SHAPEv1.0 scoring curves and peer group benchmarks for dynamic soil health indicators

Authors: NUNES, MARCIO - University Of Florida; Veum, Kristen; PARKER, PAUL - University Of California Santa Cruz; HOLAN, SCOTT - University Of Missouri; AMSILI, JOSEPH - Cornell University; VAN ES, HAROLD - Cornell University; WILLIS, SKYE - Natural Resources Conservation Service (NRCS, USDA); SEYBOLD, CATHY - Natural Resources Conservation Service (NRCS, USDA); KARLEN, DOUGLAS - Retired ARS Employee

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2024
Publication Date: 4/11/2024
Citation: Nunes, M.R., Veum, K.S., Parker, P.A., Holan, S.H., Amsili, J.P., van Es, H.M., Willis, S.A., Seybold, C.A., Karlen, D.L. 2024. SHAPEv1.0 scoring curves and peer group benchmarks for dynamic soil health indicators. Soil Science Society of America Journal. 88(3):858–875. https://doi.org/10.1002/saj2.20668.
DOI: https://doi.org/10.1002/saj2.20668

Interpretive Summary: Producers and other landowners need a robust and regionally relevant soil health interpretation tool to understand a wide range of available soil health measurements. The Soil Health Assessment Protocol and Evaluation (SHAPE) is a flexible tool that accounts for site-specific characteristics using a soil ‘peer group’ approach and provides soil health scores and benchmarks for a suite of soil health indicators. The SHAPE scores and benchmarks can be used to provide soil health targets, calculate the soil health opportunity gap, and help landowners understand how their management practices are impacting soil health. The SHAPEv1.0 tool includes scoring curves for soil organic carbon, two aggregate stability methods, active carbon, total protein, and four-day microbial respiration. This tool benefits landowners and supports local and national policies and programs related to soil health and sustainable agriculture.

Technical Abstract: The soil health concept has evolved over the past several decades, recognizing that the response of dynamic soil properties to management and land use is dependent on site-specific factors that must thus be considered when interpreting soil health indicators. The Soil Health Assessment Protocol and Evaluation (SHAPE) is a flexible tool that accounts for the interaction of inherent climate and edaphic factors when interpreting changes in dynamic soil health indicators and provides benchmark values based on site-specific characteristics. The SHAPEv1.0 tool was initially developed for soil organic carbon (SOC), and its interpretation curves produce scores between 0 and 100% for measured laboratory values that reflect the quantile within a population conditional cumulative distribution function (CDF) along with measures of uncertainty. Bayesian regression modeling was used to derive parameter estimates of the conditional CDF for two wet aggregate stability methods, permanganate oxidizable organic carbon (POXC), autoclaved citrate extractable protein (ACE protein), and four-day microbial respiration based on edaphic-climatic peer groups defined by soil texture and suborder and adjusted for mean annual temperature and precipitation. In addition, SHAPE provides site-specific benchmark values that are equivalent to the 90th, 95th, and 99th percentiles within a given soil peer group, where the difference between the actual measured value and the selected benchmark value represents the soil health opportunity gap. Modeling data were compiled from the Cornell Assessment of Soil Health (CASH) and the Kellogg Soil Survey Laboratory (KSSL) databases. Case studies in Missouri and Texas show that the SHAPE scoring curves for aggregate stability, POXC, ACE protein and respiration are sensitive to land-use and management practices across multiple soil types and provide a regionally relevant interpretation of key soil health indicators. The SHAPEv1.0 scoring curves and instructions for batch scoring are publicly available on GitHub at https://github.com/paparker/SHAPE