Beneficial Insects and Other Arthropodsby W.S. Cranshaw 1
(2/09)Quick Facts... Beneficial arthropods can prevent or liit pest
probles in the yard and !arden. "hese #friends# can be cate!ori$ed
broadly as either insect predators or parasites. %redators
incl&de lady beetles' lacewin!s and spiders. Coon insect
parasites are the tachinid flies' the braconid and the
ichne&onid wasps. When insecticides are needed' choose ones
that are selective and less li(ely to har insect predators and
parasites.)ost insects and other arthropods fo&nd in the yard
and !arden do not feed on or har plants. )any of these are *&st
passin! thro&!h or have innoc&o&s habits. +thers feed
on and destroy pest species. ,n any cases' the activities of these
beneficial species can copletely prevent or !reatly liit pest
probles. ,t is iportant to reco!ni$e these beneficial arthropods so
they ay be appreciated and conserved.Beneficial arthropods are
cate!ori$ed broadly as either predators or parasites. -d< or
iat&re sta!es of insect predators' or both' actively search
o&t and eat prey insects. %redators incl&de lady beetles'
lacewin!s and spiders. ,nsect parasites develop in or on a sin!le
host fro e!!s or larvae deposited by the ad< parasite. Coon
insect parasites are tachinid flies and the braconid and
ichne&onid wasps.Insect PredatorsLady Beetles+ften called
ladyb&!s' ladybeetles (.i!&re 1) are theost failiar insect
predator.)ost ad< lady beetles arero&nd to oval' bri!htly
coloredand often spotted. /ady beetles are f&rther
disc&ssed in fact sheet 0.091' Lady Beetles. "he iat&re or
larvae sta!es' however' loo( very different and often are
overloo(ed or isidentified. /ady beetle larvae are elon!ated'
&s&ally dar( colored' and flec(ed with oran!e or yellow
(.i!&re 2).-d< and larvae feed on lar!e n&bers of
sall' soft2bodied insects s&ch as aphids. +ne !ro&p of
sall' blac( lady beetles (Stethorus) is iportant in controllin!
spider ites and others speciali$e in scale insects. /ady beetles
can rapidly control any developin! insect probles' partic&larly
if teperat&res are war..i!&re 13 "wospotted lady beetle
layin! e!!s. .i!&re 23 "ypical lady beetle larva.+ne species of
lady beetle' however' the )e4ican bean beetle' is a plant pest.
"his coon Colorado insect is fo&nd feedin! on bean leaves. ,t
is distin!&ished fro other lady beetles by spottin! and color
in the ad< sta!e. /arvae of the )e4icanbean beetle are yellow
and spiny.Green LacewingsSeveral !reen lacewin! species (.i!&re
5)are coonly fo&nd in !ardens. "he ad<sta!e is failiar to
ost !ardeners3 a pale!reen insect with lar!e' clear'
hi!hly2veinedwin!s that are held over the body when atrest.
-d< !reen lacewin!s priarily feedon nectar and other
fl&ids' b&t soe species also cons&e a few sall
insects.6reen lacewin!s lay a distinctive stal(ed e!!. /acewin!
larvae eer!e in fo&r to 10 days. "hese larvae' soeties called
aphid lions' are voracio&s predators capable of feedin! on sall
caterpillars and beetles' as well as aphids and other insects. ,n
!eneral shape and si$e' lacewin! larvae are s&perficially
siilar to lady beetle larvae. 7owever' iat&re lacewin!s
&s&ally are li!ht brown and have a lar!e pair of hoo(ed
*aws stic(in! o&t fro the front of the head (.i!&re
1).Syrphid Flies"hese flies are called by severalnaes' s&ch as
flower flies orhover flies. )ost are bri!htlycolored' yellow or
oran!e andblac(' and ay reseble bees or yellow*ac(et wasps.
7owever' syrphid flies are harless to people. 8s&ally they can
be seen feedin! on flowers.,t is the larval sta!e of the syrphid
fly that preys on insects. 9ario&sly colored' the tapered
a!!ots crawl over folia!e and can eat do$ens of sall' soft2bodied
insects each day. Syrphid flies are partic&larly iportant in
controllin! aphid infestations early in the season' when cooler
teperat&res ay inhibit other predators. Siilar in appearance to
syrphid fly larvae is a sall' bri!ht oran!e predatory id!e
(Aphidoletes). "hese insects often can be seen feedin! within aphid
colonies late in the season.Predatory Bugs"r&e b&!s (+rder3
7eiptera) are predators of insects and ites. -ll feed by piercin!
the prey with their narrow o&thparts and s&c(in! o&t
body fl&ids. - red and blac( species of predatory stin(
b&!' capable of.i!&re 53 6reen lacewin! ad<.
.i!&re 13 6reen lacewin! nyph. %hoto co&rtesy of 7arold
/arsen..i!&re 03 Syrphid fly ad<. .i!&re :3 Syrphid
fly larva.feedin! on fairly lar!e insects s&ch as caterpillars
and potato beetle larvae' is ost conspic&o&s. )ore coon'
b&t less fre;&ently observed' are the vario&s li!ht
brown dasel b&!s' also called nabid b&!s. ) technolo!y as a
potentially val&able tool that can help farer3 develop farin!
systes that are econoically' environentally' and socially
s&stainable.)' as icrobial inoc&lants for shiftin! the soil
icrobiolo!icale;&ilibri& in ways that can iprove soil
;&ality' enhance crop prod&ction and protection' conserve
nat&ral reso&rces' and <iately create a ore
s&stainable a!ric<&re and environent "he report also
disc&sses strate!ies on how beneficial icroor!aniss'
incl&din! >). can be ore effective after inoc&lation
into soils. 'H+ $O,$+P' OF +F'+$'I/+ 0I$1OO12A,I303:'H+I1 1O-+ A,.
APP-I$A'IO,Contents"he concept of effective icroor!aniss (>))
was developed by %rofessor "er&o 7i!a' 8niversity of the
Cy&(y&s' +(inawa' Dapan (7i!a' 1991J 7i!a and Wididana'
1991a). >) consists of i4ed c<&res of beneficial an
nat&rally2occ&rrin! icroor!aniss that can be applied as
inoc&lants to increase the icrobial diversity of soils and
plant. Cesearch has shown that the inoc&lation of >)
c<&res to the soil/plant ecosyste can iprove soil
;&ality' soil health' and the !rowth' yield' and ;&ality of
crops. >) contains selected species of icroor!aniss
incl&din! predoinant pop&lations of lactic acid bacteria
and yeasts and saller n&bers of photosynthetic bacteria'
actinoycetes andother types of or!aniss. -ll of these are
&t&ally copatible with one another and cancoe4ist in
li;&id c<&re.>) is not a s&bstit&te for
other ana!eent practices. ,t is' however' an added diension for
optii$in! o&r best soil and crop ana!eent practices s&ch as
crop rotations' &se of or!anic aendents' conservation tilla!e'
crop resid&e recyclin!' and biocontrol of pests. ,f &sed
properly' >) can si!nificantly enhance the beneficial effects of
these practices (7i!a and Wididana' 1991b)."hro&!ho&t the
disc&ssion which follows' we will &se the ter #beneficial
icroor!aniss# ,n a !eneral way to desi!nate a lar!e !ro&p of
often &n(nown or ill2defined icroor!aniss that interact
favorably in soils and with plants to render beneficial effects
which are soeties diffic< to predict. We &se the ter
#effective icroor!aniss# or >) to denote specific i4ed
c<&res of (nown' beneficial icroor!aniss that are bein!
