I have to fall into the 'soil test' parade. I did find out that a high PH will produce effects similar to a nitrogen deficiency, a lack of iron. So adding nitrogen will just add to the problem, in my case I needed aluminum sulphate.
Heres a link
http://www.google.ca/search?q=acidifying+soil&ie=utf-8&oe=utf-8&aq=t&rls=com.ubuntu:en-US:unofficial&client=firefox-a
It does deal with Blueberries, but the principal is the same.