Re: [compost_tea] EM leachate "tea"

From: Mike Harvey <mharvey_at_westnet.com.au>
Date: Fri, 22 Oct 2004 09:51:32 +0800
Some info that I found  extremely interesting especially for Australian
conditions where Phosphate lock up is so much of a problem. The reference to
this article may have been posted here previously or may be from another
list serve. The anerobic microsites are the sites in the soil where only
anerobic bacteria can survive it is there niche.

By Robyn Francis

This is an abstract from an article first published in the Permaculture
International Journal.

ETHYLENE PRODUCTION IN SOIL

Our research shows that ethylene, a simple gaseous compound, is produced in
these anaerobic microsites. Furthermore, this ethylene is a critical
regulator of the activity of soil micro-organisms and, as such, affects the
rate of turnover of organic matter, the recycling of plant nutrients and the
incidence of soil-borne plant diseases. Concentrations of ethylene in the
soil atmosphere rarely exceed 1 to 2 parts per million. Ethylene does not
act by killing soil micro-organisms, but simply by temporarily inactivating
them - when concentrations of ethylene in coil fall, microbial activity
recommences.

Soil ethylene is produced in what we call the OXYGEN-ETHYLENE CYCLE.
Initially, the soil micro-organisms proliferate on the plant root exudates
and deplete the soil of oxygen at microsites. Ethylene is them produced in
these microsites and diffuses out, inactivating without killing the soil
micro-organisms. When this occurs the demand for oxygen diminishes and
oxygen diffuses back into the microsites. This stops or greatly reduces
ethylene production, which enables the soil micro-organisms to recommence
activity. Favourable conditions are then recreated for ethylene production
and the cycle is continuously repeated.

In undisturbed soils, such as found under forest and grasslands, ethylene
can be continually detected in the soil atmosphere, indication that the
oxygen-ethylene cycle is operation efficiently. Conversely, in most
agricultural soils, ethylene concentrations are extremely low or
non-existent. This is to be expected if ethylene plays an important role in
regulation microbial activity in soil. It is well established that in
undisturbed ecosystems where there is a slow, balanced turnover of organic
matter, efficient recycling of plant nutrients and soil-borne plant diseases
are unimportant. When these ecosystems are disturbed for agricultural of
forestry usage the situation changes dramatically, There is an alarming
decline in the amount of soil organic matter, deficiencies of plant
nutrients become commonplace and the incidence of plant disease increases
dramatically. We attempt to overcome these problems by additions of
inorganic fertilisers and by the use of pesticides, which increase our
production costs considerably. It is also generally true that the longer we
farm soil, more and more of these inputs are necessary to maintain our
yields.

We argue that the trend could be reversed, at least partially, if we could
create favourable conditions for ethylene production in these disturbed
soils. We now know that one of the major reasons why disturbed, agricultural
soils fail to produce ethylene is because our techniques cause a change in
the form of nitrogen in soil. In undisturbed soils, such as under forests or
grasslands, virtually all the nitrogen present is in the ammonium form with
just a trace of nitrate nitrogen present. When these ecosystems are
disturbed for agricultural usage, virtually all the soil nitrogen occurs in
the nitrate form. This change in form of nitrogen occurs because the
disturbance associated with agricultural operations stimulates activity of a
specific group of bacteria which convert ammonium nitrogen to nitrate
nitrogen. Plants and micro-organisms can use either form of nitrogen, but
our research has conclusively shown that ethylene production in soil in
inhibited whenever the nitrate form is present at more than trace amounts.
Ammonium nitrogen has no such inhibitory effect on ethylene production.

Nitrate nitrogen stops ethylene production because it interferes with the
formation of the anaerobic microsites. When all the oxygen is consumed in
the microsite a series of complex chemical changes then occur. One of the
most important changes that occurs is that iron goes form the oxidised or
ferric form to the reduced or ferrous form. Iron is one of the major
constituents of soil, making up somewhere between 2 and 12% of its weight.
In adequately aerated soil virtually all the iron exists as minute crystals
of iron oxide and in this oxidised or ferric form is immobile in soil. If
oxygen is completely consumed in microsites in soil, and reducing conditions
exist, these minute crystals break down and iron is then transformed into
the highly mobile ferrous or reduced form. Again our research has shown that
ethylene production occurs is soil only when iron is in the reduced or
ferrous form. In other words, ferrous iron is a specific trigger for
ethylene production. If there is no oxygen in the microsites, but nitrate
nitrogen is presents. then the complex chemical changes leading to the
reduction of iron form the ferric to the ferrous form are inhibited. This is
how nitrate nitrogen stops ethylene production.

