Why is the difference in soil pH and buffer pH on the soil test report?
pH is an unbuffered measure of the hydrogen ion concentration in the soil (active acidity) whereas buffer pH is a measurement of total soil acidity (active + reserve acidity). Soils with low buffering capacities (low cation exchange capacity or CEC) usually have less total acidity than soils with a high CEC if the pH is the same. Therefore, it takes less lime to correct the total acidity in a soil with a low CEC. The buffer pH on the soil test report is used to calculate how much lime is needed to correct both the active and reserve acidity. When soil pH is 6.5 or greater, the buffer index will not be reported on the soil test report due to its irrelevance. • How often should I apply lime? The answer to this question depends on a variety of considerations. A soil with a low CEC does not require a lot of lime to correct soil pH, but may need to be limed frequently. A soil with a high CEC requires a large amount of lime to initially correct pH, but it may be several years before another
