I know this is old, but just thought I should post this for future readers. Have you ever thought of using wood ashes? They are very alkaline and a little goes a long way. The alkalinity WILL move into the soil if used as a top dressing OR if "dissolved" into some water. Also, great source of K. In order for the ashes to work, they need to be fairly new and not from a 3 year old bon fire.