A number of our farmers in the Maritimes - especially those who are primarily forage/hay suppliers add lime or wood ash - to the soil on a yearly basis. One of our friends adds about a 1/2 ton/acre to help improve his yield. He also applies it to his paddocks for the Alpacas.
Yup, Bill is correct, you need soil analysis to properly determine how much lime/ash/fertilizer etc., to apply as a general rule of thumb. My father-in-law regularly applied his winter wood worth of ash to his big garden every year and that garden produced big time. He also tilled his soil every spring to thoroughly chop up the remnants from the previous year's crops at the same time as mixing the ash in. I know that most of my land needs big time amendments as much of it has little to no nutrition it it, just what has been left year after year the last few years from our terra-forming project. My plan this summer is to spread ash, disc, seed with red rye and then disc it in around the 1st week of July then replant. I need to add a lot of vegetable matter/green manure and other amendments to help balance the soil.
One of the problems in the Maritimes is Acid Rain that hits us from the US industrial heartland and of course Southern Ontario. It has been proven that our soils here are quite acidid (which explains a lot of the problems I have had over the last few years raising foodstuffs), and wood ash is more soluble than lime or fertilizers so it helps balance the ph much quicker. And we get a lot of acid rain, it is one of our major agricultural challenges. Acid rain is a fact of life here and I am really glad to see that we have a mitigating agent here in abundance. I really like mother nature's fixes
Here are some interesting articles that I found googling one particular paper : Wood Ash paper by Lise LeBlanc of LP Consulting
Disposing of wood ash at a landfill unnecessarily fills up the land fills. After spending a few years on the planning committee for our Waste Disposal System - Westmorland-Albert Solid Waste Commission, it became very clear to me that we need to re-purpose much of what we use/expend in our daily lives. We also have a project here that is working wonders and it is our Gardener's Gold program which uses sewage solids mixed with bark and greens - composted and then utilized. This product allowed CFB Gagetown to regreen/reforest the bases artillery ranges that were contaminated with cordite etc. No other mulch or soil amendment product tried in the previous 40 years worked but Gardern's Gold did.
It all depends on where you are and what your soils are like. I do not like blanket solutions as they do not satisfactorily address local conditions. We do not have Extension Offices like the US does but we do have our Experimental Farms and such which provide much of the same data for our farmers up here.