How does ferrous iron trigger the release of soil ethylene? This form of
iron reacts with a precursor of ethylene that is already present in the soil
and a reaction occurs that results in the release of ethylene. Our work has
established that this precursor originates from plants and, more
importantly, it accumulates to appreciable amounts only in old, senescent
plant leaves. When these old leaves fall to the ground and decompose, the
precursor accumulates the soil. Then, when conditions become favourable for
mobilisation of ferrous iron, ethylene is produced.

We have also show that different plant species vary markedly in the
quantities of precursor that accumulate in their old leaves. This is
important to know when selection plant species to use as cover crops to
increase the ability of agricultural soils to produce ethylene. A few of the
plant species that produce high concentrations of precursor are rice,
phalaris, chrysanthemum, avocado, bullrush and Pinus radiata. Some of the
low producers include Dolichos, paspalum, lucerne and bracken fern.

In retrospect it should not be too surprising that the ethylene precursor
accumulates appreciably only in old, dead plant leaves. After all, in
natural communities of plants old dead leaves comprise the bulk of the
litter that falls on to soil. Also, it is equally clear that in agricultural
situation most of the old plant leaves are removed either during harvest or
by grazing or by burning crop residues. Thus, agricultural soils are usually
deficient in precursor.

It is now possible to specify the soil conditions necessary for ethylene
production - (1) there must initially be intense aerobic microbial activity,
at least in the rhizosphere, to ensure that oxygen-free, anaerobic
microsites form; (2) conditions in the microsites must become sufficiently
reduced to mobilise ferrous iron to trigger ethylene release; (3)
concentrations of nitrate nitrogen in soil must be kept to trace amounts,
otherwise ferrous iron will not be mobilised; (4) there must be adequate
reserves of the ethylene precursor in soil.

MOBILISATION OF ESSENTIAL PLANT NUTRIENTS

A major limitation to plant growth in most agricultural soils is an
inadequate supply of essential plant nutrients. This occurs even though
there are adequate reserves of these nutrients in soil, but they are held in
highly insoluble forms. Their high degree of insolubility prevents loss from
the soil by leaching, but since they are only available to the plant in the
soluble form, problems of supply rate to plants are created. Formation of
anaerobic microsites in the rhizosphere of plants, which is of such
paramount importance to ethylene production, can play a critical role in the
mobilisation and thus supply rate of these essential nutrients to plants.

This mechanism revolves around the importance of iron in soil. As already
discussed, under normal conditions in soil most of the iron occurs as minute
crystals of iron oxide. These crystals have a large surface area and are
highly charged. As a result plant nutrients such as phosphate, sulphate and
trace elements are tightly bound to the surfaces of these crystals. In this
form they are virtually unavailable to plants. If, however, anaerobic
microsites develop, these crystals break down and the bound nutrients are
released for uptake by the plant.

At the same time high concentrations of ferrous (reduced and mobile form)
iron are released into the soil solution in the microsite. The other
essential plant nutrients, including calcium, potassium, magnesium and
ammonium, are held on the surfaces of clay and organic matter. When
concentrations of ferrous iron increase so much, these nutrients are
displaced by the ferrous iron into the soil solution, where they too are now
available for uptake by plant roots. Since anaerobic microsites are most
likely to form in the rhizosphere of plants, the nutrients are mobilised
exactly where they are required by the plant. An additional advantage of
this mechanism is that if the released nutrients are not utilised by plant
roots they cannot be leached in the soil. As soon as they migrate to the
edge of the anaerobic microsite, reoxidation of the iron occurs with
recrystallisation of iron oxide. These crystals then rebind the nutrients
and prevent their loss by leaching.

