SLAKES Smartphone Application to Identify the Difference in Soil Aggregate Stability Under Cover Crop Management for Soils with Fragipan Horizon

Authors: Chatterjee, Amitava; Rivera Santiago, Eric; HUMMES, ANA - Oak Ridge Institute For Science And Education (ORISE); Dinnes, Dana; Olk, Daniel

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2025
Publication Date: 1/12/2025
Citation: Chatterjee, A., Rivera Santiago, E.E., Hummes, A., Dinnes, D.L., Olk, D.C. 2025. SLAKES Smartphone Application to Identify the Difference in Soil Aggregate Stability Under Cover Crop Management for Soils with Fragipan Horizon. Communications in Soil Science and Plant Analysis. https://doi.org/10.1080/00103624.2025.2452177.
DOI: https://doi.org/10.1080/00103624.2025.2452177

Interpretive Summary: An aggregate is a group of soil particles that attach to each other, and their stability against breakdown represents the binding forces between them that withstand an applied disruptive force. The stability of aggregate in water is a common measurement for the strength of the soil physical structure against disruption. "Slakes", a smartphone application provides a score of aggregate stability based on the analysis of images taken during the break down of soil clods soon after they are immersed in water. This study was conducted to determine the possibility of using this application to (1) identify the fragipan, a brittle compacted soil layer below the soil surface, and (2) identify the changes in soil structure after annual ryegrass is grown following harvest of the main crop at two farmer fields in southern Illinois. Results showed that the score provided by the application can identify the difference between surface and subsurface soil layers but not between the fragipan layer and neighboring soil layers. Scores were affected in the surface soil by growing annual ryegrass, but they changed in different manners between the two sites. These findings will be useful to further development of this application, as they recommend adjustment of the measurement time to better describe the difference between fragipan and non-fragipan layers. Findings could be of interest to scientists who will further develop the application and professionals who want to use the Slakes application to identify the effects of agricultural management practices on soil properties.

Technical Abstract: Dispersion of soil particles in water, or slaking indicates the stability of soil aggregates. The Soil Health Institute has introduced ‘Slakes’, a smartphone app, to measure the stability of dry soil aggregates to resist dispersion once rewetted. Using image analysis, the app provides a rating, the aggregate stability index (ASI), which is scored on a 0-1 scale, where 1 describes the maximum stability. We compared ASI values for treatments with (CC) and without (NCC) a cover crop mix for two on-farm fields with fragipan subsoil horizons in southern Illinois. For both sites, the Ap horizon had the highest ASI score (0.48) and significantly declined for the Bt horizon (0.29). However, the fragipan horizon (Btx) and its overlying the non-fragipan horizons above it (Bt and E), all had similar ASI score. For the Ap horizon, the ASI score of CC was higher than that of NCC at one site but the opposite trend was observed for the other site. The relationship between ASI score and soil properties also varied with site. The measurement time of 10 min might be too long to capture the difference in rate of disintegration between the fragipan and adjacent non-fragipan horizons. Only at the surface A horizon, the ASI score appeared to describe crop management only in the Ap horizon and not at any of the lower horizons. Use of the Slakes app needs to be further validated before its widespread adoption can be recommended.