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  • From: Lawrence London <lfljvenaura@gmail.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: [permaculture] BENEFICIAL AND EFFECTIVE MICROORGANISMS
  • Date: Sun, 24 Mar 2013 16:30:28 -0400

BENEFICIAL AND EFFECTIVE MICROORGANISMS
http://www.agriton.nl/higa.html

[image: Logo]TO HOMEPAGE <http://www.agriton.nl/homeeng.html>
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*

BENEFICIAL AND EFFECTIVE
MICROORGANISMS

[image: Microorganisms]

FOR A
SUSTAINABLE AGRICULTURE
AND ENVIRONMENT
*



Dr. Teruo Higa
Professor of Horticulture
University of the Ryukyus
Okinawa, Japan

and

Dr. James F. Parr
Soil Microbiologist
Agricultural Research Service
US. Department of Agriculture
Beltsville, Maryland, USA





International Nature Farming Research Center
Atami, Japan
1994





------------------------------
*

TABLE OF CONTENTS
*

*

FORWARD * <http://www.agriton.nl/higa.html#1>

INTRODUCTION * <http://www.agriton.nl/higa.html#2>
1. THE CONCEPT OF EFFECTIVE MICROORGANISMS:
THEIR ROLE AND APPLICATION * <http://www.agriton.nl/higa.html#3>

*
2. *UTILIZATION OF BENEFICIAL MICROORGANISMS IN AGRICULTURE
*<http://www.agriton.nl/higa.html#4>
*
2.1 What Constitutes an Ideal Agricultural System.
*<http://www.agriton.nl/higa.html#5>
2.2 Efficient Utilization and Recycling of Energy
*<http://www.agriton.nl/higa.html#6>
2.3 Preservation of Natural Resources and the Environment.
*<http://www.agriton.nl/higa.html#7>
2.4 Beneficial and Effective Microorganisms for a Sustainable
Agriculture * <http://www.agriton.nl/higa.html#8>
2.4.1 Optimum Yields of High Quality Crops
*<http://www.agriton.nl/higa.html#8>

3. *CONTROLLING THE SOIL MICROFLORA:
PRINCIPLES AND STRATEGIES * <http://www.agriton.nl/higa.html#10>*
3.1 Principles of Natural Ecosystems and the Application of
Beneficial and Effective Microorganisms
*<http://www.agriton.nl/higa.html#11>
3.2 Controlling the Soil Microflora for Optimum Crop Production and
Protection * <http://www.agriton.nl/higa.html#12>
3.3 Application of Beneficial and Effective Microorganisms: A New
Dimension * <http://www.agriton.nl/higa.html#13>
3.4 Application of Beneficial and Effective Microorganisms:
Fundamental Considerations * <http://www.agriton.nl/higa.html#14>

*
4. CLASSIFICATION OF SOILS BASED ON THEIR MICROBIOLOGICAL
PROPERTIES *<http://www.agriton.nl/higa.html#15>
*
4.1 Functions of Microorganisms: Putrefaction, Fermentation, and
Synthesis * <http://www.agriton.nl/higa.html#16>
4.2 Relationships Between Putrefaction, Fermentation, and
Synthesis *<http://www.agriton.nl/higa.html#17>
4.3 Classification of Soils Based on the Functions of
Microorganisms *<http://www.agriton.nl/higa.html#18>
4.3.1 Disease-Inducing Soils * <http://www.agriton.nl/higa.html#19>
4.3.2 Disease-Suppressive Soils *<http://www.agriton.nl/higa.html#20>
4.3.3 Zymogenic Soils * <http://www.agriton.nl/higa.html#21>
4.3.4 Synthetic Soils * <http://www.agriton.nl/higa.html#22>
*

SUMMARY AND CONCLUSIONS * <http://www.agriton.nl/higa.html#23>

REFERENCES * <http://www.agriton.nl/higa.html#24>

TABLE 1 * <http://www.agriton.nl/higa.html#25>

FIGURE 1 * <http://www.agriton.nl/higa.html#Fig1>

FIGURE 2 * <http://www.agriton.nl/higa.html#Fig2>
*

*

FORWARD
*

ðContents <http://www.agriton.nl/higa.html#terug>

In 1989, the National Research Council of the National Academy of Sciences
issued a highly significant report on "Alternative Agriculture" which was
defined as a system of food and fiber production that applies management
skills and information to reduce costs, improve efficiency, and maintain
production levels through such practices as crop rotations, proper
integration of crops and livestock, nitrogen fixing legumes, integrated
pest management, conservation tillage, and recycling of on-farm wastes as
soil conditioner: and biofertilizers. The report encouraged the collective
adoption of these practices by U.S. farmers as the best alternative to the
continued and intensive use of chemical fertilizers and pesticides which
have often impaired the quality of our soil, water, and food.

Again, in 1993 the National Academy of Sciences left no doubt as to these
earlier concerns when the National Research Council released a report on
"Pesticides in the Diets of Infants and Children" which concluded that
people in this age group could be at considerable health risk from
consumption of foods containing pesticide residues.

Both of these reports have raised considerable speculation about the future
of our chemical-based agricultural production system. A growing consensus
of consumers, environmentalists, legislators, and many farmers is that our
current farming practices will have to change considerably to achieve a
significant reduction in pesticide usage in U.S. agriculture. The ultimate
goal of sustainable agriculture according to the National Research Council,
and other sources as well, is to develop farming systems that are
productive, profitable, energy conserving, environmentally sound,
conserving of natural resources, and that ensure food safety and quality.
Consequently, the leading question that U.S. farmers are asking is, "How
can I make these changes, reduce my chemical inputs, and achieve an
acceptable level of economic and environmental sustainability?"

A successful transition from chemical-based farming systems to a more
sustainable agriculture will depend largely on what farmers do to improve
and maintain the quality of their agricultural soils. Indeed, soil quality
is the "key" to a sustainable agriculture. Not surprisingly, the
alternative agricultural practices advocated by the National Research
Council are mainly those that can improve and maintain soil quality.
Experience has shown that the transition from conventional agriculture to
nature farming or organic farming can involve certain risks, such as
initially lower yields and increased pest problems. Once through the
transition period, which might take several years, most farmers find their
new farming systems to be stable, productive, manageable and profitable
without pesticides.

