O.K. here's one for ya...got a 3/4 acre pond that I have to lime every year because my water source is runoff from a hemlock bog, plus acid rain,I suppose. Instead of lime I thought I'd use wood ashes from over the winter, they work the same as lime on the lawn. Only thing that scares me is that I HAD a problem with duckweed until I stopped fertilizing and am wondering if there would be anything in the ashes that would bring on my duckweed problem again. If it makes any difference, my firewood is mostly ash with a little maple. Opinions?
Tyler

Don't know the specifics of your area or pond (what elements N-P-K are there or missing , three primary ingredients of nitrogen (N), phosphorus (P) and potassium/potash (K), often described as NPK fertilizers) but here is some info on the matter.


Potash (or carbonate of potash) is an impure form of Potassium carbonate (K2CO3) mixed with other potassium salts. Potash has been used since antiquity in the manufacture of glass and soap, and as a fertilizer. The name comes from the English words pot and ash, referring to its discovery in the water-soluble fraction of wood ash.

The term has become somewhat ambiguous due to the substitution in fertilizers of cheaper potassium salts such as potassium chloride (KCl) or potassium oxide (K2O), to which the same common name is now sometimes also applied. In addition, potassium hydroxide (KOH) is commonly called caustic potash, an additional source of confusion.

The element potassium derives its English name from potash. A number of chemical compounds containing potassium use the word potash in their traditional names:

Until the 20th century, potash was one of the most important industrial chemicals .... it was refined from the ashes of broadleaved trees.


Potash, or carbonate of potash, is in fact a mixture of potassium salt with impure form of potassium carbonate (K2CO3). In other words, it is the common term used for the fertiliser forms of the element potassium (K). The name has been derived from the collection water-soluble fraction of wood ash in metal pots when its beneficial fertiliser properties were first recognised many centuries ago.

Thanks for the info, ewest. I know nothing of chemistry and can only test my pond for alkalinity. I guess I'm just hoping that the wood ashes have the same effect as lime and not a wholelot of fertilizer value, at least not enough to bring on the duckweed.
Tyler

I'm planning on doing lots of burning of trees cut down last year also. I am thinking(hoping) is will raise the alkalinity level some, but I know not the hardness, as it washes in. I dont think it will have a detrimental affect. I have put in 5 tons lime in and around 1/2 acre, and still have only about 20ppm hardness. Lots of pines, you know.
I think too much N2 is usually the culprit, and raising alkalinity allows it to be released, so it should have a similar effect as lime.

Some trees are quite acidic. The ashes will be acidic too. Depending on your PH it may be a good thing.

The adding of potash which is what comes from burned trees will add potassium/potash (K) to the pond. It will also add carbonates (CO3) to the pond which is part of what lime contains ie
calcitic limestone (CaCO3)or dolomitic limestone
[CaMg(CO3)2]. Read the link below on water quality.

http://srac.tamu.edu/tmppdfs/10464902-464fs.pdf

If you have fertile water that is low on K and you add K it will be adding the missing link in the NPK formula and it will act like fertilizer. Most ponds that need NPK fert. are low on either N or P. The only way to know short of running your on test as per a recent PB mag. article is to have the water/soil tested. I think it is wise for all ponds to be tested (water and soil) so you know what you have to work with. Do you have a natural plankton bloom in the pond?

My guess ,and it is that, is the potash in reasonable amounts, will help your pond ,may add a little fertility, will not make it more acid but will not replace the need if it exists for lime because lime also adds critical Ca and Mg not in potash. You should get the water/soil tested as it is easy and cheap from your extension service.

Thank you all for your opinions. Looks like my best bet is as ewest advises, head to the extension service. I'll let you know what the results are. Thanks again.
Tyler