Which test is an acidic extraction method used to determine soil phosphorus availability?

The Bray Test is specifically designed as an acidic extraction method to assess soil phosphorus availability. This test utilizes a solution that has a low pH, which helps to extract phosphorus from the soil in a form that plants can readily absorb. The acid serves to solubilize phosphorus compounds in the soil, making it available for plant uptake.

This method is particularly effective in acidic or neutral soils, which are common in many agricultural regions, including parts of California. The Bray Test has been widely adopted because it provides a reliable estimate of plant-available phosphorus, playing a crucial role in soil fertility management and crop production.

The other methods listed, such as the Olsen Test, are more suited for alkaline soils, while the Mehlich Test can be used in various soil types but involves a different extraction solution. The Composite Test, on the other hand, refers more to sampling technique rather than a specific extraction method for phosphorus. Thus, the effectiveness and precision of the Bray Test in determining available phosphorus in typical agricultural soils makes it the correct choice.