CEC Calculator

Estimated CEC in this calculator measures the soil's total capacity to hold exchangeable cations, which comes from Clay Content and Organic Matter alone -- Calcium, Magnesium, and Potassium describe how much of that existing capacity is currently occupied, not how large the capacity itself is, so changing them shifts Base Saturation and the individual cation percentages without touching Estimated CEC.

This calculator uses roughly 2.0 meq/100g per percent of Organic Matter versus about 0.5 meq/100g per percent of Clay Content, reflecting that organic matter typically carries a much higher charge density than most clay minerals -- a small increase in organic matter often raises CEC more than an equivalent increase in clay percentage.

The commonly cited Albrecht base-cation-saturation-ratio targets used here are roughly 60-70% calcium, 10-20% magnesium, and 2-5% potassium saturation of CEC -- values outside those ranges are flagged Low or High for that cation, though soil scientists disagree on how strongly these specific ratios predict crop performance versus simpler sufficiency-level testing.

A Low CEC soil (generally under 5 meq/100g, often sandy with little organic matter) holds fewer nutrients against leaching and needs more frequent, smaller fertilizer applications, while a High or Very High CEC soil (typically clay-rich or high in organic matter) buffers nutrient supply better but can also require more lime to shift pH, since it holds onto more exchangeable acidity.

It doesn't distinguish between clay mineral types, which vary enormously in charge density per percent clay (kaolinite holds far less CEC than smectite, for example), doesn't factor in soil pH even though CEC measured at native pH differs from CEC measured at pH 7, and doesn't account for aluminum or hydrogen saturation beyond a simple 100-minus-base-saturation estimate.