I have heard that potash increases potato yield and also that wood ashes cause scab...since I have a lot of wood ashes should I use them or not?
Depends on your present soil ph. Scab becomes a big problem as you get higher than 5.5. It can be difficult to get high fertility without raising the ph. Leaf-compost is good for that purpose, I had a bumper crop using that last year.
Use ashes on potatoes? NO. Too much lime in them.
All plant material and manures will modestly raise your PH and improve structure. It is a far safer and totally beneficial way to improve your soil. Be extremely careful with wood ashes and fowl manure.
Wood ashes helps make grandma's lye soap and grits for fighting snow in your driveway.
Wood ash has been used for generations as a dip on the cut end of potatoes to prevent rot. As for yield, the link below suggests not. It does say it would be an adaquate replacement for lime should liming be needed and it will provide some nutrients. But, again, you need an acid soil to begin with (the article is from Maine).
Here is a link that might be useful: Search on wood ash
If you have reason to believe the soil is quite acid, then wood-ash is an option. I broke open some virgin humussy soil a few days ago, and i am adding a bit of ash even to the potatoes. If it brings above 5.5 it's not a disaster. In this part of the continent the chances of getting the soil near 6 with one application is about zero. Scab gets bad around 6 and above.
Scab on the tubers is one of the ways I monitor ph.
Many thanks to everyone. I dont know what the ph is, I have never grown potatoes in that soil, (only squash) and so I should probably find out.
I think I will just use some of Gardens Alive balanced root formula and hope for the best.