&sed effectively as icrobial inoc&lants.*'I-I7A'IO, OF
B+,+FI$IA- 0I$1OO12A,I303 I, A21I$*-'*1+ContentsWhat Constitutes an
Ideal gricultural System!ContentsConcept&al desi!n is iportant
in developin! new technolo!ies for &tili$in! beneficial and
effective icroor!aniss for a ore s&stainable
a!ric<&re and environent. "he basis of a concept&al
desi!n is iply to first conceive an ideal or odel and then to
devise a strate!y and ethod for achievin! the reality. 7owever it
is necessary to caref&lly coordinate the aterials' the
environent' and the technolo!ies constit&tin! the ethod.
)oreover one sho&ld adopt a philosophical attit&de in
applyin! icrobial technolo!ies to a!ric<&ral
prod&ction and conservation systes."here are any opinions on
what an ideal a!ric<&ral syste is. )any wo&ld a!ree
thats&ch an ideali$ed syste sho&ld prod&ce food on a
lon!2ter s&stainable basis. )any wo&ld also insist that it
sho&ld aintain and iprove h&an health' be econoically and
spirit&ally beneficial to both prod&cers and cons&ers'
actively preserve and protect the environent' be self2contained and
re!enerative' and prod&ce eno&!h food for an increasin!
world pop&lation (7i!a' 1991)."##icient $tili%ation and
&ecycling o# "nergyContents-!ric<&ral prod&ction
be!ins with the process of photosynthesis by !reen plants which
re;&ires solar ener!y' water' and carbon dio4ide. ,t occ&rs
thro&!h the plants ability to &tili$e solar ener!y in
#fi4in!# atospheric carbon into carbohydrates. "he ener!y obtained
is &sed for f&rther biosynthesis in the plant'
incl&din! essential aino acids and proteins. "he aterials
&sed for a!ric<&ral prod&ction are ab&ndantly
available with little initial cost. 7owever' when it is observed as
an econoic activity' the fi4ation of carbon by photosynthesis has
an e4treely low efficiency ainly beca&se of the low
&tili$ation rate of solar ener!y by !reen plants. "herefore' an
inte!rated approach is needed to increase the level of solar ener!y
&tili$ation by plants so that !reater ao&ntsof atospheric
carbon can be converted into &sef&l s&bstrates (7i!a
and Wididana' 1991a).-ltho&!h the potential &tili$ation
rate of solar ener!y by plants has been estiated theoretically at
between 10 and 20K' the act&al &tili$ation rate is less
than 1K. >ven the&tili$ation rate of C1 plants' s&ch as
s&!ar cane whose photosynthetic efficiency is very hi!h' barely
e4ceeds : or @K d&rin! the a4i& !rowth period. "he
&tili$ation rate is norally less than 5K even for opti&
crop yields.%ast st&dies have shown that photosynthetic
efficiency of the chloroplasts of host crop plants cannot be
increased &ch f&rtherJ this eans that their bioass
prod&ction has reached a a4i& level. "herefore' the best
opport&nity for increasin! bioass prod&ction is to soehow
&tili$e the visible li!ht' which chloroplasts cannot presently
&se' and the infrared radiationJ to!ether' these coprise
abo&t =0K of the total solar ener!y. -lso' we &st e4plore
ways of recyclin! or!anic ener!y contained in plant and anial
resid&es thro&!h direct &tili$ation of or!anic
olec&les by plants (7i!a and Wididana' 1991a)."h&s' it is
diffic< to e4ceed the e4istin! liits of crop prod&ction
&nless the efficiency of&tili$in! solar ener!y is
increased' and the ener!y contained in e4istin! or!anic
olec&les (aino acids' peptides and carbohydrates) is
&tili$ed either directly or indirectly by the plant. "his
approach co&ld help to solve the probles of environental
poll&tion and de!radation ca&sed by the is&se and
e4cessive application of cheical fertili$ers and pesticides to
soils. "herefore' new technolo!ies that can enhance the
econoic2viability of farin! systes with little or no &se of
cheical fertili$ers and pesticides are &r!ently needed and
sho&ld be a hi!h priority of a!ric<&ral research both
now and in the iediate f&t&re (Eational -cadey of Sciences'
19=9J 1995).Preser'ation o# (atural &esources and the
"n'ironmentContents"he e4cessive erosion of topsoil fro farland
ca&sed by intensive tilla!e and row2cropprod&ction has
ca&sed e4tensive soil de!radation and also contrib&ted to
the poll&tion of both s&rface and !ro&ndwater. +r!anic
wastes fro anial prod&ction' a!ric<&ral and arine
processin! ind&stries' and &nicipal wastes (e.i.' sewa!e
and !arba!e)' have becoe a*or so&rces of environental
poll&tion in both developed and developin! co&ntries.
