Don't use wood ashes in compost or organic garden??

I have just been researching the subject to see where I can use the ashes from our wood stove. Most sources are very positive and informative, but I did find a very disturbing article at http://burningissues.org/radwaste1.html . In our area we do have a nuclear plant, but that is not really the issue. The regulations in the US are more strict since the 50's and 60's. Although most of the wood we burn is from our property, pollutants come from all over the world. Can anyone comment on the information in the article? Are we making a mistake to use our wood ashes in our organic garden?

This message was edited Jan 23, 2008 1:33 PM

Well, burning doesn't create those toxic things that they mention in the article, those were already present in the wood before it was burned. So if those things are in the soil and being absorbed by trees and other plants, then they're going to be in any mulch you use, any plant material that you use as soil amendments, etc. So the only difference with the ash is that you've burned away a lot of the wood, leaving a higher concentration of the metals and toxins than there would have been in the log before it was burned.

You clarified my question. I do agree that whatever toxins there may be in this environment, are already in the soil and mulch that is already in my garden, and any harmful elements in the environment will continue to be absorbed by my plants as they grow. The question that remains is how much truth is there in the article? If it is valid, then do I need to feed my vegetable gardens with the extra toxins in the ashes or should I just work in some lime as suggested in the article?

This message was edited Jan 23, 2008 7:33 PM

This message was edited Jan 23, 2008 7:34 PM

My honest opinion is I'd take it with a grain of salt. This was from 1991, so if you haven't turned up any similar references, my guess is this was some fringe research that the scientific community never really got behind. Maybe their data was flawed, or maybe someone else did some followup studies and couldn't reproduce the results, it's hard to say. But if their data was good and the amounts present really represented a problem, I think there would be info out there from other sources saying the same thing. And gardening aside, given the number of people who have woodburning fireplaces in their houses, I have to think if this was a real problem, it would have been all over the news. I can't imagine the news media wouldn't immediately latch on to a story about nuclear waste in your fireplace endangering the lives of you and your children! If you live real near to Three Mile Island then maybe there's more cause for concern, but for most of the country I think there's minimal risk.

ecrane3 - I was inclined to do as you suggest, take it with a grain of salt, but my inquisitive nature pushed me to go back to the original site and see how credible it was. So I went to http://burningissues.org. I don't know if I will be sorry I did as there may be just too much information for an old geezer like myself, but I did leave a post there, and will see if anything new comes of it. I have had so much trouble with this darn organic garden that I might just forget the ashes and save myself the time it will take to come to a better understanding of the ashes issue.

They just talked about that in our Master Gardener's class. They said to only use a small amount of wood ash spread over a large area....reason being that only the minerals are left after burning and it increases the salinity of the soil. Salt kills.

ByndeweedBeth - Wow! I am finding out a lot more than I can handle from the above site, but as of now, I think I will pass on using the ashes for food crops. There is not a lot of data on the subject, but what I am reading does leave too many questions unanswered. It seems that a lot depends on what kind of wood you burn, the temperature at which it was burned, the source of the wood etc. A study done on "Controlling Metals and Dioxins in Fertilizers" by Washington State in 1998 includes the following: "The state departments of Agriculture and Ecology tested 55 fertilizers for their metals content....Wood ash, a by-product of burning wood for electricity or steam generation, was the only waste-derived fertilizer product to violate biosolids standards. Wood ash is not used on food crops." If anyone is interested in more detail it is at http://www.ecy.wa.gov/news/1998news/fert.html.

Another more recent link that was cited is from 2006. It gives more technical data: "Wood ash use in forestry - a review of the environmental impacts," http://www.ingentaconnect.com/content/oup/foresj/2006/00000079/00000005/art00563.

It is beyond my ability to interpret all of this information so I think I will not put my wood ashes in my vegetable garden. There are many ways to enrich the soil easily and inexpensively without the potential problems that wood ash introduces.

Well, one thing about the cesium and whatnot is that the guy must have been using firewood from 50-60-year-old trees. So one solution to that problem is to use wood that was coppiced instead.

I like a wood fire as much as the next fellow, but one of the things I love about the city is that no one burns garbage in their fireplace like folks used to burn garbage in their woodstove out in the country. The guy across the road from me would burn styrofoam--which he considered to be "paper." The smoke would come right down the hill into my house. Talk about a stench. And poison. Makes cesium seem practically certified organic in comparison.

Good country living! I had to give it up for my health.:)

paracelsus - I thought all the writers were on strike! Love your comment - both from a practical and humorous point of view!!

Thanks, mygardens! Living in Elmira forces a person to develop a sense of humor.

Sorry, this is a bit long, but I just get so curious… and suspicious…

The article is factual about cesium levels only. It says, “100 times … that which can be released from nuclear plants (about 100 picocuries per kilogram of sludge.“ So the levels he found were 10,000 pC/kg (2.2 lbx.) of sludge. This sounds alarming, however:

I think picoCuries are more often written in parts per gram, not kilogram. So, that would be 10 pC/g.

Cesium is a type of radionuclide from man-made fallout, but how does that compare with the concentrations of natural radiation from the earth? For example, there are 0.945 pC/g of Uranium-238 in your average garden soil. Phosphate fertilizer can contain as much as 2,700 pC/g of Radium-226. There can be 17.55 pC/g of Thorium-232 in glazed ceramic tile. (From article: “Sources of Background Radioactivity” - EPA website.)

Also, he never says it’s a health hazard. His point is that it costs the nuclear plants a lot to handle their sludge which isn’t as radioactive as the wood ashes. My sense is that “Burning Issues” hijacked his findings to make their point about using wood as fuel.

I would think it’s the alkalinity of wood ashes gardeners have to watch. Some of my findings/calculations:

They are a really good source of potassium (the “K” in NPK fertilizer) carbonate. One of a few organic sources of potassium. (Others include cottonseed, peanut, or soybean meal; greensand; and hay.) They contain about 6 percent potassium and about 1.75 percent phosphorus. Wood ashes are highly alkaline (drip water through ashes and you have lye). Since ashes are highly water soluble they change the pH of the soil quickly and can cause a build up of salts. 1-½ cups of ashes should raise the pH of 20 sq ft (a 20’ row) of average soil about 1 point - for example, from 5.5 to 6.5. (This is equivalent of using about 4.4 lbs of lime.) I would test my pH before adding this amount of ashes.

I would do a mere dusting of ashes once a year (and on the compost) and be grateful for a “free” source of potassium. I hear it deters slugs too. But I don’t have a fireplace : (

Just last month I put ashes from clearng of small trees and limbs off hundred yr. old trees in my garden .Hope it is ok since it's already a done deal .

Farmers have been using burns for centuries.Most in rural Florida still do. Seems like to me there is more cancer and health problems now than then .Add to it all the hormones and antibiotics and bio seeds and we are in trouble.

After reading this I may not be using wood ash until further study .

Wood ashes will increase the pH of your soil. If you have a high pH soil then add wood ashes you may drive the pH above what your garden will grow vegetables.

Gary

our soil pH is 5.4 so wood ashes help , i heard that ashes from wood
are ok but from firelogs not ? or maybe it was charcoal briquets ? composting
may help , i guess you could have your soil tested before and after, soil
tests only cost us $10 at university of minnesota and michigan state university.