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Dr. Ingham's E-Zine Addendum



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Dr. Ingham's Talks on the Soil Foodweb
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E-Zine Issue #2     November, 1999

Addendum....to Issue #1
"Interpretation of Foodweb Information--
Explanation of Assays"

http://www.soilfoodweb.com




Greeting fine people...

Samuel here... I was going through the submissions that Dr. Ingham had sent
to place in her E-zine and I found the following information that should
be sent as a followup to the previous Newsletters...  This is specific
info that should help give a bit of direction when it comes to testing.
Just what are we looking for?  It's quite long so I thought I'd break it
up for you into two letters....

So, that said... Read on please.  It's a long piece....

Also, attached below is a new Q&A session that resulted from our 
last newsletter...

Peace,
Samuel Anthony Ettaro II
Unisun Communiations
Dr. Ingham/SFI Newsletter Administrator
http://www.unisun.org
sam@unisun.org
(541)367-8980

A few quick notes....

Just a reminder about our new
affiliate program... If you've got a site and 
are interested in distributing Dr. Ingham's CDs...

Go to the below page to get ALL the details:
**********************************************
http://www.unisun.org/affiliatesignuppage.html
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E-Zine Reader Reply-thought we'd share this!
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Dear Dr. Ingham:
First let me thank you for the soil web web site, I have radically
modified several of my composting techniques
with great success thanks to the information posted there.
Secondly after reading the first E-zine, I am convinced of the
practicality of raised bed gardening. Not having to deal with
soil compaction and maintaining a high compost to soil ratio have
certainly made gardening a lot more productive.

name withheld






Main Body Text.....
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Soil Foodweb Inc: Interpretation of Foodweb Information
Explanation of Assays
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Soil Foodweb Inc. provides information on total and active bacterial
biomass, total and active fungal biomass, protozoan numbers, nematode
numbers and community structure and VAM colonization of plant roots. 

Soil sampling should result in three samples from any particular area
(field or forest stand for example), such that the variability of that area
can be assessed. We suggest that the area to be sampled be split into
three or more equal areas. Randomly chose three areas and remove from each
area between three and ten small soil cores (0-5 cm depth, about 2.5 cm or
1 inch diameter core). All the cores from a area should be mixed and about
50 grams of soil (the amount of soil that would be held in a typical coffee
cup) removed from this mixture and placed in a ziplock plastic baggie.
Ship by overnight mail to Soil Foodweb Inc., 1128 NE 2nd St., Suite 120,
Corvallis, OR 97330. We ask that you fill out the sample submission form,
or tell us about the soil type, vegetation type, management of the field,
especially recent pesticide use and cropping practices. This information
is needed to properly interpret your data. 

The measures outlined below can be performed on any kind of material, from
lake sediment, to rumen material from cattle. However, our expertise in
interpreting the information is in soil-related material, although this
includes logs, litter, surfaces of plants, and sewage-sludge.

Ratio of total fungal to total bacterial biomass
In work with the structure of the soil foodweb in a range of soils, we have
discovered that all grassland soil and most agricultural soils have ratios
of total fungal to total bacterial biomass less than one, that is,
bacterial biomass is greater than fungal biomass in these soils. 

In high yield agricultural production, the ratio of total fungal to total
bacterial biomass is about one, or the biomass of fungi and bacteria is
about even. When agricultural soils become fungal-dominated, productivity
is reduced, and in most cases, liming and mixing of the soil (plowing) is
needed to return the system to a bacterial-dominated soil.

All conifer forest soils are fungal dominated, and the ratio is all forest
soils in which seedling regeneration occurs is above 10. More productive
forest soils have fungal to bacterial biomass ratios of greater than 100.
This means that fungal biomass strongly outweighs that of bacteria in
forest soils. In the case where forest soils lose this fungal-dominance,
it has been impossible to re-establish seedlings in the soil. 

