What is the potassium percentage of Cation Exchange Capacity (CEC) calculated from 195 PPM K in soil?

To determine the potassium percentage of Cation Exchange Capacity (CEC) from a measured concentration of potassium in the soil, we use the relationship between parts per million (PPM) and percentage.

The PPM value indicates how many parts of a substance are present in a million parts of the total, which is the same as milligrams of potassium per kilogram of soil. To convert from PPM to a percentage, we can apply the following conversion:

1. Convert PPM to a weight basis: 195 PPM means there are 195 mg of potassium per kg of soil.

2. To express this as a percentage, we divide the amount of potassium by 10,000 mg, since 1% corresponds to 10,000 mg in 1 kg (as 1 kg = 1,000 g or 1,000,000 mg):

[

\text{Potassium percentage} = \frac{195 , \text{mg}}{10,000 , \text{mg}} \times 100 = 1.95%

]

However, when calculating potassium's contribution to CEC, it's common to assume that the CEC is equivalent to the total cation exchange capacity