There are problems. msbadger said it-- 50# of ash is a lot of ash.
You've got a lot of bulk. You also have a lot of reactivity-- water + ash = lye. It also is light and flies away as you spread it. You need a lot to do a plot.
It's also a good source of . . .well, potash (Potassium). I spread it in my yard at the dripline of my trees. They seem to love it. I have a couple soft maples and a catalpa that have been rejuvinated as a result of a diet of ash in the winter. I also have a pin oak that's turning into a monster. I haven't thought about it before, but I could probably feed the oaks around my stand with it too.
The other big DIY fertilizer is extremely close at hand and is a ready source of nitrogen. It also gives a whole new meaning to "DIY." Again, if you saved enough of it and spread it on your plots, the results would be spectacular. The problem with this, as well as the ash, is that they're both a little icky to handle. I pipe mine straight out into the pasture behind the house and you can see the results in all the green forbes that grow at the end of the pipe. I just wish I could figure an easy way to pipe it out to my clover plots.