How are the cation exchange capacity (CEC) and percent base saturation calculated for the soil test report?

To determine the cation exchange capacity (CEC), calculate the milliequivalents of H, K, Mg, and Ca per 100g of soil (meq/100g soil) by using the following formulas:

H, meq/100g soil = 8 (8.00 - buffer pH)
K, meq/100g soil = lbs/acre extracted K ÷ 782
Mg, meq/100g soil = lbs/acre extracted Mg ÷ 240
Ca, meq/100g soil = lbs/acre extracted Ca ÷ 400
Na, meq/100g soil = lbs/acre extracted Na ÷ 460

The total CEC will be the sum of the calculations from the 5 previous equations.

EXAMPLE
LAB
NO.		SAMPLE
NO.		SOIL
CODE		SOIL
PH		BUF.
PH		PKMgCaNa
113282345.17.70 168
VH		221
H+		28
L+		400
L+		12

H, meq/100g soil = 8 (8.00 - 7.70) = 2.40
K, meq/100g soil = 221 ÷ 782 = 0.28
Mg, meq/100g soil = 28 ÷ 240 = 0.12
Ca, meq/100g soil = 400 ÷ 400 = 1.00
Na, meq/100g soil = 12 ÷ 460 = 0.03
--------
Total CEC = 3.83 meq/100g soil

To calculate the percent base saturation, divide the sum of the K, Mg, Ca, and Na (the bases) in meq/100g soil by the CEC (all these values were calculated above). Multiply the result by 100%.

EXAMPLE
K = 0.28 meq/100g soil
Mg = 0.12 meq/100g soil
Ca = 1.00 meq/100g soil
Na = 0.03 meq/100g soil
CEC= 3.83 meq/100g soil
Total for bases = K + Mg + Ca + Na = 1.43 meq/100g soil
Percent base saturation = (1.43 ÷ 3.83)(100%) = 37%


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