If you put a tsp of the soil from under the top layer in a container add 300ml of distilled water, let sit for 24 hours, stir let settle and test. You should have a good idea. The longer you let sit, the more accurate it will be. 3 days is optimal.
If you put a tsp of the soil in a 300ml container and let sit for 24 hours, stir let settle and test. You should have a good idea. The longer you let sit, the more accurate it will be. 3 days is optimal.