Soil Test Calculations

These calculations are used in a PSL soil test results report. The actual formulas and a brief description are given below.

Cation Exchange Capacity (CEC)

CEC is a measure of a soils ability to retain nutrients. Higher CEC values mean a greater ability to retain nutrients rather than lose them to hydrological activity.

CEC = [Na] + [K] + [Ca] + [Mg] + [H+] - all in cmol[+]/kg

Base Saturation (BS%)

Base saturation is the ratio of base cations to total cations expressed as a percentage.

BS = ( [K] + [Ca] + [Mg]) * 100 / CEC - all in cmol[+]/kg

Base Cation Saturation

Base cation saturation is the same as BS except it expresses individual base cations as a percentage.

BCS = [Ca] / CEC * 100 - shown for Calcium - all in cmol[+]/kg

Exchangable Acidity

Exchangeable acidity is the concentration of protons which are retained by the soil along with the other cations.

EH+ = (Buf_pH - 6.4) / 0.25

Phosphorous Index