Using Dynamic Soil Properties and Ecological Sites to set Soil Health Indicator Reference Conditions for Soil Survey

Abstract:

The Soil and Plant Science Division of NRCS is coordinating a project called Dynamic Soil Properties (DSPs) for Soil Health Assessment as part of a broader Science of Soil Health Initiative. The project consists of nine individual cooperative agreements with land grant universities (CA, KS, IL, MN, NC, OR, TX, WA, WI) that use common protocols and procedures to evaluate proposed soil health metrics. We will use the concept of ecological sites and state and transition models to assign reference values for soil health indicators including aggregate stability, active carbon, soil enzymatic activity (B-glucosidase), and microbial community structure assessed with the phospholipid fatty acids (PLFA) method. Given the spatial and temporal variation in properties, the difficulty collecting random and representative samples and the need to extrapolate results across regions – we will use conceptual models that are often employed in survey and mapping exercises. When possible, simple tests are used to test conceptual assumptions made. Results vary by property, soil and management systems evaluated. In general, the highest values for all properties were found in reference conditions with perennial vegetation. While there is variability across soils, there are generally few meaningful differences between the conventional and soil health management systems evaluated. The magnitude of biological indicators differs largely by region and soil evaluated, management systems impact biological parameters within soils, and sample locations within individual fields also vary significantly. Aggregate stability also tended to vary by soil texture and reference vegetation type. While these results indicate that these DSPs can be used to set typical and potential values for soil health indicators within ecological sites; further work is needed to asses their usefulness for soil health interpretation.