.&rtherore' the prod&ction of ethane fro paddy fields and
r&inant anials and of carbon dio4ide fro the b&rnin! of
fossil f&els' land clearin! and or!anic atter decoposition have
been lin(ed to !lobal warin! as #!reenho&se !ases# (%arr and
7ornic(' 1992b).Cheical2based' conventional systes of
a!ric<&ral prod&ction have created any so&rces of
poll&tion that' either directly or indirectly' can
contrib&te to de!radation of the environent and destr&ction
of o&r nat&ral reso&rce base. "his sit&ation
wo&ld chan!e si!nificantly if these poll&tants co&ld be
&tili$ed in a!ric<&ral prod&ction as so&rces
of ener!y."herefore' it is necessary that f&t&re
a!ric<&ral technolo!ies be copatible with the !lobal
ecosyste and with sol&tions to s&ch probles in areas
different fro those of conventional a!ric<&ral
technolo!ies. -n area that appears to hold the !reatest proise for
technolo!ical advances in crop prod&ction' crop protection' and
nat&ral reso&rce conservation is that of beneficial and
effective icroor!aniss applied as soil' plant and environental
inoc&lants (7i!a' 1990).Bene#icial and "##ecti'e Microorganisms
#or a Sustaina)le gricultureTowards griculture Without Chemicals
and With *ptimum +ields o# High
,ualityCrops-Contents-!ric<&re in a broad sense' is not
an enterprise which leaves everythin! to nat&re witho&t
intervention. Cather it is a h&an activity in which the farer
attepts to inte!rate certain a!roecolo!ical factors and
prod&ction inp&ts for opti& crop and livestoc(
prod&ction. "h&s' it is reasonable to ass&e that farers
sho&ld be interested in ways and eans of controllin! beneficial
soil icroor!aniss as an iportant coponent of the
a!ric<&ral environent. Eevertheless' this idea has often
been re*ected by nat&ralists and proponents of nat&re
farin! and or!anic a!ric<&re. "hey ar!&e that
beneficial soil icroor!aniss will increase nat&rally when
or!anic aendents are applied to soils as carbon' ener!y and
n&trient so&rces. "his indeed ay be tr&e where an
ab&ndance of or!anic aterials are readily available for
recyclin!which often occ&rs in sall2scale farin!. 7owever' in
ost cases' soil icroor!aniss' beneficial or harf&l' have often
been controlled advanta!eo&sly whencrops in vario&s
a!roecolo!ical $ones are !rown and c<ivated in proper
se;&ence (i.e.'crop rotations) and witho&t the &se of
pesticides. "his wo&ld e4plain why scientists havelon! been
interested in the &se of beneficial icroor!aniss as soil and
plant inoc&lantsto shift the icrobiolo!ical e;&ilibri&
in a way that enhances soil ;&ality and the yield and
;&ality of crops (7i!a and Wididana' 1991bJ 7i!a'
199131990).)ost wo&ld a!ree that a basic r&le of
a!ric<&re is to ens&re that specific crops are !rown
accordin! to their a!rocliatic and a!roecolo!ical re;&ireents.
7owever' in any cases the a!ric<&ral econoy is based on
ar(et forces that deand a stable s&pply of food' and th&s'
it becoes necessary to &se farland to its f&ll
prod&ctive potential thro&!ho&t the year."he
p&rpose of crop breedin! is to iprove crop prod&ction' crop
protection' and crop ;&ality. ,proved crop c<ivars alon!
with iproved c<&ral and ana!eent practiceshave ade it
possible to !row a wide variety of a!ric<&ral and
hortic<&ral crops in areas where it once wo&ld not
have been c<&rally or econoically feasible. "he
c<ivation of these crops in s&ch diverse environents has
contrib&ted si!nificantly to astable food s&pply in any
co&ntries. 7owever' it is soewhat ironic that new crop
c<&res are alost never selected with consideration of
their n&tritional ;&ality or bioavailability after
in!estion (7ornic(' 1992).-s will be disc&ssed later' crop
!rowth and developent are closely related to the nat&re of the
soil icroflora' especially those in close pro4iity to plant roots'
i.e.' the rhi$osphere. "h&s' it will be diffic< to
overcoe the liitations of conventional a!ric<&ral
technolo!ies witho&t controllin! soil icroor!aniss. "his
partic&lar tenet is f&rther reinforced beca&se the
evol&tion of ost fors of life on earth and their environents
are s&stained by icroor!aniss. )ost biolo!ical activities are
infl&encedby the state of these invisible' in&sc&le
&nits of life. "herefore' to si!nificantly increasefood
prod&ction' it is essential to develop crop c<ivars with
iproved !enetic capabilities (i.e.' !reater yield potential'
disease resistance' and n&tritional ;&ality) and with a
hi!her level of environental copetitiveness' partic&larly
&nder stress conditions (i.e.' low rainfall' hi!h
teperat&res' n&trient deficiencies' and a!ressive weed
!rowth)."o enhance the concept of controllin! and &tili$in!
beneficial icroor!aniss for crop prod&ction and protection' one
&st haronio&sly inte!rate the essential coponents for plant
!rowth and yield incl&din! li!ht (intensity' photoperiodicity
and ;&ality)' carbon dio4ide' water' n&trients
(or!anic2inor!anic) soil type' and the soil icroflora. Beca&se
ofthese vital interrelationships' it is possible to envision a new
technolo!y and a ore ener!y2efficient syste of biolo!ical
prod&ction./ow a!ric<&ral prod&ction efficiency
is closely related to a poor coordination of ener!y conversion
which' in t&rn' is infl&enced by crop physiolo!ical
factors' the environent' and other biolo!ical factors incl&din!
soil icroor!aniss. "he soil and rhi$osphere icroflora can
accelerate the !rowth of plants and enhance their resistance to
disease and harf&l insects by prod&cin! bioactive
s&bstances. "hese icroor!aniss aintainthe !rowth environent of
plants' and ay have secondary effects on crop ;&ality. - wide
ran!e of res<s are possible dependin! on their predoinance
and activities at any one tie. Eevertheless' there is a !rowin!
consens&s that it is possible to attain a4i& econoic crop
yields of hi!h ;&ality' at hi!her net ret&rns' witho&t
the application of cheical fertili$ers and pesticides. 8ntil
recently' this was not tho&!ht to be a very li(ely possibility
&sin! conventional a!ric<&ral ethods. 7owever' it is
iportant to reco!ni$e that the best soil and crop ana!eent
practices to achieve a ore s&stainable a!ric<&re will
also enhance the !rowth' n&bers and activities of beneficial
soil icroor!aniss that' in t&rn' can iprove the !rowth' yield
and ;&ality of crops (Eational -cadey of Sciences' 19=9J
7ornic(' 1992J %arr et al.' 1992). $O,'1O--I,2 'H+ 3OI-
0I$1OF-O1A:P1I,$IP-+3 A,. 3'1A'+2I+3Principles o# (atural
"cosystems and the pplication o# Bene#icial and "##ecti'e
MicroorganismsContents"he is&se and e4cessive &se of
cheical fertili$ers and pesticides have often adversely affected
the environent and created any a) food safety and ;&ality and
b) h&an and anial health probles. Conse;&ently' there has
been a !rowin! interest in nat&re farin! and or!anic
a!ric<&re by cons&ers and environentalists as
possible alternatives to cheical2based' conventional
a!ric<&re.-!ric<&ral systes which confor to the
principles of nat&ral ecosystes are now receivin! a !reat deal
of attention in both developed and developin! co&ntries. -
n&ber of boo(s and *o&rnals have recently been
p&blished which deal with any aspects of nat&ral farin!
systes. Eew concepts s&ch as alternative a!ric<&re'
s&stainable a!ric<&re' soil ;&ality' inte!rated
pest ana!eent' inte!rated n&trient ana!eent and even beneficial
icroor!aniss are bein! e4plored by the a!ric<&ralresearch
establishent (Eational -cadey of Sciences' 19=9J Ce!anold et al.'
