Research Scientist USDA-ARS Fort Collins, Colorado, United States
Abstract: Soil health is the result of complex interactions between the chemical, physical, and biotic properties of the soil itself, potential climatic constraints, and management. There has been a lot of work on development of laboratory assessments or soil health indicators that represent key functions of soils. Similarly, many studies have evaluated the effect of independent management practices on said indicators and overall soil health scores based on laboratory indicators have been proposed. Management practices aimed to improve soil health may address multiple principles, which independently and collectively influence soil health. To date, a framework does not exist that evaluates soil health at the principle level and how laboratory indicators respond at various scales. This approach requires translating practices targeting the soil health principles into quantitative/semi-quantitative scores. Then an overall management index could be estimated which may provide land managers with a more integrated and responsive assessment of management factors/decisions on soil health. Our main goal was to use management practice information to develop Soil Health Management Indices (SHMI) that reflect the principles of disturbance, plant diversity, and duration of living roots/soil cover. We then used these indices to estimate the magnitude and direction of the relationship between soil health indicators and management while simultaneously accounting for the influence of climate and edaphic factors. We used a national survey representing over 400 soil samples from a variety of soil types and climate zones and under a suite of agronomic and rangeland practices to test this relationship. Samples were submitted to Cornell Soil Health Lab for Comprehensive Assessment for Soil Health, University of Missouri for Microbial Community Assessment (PLFA), and USDA-ARS for microbial abundance (DNA). At each site spanning 22 states we collected management histories (1-3 years) and created four soil health indices that represent the (i) level of disturbance, (ii) duration of vegetative cover/living roots, (iii) plant biodiversity, and (iv) an overall SHMI. We then developed a structural equation model (SEM) linking the indices with seven soil health indicators and two measures of microbial abundance. A significant positive relationship between SHMI and all soil health indicators was observed; however, the impact was moderated by both soil clay+silt contents and atmospheric vapor pressure deficits. Our approach provides a robust framework to translate management into soil health principles and their impact on soil health indicators that is applicable at national, regional, and field levels.