Dr. Teruo Higa, Professor of Horticulture, University of the Ryukyus,
Okinawa, Japan has conducted pioneering work in advancing the concept of
"Effective Microorganisms" (EM). He has developed microbial inoculants that
have been shown to improve soil quality, crop growth and yield and have
gained attention worldwide. As farmer: seek to change from chemical-based,
conventional farming systems to more sustainable kinds of agriculture they
will need to utilize the most effective means available if they are to be
successful. Certainly, this includes the aforementioned alternative
agricultural practices recommended by the National Research Council. We
view EM technology as a potentially valuable tool that can help farmer:
develop farming systems that are economically, environmentally, and
socially sustainable.

Dr. James F. Parr
Agricultural Research Service
U.S. Department of Agriculture
Beltsville, Maryland, USA




*

INTRODUCTION
*

ðContents <http://www.agriton.nl/higa.html#terug>

The uniqueness of microorganisms and their often unpredictable nature and
biosynthetic capabilities, given a specific set of environmental and
cultural conditions, has made them likely candidates for solving
particularly difficult problems in the life sciences and other fields as
well. The various ways in which microorganisms have been used over the past
50 years to advance medical technology, human and animal health, food
processing, food safety and quality, genetic engineering, environmental
protection, agricultural biotechnology, and more effective treatment of
agricultural and municipal wastes provide a most impressive record of
achievement. Many of these technological advances would not have been
possible using straightforward chemical and physical engineering methods,
or if they were, they would not have been practically or economically
feasible.

Nevertheless, while microbial technologies have been applied to various
agricultural and environmental problems with considerable success in recent
years, they have not been widely accepted by the scientific community
because it is often difficult to consistently reproduce their beneficial
effects. Microorganisms are effective only when they are presented with
suitable and optimum conditions for metabolizing their substrates Including
available water, oxygen (depending on whether the microorganisms are
obligate aerobes or facultative anaerobes), pH and temperature of their
environment. Meanwhile, the various types of microbial cultures and
inoculants available in the market today have rapidly increased because of
these new technologies. Significant achievements are being made in systems
where technical guidance is coordinated with the marketing of microbial
products. Since microorganisms are useful in eliminating problems
associated with the use of chemical fertilizers and pesticides, they are
now widely applied in nature farming and organic agriculture (Higa, 1991;
Parr et al 1994).

Environmental pollution, caused by excessive soil erosion and the
associated transport of sediment, chemical fertilizers and pesticides to
surface and groundwater, and improper treatment of human and animal wastes
has caused serious environmental and social problems throughout the world.
Often engineers have attempted to solve these problems using established
chemical and physical methods. However, they have usually found that such
problems cannot be solved without using microbial methods and technologies
in coordination with agricultural production (Reganold et al., 1990; Parr
and Hornick, l992a).

For many years, soil microbiologists and microbial ecologists have tended
to differentiate soil microorganisms as beneficial or harmful according to
their functions and how they affect soil quality, plant growth and yield,
and plant health. As shown in Table 1, beneficial microorganisms are those
that can fix atmospheric nitrogen, decompose organic wastes and residues,
detoxify pesticides, suppress plant diseases and soil-borne pathogens,
enhance nutrient cycling, and produce bioactive compounds such as vitamins,
hormones and enzymes that stimulate plant growth. Harmful microorganisms
are those that can induce plant diseases, stimulate soil-borne pathogens,
immobilize nutrients, and produce toxic and putrescent substances that
adversely affect plant growth and health.

A more specific classification of beneficial microorganisms has been
suggested by Higa (1991; 1994; 1995) which he refer to as "Effective
Microorganisms" or EM. This report presents some new perspectives on the
role and application of beneficial microorganism, including EM, as
microbial inoculants for shifting the soil microbiological equilibrium in
ways that can improve soil quality, enhance crop production and protection,
conserve natural resources, and ultimately create a more sustainable
agriculture and environment The report also discusses strategies on how
beneficial microorganisms, including EM. can be more effective after
inoculation into soils.


*

THE CONCEPT OF EFTECTIVE MICROORGANISMS:
THEIR ROLE AND APPLICATION
*

ðContents <http://www.agriton.nl/higa.html#terug>

The concept of effective microorganisms (EM) was developed by Professor
Teruo Higa, University of the Ryukyus, Okinawa, Japan (Higa, 1991; Higa and
Wididana, 1991a). EM consists of mixed cultures of beneficial an
naturally-occurring microorganisms that can be applied as inoculants to
increase the microbial diversity of soils and plant. Research has shown
that the inoculation of EM cultures to the soil/plant ecosystem can improve
soil quality, soil health, and the growth, yield, and quality of crops. EM
contains selected species of microorganisms including predominant
populations of lactic acid bacteria and yeasts and smaller numbers of
photosynthetic bacteria, actinomycetes and other types of organisms. All of
these are mutually compatible with one another and can coexist in liquid
culture.

EM is not a substitute for other management practices. It is, however, an
added dimension for optimizing our best soil and crop management practices
such as crop rotations, use of organic amendments, conservation tillage,
crop residue recycling, and biocontrol of pests. If used properly, EM can
significantly enhance the beneficial effects of these practices (Higa and
Wididana, 1991b).

Throughout the discussion which follows, we will use the term "beneficial
microorganisms" In a general way to designate a large group of often
unknown or ill-defined microorganisms that interact favorably in soils and
with plants to render beneficial effects which are sometimes difficult to
predict. We use the term "effective microorganisms" or EM to denote
specific mixed cultures of known, beneficial microorganisms that are being
used effectively as microbial inoculants.


**

*UTILIZATION OF BENEFICIAL MICROORGANISMS IN AGRICULTURE
*

ðContents <http://www.agriton.nl/higa.html#terug>

*What Constitutes an Ideal Agricultural System?*

ðContents <http://www.agriton.nl/higa.html#terug>

Conceptual design is important in developing new technologies for utilizing
beneficial and effective microorganisms for a more sustainable agriculture
and environment. The basis of a conceptual design is imply to first
conceive an ideal or model and then to devise a strategy and method for
achieving the reality. However it is necessary to carefully coordinate the
materials, the environment, and the technologies constituting the method.
Moreover one should adopt a philosophical attitude in applying microbial
technologies to agricultural production and conservation systems.

There are many opinions on what an ideal agricultural system is. Many would
agree that such an idealized system should produce food on a long-term
sustainable basis. Many would also insist that it should maintain and
improve human health, be economically and spiritually beneficial to both
producers and consumers, actively preserve and protect the environment, be
self-contained and regenerative, and produce enough food for an increasing
world population (Higa, 1991).
*

Efficient Utilization and Recycling of Energy
*

ðContents <http://www.agriton.nl/higa.html#terug>

Agricultural production begins with the process of photosynthesis by green
plants which requires solar energy, water, and carbon dioxide. It occurs
through the plants ability to utilize solar energy in "fixing" atmospheric
carbon into carbohydrates. The energy obtained is used for further
biosynthesis in the plant, including essential amino acids and proteins.
The materials used for agricultural production are abundantly available
with little initial cost. However, when it is observed as an economic
activity, the fixation of carbon by photosynthesis has an extremely low
efficiency mainly because of the low utilization rate of solar energy by
green plants. Therefore, an integrated approach is needed to increase the
level of solar energy utilization by plants so that greater amounts of
atmospheric carbon can be converted into useful substrates (Higa and
Wididana, 1991a).

