How does soil type and chemistry affect glomalin-related soil protein accumulation?

Introduction Glomalin-related soil protein (GRSP) serves as a critical indicator of soil health, reflecting particularly microbial activity and soil aggregate stability. Despite the known effects of management practices for GRSP accumulation, the role of soil properties remains under-researched. Methods This study aimed to evaluate how soil chemical properties and soil type influence GRSP accumulation across a diverse range of soils in the Czech Republic, including fields representing arable land with very similar (conventional) management and crop rotation structures. Results No direct significant effect of soil type on GRSP content was observed. Nevertheless, distinct GRSP associations with specific soil properties were identified across different soil type groups. Marked differences were noted in the relationships between GRSP and cation exchange capacity (CEC), calcium content (Ca), and pH. Positive correlations between these parameters and GRSP were identified in luvisols, regosols, stagnosols, and podzols, while negative correlations were detected in chernozems, vertisols, calcisols, and phaeozems. Similar patterns were observed related to climatic regions, with positive correlations in moderately warm regions and negative correlations in very warm regions. In contrast, GRSP exhibited a positive correlation with soil organic carbon (SOC) and the humic-to-fulvic acid (HA/FA) ratio across all soil types and almost all climatic regions. The variability in the relationships among CEC, Ca, pH, and GRSP is attributed to a nonlinear peak relationship, indicating that GRSP accumulates at specific CEC, Ca, and pH ranges. The highest accuracy of GRSP prediction was achieved with Ca and CEC, at 43% and 37%, respectively, whereas for linear relationships with HA/FA or SOC, it was only 26% and 10%, respectively. Discussion Overall, our findings show that integrating linear and nonlinear predictors enables reliable estimation of GRSP accumulation potential across contrasting soil environments, thereby providing a practical tool for identifying soil conditions that support higher GRSP levels and, consequently, greater soil quality and aggregation potential.