What is the method used to extract base cations for CEC estimation in lab tests?

The correct method for extracting base cations for cation exchange capacity (CEC) estimation in laboratory tests is through the use of ammonium acetate solutions. Ammonium acetate is highly effective because it displaces base cations from the soil's cation exchange sites, making them available for quantification.

When ammonium acetate is applied, the ammonium ions (NH4+) take the place of other cations such as calcium (Ca²+), magnesium (Mg²+), potassium (K+), and sodium (Na+). This process allows for the determination of the total amount of these base cations in the soil, which is crucial for assessing soil fertility and nutrient management practices.

The other methods listed are not suitable for CEC estimation. Using distilled water would not effectively displace the base cations and would largely provide a measure of water-soluble ions rather than the total cation exchange capacity. Sodium chloride solutions could provide a measure of salinity but are not appropriate for estimating CEC, as they do not effectively displace the cations of interest. Similarly, nitric acid solutions are generally used for extracting certain nutrients or metals rather than for cation exchange capacity assessment. Hence, the use of ammonium acetate stands out as the reliable