Although the potential utilization rate of solar energy by plants has been
estimated theoretically at between 10 and 20%, the actual utilization rate
is less than 1%. Even the utilization rate of C4 plants, such as sugar cane
whose photosynthetic efficiency is very high, barely exceeds 6 or 7% during
the maximum growth period. The utilization rate is normally less than 3%
even for optimum crop yields.

Past studies have shown that photosynthetic efficiency of the chloroplasts
of host crop plants cannot be increased much further; this means that their
biomass production has reached a maximum level. Therefore, the best
opportunity for increasing biomass production is to somehow utilize the
visible light, which chloroplasts cannot presently use, and the infrared
radiation; together, these comprise about 80% of the total solar energy.
Also, we must explore ways of recycling organic energy contained in plant
and animal residues through direct utilization of organic molecules by
plants (Higa and Wididana, 1991a).

Thus, it is difficult to exceed the existing limits of crop production
unless the efficiency of utilizing solar energy is increased, and the
energy contained in existing organic molecules (amino acids, peptides and
carbohydrates) is utilized either directly or indirectly by the plant. This
approach could help to solve the problems of environmental pollution and
degradation caused by the misuse and excessive application of chemical
fertilizers and pesticides to soils. Therefore, new technologies that can
enhance the economic-viability of farming systems with little or no use of
chemical fertilizers and pesticides are urgently needed and should be a
high priority of agricultural research both now and in the immediate future
(National Academy of Sciences, 1989; 1993).
*

Preservation of Natural Resources and the Environment
*

ðContents <http://www.agriton.nl/higa.html#terug>

The excessive erosion of topsoil from farmland caused by intensive tillage
and row-crop production has caused extensive soil degradation and also
contributed to the pollution of both surface and groundwater. Organic
wastes from animal production, agricultural and marine processing
industries, and municipal wastes (e.i., sewage and garbage), have become
major sources of environmental pollution in both developed and developing
countries. Furthermore, the production of methane from paddy fields and
ruminant animals and of carbon dioxide from the burning of fossil fuels,
land clearing and organic matter decomposition have been linked to global
warming as "greenhouse gases" (Parr and Hornick, 1992b).

Chemical-based, conventional systems of agricultural production have
created many sources of pollution that, either directly or indirectly, can
contribute to degradation of the environment and destruction of our natural
resource base. This situation would change significantly if these
pollutants could be utilized in agricultural production as sources of
energy.

Therefore, it is necessary that future agricultural technologies be
compatible with the global ecosystem and with solutions to such problems in
areas different from those of conventional agricultural technologies. An
area that appears to hold the greatest promise for technological advances
in crop production, crop protection, and natural resource conservation is
that of beneficial and effective microorganisms applied as soil, plant and
environmental inoculants (Higa, 1995).
*

Beneficial and Effective Microorganisms for a Sustainable Agriculture
Towards Agriculture Without Chemicals and With Optimum Yields of High
Quality Crops.
*

ðContents <http://www.agriton.nl/higa.html#terug>

Agriculture in a broad sense, is not an enterprise which leaves everything
to nature without intervention. Rather it is a human activity in which the
farmer attempts to integrate certain agroecological factors and production
inputs for optimum crop and livestock production. Thus, it is reasonable to
assume that farmers should be interested in ways and means of controlling
beneficial soil microorganisms as an important component of the
agricultural environment. Nevertheless, this idea has often been rejected
by naturalists and proponents of nature farming and organic agriculture.
They argue that beneficial soil microorganisms will increase naturally when
organic amendments are applied to soils as carbon, energy and nutrient
sources. This indeed may be true where an abundance of organic materials
are readily available for recycling which often occurs in small-scale
farming. However, in most cases, soil microorganisms, beneficial or
harmful, have often been controlled advantageously when crops in various
agroecological zones are grown and cultivated in proper sequence (i.e.,
crop rotations) and without the use of pesticides. This would explain why
scientists have long been interested in the use of beneficial
microorganisms as soil and plant inoculants to shift the microbiological
equilibrium in a way that enhances soil quality and the yield and quality
of crops (Higa and Wididana, 1991b; Higa, 1994:1995).

Most would agree that a basic rule of agriculture is to ensure that
specific crops are grown according to their agroclimatic and agroecological
requirements. However, in many cases the agricultural economy is based on
market forces that demand a stable supply of food, and thus, it becomes
necessary to use farmland to its full productive potential throughout the
year.

The purpose of crop breeding is to improve crop production, crop
protection, and crop quality. Improved crop cultivars along with improved
cultural and management practices have made it possible to grow a wide
variety of agricultural and horticultural crops in areas where it once
would not have been culturally or economically feasible. The cultivation of
these crops in such diverse environments has contributed significantly to a
stable food supply in many countries. However, it is somewhat ironic that
new crop cultures are almost never selected with consideration of their
nutritional quality or bioavailability after ingestion (Hornick, 1992).

As will be discussed later, crop growth and development are closely related
to the nature of the soil microflora, especially those in close proximity
to plant roots, i.e., the rhizosphere. Thus, it will be difficult to
overcome the limitations of conventional agricultural technologies without
controlling soil microorganisms. This particular tenet is further
reinforced because the evolution of most forms of life on earth and their
environments are sustained by microorganisms. Most biological activities
are influenced by the state of these invisible, minuscule units of life.
Therefore, to significantly increase food production, it is essential to
develop crop cultivars with improved genetic capabilities (i.e., greater
yield potential, disease resistance, and nutritional quality) and with a
higher level of environmental competitiveness, particularly under stress
conditions (i.e., low rainfall, high temperatures, nutrient deficiencies,
and agressive weed growth).

To enhance the concept of controlling and utilizing beneficial
microorganisms for crop production and protection, one must harmoniously
integrate the essential components for plant growth and yield including
light (intensity, photoperiodicity and quality), carbon dioxide, water,
nutrients (organic-inorganic) soil type, and the soil microflora. Because
of these vital interrelationships, it is possible to envision a new
technology and a more energy-efficient system of biological production.