1990J %arr et al.' 1992). -ltho&!h these concepts and
associated ethodolo!ies hold considerable proise' they also have
liitations. .or e4aple' the ain liitation in &sin! icrobial
inoc&lants is the proble of reprod&cibility and lac( of
consistent res<s.8nfort&nately certain icrobial
c<&res have been prooted by their s&ppliers as bein!
effective for controllin! a wide ran!e of soil2borne plant diseases
when in fact they were effective only on specific patho!ens
&nder very specific conditions. Soe s&ppliers have
s&!!ested that their partic&lar icrobial inoc&lant is
a(in to a pesticide that wo&ld s&ppress the !eneral soil
icrobial pop&lation while increasin! the pop&lation of a
specific beneficial icroor!anis. Eevertheless' ost of the clais for
these sin!le2c<&re icrobial inoc&lants are !reatly
e4a!!erated and have not proven to be effective&nder field
conditions. +ne i!ht spec&late that if all of the icrobial
c<&res and inoc&lants that are available as ar(eted
prod&cts were &sed soe de!ree of s&ccess i!ht be
achieved beca&se of the increased diversity of the soil
icroflora and stability that is associated with i4ed
c<&res. While this' of co&rse' is a hypothetical
e4aple' the fact reains that there is a !reater li(elihood of
controllin! the soil icroflora by introd&cin! i4ed' copatible
c<&res rather than sin!le p&re c<&res
(7i!a' 1991).>ven so' the &se of i4ed c<&res in
this approach has been critici$ed beca&se it is diffic<
to deonstrate concl&sively which icroor!aniss are responsible
for the observed effects' how the introd&ced icroor!aniss
interact with the indi!eno&s species' and how these new
associations affect the soil/plant environent. "h&s' the
&se of i4ed c<&res of beneficial icroor!aniss as soil
inoc&lants to enhance the !rowth' health' yield' and
;&ality of crops has not !ained widespread acceptance by
thea!ric<&ral research establishent beca&se
concl&sive scientific proof is often lac(in!."he &se of
i4ed c<&res of beneficial icroor!aniss as soil
inoc&lants is based on the principles of nat&ral ecosystes
which are s&stained by their constit&entsJ that is' by the
;&ality and ;&antity of their inhabitants and specific
ecolo!ical paraeters' i.e.' the !reater the diversity and n&ber
of the inhabitants' the hi!her the order of their interaction and
the ore stable the ecosyste. "he i4ed c<&re approach is
siply aneffort to apply these principles to nat&ral systes
s&ch as a!ric<&ral soils' and to shift the
icrobiolo!ical e;&ilibri& in favor of increased plant
!rowth' prod&ction and protection (7i!a' 1991J 1991J%arr et
al.' 1991).,t is iportant to reco!ni$e that soils can vary
treendo&sly as to their types and n&bers of icroor!aniss.
"hese can be both beneficial and harf&l to plants and often the
predoinance of either one depends on the c<&ral and
ana!eent practices that are applied. ,t sho&ld also be
ephasi$ed that ost fertile and prod&ctive soils have a hi!h
content of or!anic atter and' !enerally' have lar!e'
pop&lations of hi!hly diverse icroor!aniss (i.e.' both species
and !enetic diversity). S&ch soils will also &s&ally
have a wide ratio of beneficial to harf&l icroor!aniss (7i!a
and Wididana' 1991b).Controlling the Soil Micro#lora #or *ptimum
Crop Production and ProtectionContents"he idea of controllin! and
anip&latin! the soil icroflora thro&!h the &se of
inoc&lantsor!anic aendents and c<&ral and ana!eent
practices to create a ore favorable soil icrobiolo!ical environent
for opti& crop prod&ction and protection isnot new. .or
alost a cent&ry' icrobiolo!ists have (nown that or!anic wastes
and resid&es' incl&din! anial an&res' crop
resid&es' !reen an&res' &nicipal wastes (both raw and
coposted)' contain their own indi!eno&s pop&lations of
icroor!aniss often with broad physiolo!ical capabilities.,t is also
(nown that when s&ch or!anic wastes and resid&es are
applied to soils any of these introd&ced icroor!aniss can
f&nction as biocontrol a!ents by controllin! or s&ppressin!
soil2borne plant patho!ens thro&!h their copetitive and
anta!onistic activities. While this has been the theoretical basis
for controllin! the soil icroflora' in act&al practice the
res<s have been &npredictable and inconsistent' and the
role of specific icroor!aniss has not been well2defined..or' any
years icrobiolo!ists have tried to c<&re beneficial
icroor!aniss for &se as soil inoc&lants to overcoe the
harf&l effects of phytopatho!enic or!aniss' incl&din!
bacteria' f&n!i and neatodes. S&ch attepts have
&s&ally involved sin!le applications of p&re
c<&res of icroor!aniss which have been lar!ely
&ns&ccessf&l for several reasons. .irst' it is
necessary to thoro&!hly &nderstand the individ&al
!rowth and s&rvival characteristics of each partic&lar
beneficial icroor!anis' incl&din! their n&tritional and
environental re;&ireents. Second' we &st &nderstand
their ecolo!ical relationships and interactions with other
icroor!aniss' incl&din! their ability to coe4ist in i4ed
c<&res and after application to soils (7i!a' 1991J
1991)."here are other probles and constraints that have been a*or
obstacles to controllin! the icroflora of a!ric<&ral
soils. .irst and foreost is the lar!e n&ber of types of
icroor!aniss that are present at any one tie' their wide ran!e of
physiolo!ical capabilities' and the draatic fl&ct&ations in
their pop&lations that can res< fro anLMNs
c<&ral and ana!eent practices applied to a partic&lar
farin! syste. "he diversity of the total soil icroflora depends on
the nat&re of the soil environent and those factors which
affect the !rowth and activity of each individ&al or!anis
incl&din! teperat&re' li!ht' aeration' n&trients'
or!anic atter' p7 and water. While there are any icroor!aniss that
respond positively to these factors' or a cobination thereof' there
are any that do not. )icrobiolo!ists have act&ally st&died
relatively few of the icroor!aniss that e4ist in ost
a!ric<&ral soil' ainly beca&se we don?t (now how to
c<&re theJ i.e.' we (now very little abo&t their
!rowth' n&tritional' and ecolo!ical re;&ireents."he
#diversity# and #pop&lation# factors associated with the soil
icroflora have disco&ra!ed scientists fro cond&ctin!
