Aggregate stability is defined as the ability of a soil to maintain its physical structure and withstand external forces. Aggregate stability is related to physical, chemical, and biological soil properties, and is sensitive to changes in soil management, which makes it a useful indicator of soil health.
Several methods for quantifying aggregate stability exist; however, the methods differ greatly in the amount and type of external force applied, size and weight of aggregates used, output unit and scale used to quantify aggregate stability, and cost of each analysis. These differences make comparing aggregate stability values for soil health management difficult and raise the need for a universal method for quantifying aggregate stability.
For the North American Project to Evaluate Soil Health Measurements (NAPESHM), scientists at the Soil Health Institute compared four aggregate stability methods, including the Cornell Rainfall Simulator, Wet Sieve Procedure, SLAKES smartphone application, and Soil Stability Index. Each method was evaluated for sensitivity to inherent soil properties, sensitivity to management, and overall utility for stakeholders.
Overall, the methods showed minimal sensitivity to soil organic carbon, as soil organic carbon was poorly correlated with aggregate stability. All methods were sensitive to changes in tillage, with significant increases in aggregate stability when tillage intensity decreased. The Cornell Rainfall Simulator and SLAKES methods also responded significantly to the implementation of cover crops, as well as the removal of crop residue. Based on the results from this study, the SLAKES method is recommended for evaluating aggregate stability due to its high sensitivity to changes in management, low cost, and fast turnaround time for results.
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