Low agricultural production efficiency is closely related to a poor
coordination of energy conversion which, in turn, is influenced by crop
physiological factors, the environment, and other biological factors
including soil microorganisms. The soil and rhizosphere microflora can
accelerate the growth of plants and enhance their resistance to disease and
harmful insects by producing bioactive substances. These microorganisms
maintain the growth environment of plants, and may have secondary effects
on crop quality. A wide range of results are possible depending on their
predominance and activities at any one time. Nevertheless, there is a
growing consensus that it is possible to attain maximum economic crop
yields of high quality, at higher net returns, without the application of
chemical fertilizers and pesticides. Until recently, this was not thought
to be a very likely possibility using conventional agricultural methods.
However, it is important to recognize that the best soil and crop
management practices to achieve a more sustainable agriculture will also
enhance the growth, numbers and activities of beneficial soil
microorganisms that, in turn, can improve the growth, yield and quality of
crops (National Academy of Sciences, 1989; Hornick, 1992; Parr et al.,
1992).


*

CONTROLLING THE SOIL MICROFLORA:
PRINCIPLES AND STRATEGIES

Principles of Natural Ecosystems and the Application of Beneficial and
Effective Microorganisms
*

ðContents <http://www.agriton.nl/higa.html#terug>

The misuse and excessive use of chemical fertilizers and pesticides have
often adversely affected the environment and created many a) food safety
and quality and b) human and animal health problems. Consequently, there
has been a growing interest in nature farming and organic agriculture by
consumers and environmentalists as possible alternatives to chemical-based,
conventional agriculture.

Agricultural systems which conform to the principles of natural ecosystems
are now receiving a great deal of attention in both developed and
developing countries. A number of books and journals have recently been
published which deal with many aspects of natural farming systems. New
concepts such as alternative agriculture, sustainable agriculture, soil
quality, integrated pest management, integrated nutrient management and
even beneficial microorganisms are being explored by the agricultural
research establishment (National Academy of Sciences, 1989; Reganold et
al., 1990; Parr et al., 1992). Although these concepts and associated
methodologies hold considerable promise, they also have limitations. For
example, the main limitation in using microbial inoculants is the problem
of reproducibility and lack of consistent results.

Unfortunately certain microbial cultures have been promoted by their
suppliers as being effective for controlling a wide range of soil-borne
plant diseases when in fact they were effective only on specific pathogens
under very specific conditions. Some suppliers have suggested that their
particular microbial inoculant is akin to a pesticide that would suppress
the general soil microbial population while increasing the population of a
specific beneficial microorganism. Nevertheless, most of the claims for
these single-culture microbial inoculants are greatly exaggerated and have
not proven to be effective under field conditions. One might speculate that
if all of the microbial cultures and inoculants that are available as
marketed products were used some degree of success might be achieved
because of the increased diversity of the soil microflora and stability
that is associated with mixed cultures. While this, of course, is a
hypothetical example, the fact remains that there is a greater likelihood
of controlling the soil microflora by introducing mixed, compatible
cultures rather than single pure cultures (Higa, 1991).

Even so, the use of mixed cultures in this approach has been criticized
because it is difficult to demonstrate conclusively which microorganisms
are responsible for the observed effects, how the introduced microorganisms
interact with the indigenous species, and how these new associations affect
the soil/plant environment. Thus, the use of mixed cultures of beneficial
microorganisms as soil inoculants to enhance the growth, health, yield, and
quality of crops has not gained widespread acceptance by the agricultural
research establishment because conclusive scientific proof is often lacking.

The use of mixed cultures of beneficial microorganisms as soil inoculants
is based on the principles of natural ecosystems which are sustained by
their constituents; that is, by the quality and quantity of their
inhabitants and specific ecological parameters, i.e.,* *the greater the
diversity and number of the inhabitants, the higher the order of their
interaction and the more stable the ecosystem. The mixed culture approach
is simply an effort to apply these principles to natural systems such as
agricultural soils, and to shift the microbiological equilibrium in favor
of increased plant growth, production and protection (Higa, 1991; 1994;Parr
et al., 1994).

It is important to recognize that soils can vary tremendously as to their
types and numbers of microorganisms. These can be both beneficial and
harmful to plants and often the predominance of either one depends on the
cultural and management practices that are applied. It should also be
emphasized that most fertile and productive soils have a high content of
organic matter and, generally, have large, populations of highly diverse
microorganisms (i.e.,* *both species and genetic diversity). Such soils
will also usually have a wide ratio of beneficial to harmful microorganisms
(Higa and Wididana, 1991b).
*

Controlling the Soil Microflora for Optimum Crop Production and Protection
*

ðContents <http://www.agriton.nl/higa.html#terug>

The idea of controlling and manipulating the soil microflora through the
use of inoculants organic amendments and cultural and management practices
to create a more favorable soil microbiological environment for optimum
crop production and protection is not new. For almost a century,
microbiologists have known that organic wastes and residues, including
animal manures, crop residues, green manures, municipal wastes (both raw
and composted), contain their own indigenous populations of microorganisms
often with broad physiological capabilities.

It is also known that when such organic wastes and residues are applied to
soils many of these introduced microorganisms can function as biocontrol
agents by controlling or suppressing soil-borne plant pathogens through
their competitive and antagonistic activities. While this has been the
theoretical basis for controlling the soil microflora, in actual practice
the results have been unpredictable and inconsistent, and the role of
specific microorganisms has not been well-defined.

For, many years microbiologists have tried to culture beneficial
microorganisms for use as soil inoculants to overcome the harmful effects
of phytopathogenic organisms, including bacteria, fungi and nematodes. Such
attempts have usually involved single applications of pure cultures of
microorganisms which have been largely unsuccessful for several reasons.
First, it is necessary to thoroughly understand the individual growth and
survival characteristics of each particular beneficial microorganism,
including their nutritional and environmental requirements. Second, we must
understand their ecological relationships and interactions with other
microorganisms, including their ability to coexist in mixed cultures and
after application to soils (Higa, 1991; 1994).

There are other problems and constraints that have been major obstacles to
controlling the microflora of agricultural soils. First and foremost is the
large number of types of microorganisms that are present at any one time,
their wide range of physiological capabilities, and the dramatic
fluctuations in their populations that can result from man’s cultural and
management practices applied to a particular farming system. The diversity
of the total soil microflora depends on the nature of the soil environment
and those factors which affect the growth and activity of each individual
organism including temperature, light, aeration, nutrients, organic matter,
pH and water. While there are many microorganisms that respond positively
to these factors, or a combination thereof, there are many that do not.
Microbiologists have actually studied relatively few of the microorganisms
that exist in most agricultural soil, mainly because we don't know how to
culture them; i.e.,* *we know very little about their growth, nutritional,
and ecological requirements.

