Wood Ash vs Charcoal Fertilizer: Comparing Nutrients

[gary350]

I took 2 chemistry classes in college but that was 50 years ago, I have forgotten more than I ever knew. I watched several educational chemistry classes on YouTube then realized it will be a very long time before I can answer this question on my own.

Questions is. Wood ash is an excellent garden fertilizer it contains 20% to 30% calcium depending on the wood that is burned plus it contains, phosphorus and potash = potassium and several trace elements. Wood ash fertilizer is 0-1-3 or 0-1-4 depending on what type wood is burned. 1st number 0 is nitrogen. 2nd number 1 is phosphorus, 3nd number is potassium. After burning a pile of wood there is about 10% charcoal that does not burn up. I assume charcoal contains the same amount of, calcium, potassium, phosphorus, trace elements, as wood ash is that correct? If so then powder charcoal should be a good 0-1-3 or 0-1-4 fertilizer too?

 

[jim mcnamara]

I do know: charcoal would have those nutrients, and slightly more. Because some nutrients are lost during burning through particulates leaving with the smoke. So not all the nutrients make it into ash residue. The nutrients are there, but they may be bound up and slower to utilize for plants.

Also ash can change the pH (acidity) of soils. - see 'using wood ash as a liming agent' in the blue link below.

This is the USDA extension service publication on using ash for fertilizer - from U Maine
https://extension.umaine.edu/publications/2279e/

This has everything you need to know

 

[chemisttree]

...If so then powder charcoal should be a good 0-1-3 or 0-1-4 fertilizer too?

Nope! You need to reduce the wood entirely to ash to see those numbers. The ash contains no carbon but the charcoal has a significant amount. You will have the P and K but it will be diluted by the remaining carbon in the charcoal. No way for us to tell you just what the NPK values would be for the charcoal. A guess would be something on the order of 0-0.25-0.75 or less.

 

[Rive]

On the other hand, maybe you should check on 'biochar' first, before deciding on further action.

 

[gary350]

On the other hand, maybe you should check on 'biochar' first, before deciding on further action.

I have been using wood ash in my vegetable garden for many years it works great potassium promotes lots of blossoms that turns into lots from vegetables and calcium prevents BER. I was told about Biochar and watched several video and read lots of information then tried it several times but I am not seeding the same good fertilizer from biochar I get from wood ash. Lots of biochar claims but no scientific facts. I know wood ash is instant food for plants, calcium, potassium, phosphorus, but charcoal does not seem to be instant food for plants. It seems to me charcoal is carbon just like dry dead plants are carbon they pull all the nitrogen from the soil so they can decompose.

 

[Rive]

Lots of biochar claims but no scientific facts.

Sure, that happens every time something got hyped up. Your observation is right: the function of the charcoal in the soil is not directly a fertilizer, since it has barely anything what would be useful for plants. However it acts as a buffer and helps to retain nutrients, just like the natural compost/humus present in the soil: also, it should have no effect on nitrogen, unlike natural compost.
It also can modify the soil structure.

In short: if you already have the charcoal, then it would be a waste to not use it.