Slakes Soil Aggregate Stability App

Comparing Aggregate Stability Methods

Soil Health Institute scientists and partners conducted a study to evaluate over 30 soil health measurements at 124 long-term agricultural research sites across the U.S., Canada, and Mexico. We compared four common methods of measuring aggregate stability: water stable aggregates using the Cornell Rainfall Simulator, wet sieved water stable aggregates (Yoder method), slaking captured and adapted from SLAKES smart-phone image recognition software, and the mean weight diameter of water stable aggregates. We evaluated each indicator’s sensitivity to climate and inherent soil properties. Additionally, we explored each indicator’s sensitivity to long-term adoption of soil health management practices, including rotation diversity, number of cash crops, residue management, organic nutrient amendments, cover crops, and tillage. Finally, we examined the cost and availability of each indicator to determine its scalability.

All four indicators were sensitive to climate and inherent soil properties to a certain extent. This means that the indicators should only be compared among similar soils within similar climates. None of the indicators detected differences between diverse and monoculture rotations or increases in the number of different cash crops included in the rotation. All four methods, to a certain degree, were sensitive to organic nutrient amendments, cover crops, and tillage. Considering these results, no single method was clearly superior and all four are viable options for measuring aggregate stability. Although all measurements responded to management, SLAKES was the most practical in terms of time and cost. Therefore, we concluded that slaking via image recognition measured on intact 4-10 mm diameter aggregates was the most suitable method for scaling up assessments of aggregate stability as a soil health indicator.

Website:
Soil Health Institute

App available for iOS and Android

Materials

Materials needed are simple and low budget.

-Smart Phone
Android or Apple

-3 Soil aggregates
Air Dried for 24 hours.

-2 Clear Dishes
I purchased 2x petri dishes with 3 separate compartments to keep the aggregates from attracting to each other during test. Amazon $9

-Water
Any clean water will do, keep particles out if obtaining from a pond or river. they could potentially skew the overall results.

-Mount for Phone
Something that can maintain a 10 minute suspension of your phone above the Dish during analysis. 4-6" height.

Procedure

Step 1:
Collect and Dry Aggregates: Remove an intact clod from the top 2 inches of the soil, gently break apart into pea-sized aggregates, and dry overnight.

Step 2:
Set-up: Mount smart phone approximately 4 – 6 inches above empty clear plastic dish, select 3 aggregates and place in dish. Fill the second dish with water.

Step 3:
Start Test: Tap ‘Start Aggregate Stability Test’ to enter sample ID and capture initial image of dry soil in dish. Move the second dish filled with water into camera view, gently transfer aggregates to the water filled dish, and take pic to start test.

Step 4:
Complete Test and Receive Results: After 10 minutes, the app will automatically capture the final image and display the aggregate stability index value for the sample.

Step 5:
Export & Interpret Data: On the My Results Tab, tap ‘Export Test Results’. Upload results to a computer, add management and location data, and track changes in aggregate stability index values.

Resources