The soil conditions necessary for this mechanism to operate are identical
with those required for ethylene production. Thus in agricultural soils,
where ethylene production is inhibited or impaired, this mechanism of
nutrient mobilisation is also restricted. Again, under these conditions, the
elevated concentrations of nitrate nitrogen that occur in agricultural soils
are a major inhibitor of efficient nutrient mobilisation.

Successful management of soils to increase the likeihood of anaerobic
microsite formation, which will help ensure a balanced oxygen-ethylene cycle
and enhance mobilisation of essential plant nutrients, will demand
alterations to some of the established practices in agriculture. For
example, techniques aimed at increasing aeration and the oxidation states of
soil, which give short-term increases in plant growth but rapidly create
lone-term problems of nutrient depletion and increased plant disease
incidence, will require modification. Treatments which stimulate rates of
nitrification (transformation of ammonium nitrogen to nitrate nitrogen),
such as excessive use of nitrogenous fertilisers, overuse of legume dominant
pastures, or excessive removal of plants by overgrazing or forestry
operations, require re-examination.

Some practical guidelines for successful management of soils include:-

(1) It is essential that organic residues be returned continually to the
soil. Organic residues contain essential plant nutrients for recycling,
stimulate microbial activity in soil, supply ethylene precursor, and
restrict the rate of nitrification in soil. It is best to use mature plants
as a source of organic amendments and it is better to return the residues to
the soil surface rather than incorporate the into the soil.

(2) Techniques of minimum tillage should be utilised wherever practical.
This ensures that plants are growing in soil virtually continually, that
there is a minimum of disturbance to the soil and increases the amount of
organic matter that is returned to the soil. Again, nitrification is
restricted when these techniques are used.

(3) Whenever soil is amended with nitrogenous fertiliser it is best to apply
the nitrogen in the ammonium form and to apply it in several small
applications rather than one or two heavy dressings. This again restricts
the chance of nitrification.

(4) In some situations it will be advisable to add chemical inhibitors of
nitrification (e.g. N-Serve or Terrazole) to soil with the nitrogenous
amendments to further ensure that nitrification is restricted.

Robyn Francis is currently Director of the Djanbung Gardens Permaculture
Education Centre

Permaculture Education ERDA Institute Trust

Nimbin Eco-Village Project Office

PO Box 379,

Nimbin NSW 2480 Australia

Ph 02-6689 1755 Fax 02-6689 1225

----- Original Message -----
From: "David Anderson" <squtch_at_gmail.com>
To: <compost_tea_at_yahoogroups.com>
Sent: Friday, October 22, 2004 2:27 AM
Subject: [compost_tea] EM leachate "tea"


>
> Well, now that the EM subject has been broached, I might as well toss
> in some of the questions and comments that I have been thinking about
> lately. I would really like the input of people that do not have a
> vested interest in EM, yet have looked into the biology and results
> derived with it.
>
> When I first heard about it at the fair at the Yelm Worm Farm, I was
> skeptical. After all, the woman was pitching an anerobic process, and
> anerobic is "bad". But I looked into it anyway.
>
> Of course the true believers use it for anything and everything. I
> would not be at all surprised to hear that someone mixes it in their
> house paint to increase the insulating value. It is *really* hard to
> take any of them seriously.
>
> Up till this discussion, the only thing that really interested me was
> to do the bokashi thing with my food waste between building compost
> piles. And I figured that adding the bokashi/food mix to the compost
> pile would help inoculate any anaerobic pockets with "good" anaerobes.
>
> I don't like the idea of adding it straight to the garden, because
> their own description of the process seems to imply that you have to
> actually let it go aerobic for a couple of weeks before it is safe for
> plants.
>
> The true believers push using the leachate from the bokashi/food
> buckets as a foliar spray. Does anyone know how well this works?  Are
> there any potential bad effects?
>
> How about innoculating a batch of ACT with the leachate, as Elaine was
> talking about with EM?
>
> What is the behaviour of the EM critters in an aerobic environment? It
> seems to me that they are not all strict anaerobes. Are they just less
> competitive? Do they produce different byproducts in an aerobic
> environment?
>
> I guess that is enough questions for now.
>
> Dave
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>


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Received on Thu Oct 21 2004 - 22:35:12 EDT

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