research to develop control strate!ies. )any believe that' even
when beneficial icroor!aniss are c<&red and
inoc&lated into soils' their n&ber is relatively sall
copared with the indi!eno&s soil inhabitants' and they
wo&ld li(ely be rapidly overwheled by the established soil
icroflora. Conse;&ently' any wo&ld ar!&e that even if
the application of beneficial icroor!aniss is s&ccessf&l
&nder liited conditions (e.!.' in the laboratory) it wo&ld
be virt&ally ipossible to achieve the sae s&ccess &nder
act&al field conditions. S&ch thin(in! still e4ists today'
and serves as a principle constraint to the concept of controllin!
the soil icroflora (7i!a' 1991).,t is noteworthy that ost of the
icroor!aniss enco&ntered in any partic&lar soil are harless
to plants with only a relatively few that f&nction as plant
patho!ens or potentialpatho!ens. 7arf&l icroor!aniss becoe
doinant if conditions develop that are favorable to their !rowth'
activity and reprod&ction. 8nder s&ch conditions'
soil2borne patho!ens (e.!.' f&n!al patho!ens) can rapidly
increase their pop&lations with devastatin! effects on the
crop. ,f these conditions chan!e' the patho!en pop&lation
declines *&st as rapidly to its ori!inal state. Conventional
farin! systes that tend toward the consec&tive plantin! of the
sae crop (i.e.' onoc<&re) necessitate the heavy &se
of cheical fertili$ers and pesticides. "his' in t&rn' !enerally
increases the probability that harf&l' disease2prod&cin!'
plant patho!enic icroor!aniss will becoe ore doinant in
a!ric<&ral soils (7i!a' 1991J 1991J %arr and 7ornic('
1991). Cheical2based conventional farin! ethods are not &nli(e
syptoatic therapy. >4aples of this are applyin! fertili$ers when
crops show syptos of n&trient2deficiencies' and applyin!
pesticides whenever crops are attac(ed by insects and diseases. ,n
efforts to control the soil icroflora soe scientists feel that the
introd&ctionof beneficial icroor!aniss sho&ld follow a
syptoatic approach. 7owever' we do not a!ree. "he act&al soil
conditions that prevail at any point in tie ay be ost
&nfavorable to the !rowth and establishent of
laboratory2c<&red' beneficial icroor!aniss. "o facilitate
their establishent' it ay re;&ire that the farer a(e certain
chan!es in his c<&ral and ana!eent practices to
ind&ce conditions that will (a) allow the !rowth and
s&rvival of the inoc&lated icroor!aniss and (b)
s&ppress the!rowth and activity of the indi!eno&s plant
patho!enic icroor!aniss (7i!a' 1991J %arr et al.' 1991).-n e4aple
of the iportance of controllin! the soil icroflora and how certain
c<&ral and ana!eent practices can facilitate s&ch
control is &sef&l here. 9e!etable c<ivarsare often
selected on their ability to !row and prod&ce over a wide ran!e
of teperat&res. 8nder cool' teperate conditions there are
!enerally few pest and disease probles. 7owever' with the onset of
hot weather' there is a concoitant increase in the incidence of
diseases and insects a(in! it rather diffic< to obtain
acceptable yields witho&t applyin! pesticides. With hi!her
teperat&res' the total soil icrobial pop&lation increases
as does certain plant patho!ens s&ch as .&sari&' which
is one of the ain p&trefactive' f&n!al patho!ens in soil.
"he incidence and destr&ctive activity of this patho!en can be
!reatly inii$ed by adoptin! red&ced tilla!e ethods and by
shadin! techni;&es to (eep the soil cool d&rin! hot
weather. -nother approach is to inoc&late the soil with
beneficial' anta!onistic' antibiotic2prod&cin! icroor!aniss
s&ch as actinoycetes and certain f&n!i (7i!a and Wididana'
1991aJ 1991b).pplication o# Bene#icial and "##ecti'e
Microorganisms.(ew /imensionContents)any icrobiolo!ists believe
that the total n&ber of soil icroor!aniss can be increased by
applyin! or!anic aendents to the soil. "his is !enerally tr&e
beca&se ost soil icroor!aniss are heterotrophic' i.e.' they
re;&ire cople4 or!anic olec&les of carbon and nitro!en for
etabolis and biosynthesis. Whether the re!&laraddition of
or!anic wastes and resid&es will !reatly increase the n&ber
of beneficial soil icroor!aniss in a short period of tie is
;&estionable. 7owever' we do (now thatheavy applications of
or!anic aterials' s&ch as seaweed' fish eal' and chitin fro
cr&shed crab shells' not only helps to balance the
icron&trient content of a soil b&t also increases the
pop&lation of beneficial antibiotic2prod&cin! actinoycetes.
"his chan!es the soil to a disease2s&ppressive condition within
a relatively short period."he probability that a partic&lar
beneficial icroor!anis will becoe predoinant' even with or!anic
farin! or nat&re farin! ethods' will depend on the ecosyste and
environental conditions. ,t can ta(e several h&ndred years for
vario&s species of hi!her and lower plants to interact and
develop into a definable and stable ecosyste. >ven if the
pop&lation of a specific icroor!anis is increased thro&!h
c<&ral and ana!eent practices' whether it will be
beneficial to plants is another ;&estion. "h&s' the
li(elihood of a beneficial' plant2associated icroor!anis becoin!
predoinant &nder conservation2based farin! systes is
virt&ally ipossible to predict. )oreover' itis very
&nli(ely that the pop&lation of &sef&l anaerobic
icroor!aniss' which &s&ally coprise only a sall part of the
soil icroflora' wo&ld increase si!nificantly even
&ndernat&ral farin! conditions."his inforation then
ephasi$es the need to develop ethods for isolatin! and selectin!
different icroor!aniss for their beneficial effects on soils and
plants. "he <iate !oal is to select icroor!aniss that are
physiolo!ically and ecolo!ically copatible with each other and that
can be introd&ced as i4ed c<&res into soil wheretheir
beneficial effects can be reali$ed (7i!a' 1991J 1991J
1990).pplication o# Bene#icial and "##ecti'e Microorganisms.
