[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: soil compost extractions
I'm forwarding this message from Paul Krombholz together with another
one he subsequently sent me. A middle message from me is hiding in the
quotations of the second message.
>Paul, I was wondering if you are still using soil compost extractions
>for feeding your plants? How do you keep those extractions from growing
>bacteria and fungi? How long do they keep?
>Are these extractions a good source for Ca, K or Mg? or are the ratios
>of N and P a little too high? Have you ever had analysis done on these?
>I am using kitchen wastes to grow red worms. Or I am using red worms to
>process my kitchen waste into soil (whichever you prefer). It strikes me
>that I might have a good nutrient source here. Is there a way to
>incorporate these nutrients into a clay ball so as to sequester it more
>effectively into the substrate?
>Steve Pushak Vancouver, BC, CANADA
The extract may grow a small amount of bacteria, but not very much,
I let the compost 'compost' long enough so that nearly all, if not all,
easily decomposable organic matter has been decomposed, and only
organic matter remains. Recently, I have been putting the extract in a
shallow pan and letting it evaporate down to about 1/5 the original
before storing in soda pop bottles. The extractions should keep for
The only thing that might be lost would be a little nitrate, and that
only happen if the extract in the soda pop bottle became anaerobic. I
never seen this happen, but, sometimes, when I have loosened the cap on
bottle that has been sitting around for a year or two, I see that a
vacuum has developed, indicating continued, slow oxygen consumption. It
might be a good idea to air out the soda pop bottles every year or so.
The extracts no doubt have Ca, but I have not made any measurments.
Probably a better way to ensure Ca would be to put some ground limestone
lime in the tank. I know that they are a good source of K as long as
are composting plant materials that contain a 'good' amount of K as
to, for example, composting liver pieces that would have a low K/N
I assume that Mg released in decomposition gets into the extract. I
not heard that decomposition releases any Mg compounds that are
You probably do have a good source of nutrients from the kitchen wastes.
Also, extracting the compost very likely makes it a better home for the
worms. Continued build up of nutrients in the soil will eventually make
the solution in the soil water so concentrated that it becomes harmful
the worms. This may be why it is recommended to start the worms in new
soil when an old culture begins to go down hill.
I suppose you could have clay soil in a pan and pour the concentracted
extract on it and let it dry out. Then moisten just enough to shape the
clay into balls. I doubt that very many of the nutrients would be held
adsorbtion to the clay particles. Most of them would probably diffuse
of the clay ball.
Paul Krombholz, in moist, cloudy, central Mississippi
Subject: Re: soil compost extractions
Date: Thu, 10 Dec 1998 17:24:13 -0600
From: krombhol at teclink_net (Paul Krombholz)
To: Steve Pushak <teban at powersonic_bc.ca>
>I wonder if these extracts are really mainly bacterial colonies then? I
>would think that as long as there was entropy available to fuel some
>type of biological life form, that life forms would exist. If light were
>available, then algae would try to grow. I wonder what the lowest
>entropy state would be for such nutrient solutions. It would be
>different if aerobic or anaerobic I think and so I wonder if
>periodically adding oxygen would be good or bad. I suspect as long as
>there was nitrate, then it would serve as fuel until it was converted to
>nitrogen. That doesn't match with your observation of a vacuum
>developing does it? But if the oxygen were removed, the oxygen partial
>pressure drops and so must the total pressure.
The bacteria use the remaining organic matter in the extract. Although
resistant to decay, this organic matter is slowly broken down by the
bacteria. The lowest entropy state would be when all the organic matter
decomposed. It would probably take hundreds or thousands of years to
that state. It is best to add oxygen because, if the extract went
anaerobic, then denitrification would occur with nitrate being converted
N2 gas, which is unavailable to plants. The bad thing about that is
you are losing nitrate. The 'slight vacuum' that I have seen in bottles
left with the cap on for a year or so is due to removal of some of the
oxygen from the air in the bottles. I always keep the bottles with air
1/3 to 1/2 of their volume to serve as a reservoir of oxygen. I never
>> The extracts no doubt have Ca, but I have not made any measurments.
>I expect the Ca might form insoluble complexes easily but that's pure
>guess work. A gas spectrograph would tell the elemental proportions
I doubt that any of the calcium released by decomposition of the
added for composting would be precipitated in the soil and not make it
the extract. The only forms I can think of that would not all dissolve
would be calcium carbonate or calcium phosphate, and I am pretty sure
the amounts of calcium in plant material are not so great that any of it
would precipitate out of the soil solution in these forms when the plant
material is decomposed. My extracts always test somewhat acidic with a
around 6. I wouldn't expect calcium to be deposited at this pH, except
very high concentrations. In ordinary soil, outdoors, egg shells and
gradually dissolve, and I assume that, with periodic extractions of the
compost, the same thing would happen.
