chemical components. In this environment, soil health showed strong correlations with chemical (ρ=0.85) and physical (ρ=0.55) components, while the correlation with carbon stock was weak (ρ=−0.10), indicating that the index captures functional changes prior to increases in soil carbon. In clayey soils, variation in soil health among managements was moderate, with a 4% increase in the index. However, a strong positive correlation between soil health and carbon stock was observed (ρ=0.70), highlighting the integration of soil attributes with organic matter stabilization processes. These results indicate that KITSOHMA® effectively assess soil processes associated with carbon stabilization, showing greater sensitivity as a functional indicator in sandy soils and stronger association with carbon in clayey soils.