The soil health assessment protocol and evaluation applied to soil organic carbon

Authors: NUNES, MARCIO - Orise Fellow; Veum, Kristen; PARKER, PAUL - University Of Missouri; HOLAN, SCOTT - University Of Missouri; KARLEN, DOUGLAS - Retired ARS Employee; AMSILI, JOSEPH - Cornell University; VAN ES, HAROLD - Cornell University; WILLS, SKYE - Natural Resources Conservation Service (NRCS, USDA); SEYBOLD, CATHY - Natural Resources Conservation Service (NRCS, USDA); Moorman, Thomas

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2021
Publication Date: 3/4/2021
Citation: Nunes, M.R., Veum, K.S., Parker, P.A., Holan, S.H., Karlen, D.L., Amsili, J.P., Van Es, H.M., Wills, S.A., Seybold, C.A., Moorman, T.B. 2021. The soil health assessment protocol and evaluation applied to soil organic carbon. Soil Science Society of America Journal. 85(4):1196-1213. https://doi.org/10.1002/saj2.20244.
DOI: https://doi.org/10.1002/saj2.20244

Interpretive Summary: The concept of soil health has evolved over the past several decades, and a flexible, science-based tool is necessary to advance soil health assessment and interpretation across the United States (U.S.) and globally. Previous work has demonstrated that soil health indicator values are highly dependent on site-specific factors (i.e., soil type and climate), highlighting the need to consider those factors in the interpretation of soil health measurements. The Soil Health Assessment Protocol and Evaluation (SHAPE) tool is a quantitative approach that uses a dataset of 14,680 soil organic carbon (SOC) observations from across the U.S. and assigns scores (0 to 100%) relative to a defined soil peer group, or cohort based on soil and climate information. This flexible framework is sensitive to management and provides a useful and regionally relevant interpretation of soil health indicators that will benefit landowners, agency specialists, and consultants.

Technical Abstract: The concept of soil health has evolved over the past several decades, recognizing that dynamic soil property response to management and land use is highly dependent on site-specific factors that must be considered when interpreting soil health measurements. Initially, the Soil Management Assessment Framework (SMAF) and Comprehensive Assessment of Soil Health (CASH) were developed and used globally for scoring soil health indicators. However, both SMAF and CASH frameworks were developed using a relatively small dataset and their interpretation curves were not validated at the nationwide scale. Expanding upon these concepts, we propose the Soil Health Assessment Protocol and Evaluation (SHAPE) tool. SHAPE was developed using 14,680 soil organic carbon (SOC) observations from across the United States and accounts for edaphic and climate factors at the continental scale. Data were compiled from the literature, the Cornell Soil Health Laboratory, and the Kellogg Soil Survey Laboratory. In this approach, scoring curves are Bayesian model-based estimates of the conditional cumulative distribution function (CDF) for defined soil peer groups reflecting five soil texture and five soil suborder classes adjusted for mean annual temperature and precipitation. Specifically, SHAPE produces scores between 0 and 1 (0 to 100%) for measured SOC values that reflect the quantile or position within the conditional CDF along with measures of uncertainty. Herein, we focus on development of the SHAPE scoring curve for SOC with four case studies. SHAPE is a flexible, quantitative tool that provides a regionally relevant interpretation of this key soil health indicator.