Growing azolla in an aquarium with water and wood ash. Forcing it to fix nitrogen from the air!

Wood ash is full of minerals, lots of P and K but no N,  it has zero nitrate.  So if azolla grows in water above wood ash,  it has to fix nitrogen from the air,  there is nowhere else it can get it!  The Iran war has stopped 30% of the world's nitrate production so we have to fall back on the natural world to fill the gap and it simply cannot.  I read somewhere that Azolla can fix nitrogen twice as fast as any other higher plant, so it has that going for it!   On 28 April, i put 50 grams of wood ash into an aquarium (surface area 1127 sq centimeter, along with 25.9 liters of water and 30 grams of azolla.  I also conducted the experiment in a larger aquarium. In that one I added 100g wood ash, 51 liters of water and 111g of azolla, its surface area was 2250 sq cm.  The big aquarium was in a more sheltered area.   I didn't even know if the azolla could grow with that much wood ash, (it makes the water pretty alkaline). There were a few things swimming when I added the water but by 2 days after, I didn't see any animal life in either aquarium.  Probably killed by the alkalinity or maybe toxic stuff in the ash.  About 2 weeks later I weighed the azolla. In the little aquarium it had more than doubled in weight (2.93 times  on may 14th), but was still not covering the surface. In the big one it covered the surface but had only increased from 111 to 254 grams,  2.28 times the amount I started with.   So I harvested some and filled both aquariums with Azolla again, (almost covering the surface in both of them.)  Anyway, next stage is to harvest some every week (1/7 of the surface area, I guess) and get it to a steady state of growth.  I plan to expand the experiment to several shallow containers too.  Small scale farmers across Africa and Asia grow azolla, but their ponds are often fertilized with chicken manure, or pig or cow manure, which contain nitrates so this means their azolla is probably not fixing so much nitrogen, because the plant gets it from the water if it can. (it takes less energy to suck it up than to make it!)    Anyway,  my experiment shows that Azolla can survive with that much ash in the water.   Maybe in the future other people will grow azolla in Ash ponds?   I think it is a good way of converting the ash into a full spectrum  fertilizer!  And if you don't want to spread the azolla as a mulch, you can always feed it to your animals or fish as part of a varied diet.   I think I will harvest some azolla, solar cook it, and then mix it up with pure  sand in a pot, then grow some plants (not legumes) in the mixture.  I will probably mulch it with azolla too too.  So whatever grows in the pot, its only source of nitrogen is the decomposing azolla in the pot.       Here is a brief video about the Azolla experiment.  Please don't be shy and leave a comment.  The haters are usually not shy, and they freak out at new (to them) ideas,  so help balance them out.      Thanks Brian

If I understand this, you are making fertilizer to water other plants.  Super great idea.

the azolla has a cyanobacteria host in its leaf , this photosynthesizes the nitrogen out from the air for the plant--its an advantage over duckweed so it can grow in stagnant depleted waters---not sure about how much heavy metals  would be taken in---some studies must have be done.

Anne Miller wrote:If I understand this, you are making fertilizer to water other plants.  Super great idea.

 No, I am making green manure,  from ashes, to use as a nitrogen rich mulch or soil additive on other plants. It says on the internet azolla contains about 4% N,  0.5% phosphorus and about 3 percent potassium.   That is the N, P and K in artificial fertilizers.  When you grow Azolla on wood ash, the entire amount of N in it is fixed from atmospheric nitrogen.  And that is pretty cool!   I will actually be topping up the water and changing the water  from time to time and adding a little more ash,  so, yeah, I will be using the water on plants too.   But the water won't be high in nitrogen.   Thanks Brian.  

Brian White wrote:

Anne Miller wrote:If I understand this, you are making fertilizer to water other plants.  Super great idea.

 No, I am making green manure,  from ashes, to use as a nitrogen rich mulch or soil additive on other plants. It says on the internet azolla contains about 4% N,  0.5% phosphorus and about 3 percent potassium.   That is the N, P and K in artificial fertilizers.  When you grow Azolla on wood ash, the entire amount of N in it is fixed from atmospheric nitrogen.  And that is pretty cool!   I will actually be topping up the water and changing the water  from time to time and adding a little more ash,  so, yeah, I will be using the water on plants too.   But the water won't be high in nitrogen.   Thanks Brian.  

 I don't think there is much heavy metal in wood ash.  

Interesting experiment! Aquatic plants are known to be high in nitrogen, which is why they stink to high heaven when pulled out of the water and left to decompose.

Azolla is listed as an invasive species in some areas. So it seems that experiments require some caution -- not creating any situation where it could ever get into natural water bodies. (Think about 100 year floods and such. That's when things get away from us. Flushing down the toilet isn't a confirmed kill either. End of speech.)

Edit: I am also interested in potential toxicity from the cyanobacteria symbiant (if that is the correct term). Much potential, many questions.

If anyone wants to go down the rabbit hole, here are some links. Both very interesting (to me, anyway).
https://en.wikipedia.org/wiki/Azolla
https://theazollafoundation.org/azolla/

Douglas Alpenstock wrote:Interesting experiment! Aquatic plants are known to be high in nitrogen, which is why they stink to high heaven when pulled out of the water and left to decompose.

Azolla is listed as an invasive species in some areas. So it seems that experiments require some caution -- not creating any situation where it could ever get into natural water bodies. (Think about 100 year floods and such. That's when things get away from us. Flushing down the toilet isn't a confirmed kill either. End of speech.)

Edit: I am also interested in potential toxicity from the cyanobacteria symbiant (if that is the correct term). Much potential, many questions.

No worries on the prairies, the winters are much too cold for it to survive. Here in Victoria, it has already successfully invaded.  Actually I advocate for them to remove it in the local pretty Swan lake, because when you remove it,  it removes excess phosphorous too,  but so far swan lake nature park just lets it build up and later rot. Azolla is a standard "crop" in Kenya, the Philippines, etc. as poultry and animal feed.  So yeah, across most of the USA and Canada, it is much too cold in the winter for Azolla to survive. There are lots of videos online about growing it. Until about a decade ago, it didn't survive Victoria winters, but it has warmed up and now, I see it a lot more. Excessive phosphorus in the water is the main reason that it expands its range here, I think.  Mine is the first video about growing it in water enriched with wood ash.  Farmers put chicken poo or cow poo in the water to make it grow faster.  But in that case, it isn't fixing nitrogen, it is just absorbing nitrate from the chicken poop.  In the winter when there is mass starvation, it might be better to grow azolla over wood ash and save the chicken poop for the vegetable  fields.  They find cooked azolla is better for poultry.  

I found this a while ago.   It makes the case for harvesting azolla wherever you see it.  Azolla isn't simply growing in all sorts of new places because of climate change,  it is also growing because there is a lot more phosphate and nitrate in the water.  It is a symptom,  (and if you harvest it,  a cure,)  for too much phosphate in the water!  If you leave the phosphate there,  and kill the azolla in place (people use herbicides) then you create the ideal conditions for toxic algal blooms that will kill all the fish in the water  and low oxygen in the water as the azolla rots.   This video explains it better than I can.