Statistics, scoring functions, and regional analysis of a comprehensive soil health database

Soil health (SH) refers to the ability of a soil to function and provide ecosystem services. The Comprehensive Assessment of Soil Health (CASH) is an approach that measures 15 physical, biological, and chemical soil indicators, which are interpreted through scoring functions. This study reports on the SH status of 5767 samples from the Mid-Atlantic, Midwest, and Northeast regions of the USA as evaluated using CASH. Descriptive statistics and ANOVAs of subdatasets by region and soil textural group for SH indicators, in addition to correlation coefficients, principal component (PC) analysis, and best subsets regression (BSR) were performed. From these analyses, new CASH scoring functions were developed. Separate scoring functions by textural group (fine, medium, coarse) were necessary for Wet Aggregate Stability (WAS), Available Water Capacity (AWS), Organic Matter (OM), Active Carbon (AC), and Protein. Differences existed among regions, especially for WAS, OM, Protein, and Respiration (Resp), where the Midwest had relatively lower mean values compared to the Mid-Atlantic and Northeast. Biological properties and WAS showed moderately strong correlations (r = 0.58-0.78) and the highest loadings for the first two PCs. BSR results using the overall soil quality index as the response variable indicated that AC accounts for 45% of the variation, with additional predictability from Penetration Resistance, Resp, and WAS (68%). These four indicators are suggested for simplified SH tests. We conclude that the CASH approach can be successfully applied to evaluate the health status of soils with differing pedogenetic histories.