pH Buffering Capacity (BC)
1. Determine the soil pH according to instructions on pH page.
2. Measure 10g of air dried soil sample into each of four 100 mL beakers and label 2 - 5.
3. Add 25 ml of solutions as shown below. See "solution" link for mixing each solution.
| Beaker No. | Solution | meq KOH added per 100 g soil |
| 1 (From pH page) | distilled water | 0.0 |
| 2 | 0.005 M KOH | 1.25 |
| 3 | 0.01 M KOH | 2.50 |
| 4 | 0.02 M KOH | 5.00 |
| 5 | 0.04 M KOH | 10.00 |
4. Shake the soil suspension intermittently for 1 hour.
5. Measure the pH of each suspension, using a glass electrode pH meter.
6. Graph meq KOH added/100g sol (ordinate) relative to soil pH (abscissa).
7. From the resulting graph, solve for the slope of the line according
to the following algebraic equation:
Slope equals buffering capacity.
M(slope) = (y2-y1)/(x2-x1) = (10.0-0.0)/pH in vial 5 - ph in vial 1)
8. Repeat with other soil samples
9. Rinse all glassware and place on drying surface.
References: Salvatore Engel Di-Mauro, July 2001, Selected laboratory
procedures for investigating general soil characteristics and acidification
processes, Manuscript