The "diversity" and "population" factors associated with the soil
microflora have discouraged scientists from conducting research to develop
control strategies. Many believe that, even when beneficial microorganisms
are cultured and inoculated into soils, their number is relatively small
compared with the indigenous soil inhabitants, and they would likely be
rapidly overwhelmed by the established soil microflora. Consequently, many
would argue that even if the application of beneficial microorganisms is
successful under limited conditions (e.g., in the laboratory) it would be
virtually impossible to achieve the same success under actual field
conditions. Such thinking still exists today, and serves as a principle
constraint to the concept of controlling the soil microflora (Higa, 1994).

It is noteworthy that most of the microorganisms encountered in any
particular soil are harmless to plants with only a relatively few that
function as plant pathogens or potential pathogens. Harmful microorganisms
become dominant if conditions develop that are favorable to their growth,
activity and reproduction. Under such conditions, soil-borne pathogens
(e.g., fungal pathogens) can rapidly increase their populations with
devastating effects on the crop. If these conditions change, the pathogen
population declines just as rapidly to its original state. Conventional
farming systems that tend toward the consecutive planting of the same crop
(i.e., monoculture) necessitate the heavy use of chemical fertilizers and
pesticides. This, in turn, generally increases the probability that
harmful, disease-producing, plant pathogenic microorganisms will become
more dominant in agricultural soils (Higa, 1991; 1994; Parr and Hornick,
1994). Chemical-based conventional farming methods are not unlike
symptomatic therapy. Examples of this are applying fertilizers when crops
show symptoms of nutrient-deficiencies, and applying pesticides whenever
crops are attacked by insects and diseases. In efforts to control the soil
microflora some scientists feel that the introduction of beneficial
microorganisms should follow a symptomatic approach. However, we do not
agree. The actual soil conditions that prevail at any point in time may be
most unfavorable to the growth and establishment of laboratory-cultured,
beneficial microorganisms. To facilitate their establishment, it may
require that the farmer make certain changes in his cultural and management
practices to induce conditions that will (a) allow the growth and survival
of the inoculated microorganisms and (b) suppress the growth and activity
of the indigenous plant pathogenic microorganisms (Higa, 1994; Parr et al.,
1994).

An example of the importance of controlling the soil microflora and how
certain cultural and management practices can facilitate such control is
useful here. Vegetable cultivars are often selected on their ability to
grow and produce over a wide range of temperatures. Under cool, temperate
conditions there are generally few pest and disease problems. However, with
the onset of hot weather, there is a concomitant increase in the incidence
of diseases and insects making it rather difficult to obtain acceptable
yields without applying pesticides. With higher temperatures, the total
soil microbial population increases as does certain plant pathogens such as
Fusarium, which is one of the main putrefactive, fungal pathogens in soil.
The incidence and destructive activity of this pathogen can be greatly
minimized by adopting reduced tillage methods and by shading techniques to
keep the soil cool during hot weather. Another approach is to inoculate the
soil with beneficial, antagonistic, antibiotic-producing microorganisms
such as actinomycetes and certain fungi (Higa and Wididana, 1991a; 1991b).
*

Application of Beneficial and Effective Microorganisms: A New Dimension
*

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Many microbiologists believe that the total number of soil microorganisms
can be increased by applying organic amendments to the soil. This is
generally true because most soil microorganisms are heterotrophic, i.e.,
they require complex organic molecules of carbon and nitrogen for
metabolism and biosynthesis. Whether the regular addition of organic wastes
and residues will greatly increase the number of beneficial soil
microorganisms in a short period of time is questionable. However, we do
know that heavy applications of organic materials, such as seaweed, fish
meal, and chitin from crushed crab shells, not only helps to balance the
micronutrient content of a soil but also increases the population of
beneficial antibiotic-producing actinomycetes. This changes the soil to a
disease-suppressive condition within a relatively short period.

The probability that a particular beneficial microorganism will become
predominant, even with organic farming or nature farming methods, will
depend on the ecosystem and environmental conditions. It can take several
hundred years for various species of higher and lower plants to interact
and develop into a definable and stable ecosystem. Even if the population
of a specific microorganism is increased through cultural and management
practices, whether it will be beneficial to plants is another question.
Thus, the likelihood of a beneficial, plant-associated microorganism
becoming predominant under conservation-based farming systems is virtually
impossible to predict. Moreover, it is very unlikely that the population of
useful anaerobic microorganisms, which usually comprise only a small part
of the soil microflora, would increase significantly even under natural
farming conditions.

This information then emphasizes the need to develop methods for isolating
and selecting different microorganisms for their beneficial effects on
soils and plants. The ultimate goal is to select microorganisms that are
physiologically and ecologically compatible with each other and that can be
introduced as mixed cultures into soil where their beneficial effects can
be realized (Higa, 1991; 1994; 1995).
*

Application of Beneficial and Effective Microorganisms: Fundamental
Considerations
*

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Microorganisms are utilized in agriculture for various purposes; as
important components of organic amendments and composts, as legume
inoculants for biological nitrogen fixation as a means of suppressing
insects and plant diseases to Improve crop quality and yields, and for
reduction of labor. All of these are closely related to each other. An
important consideration in the application of beneficial microorganisms to
soils is the enhancement of their synergistic effects. This is difficult to
accomplish if these microorganisms are applied to achieve symptomatic
therapy, as in the case of chemical fertilizers and pesticides (Higa, 1991;
1994).

If cultures of beneficial microorganisms are to be effective after
inoculation into soil, it is important that their initial populations be at
a certain critical threshold level. This helps to ensure that the amount of
bioactive substances produced by them will be sufficient to achieve the
desired positive effects on crop production and/or crop protection. If
these conditions are not met, the introduced microorganisms, no matter how
useful they are, will have little if any effect. At present, there are no
chemical tests that can predict the probability of a particular
soil-inoculated microorganism to achieve a desired result. The most
reliable approach is to inoculate the beneficial microorganism into soil as
part of a mixed culture, and at a sufficiently high inoculum density to
maximize the probability of its adaptation to environmental and ecological
conditions (Higa and Wididana, 1991b; Parr et al., 1994).

