Soil health indicator variability and management sensitivity across soils, bioregions, and agricultural systems

Soil health indicators inherently vary across soils and landscapes due to soil-forming factors unrelated to land management and thus should be interpreted in pedogenic-specific contexts. Dynamic Soil Properties for Soil Health (DSP4SH) is a nationwide effort organized by United States Department of Agriculture - Natural Resources Conservation Service to evaluate the inclusion of soil health indicators in soil survey mapping products. Twelve chemical, biological, and physical soil health indicators were measured with consistent methodologies across a wide range of soil types, bioregions, and agricultural production systems. We found significant variability in soil health indicators corresponding with soil taxonomic suborder, supporting the importance of context-specific soil health benchmarks. Relative values of all soil health indicators differed significantly between perennial reference ecosystems and agricultural systems, and about half of the indicators examined (soil organic carbon, autoclaved-citrate extractable [ACE] protein, permanganate-oxidizable carbon, β-glucosidase activity, and arylsulfatase activity), were also significantly higher in soil health management agricultural systems compared to conventional agricultural systems. Aggregate stability, soil respiration, and enzyme activities exhibited the most variability between project locations. We found that ACE protein was highly sensitive to management and strongly correlated with soil organic carbon and warrants further investigation as a soil health indicator. Surprisingly, arylsulfatase activity exhibited the largest overall effect size, as well as greater observed management sensitivity in warmer, drier sites. However, additional research into method replicability and interpretation is needed for either metric to be suitable for soil survey adoption.