In studies of riparian soils, some deciduous riparian forest soils, such as
in aspen, and beech soils, the soils are bacterial-dominated. But in
poplar, oak and maple soils, the soil is fungal-dominated, although not to
the extent observed in conifer systems. No studies on establishment of
seedlings in these systems have been performed.

The ratio of total fungal to total bacterial biomass is not the only thing
that needs to be examined. Numbers of active and total bacteria and length
of active and total fungi are indicative of the health of soil, although
these values must be determined relative to the desired vegetation in the
system, just as the optimal ratios of total fungal to total bacterial
biomass are different for different vegetative regimes.

Biomass of total fungi
Fungal biomass is extremely important in all soils as a means of retaining
nutrients that plants need in the upper layers of the soil, i.e., in the
root-zone. Without these organisms to take-up nutrients, and either retain
those nutrients in their biomass, or to sequester those nutrients in soil
organic matter, nutrients would ash through the soil and into ground or
surface water. Plants would suffer from lack of nutrients cycling into
forms that the roots can take-up, if these nutrients weren't first
immobilized in the soil through the action of fungi, or bacteria. For
forest soils, fungi sequester most of the nutrients, although significant
portions are immobilized by bacteria as well. In soil in which only fungi
are present, the soil will become more acidic, from the secondary
metabolites produced by fungi, the aggregates will be larger than in
bacterial-dominated soils, and the major form of N is ammonium, since fungi
are not capable of nitrifying N. Clearly, these conditions are more
beneficial for certain shrubs, and most trees.

Total fungal biomass varies depending on exactly which soil type is being
considered, as well as the vegetation type, organic matter levels, recent
pesticide use, soil disturbance and a variety of other factors, many of
which have not been researched completely yet. However, for normal
grassland soils, total fungal biomass levels are usually around 50 to 500
meters per gram of soil. For agricultural soils, fungal biomass is around
1 to 50 meters per gram soil, while for forest soils, fungal biomass is
between 500 to 60 km per gram of soil. Quite a bit more work is necessary
to establish what the optimal fungal biomass value should be for each type
of crop, soil, organic matter, climate, etc. Very little information is
available for tropical systems, but that small amount of data indicates
that temperate systems work very differently from tropical soils.

The average diameter of hyphae in most soils is about 2.5 micrometers,
indicating a typical mixture of zygomycete, ascomycete and basidiomycete
species present in the soil. On occasion the average diameter may be
greater than 2.5 micrometers, indicating a greater than normal component of
basidiomycete hyphae, while on other occasions, the average diameter of
hyphae may be less than 2.5 micrometers, indicating a change in species
composition of soil fungi to a greater proportion of lower fungi. In most
cases, actinomycetes are not differentiated from fungi, since they are
hyphal in morphology and are rarely of significant biomass. However, in
some agricultural soils, these narrow diameter "hyphae" are of considerable
importance, as demonstrated by Dr. Van Brueggan following cover cropping in
some soil types. 

Biomass of active fungi
There is a typical seasonal fluctuation of active fungal biomass in all
systems. This cycle seems to be related to optimal temperature and
moisture, such that a peak in activity usually occurs in the spring as
temperature and moisture become optimal after the winter freeze. However,
in systems where snow accumulates on the soil surface, such that the
temperature does not actually freeze, fungal activity may continue at high
levels throughout the winter in litter, where adequate organic matter is
available. In fact, decomposition may continue at the highest rates
through the winter under the snow in the litter. In systems where moisture
becomes limiting in the summer, activity may reach levels even lower than
in frozen soil or litter in the winter. When temperatures remains warm
enough in the fall, before temperature becomes too low, and rain begins
again after the summer drought, such as in Mediterranean climates, a second
peak may be observed in the fall. If these peaks are not observed, this
suggests inadequate organic matter in the soil.