The application of beneficial microorganisms to soil can help to define the
structure and establishment of natural ecosystems. The greater the
diversity of the cultivated plants that are grown and the more chemically
complex the biomass, the greater the diversity of the soil microflora as to
their types, numbers and activities. The application of a wide range of
different organic amendments to soils can also help to ensure a greater
microbial diversity. For example, combinations of various crop residues,
animal manures, green manures, and municipal wastes applied periodically to
soil will provide a higher level of microbial diversity than when only one
of these materials is applied. The reason for this is that each of these
organic materials has its own unique indigenous microflora which can
greatly affect the resident soil microflora after they are applied, at
least for a limited period.


*

CLASSIFICATION OF SOILS BASED ON THEIR MICROBIOLOGICAL PROPERTIES
*

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Most soils are classified on the basis of their chemical and physical
properties; little has been done to classify soils according to their
physicochemical and microbiological properties. The reason for this is that
a soil's chemical and physical properties are more readily defined and
measured than their microbiological properties. Improved soil quality is
usually characterized by increased infiltration; aeration, aggregation and
organic matter content and by decreased bulk density, compaction, erosion
and crusting. While these are important indicators of potential soil
productivity, we must give more attention to soil biological properties
because of their important relationship (though poorly understood) to crop
production, plant and animal health, environmental quality, and food safety
and quality. Research is needed to identify and quantify reliable and
predictable biological/ecological indicators of soil quality. Possible
indicators might include total species diversity or genetic diversity of
beneficial soil microorganisms as well as insects and animals (Reganold et
al., 1990; Parr et al., 1992).

The basic concept here is not to classify soils for the study of
microorganisms but for farmers to be able to control the soil microflora so
that biologically-mediated processes can improve the growth, yield, and
quality of crops as well as the tilth, fertility, and productivity of
soils. The ultimate objective is to reduce the need for chemical
fertilizers and pesticides (National Academy of Sciences, 1989; 1993).
*

Functions of Microorganisms: Putrefaction, Fermentation, and Synthesis
*

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Soil microorganisms can be classified into decomposer and synthetic
microorganisms. The decomposer microorganisms are subdivided into groups
that perform oxidative and fermentative decomposition. The fermentative
group is further divided into useful fermentation (simply called
fermentation) and harmful fermentation (called putrefaction). The synthetic
microorganisms can be sub-divided into groups having the physiological
abilities to fix atmospheric nitrogen into amino acids and/or carbon
dioxide into simple organic molecules through photosynthesis. Figure 1
(adapted from Higa) is a simplified flow chart of organic matter
transformations by soil microorganisms that can lead to the development of
disease-inducing, disease-suppressive, zymogenic, or synthetic soils.

Fermentation is an anaerobic process by which facultative microorganisms
(e.g., yeasts) transform complex organic molecules (e.g., carbohydrates)
into simple organic compounds that often can be absorbed directly by
plants. Fermentation yields a relatively small amount of energy compared
with aerobic decomposition of the same substrate by the same group of
microorganisms. Aerobic decomposition results in complete oxidation of a
substrate and the release of large amounts of energy, gas, and heat with
carbon dioxide and water as the end products. Putrefaction is the process
by which facultative heterotrophic microorganisms decompose proteins
anaerobically, yielding malodorous incompletely oxidized, metabolites
(e.g., ammonia, mercaptans and indole) that are often toxic to plants and
animals.

The term "synthesis" as used here refers to the biosynthetic capacity of
certain microorganisms to derive metabolic energy by "fixing" atmospheric
nitrogen and/or carbon dioxide. In this context we refer to these as
"synthetic" microorganisms, and if they should become a predominant part of
the soil microflora, then the soil would be termed a "synthetic" soil.

Nitrogen-fixing microorganisms are highly diverse, ranging from
"free-living" autotrophic bacteria of the genus Azotobacter to symbiotic,
heterotrophic bacteria of the genus Rhizobium, and blue-green algae (now
mainly classified as blue-green bacteria), all of which function
aerobically. Photosynthetic microorganisms fix atmospheric carbon dioxide
in a manner similar to that of green plants. They are also highly diverse,
ranging from blue-green algae to green algae that perform complete
photosynthesis aerobically to photosynthetic bacteria which perform
incomplete photosynthesis anaerobically.
*

Relationships Between Putrefaction, Fermentation, and Synthesis
*

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The processes of putrefaction, fermentation, and synthesis proceed
simultaneously according to the appropriate types and numbers of
microorganisms that are present in the soil. The impact on soil quality
attributes and related soil properties is determined by the dominant
process. The production of organic substances by microorganisms results
from the intake of positive ions, while decomposition serves to release
these positive ions. Hydrogen ions play a pivotal role in these processes.
A problem occurs when hydrogen ions do not recombine with oxygen to form
water but are utilized to produce methane, hydrogen sulfide, ammonia,
mercaptans and other highly reduced putrefactive substances most of which
are toxic to plants and produce malodors. If a soil is able to absorb the
excess hydrogen ions during periods of soil anaerobiosis and if synthetic
microorganisms such as photosynthetic bacteria are present, they will
utilize these putrefactive substances and produce useful substrates from
them which helps to maintain a healthy and productive soil.

The photosynthetic bacteria, which perform incomplete photosynthesis
anaerobically, are highly desirable, beneficial soil microorganisms because
they are able to detoxify soils by transforming reduced, putrefactive
substances such as hydrogen sulfide into useful substrates. This helps to
ensure efficient utilization of organic matter and to improve soil
fertility. Photosynthesis involves the photo-catalyzed splitting of water
which yields molecular oxygen as a by-product. Thus, these microorganisms
help to provide a vital source of oxygen to plant roots.

Reduced compounds such as methane and hydrogen sulfide are often produced
when organic materials are decomposed under anaerobic conditions. These
compounds are toxic and can greatly suppress the activities of
nitrogen-fixing microorganisms. However, if synthetic microorganisms, such
as photosynthetic bacteria that utilize reduced substances, are present in
the soil, oxygen deficiencies are not likely to occur. Thus,
nitrogen-fixing microorganisms, coexisting in the soil with photosynthetic
bacteria, can function effectively in fixing atmospheric nitrogen even
under anaerobic conditions.

Photosynthetic bacteria not only perform photosynthesis but can also
fix-nitrogen. Moreover, it has been shown that, when they coexist, in soil
with species of Azotobacter, their ability to fix nitrogen is enhanced.
This then is an example of a synthetic soil. It also suggests that by
recognizing the role, function, and mutual compatibility of these two
bacteria and utilizing them effectively to their full potential, soils can
be induced to a greater synthetic capacity. Perhaps the most effective
synthetic soil system results from the enhancement of zymogenic and
synthetic microorganisms; this allows fermentation to become dominant over
putrefaction and useful synthetic processes to proceed.
*

Classification of Soils Based on the Functions of Microorganisms
*

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As discussed earlier (Figure 1), soils can be characterized according to
their indigenous microflora which perform putrefactive, fermentative,
synthetic and zymogenic reactions and processes. In most soils, these three
functions are going on simultaneously with the rate and extent of each
determined by the types and numbers of associated microorganisms that are
actively involved at any one time.

