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Calcimator

Water Stable Aggregate Calculator

Calculate water-stable aggregate percentage from wet-sieving test results to assess soil structural health and erosion resistance.

Inputs

%

Results

Water-stable aggregates (%)

51.1%

Stability score (0-100)75
Est. mean weight diameter (mm)1.32
Est. infiltration rate (in/hr)3.1
vs. Expected (%)17.1
RatingStable
Erosion RiskModerate
Crust RiskLow
How to Use This Calculator
  1. Collect a representative 100g soil sample and enter the percentage of aggregates that remain stable after wet sieving.
  2. Input your soil texture class and organic matter percentage.
  3. Set the tillage intensity to contextualize the aggregate stability result.
  4. Review the Mean Weight Diameter and the Aggregate Stability Score.
  5. Use the Erosion Risk Rating to decide whether cover crops or reduced tillage are needed.

What each input means

Initial sample weight (g)
Dry weight of soil aggregates placed on the sieve before wet-sieving.
Stable aggregate weight (g)
Weight of material remaining on sieve after wet-sieving (includes sand).
Sand/gravel weight (g)
Weight of sand and coarse fragments after dispersing stable aggregates (correction factor).
Soil organic matter (%)
SOM from soil test — used to compare stability vs. expected for your OM level.

What each result means

Water-stable aggregates (%)
Percent of soil aggregates stable in water (corrected for sand).
Stability score (0-100)
Normalized aggregate stability score.
Est. mean weight diameter (mm)
Estimated mean weight diameter of stable aggregates.
Est. infiltration rate (in/hr)
Estimated water infiltration rate based on aggregate stability.
vs. Expected (%)
Difference from expected WSA for your organic matter level (positive = better than expected).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Initial sample weight (g) = 10, Stable aggregate weight (g) = 5.5, Sand/gravel weight (g) = 0.8, Soil organic matter (%) = 3 = 4 input(s) provided
  2. Calculate Water-stable aggregates
    Water-stable aggregates = denominator > 0
    51.1 = 51.1%
  3. Calculate Stability score
    75 = 75
  4. Calculate Est. mean weight diameter
    Est. mean weight diameter = wsaPct * 0.02 + 0.3
    1.32 = 1.32

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