Fundamental ConsiderationsContents)icroor!aniss are &tili$ed in
a!ric<&re for vario&s p&rposesJ as iportant
coponents of or!anic aendents and coposts' as le!&e
inoc&lants for biolo!ical nitro!en fi4ation as a eans of
s&ppressin! insects and plant diseases to ,prove crop
;&ality and yields' and for red&ction of labor. -ll of
these are closely related to each other. -n iportant consideration
in the application of beneficial icroor!aniss to soilsis the
enhanceent of their syner!istic effects. "his is diffic< to
accoplish if these icroor!aniss are applied to achieve syptoatic
therapy' as in the case of cheical fertili$ers and pesticides
(7i!a' 1991J 1991).,f c<&res of beneficial icroor!aniss
are to be effective after inoc&lation into soil' it is iportant
that their initial pop&lations be at a certain critical
threshold level. "his helps toens&re that the ao&nt of
bioactive s&bstances prod&ced by the will be s&fficient
to achieve the desired positive effects on crop prod&ction
and/or crop protection. ,f these conditions are not et' the
introd&ced icroor!aniss' no atter how &sef&l they are'
will have little if any effect. -t present' there are no cheical
tests that can predict the probability of a partic&lar
soil2inoc&lated icroor!anis to achieve a desired res<.
"he ost reliable approach is to inoc&late the beneficial
icroor!anis into soil as part of a i4ed c<&re' and at a
s&fficiently hi!h inoc&l& density to a4ii$e the
probability of its adaptation to environental and ecolo!ical
conditions (7i!a and Wididana' 1991bJ %arr et al.' 1991)."he
application of beneficial icroor!aniss to soil can help to define
the str&ct&re and establishent of nat&ral ecosystes.
"he !reater the diversity of the c<ivated plants that are
!rown and the ore cheically cople4 the bioass' the !reater the
diversity of the soil icroflora as to their types' n&bers and
activities. "he application of a wide ran!e of different or!anic
aendents to soils can also help to ens&re a !reater icrobial
diversity. .or e4aple' cobinations of vario&s crop
resid&es' anial an&res' !reen an&res' and &nicipal
wastes applied periodically to soil will provide a hi!her level of
icrobial diversity than when only one of these aterials is applied.
"he reason for this is that each of these or!anic aterials has its
own &e indi!eno&s icroflora which can !reatly affect the
resident soil icroflora after they are applied' at least for a
liited period.$-A33IFI$A'IO, OF 3OI-3 BA3+. O, 'H+I1
0I$1OBIO-O2I$A- P1OP+1'I+3Contents)ost soils are classified on the
basis of their cheical and physical propertiesJ little has been
done to classify soils accordin! to their physicocheical and
icrobiolo!ical properties. "he reason for this is that a soil?s
cheical and physical properties are ore readily defined and
eas&red than their icrobiolo!ical properties. ,proved soil
;&alityis &s&ally characteri$ed by increased
infiltrationJ aeration' a!!re!ation and or!anic atter content and
by decreased b&l( density' copaction' erosion and cr&stin!.
While these are iportant indicators of potential soil
prod&ctivity' we &st !ive ore attention to soil biolo!ical
properties beca&se of their iportant relationship (tho&!h
poorly &nderstood) to crop prod&ction' plant and anial
health' environental ;&ality' and foodsafety and ;&ality.
Cesearch is needed to identify and ;&antify reliable and
predictable biolo!ical/ecolo!ical indicators of soil ;&ality.
%ossible indicators i!ht incl&de total species diversity or
!enetic diversity of beneficial soil icroor!aniss as well as
insectsand anials (Ce!anold et al.' 1990J %arr et al.' 1992)."he
basic concept here is not to classify soils for the st&dy of
icroor!aniss b&t for farers to be able to control the soil
icroflora so that biolo!ically2ediated processes can iprove the
!rowth' yield' and ;&ality of crops as well as the tilth'
fertility' and prod&ctivity of soils. "he <iate ob*ective
is to red&ce the need for cheical fertili$ers and pesticides
(Eational -cadey of Sciences' 19=9J 1995).Functions o#
Microorganisms. Putre#action0 Fermentation0 and
SynthesisContentsSoil icroor!aniss can be classified into decoposer
and synthetic icroor!aniss. "he decoposer icroor!aniss are
s&bdivided into !ro&ps that perfor o4idative and
ferentative decoposition. "he ferentative !ro&p is f&rther
divided into &sef&l ferentation (siply called ferentation)
and harf&l ferentation (called p&trefaction)."he synthetic
icroor!aniss can be s&b2divided into !ro&ps havin! the
physiolo!ical abilities to fi4 atospheric nitro!en into aino acids
and/or carbon dio4ide into siple or!anic olec&les thro&!h
photosynthesis. .i!&re 1 (adapted fro 7i!a) is a siplified flow
chart of or!anic atter transforations by soil icroor!aniss that can
lead to the developent of disease2ind&cin!'
disease2s&ppressive' $yo!enic' or synthetic soils..erentation
is an anaerobic process by which fac<ative icroor!aniss
(e.!.' yeasts) transfor cople4 or!anic olec&les (e.!.'
carbohydrates) into siple or!anic copo&nds that often can be
absorbed directly by plants. .erentation yields a relatively sall
ao&nt of ener!y copared with aerobic decoposition of the sae
s&bstrate by the sae !ro&p of icroor!aniss. -erobic
decoposition res<s in coplete o4idation of a s&bstrate
and the release of lar!e ao&nts of ener!y' !as' and heat with
carbon dio4ide and water as the end prod&cts. %&trefaction
is the process by which fac<ative heterotrophic icroor!aniss
decopose proteins anaerobically' yieldin! alodoro&s incopletely
o4idi$ed' etabolites (e.!.' aonia' ercaptans and indole) that are
often to4ic to plants and anials."he ter #synthesis# as &sed
here refers to the biosynthetic capacity of certain icroor!aniss to
derive etabolic ener!y by #fi4in!# atospheric nitro!en and/or
carbon dio4ide. ,n this conte4t we refer to these as #synthetic#
icroor!aniss' and if they sho&ld becoe a predoinant part of the
soil icroflora' then the soil wo&ld be tered a #synthetic#
soil.Eitro!en2fi4in! icroor!aniss are hi!hly diverse' ran!in! fro
#free2livin!# a&totrophic bacteria of the !en&s -$otobacter
to sybiotic' heterotrophic bacteria of the !en&s Chi$obi&'
and bl&e2!reen al!ae (now ainly classified as bl&e2!reen
bacteria)' all of which f&nction aerobically. %hotosynthetic
icroor!aniss fi4 atospheric carbon dio4ide in a anner siilar to
that of !reen plants. "hey are also hi!hly diverse' ran!in!fro
bl&e2!reen al!ae to !reen al!ae that perfor coplete
photosynthesis aerobically to photosynthetic bacteria which perfor
incoplete photosynthesis anaerobically.&elationships Between
Putre#action0 Fermentation0 and SynthesisContents"he processes of
p&trefaction' ferentation' and synthesis proceed
si<aneo&sly accordin! to the appropriate types and
n&bers of icroor!aniss that are present in the soil. "he ipact
on soil ;&ality attrib&tes and related soil properties is
deterined bythe doinant process. "he prod&ction of or!anic
s&bstances by icroor!aniss res<s fro the inta(e of
positive ions' while decoposition serves to release these positive
ions. 7ydro!en ions play a pivotal role in these processes. -
proble occ&rs when hydro!en ions do not recobine with o4y!en to
for water b&t are &tili$ed to prod&ce ethane' hydro!en
s&lfide' aonia' ercaptans and other hi!hly red&ced
p&trefactives&bstances ost of which are to4ic to plants and
prod&ce alodors. ,f a soil is able to absorb the e4cess
hydro!en ions d&rin! periods of soil anaerobiosis and if
synthetic icroor!aniss s&ch as photosynthetic bacteria are
present' they will &tili$e these p&trefactive
s&bstances and prod&ce &sef&l s&bstrates fro
the which helps to aintain a healthy and prod&ctive soil."he
photosynthetic bacteria' which perfor incoplete photosynthesis
anaerobically' are hi!hly desirable' beneficial soil icroor!aniss
beca&se they are able to deto4ify soils by transforin!