Numbers of total bacteria
Just as fungi are the important players in retaining nutrients in forest
soil, bacteria are the important players in agricultural and grassland
soils. Bacteria retain nutrients first in their biomass, and second, in
their metabolic by-products. In soil in which only bacteria are
inoculated, the soil will become more alkaline, will have small aggregates,
and generally will have nitrate/nitrite as the dominant form of N.
Clearly, these conditions are beneficial for grasses and row crop plants.

Numbers of total bacteria generally remain the same regardless of soil type
or vegetation. Total bacterial numbers range between 10 million and 100
million per gram soil. Bacterial numbers can drop below 1 million in
semi-arid agricultural soils. Bacterial numbers can be above 100 million
in decomposing logs, in anaerobic soils, and in soil amended with sewage
sludge or with high amounts of composted material. In some instances
following pesticide treatment, bacterial numbers can fall to extremely low
levels, below 100,000 per gram of soil. In this situation, crop
productivity can be quite low and can even show signs of nitrogen deficiency.

Biomass of active bacteria
As with active fungal biomass, bacterial activity usually peaks in the
spring, and decreases during the summer with drought. If the temperature
remains warm in the fall, and fall rains begin, a second peak of activity
usually occurs. The ratio of active fungal to active bacterial biomass,
even in forests, shows that bacterial biomass is usually more active than
fungal biomass. 

Protozoan numbers
Protozoa feed on bacteria, and as they feed on their prey, N is released.
It's unclear just how much N is released per individual feeding event,
since it undoubtedly depends on whether the bacterium was actively growing,
thus containing more N, or whether the bacterium is in stationary phase, or
starving and containing much less N. Several studies have shown that a
major portion of the nitrogen that cycles through in certain agricultural
soils is cycled by protozoa. Without these organisms in soil, plants may
suffer a significant reduction in available N. However the optimal
relationship between the number of bacteria and the number of protozoa has
not been quantified. 

There appears to be a great range in protozoan numbers from soil to soil,
and even from field to field. Some of the observations that have been
made, when dealing with agricultural soil (i.e., bacterial-dominated) is
that when protozoan numbers are high, bacterial-feeding nematode numbers
will be low, and vice versa. Thus there appears to be significant
competition between bacterial-feeding predators for the bacterial prey.
Whether this is indicative of the type of bacteria present in the soil, and
whether this has any relationship to productivity in agricultural
situations is not known. 

Testate amoebae are only found in significant and constant numbers in
forest soils, and are never found in temperate agricultural soils. Why
this is the case is not known, but continues to be observed. 

John Cairns (VPI) has suggested the use of protozoa as indicators of
ecosystem health, based on the rapid return of certain "opportunistic"
species of protozoa following certain types of disturbance, while other
species of protozoa are typical of less disturbed systems. While most of
Cairns work has been performed in aquatic systems, the same concepts have
been suggested for soil.

Nematode numbers, community structure
There are four major types of nematodes, which includes bacterial-feeding,
fungal-feeding, root-feeding and predatory nematodes. All nematodes are
predators, and thus reflect to some extent the availability of their prey
groups. However, other organisms prey upon these nematodes as well, and
thus nematode numbers can also reflect the balance between the availability
of nematode prey, as well as feeding by nematode predators. 

Both bacterial-feeding and fungal-feeding nematodes mineralize N from their
prey groups. Thus, bacterial-feeding nematodes are more important in
bacterial-dominated soils (agriculture and grassland systems), while
fungal-feeding nematodes are more important in fungal-dominated soils
(conifer and most deciduous forests). Between 40 and 80% of the nitrogen
in rapidly-growing crop plants has been shown to come from interactions
between bacteria or fungi and their nematode predators. Thus, the presence
and numbers of bacterial- and fungal-feeding nematodes is extremely
important for productive soils.

Root-feeding nematode numbers can be affected by competitors for roots,
including VAM fungi which may prevent root-feeding nematodes from reaching
the roots through a variety of mechanisms, nematode-trapping fungi, and
other fungi and bacteria that may be active inhibitors of nematode presence
in the rhizosphere. 