A simple diagram showing a classification of soils based on the activities
and functions of their predominant microorganisms is presented in Fig. 2.

*Disease-Inducing Soils.* In this type of soil, plant pathogenic
microorganisms such as Fusarium fungi can comprise 5 to 20 percent of the
total microflora if fresh organic matter with a high nitrogen content is
applied to such a soil, incompletely oxidized products can arise that are
malodorous and toxic to growing plants. Such soils tend to cause frequent
infestations of disease organisms, and harmful insects. Thus, the
application of fresh organic matter to these soils is often harmful to
crops. Probably more than 90 percent of the agricultural land devoted to
crop production worldwide can be classified as having disease-inducing
soil. Such soils generally have poor physical properties, and large amounts
of energy are lost as "greenhouse" gases, particularly in the case of rice
fields. Plant nutrients are also subject to immobilization into unavailable
forms.

*Disease-Suppressive Soils.* The microflora of disease-suppressive soils is
usually dominated by antagonistic microorganisms that produce copious
amounts of antibiotics. These include fungi of the genera Penicillium,
Trichoderma, and Aspergillus, and actinomycetes of the genus Streptomyces.
The antibiotics they produce can have biostatic and biocidal effects on
soil-borne plant pathogens, including Fusarium which would have an
incidence in these soils of less than 5 percent. Crops planted in these
soils are rarely affected by diseases or insect pests. Even if fresh
organic matter with a high nitrogen content is applied, the production of
putrescent substances is very low and the soil has a pleasant earthy odor
after the organic matter is decomposed. These soils generally have
excellent physical properties; for example, they readily, form water-stable
aggregates and they are well-aerated, and have a high permeability to both
air and water. Crop yields in the disease-suppressive soils are often
slightly lower than those in synthetic soils. Highly acceptable crop yields
are obtained whenever a soil has a predominance of both disease-suppressive
and synthetic microorganisms.

*Zymogenic Soils.* These soils are dominated by a microflora that can
perform useful kinds of fermentations, i.e., the breakdown of complex
organic molecules into simple organic substances and inorganic materials.
The organisms can be either obligate or facultative anaerobes. Such
fermentation-producing microorganisms often comprise the microflora of
various organic materials, i.e., crop residues, animal manures, green
manures and municipal wastes including composts. After these amendments are
applied to the soil, their number: and fermentative activities can increase
dramatically and overwhelm the indigenous soil microflora for an indefinite
period. While these microorganisms remain predominant, the soil can be
classified as a zymogenic soil which is generally characterized by a)
pleasant, fermentative odors especially after tillage, b) favorable soil
physical properties (e.g., Increased aggregate stability, permeability,
aeration and decreased resistance to tillage c) large amounts of inorganic
nutrients, amino acids, carbohydrates, vitamins and other bioactive
substances which can directly or indirectly enhance the growth, yield and
quality of crops, d) low occupancy of Fusarium fungi which is usually less
than 5 percent, and e) low production of greenhouse gases (e.g., methane,
ammonia, and carbon dioxide) from croplands, even where flooded rice is
grown.

*Synthetic Soils.* These soils contain significant populations of
microorganisms which are able to fix atmospheric nitrogen and carbon
dioxide into complex molecules such as amino acids, proteins and
carbohydrates. Such microorganisms include photosynthetic bacteria which
perform incomplete photosynthesis anaerobically, certain Phycomycetes
(fungi that resemble algae), and both green algae and blue--green algae
which function aerobically. All of these are photosynthetic organisms that
fix atmospheric nitrogen. If the water content of these soils is stable,
their fertility can be largely maintained by regular additions of only
small amounts of organic materials. These soils have a low Fusarium
occupancy and they are often of the disease-suppressive type. The
production of gases from fields where synthetic soils are present is
minimal, even for flooded rice.

This is a somewhat simplistic classification of soils based on the
functions of their predominant types of microorganisms, and whether they
are potentially beneficial or harmful to the growth and yield of crops.
While these different types of soils are described here in a rather
idealized manner, the fact is that in nature they are not always clearly
defined because they often tend to have some of the same characteristics.
Nevertheless, research has shown that a disease-inducing soil can be
transformed into disease-suppressing, zymogenic and synthetic soils by
inoculating the problem soil with mixed cultures of effective
microorganisms (Higa, 1991; 1994; Parr et al., 1994). Thus it is somewhat
obvious that the most desirable agricultural soil for optimum growth,
production, protection, and quality of crops would be the composite soil
indicated in Fig. 2, i.e.,* *a soil that is highly zymogenic and synthetic,
and has an established disease-suppressive capacity. This then is the
principle reason for seeking ways and means of controlling the microflora
of agricultural soils.


*

SUMMARY AND CONCLUSIONS
*

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Controlling the soil microflora to enhance the predominance of beneficial
and effective microorganisms can help to improve and maintain the soil
chemical and physical properties. The proper and regular addition of
organic amendments are often an important part of any strategy to exercise
such control.

Previous efforts to significantly change the indigenous microflora of a
soil by introducing single cultures of extrinsic microorganisms have
largely been unsuccessful. Even when a beneficial microorganism is isolated
from a soil, cultured in the laboratory, and reinoculated into the same
soil at a very high population, it is immediately subject to competitive
and antagonistic effects from the indigenous soil microflora and its
numbers soon decline. Thus, the probability of shifting the
"microbiological equilibrium" of a soil and controlling it to favor the
growth, yield and health of crops is much greater if mixed cultures of
beneficial and effective microorganisms are introduced that are
physiologically and ecologically compatible with one another. When these
mixed cultures become established their individual beneficial effects are
often magnified in a synergistic manner.

Actually, a disease-suppressive microflora can be developed rather easily
by selecting and culturing certain types of gram-positive bacteria that
produce antibiotics and have a wide range of specific functions and
capabilities; these organisms include facultative anaerobes, obligate
aerobes, acidophilic and alkalophilic microbes. These microorganisms can be
grown to high populations in a medium consisting of rice bran, oil cake and
fish meal and then applied to soil along with well-cured compost that also
has a large stable population of beneficial microorganisms, especially
facultative anaerobic bacteria. A soil can be readily transformed into a
zymogenic/synthetic soil with disease-suppressive potential if mixed
cultures of effective microorganisms with the ability to transmit these
properties are applied to that soil.