red&ced' p&trefactive s&bstances s&ch as hydro!en
s&lfide into &sef&l s&bstrates. "his helps to
ens&re efficient &tili$ation of or!anic atter and to iprove
soil fertility. %hotosynthesis involves the photo2cataly$ed
splittin! of water which yields olec&lar o4y!en as a
by2prod&ct. "h&s' these icroor!aniss help to provide a
vital so&rce of o4y!en to plant roots.Ced&ced copo&nds
s&ch as ethane and hydro!en s&lfide are often prod&ced
when or!anic aterials are decoposed &nder anaerobic conditions.
"hese copo&nds are to4ic and can !reatly s&ppress the
activities of nitro!en2fi4in! icroor!aniss. 7owever' if synthetic
icroor!aniss' s&ch as photosynthetic bacteria that &tili$e
red&ced s&bstances' are present in the soil' o4y!en
deficiencies are not li(ely to occ&r. "h&s' nitro!en2fi4in!
icroor!aniss' coe4istin! in the soil with photosynthetic
bacteria'can f&nction effectively in fi4in! atospheric nitro!en
even &nder anaerobic conditions.%hotosynthetic bacteria not
only perfor photosynthesis b&t can also fi42nitro!en. )oreover'
it has been shown that' when they coe4ist' in soil with species of
-$otobacter'their ability to fi4 nitro!en is enhanced. "his then is
an e4aple of a synthetic soil. ,t also s&!!ests that by
reco!ni$in! the role' f&nction' and &t&al copatibility
of these two bacteria and &tili$in! the effectively to their
f&ll potential' soils can be ind&ced to a !reater synthetic
capacity. %erhaps the ost effective synthetic soil syste
res<s fro the enhanceent of $yo!enic and synthetic
icroor!anissJ this allows ferentation to becoe doinant over
p&trefaction and &sef&l synthetic processes to
proceed.$lassification of 3oils Based on the Functions of
0icroorganissContents-s disc&ssed earlier (.i!&re 1)' soils
can be characteri$ed accordin! to their indi!eno&sicroflora
which perfor p&trefactive' ferentative' synthetic and $yo!enic
reactions and processes. ,n ost soils' these three f&nctions
are !oin! on si<aneo&sly with therate and e4tent of each
deterined by the types and n&bers of associated icroor!aniss
that are actively involved at any one tie.- siple dia!ra showin! a
classification of soils based on the activities and f&nctions
of their predoinant icroor!aniss is presented in .i!.
2..isease;Inducing 3oils. ,n this type of soil' plant patho!enic
icroor!aniss s&ch as .&sari& f&n!i can coprise 0 to
20 percent of the total icroflora if fresh or!anic atter with a
hi!h nitro!en content is applied to s&ch a soil' incopletely
o4idi$ed prod&cts can arise that are alodoro&s and to4ic to
!rowin! plants. S&ch soils tend to ca&se fre;&ent
infestations of disease or!aniss' and harf&l insects. "h&s'
the application of fresh or!anic atter to these soils is often
harf&l to crops. %robably ore than 90 percent of the
a!ric<&ral land devoted to crop prod&ction worldwide
can be classified as havin! disease2ind&cin! soil. S&ch
soils !enerally have poor physical properties' and lar!e ao&nts
of ener!y are lost as #!reenho&se# !ases' partic&larly in
the case of rice fields. %lant n&trients are also s&b*ect
to iobili$ation into &navailable fors..isease;3uppressiven if
fresh or!anic atter with a hi!h nitro!en content is applied' the
prod&ction of p&trescent s&bstances is very low and the
soil has a pleasant earthy odor after the or!anic atter is
decoposed. "hese soils !enerally have e4cellent physical
propertiesJ for e4aple' they readily' for water2stable a!!re!ates
and they are well2aerated' and have a hi!h pereability to both air
and water. Crop yields in the disease2s&ppressive soils are
often sli!htly lower than those in synthetic soils. 7i!hly
acceptable crop yields are obtained whenever a soil has a
predoinance of both disease2s&ppressive and synthetic
icroor!aniss.7"ogenic 3oils. "hese soils are doinated by a
icroflora that can perfor &sef&l (inds of ferentations'
i.e.' the brea(down of cople4 or!anic olec&les into siple
or!anic s&bstances and inor!anic aterials. "he or!aniss can be
either obli!ate or fac<ative anaerobes. S&ch
ferentation2prod&cin! icroor!aniss often coprise theicroflora
of vario&s or!anic aterials' i.e.' crop resid&es' anial
an&res' !reen an&res and &nicipal wastes incl&din!
coposts. -fter these aendents are applied to the soil' their
n&ber3 and ferentative activities can increase draatically and
overwhel the indi!eno&s soil icroflora for an indefinite
period. While these icroor!aniss reain predoinant' the soil can be
classified as a $yo!enic soil which is !enerally characteri$ed by
a) pleasant' ferentative odors especially after tilla!e' b)
favorable soil physical properties (e.!.' ,ncreased a!!re!ate
stability' pereability' aeration and decreased resistance to
tilla!e c) lar!e ao&nts of inor!anic n&trients' aino acids'
carbohydrates' vitains and other bioactive s&bstances which can
directly or indirectly enhance the !rowth' yield and ;&ality of
crops' d) low occ&pancy of .&sari& f&n!i which is
&s&ally less than 0 percent' and e) low prod&ctionof
!reenho&se !ases (e.!.' ethane' aonia' and carbon dio4ide) fro
croplands' even where flooded rice is !rown.3"nthetic 3oils. "hese
soils contain si!nificant pop&lations of icroor!aniss which are
able to fi4 atospheric nitro!en and carbon dio4ide into cople4
olec&les s&ch asaino acids' proteins and carbohydrates.
