only if soil is slightly acidic... Found this article informative.

http://www.hort.purdue.edu/ext/woodash.html

Thanks for this info Grasa I need to lower my PH. I have deposits of valcanic ash around my place that do a lot of the same things. Bentonite  has a number of trace elements in it that can be added to high PH soil. Also humate  can be added. 
Zone 8
South West TX

I think one of the biggest values of wood ashes is that it does add some micronutrients back into the soil, but if I didn't have a fireplace or woodstove, wood ashes wouldn't be my first choice for either controlling PH or supplying micronutrients.  I think it's just a convenient way to dispose of & recycle the ashes one might accumulate anyway and have some beneficial value.