The desired effects from applying cultured beneficial and effective
microorganisms to soils can be somewhat variable, at least initially. In
some soils, a single application (i.e., inoculation) may be enough to
produce the expected results, while for other soils even repeated
applications may appear to be ineffective. The reason for this is that in
some soils it takes longer for the introduced microorganisms to adapt to a
new set of ecological and environmental conditions and to become
well-established as a stable, effective and predominant part of the
indigenous soil microflora. The important consideration here is the careful
selection of a mixed culture of compatible, effective microorganisms
properly cultured and provided with acceptable organic substrates. Assuming
that repeated applications are made at regular intervals during the first
cropping season, there is a very high probability that the desired results
will be achieved.

There are no meaningful or reliable tests for monitoring the establishment
of mixed cultures of beneficial and effective microorganisms after
application to a soil. The desired effects appear only after they are
established and become dominant, and remain stable and active in the soil.
The inoculum densities of the mixed cultures and the frequency of
application serve only as guidelines to enhance the probability of early
establishment. Repeated applications, especially during the first cropping
season, can markedly facilitate early establishment of the introduced
effective microorganisms.

Once the "new" microflora is established and stabilized, the desired
effects will continue indefinitely and no further applications are
necessary unless organic amendments cease to be applied, or the soil is
subjected to severe drought or flooding.

Finally, it is far more likely that the microflora of a soil can be
controlled through the application of mixed cultures of selected beneficial
and effective microorganisms than by the use of single or pure cultures. If
the microorganisms comprising the mixed culture can coexist and are
physiologically compatible and mutually complementary, and if the initial
inoculum density is sufficiently high, there is a high probability that
these microorganisms will become established in the soil and will be
effective as an associative group, whereby such positive interactions would
continue. If so, then it is also highly, probable that they will exercise
considerable control over the indigenous soil microflora which, in due
course, would likely be transformed into or replaced by a "new" soil
microflora.


*

REFERENCES
*

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Higa, T. 1991. Effective microorganisms: A biotechnology for mankind.
p.8-14. In J.F. Parr, S.B. Hornick, and C.E. Whitman (ed.) Proceedings of
the First International Conference on Kyusei Nature Farming. U.S.
Department of Agriculture, Washington, D.C., USA.

Higa, T. and G.N. Wididana 1991a. The concept and theories of effective
microorganisms. p. 118-124. In Parr, S.B. Hornick, and C.E. Whitman (ed.)
Proceedings of the First International Conference on Kyusei Nature Farming.
U.S. Department of Agriculture, Washington, D.C., USA.

Higa, T. and G.N. Wididana 199lb. Changes In the soil microflora Induced by
effective microorganisms. p.153-162. In J.F. Parr, S.B. Hornick, and C.E.
Whitman (ed.) Proceedings of the First International Conference on Kyusei
Nature Farming. U.S. Department of Agriculture, Washington, D.C., USA.

Higa, T. 1994. Effective Microorganisms: A New Dimension for Nature
Farming. p. 20-22. In J.F. Parr, S.B. Hornick, and M.E. Simpson (ed.)
Proceedings of the Second International Conference on Kyusei Nature
Farming. U.S. Department of Agriculture, Washington, D.C, USA.

Higa, T. 1995. Effective microorganisms: Their role in Kyusei Nature
Farming and sustainable agriculture. In J.F. Parr, S.B. Hornick, and M.E.
Simpson (ed.) Proceedings of the Third International Conference on Kyusei
Nature Farming. U.S. Department of Agriculture, Washington, D.C., USA. (In
Press).

Hornick, S.B. 1992. Factors affecting the nutritional quality of crops.
Amer. J. Alternative Agric. 7:63-68.

National Academy of Sciences. 1989. Alternative Agriculture. Committee on
the Role of Alternative Agriculture Farming Methods in Modern Production
Agriculture. National Research Council, Board on Agriculture. National
Academy Press, Washington, D.C., USA. 448 p.

National Academy of Sciences. 1993. Pesticides in Diets of Infants and
Children National Research Council, Board on Agriculture. National Academy
Press, Washington, D.C., USA. 373 p.

Parr, J.F. and S.B. Hornick 1992a. Agricultural use of organic amendments:
A historical perspective. Amer. J. Alternative Agric. 7:181-189.

Parr, J.F. and S.B. Hornick. 1992b. Utilization of municipal wastes.
p.545-559. In F.B. Metting (ed.) Soil Microbial Ecology: Applications in
Agriculture and Environmental Management. Marcel Dekker, Inc., New York,
USA.

Parr, J.F., R.I. Papendick, S.B. Hornick, and R.E. Meyer. 1992. Soil
quality: Attributes and relationship to alternative and sustainable
agriculture. Amer. J. Alternative Agric. 7:5-11.

Parr, J.F. and S.B. Hornick. 1994. Assessment of the Third International
Conference on Kyusei Nature Farming: Round Table Discussion by USDA
Scientists, October 7, 1993. Published by the Nature Farming Research and
Development Foundation, Lompoc, California, USA.

Parr, J.F., S.B. Hornick, and D.D. Kaufman. 1994. Use of microbial
Inoculants and organic fertilizers in agricultural production. In
Proceedings of the International Seminar on the Use of Microbial and
Organic Fertilizers in Agricultural Production. Published by the Food and
Fertilizer Technology Center, Taipei, Taiwan.

Reganold, J.P., R.I Papendick, and J.F. Parr. 1990. Sustainable
Agriculture. Scientific American 262(6): 112-120.



*Table 1.*
Some Common Functions of Beneficial and Harmful Soil Microorganisms
as they Affect Soil Quality, Crop Production, and Plant Health.

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*

Functions of Beneficial Microorganisms
*
- Fixation of atmospheric nitrogen
- Decomposition of organic wastes and residues
- Suppression of soil-borne pathogens
- Recycling and increased availability of plant nutrients
- Degradation of toxicants including pesticides
- Production of antibiotics and other bioactive compounds
- Production of simple organic molecules for plant uptake
- Complexation of heavy metals to limit plant uptake
- Solubilization of insoluble nutrient sources
- Production of polysaccharides to improve soil aggregation



*

Functions of Harmful Microorganisms
*
- Induction of plant diseases
- Stimulation of soil-borne pathogens
- Immobilization of plant nutrients
- Inhibition of seed germination
- Inhibition of plant growth and development
- Production of phytotoxic substances



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