With snails in the aquarium having a high demand for calcium, the
provided by the compost extract might not be enough unless you added so
much extract that your nitrates, phosphates, etc. got a lot higher than
might want. That is why adding lime or limestone might be necessary to
ensure enough calcium for everybody.
>> Probably a better way to ensure Ca would be to put some ground limestone or
>> lime in the tank.
>Yes, that is what I would guess too.
>> I know that they are a good source of K as long as you
>> are composting plant materials that contain a 'good' amount of K as opposed
>> to, for example, composting liver pieces that would have a low K/N ratio.
>> I assume that Mg released in decomposition gets into the extract. I have
>> not heard that decomposition releases any Mg compounds that are insoluble.
>> You probably do have a good source of nutrients from the kitchen wastes.
>> Also, extracting the compost very likely makes it a better home for the red
>> worms. Continued build up of nutrients in the soil will eventually make
>> the solution in the soil water so concentrated that it becomes harmful to
>> the worms. This may be why it is recommended to start the worms in new
>> soil when an old culture begins to go down hill.
>My red worms live in a peat medium. There isn't any mineral content at
>all (aside from decomposition products). Would it work just as well for
>extractions? Peat doesn't give up its water easily unless you crush it
>and that tends to destroy its fibrous quality and its ability to hold
>water which is part of its desirable qualities for the worms. Also, the
>peat may not want to surrender nutrients either. They might bind to the
>cation and anion binding sites or remain dissolved within the water
>strongly bound to the peat material.
I don't try to squeeze all the water out of my compost when I make
extractions. I just gently flood the compost, wait 12 to 24 hours to
the nutrients time to diffuse into the water, and then gently drain the
compost. Since I use the compost over and over again, repeatedly adding
dried green leaves and then extracting, I figure that, very soon, the
binding sites will be all loaded up with all the nutrient cations or
they can hold, and then, after that, I will get all the nutrients
in subsequent decompositions and extractions.
>Sometimes soil is added to a worm colony to make the worms breed and
>grow to smaller sizes to be more suitable for feeding fish. That soil
>could be more easily extracted. In fact, if you took the worms with the
>soil and dried it out, the worms themselves would rapidly compost and
>surrender their own biomass.
Yes. You would have to remoisten and compost for several weeks.
>> I suppose you could have clay soil in a pan and pour the concentracted
>> extract on it and let it dry out. Then moisten just enough to shape the
>> clay into balls. I doubt that very many of the nutrients would be held by
>> adsorbtion to the clay particles. Most of them would probably diffuse out
>> of the clay ball.
>I think the way to do it might be to dry the clay, powder it and then
>mix it with the concentrated solution and then let it dry again. I don't
>think it would end up as concentrated as clay with fertilizer pellets
>inside but the ratios of nutrients might be better. Well they might
>approximate what would be found in natural soil anyhow.
It depends on how much you concentrate the extract by drying. I now dry
down to about 1/5 its original volume, and this is a very concentrated
solution. If you added this to clay twice, with two soakings and
you might have so much that it could damage the roots of the plants. A
the nitrate in there would probably be converted to N2, which would
up from the gravel.
I have tried growing aquatic plants on unextracted compost, and they do
very poorly, with their roots not penetrating into the compost at all.
concentration of nutrients is too strong. On the other hand, plants
well in extracted compost.
>We'd have to estimate the total mass of each nutrient in the ball
>according to how much nutrients would be in the solution. Your
>"Hoaglands" estimate of specific density might give us a rough handle...
>Another method might be to measure the dry residue from a litre of a
>given specific density and volume.
With a total dissolved solids meter I got a reading of 7.5 grams per
in a typical sample of extract before concentration by drying down to
the original volume. Afterwards, the solution is too concentrated to
measure because the upper limit of the meter is 19.99 grams per liter.
I have tried drying extracts all the way, and I get crystals and a small
amount of liquid, which refuses to dry any further. There must be some
materials in the extract that are highly higroscopic. Most of the
redissolve quickly when water is added, but some, probably calcium
compounds, are very resistant to redissolving.
>You can forward this to the APD if you like. I don't think you CC'd it
>on your response although I sent it to both you and the APD originally.
>As you like... It might be interesting to hear if any other of the
>scientists know what compounds are formed during anaerobic and aerobic
>soil decomposition. Microbe colonies survive a very long time in soil I
>think. Probably years in a closed system without flux.
If I may, could I leave forwarding this to the APD up to you? I am in
middle of the final exam period, now.
Paul Krombholz, in moist, cloudy, central Mississippi