S&ch icroor!aniss incl&de photosynthetic bacteria which
perfor incoplete photosynthesis anaerobically' certain %hycoycetes
(f&n!i that reseble al!ae)' and both !reen al!ae and
bl&e22!reen al!ae which f&nction aerobically. -ll of these
are photosynthetic or!aniss that fi4 atospheric nitro!en. ,f the
water content of these soils is stable' their fertility can be
lar!ely aintained by re!&lar additions of only sall ao&nts
of or!anic aterials. "hese soils have a low .&sari&
occ&pancy and they are often of the disease2s&ppressive
type. "he prod&ction of !ases fro fields where synthetic soils
are present is inial' even for flooded rice."his is a soewhat
siplistic classification of soils based on the f&nctions of
their predoinant types of icroor!aniss' and whether they are
potentially beneficial or harf&l to the !rowth and yield of
crops. While these different types of soils are described here in a
rather ideali$ed anner' the fact is that in nat&re they are not
always clearly defined beca&se they often tend to have soe of
the sae characteristics. Eevertheless' research has shown that a
disease2ind&cin! soil can be transfored into
disease2s&ppressin!' $yo!enic and synthetic soils by
inoc&latin! the proble soil with i4ed c<&res of
effective icroor!aniss (7i!a' 1991J 1991J %arr et al.' 1991).
"h&s it is soewhat obvio&s that the ost desirable
a!ric<&ral soil for opti& !rowth' prod&ction'
protection' and ;&ality of crops wo&ld be the coposite soil
indicated in .i!. 2' i.e.' a soil that is hi!hly $yo!enic and
synthetic' and has an established disease2s&ppressive capacity.
"his then is the principle reason for see(in! ways and eans of
controllin! the icroflora of a!ric<&ral soils.3*00A1: A,.
$O,$-*3IO,3ContentsControllin! the soil icroflora to enhance the
predoinance of beneficial and effective icroor!aniss can help to
iprove and aintain the soil cheical and physical properties. "he
proper and re!&lar addition of or!anic aendents are often an
iportant part of any strate!y to e4ercise s&ch
control.%revio&s efforts to si!nificantly chan!e the
indi!eno&s icroflora of a soil by introd&cin!sin!le
c<&res of e4trinsic icroor!aniss have lar!ely been
&ns&ccessf&l. >ven when a beneficial icroor!anis is
isolated fro a soil' c<&red in the laboratory' and
reinoc&lated into the sae soil at a very hi!h pop&lation'
it is iediately s&b*ect to copetitive and anta!onistic effects
fro the indi!eno&s soil icroflora and its n&berssoon
decline. "h&s' the probability of shiftin! the #icrobiolo!ical
e;&ilibri of a soil and controllin! it to favor the !rowth'
yield and health of crops is &ch !reater if i4ed
c<&res of beneficial and effective icroor!aniss are
introd&ced that are physiolo!ically and ecolo!ically copatible
with one another. When these i4ed c<&res becoe
established their individ&al beneficial effects are often
a!nified in a syner!istic anner.-ct&ally' a
disease2s&ppressive icroflora can be developed rather easily by
selectin! and c<&rin! certain types of !ra2positive
bacteria that prod&ce antibiotics and have a wide ran!e of
specific f&nctions and capabilitiesJ these or!aniss incl&de
fac<ative anaerobes' obli!ate aerobes' acidophilic and
al(alophilic icrobes. "hese icroor!aniss can be !rown to hi!h
pop&lations in a edi& consistin! of rice bran' oil ca(e and
fish eal and then applied to soil alon! with well2c&red copost
that also has a lar!e stable pop&lation of beneficial
icroor!aniss' especially fac<ative anaerobic bacteria. - soil
can be readily transfored into a $yo!enic/synthetic soil with
disease2s&ppressive potential if i4ed c<&res of
effective icroor!aniss with theability to transit these properties
are applied to that soil."he desired effects fro applyin!
c<&red beneficial and effective icroor!aniss to soils can
be soewhat variable' at least initially. ,n soe soils' a sin!le
application (i.e.' inoc&lation) ay be eno&!h to prod&ce
the e4pected res<s' while for other soils even repeated
applications ay appear to be ineffective. "he reason for this is
that in soe soils it ta(es lon!er for the introd&ced
icroor!aniss to adapt to a new set of ecolo!ical and environental
conditions and to becoe well2established as a stable' effective and
predoinant part of the indi!eno&s soil icroflora. "he iportant
consideration here is the caref&l selection of a i4ed
c<&re of copatible' effective icroor!aniss properly
c<&red and provided with acceptable or!anic
s&bstrates. -ss&in! that repeated applications are ade at
re!&lar intervals d&rin! the first croppin! season' there
is a very hi!h probability that the desired res<s will be
achieved."here are no eanin!f&l or reliable tests for onitorin!
the establishent of i4ed c<&res of beneficial and
effective icroor!aniss after application to a soil. "he desired
effects appear only after they are established and becoe doinant'
and reain stable and active in the soil. "he inoc&l&
densities of the i4ed c<&res and the fre;&ency of
application serve only as !&idelines to enhance the probability
of early establishent. Cepeated applications' especially d&rin!
the first croppin! season' can ar(edly facilitate early
establishent of the introd&ced effective icroor!aniss.+nce the
#new# icroflora is established and stabili$ed' the desired effects
will contin&e indefinitely and no f&rther applications are
necessary &nless or!anic aendents cease to be applied' or the
soil is s&b*ected to severe dro&!ht or floodin!..inally' it
is far ore li(ely that the icroflora of a soil can be controlled
thro&!h the application of i4ed c<&res of selected
beneficial and effective icroor!aniss than by the &se of sin!le
or p&re c<&res. ,f the icroor!aniss coprisin! the
i4ed c<&recan coe4ist and are physiolo!ically copatible
and &t&ally copleentary' and if the initial inoc&l&
density is s&fficiently hi!h' there is a hi!h probability that
these icroor!aniss will becoe established in the soil and will be
effective as an associative !ro&p' whereby s&ch positive
interactions wo&ld contin&e. ,f so' then it is also hi!hly'
probable that they will e4ercise considerable control over the
indi!eno&s soilicroflora which' in d&e co&rse'
wo&ld li(ely be transfored into or replaced by a #new# soil
icroflora.1+F+1+,$+3Contents7i!a' ". 1991. >ffective
icroor!aniss3 - biotechnolo!y for an(ind. p.=211. ,n D... %arr'
S.B. 7ornic(' and C.>. Whitan (ed.) %roceedin!s of the .irst
,nternational Conference on Oy&sei Eat&re .arin!. 8.S.