Bongers, in the Netherlands, has suggested the use of a Maturity Index for
nematodes in soil. Certain species of nematodes are more commonly found
following disturbance, while other species are more typical inhabitants of
less-disturbed soils. Thus, these organisms may be excellent indicators of
soil "health". 

VAM spore numbers
Vesicular-arbuscular mycorrhizal fungi are critically important for all
crop plants, except a few species of the brassica family (mustards, kale,
brassica). A number of researchers have shown that the lack of VAM
inoculum, or the lack of the appropriate inoculum can result in poor plant
growth, in poor competition with other plants or inability to reproduce or
survive under certain extreme conditions. However, most crop fields have
adequate VAM spores present, especially if crop residue is turned back into
the field. Only under a few situations, of intensive pesticide use,
fumigation, or intense fertilizer amendment will VAM spore inoculum become
so low that plant growth will be in jeopardy. In restoration studies, the
lack of appropriate inoculum is more likely to be a problem than in other
situations where sources of appropriate VAM spores are near-by. Thus, the
presence of at least 1 to 5 spores per gram of soil is more than adequate
for most crop fields. When the number of spores falls below one per gram,
then addition of compost containing high numbers of VAM spores (for example
from an alfalfa field, or other legume), or inoculation of VAM spores from
a commercial source generally results in positive effects.

Percent VAM colonization
At least 12% of the root system of grasses, including most crop plants,
should be colonized by VAM in order to obtain the minimum required benefits
from this symbiotic relationship. In most cases, colonization upwards of
40% is usually seen. In these cases, VAM colonization can limit
root-feeding nematode attack of root systems, if the nematode burden is not
high. A great deal knowledge of the relationship between plant species,
VAM species and soil type, including fertility, is needed in order to fully
predict the optimal relationship between crop plant, VAM species and soil. 

Until next time!
Dr. Elaine R. Ingham
Soil Foodweb, Inc.


*************************************************************
Q&A session between Dr. Elaine Ingham and E-zine Subscribers!
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This is a real exchange and we hope to encourage you to
ask questions and send comments.  We're very excited about this
opportunity to open a dialogue that will lead to further
learning by all of us.

If you have something to share, please email Dr. Elaine
Ingham directly at the following address:

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mailto: sfi@unisun.org
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Time permitting she will attempt to address your email
personally and maybe you'll find it posted in a future newsletter!


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Question #1----
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You wrote:
What are the downsides of using fresh goose poop (readily available in
Seattle!) in composting, hot or cold?


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Answer 1------
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Several things:

1. Probable pathogens - either plant or human. Geese carry some nasty
disease-causing organisms, both for people and plants and by spreading
goose poop directly on the plants, or working with poop with your hands,
you stand a significant chance of contracting those diseases or your plants
do. If you wash your hands carefully every time after working with poop,
you aren't likely to contract any diseases. But you also have to carefully
wash any food whose surface you might eat if it is grown in the poop.
Composting kills these pathogens if you get the heat above 135 F for at
least 3 days throughout the whole pile.

2. High nitrate levels in poop. Fowl feces are high in nitrates, can be
high in salt depending on their diet, and can contain antibiotics, again,
depedning on their diet. Direct application of high N levels to plants, or
planting seedlings in such material can result in burning the plants from
high N, or high salt. Composting can sequester such material in complex
organic forms so the plants will not be killed by such toxic material.

3. Often fowl manure is anaerobic, and highly toxic-to-plant anaerobic
metabolic products result from anaerobic decomposition. By composting in a
highly aerobic manner, these toxic materials will not be produced and
beneficial organic forms will be produced, so the plants will not be killed
by such toxic material.

Elaine


NOTE:  We'll be delving into composting very soon so keep
an eye out!


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end of Issue #1 Addendum
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