a. Weigh 20 g of soil sample into a 100 mL beaker.
b. Add 20 mL of deionized (DI) water and place on a stirrer to mix for 30 minutes.
c. Cover and let stand for an hour.
d. For the most accurate measurements, allow the buffers and the soil sample both to come to room temperature. (A difference in temperature will add error to your measurement.)
e. We recommend a 2-point calibration with a pH 7 and a pH 10 buffer solution. The electrode slope should be between 92 and 102%.
f. Rinse electrode and ATC (automatic temperature compensation) probe with DI water and blot dry. Place probes in soil sample and measure pH and record measurement.