Soil health and management assessment kit (SOHMA KIT®): Development and validation for on-farm applications

Soil health is a foundation for long-term soil multifunctionality, sustaining crop yields and enhancing crop resilience to climate change. Nevertheless, soil health assessments are often complex, costly and time-consuming, which acts as a barrier to farmers adopting them. Thus, we hypothesized that a simplified, on-farm approach to evaluate soil health, composed by key indicators, could effectively detect changes in soil health across different land management systems. This study aimed to (i) validate the Soil Health and Management Assessment Kit (SOHMA KIT®) as a reliable tool for on-farm soil health assessment, (ii) compare its performance with standard laboratory methods, and (iii) assess its sensitivity for detecting soil health improvements induced by cover crops. The validation study was conducted in two long-term field experiments in the Brazilian savanna (Cerrado biome), where different cover crop systems were evaluated. After extensive work involving literature review, selection and development of methods, the SOHMA KIT® was created. The SOHMA KIT® integrates seven soil health indicators from physical (infiltration, aggregate stability, Visual Evaluation of Soil Structure - VESS), chemical (pH), and biological (catalase enzyme, macrofauna, biogenic aggregates) components into a Soil Health Index (SHI). In the validation tests, results showed that the SHI increased around 35 % in diversified cropping systems. Strong correlations between SOHMA KIT® and standard methods were observed for key indicators (e.g., infiltration: r = 0.71, aggregate stability: r = 0.40, pH: r = 0.88). Despite its portability and cost-effectiveness, the toolkit has some limitations, such as it is recommended that users have a basic training for assessing visual indicators, and the assessment is focused only on topsoil layers. However, the SOHMA KIT® is user-friendly and scalable, being a valuable tool for on-farm decision-making, regenerative agriculture, and large-scale soil health monitoring.