Roger I’. A. (1991) Reconsidering ~e,.$iIizati~n;of l$u-q$%n .algaejn wetland rice cultivation. pp 119-141 in Biological N2 fixation

~:f..:.~~ f;-;r,-! l,;rq= F’y;L;,: .,,, 7. !, ’ . . ,^_ ,,-, ‘2 -,::.:i

IRRI,O&yOM p&-ct --<t ‘1, ;r , - y. i.7 G,’ (-;Z:$.i

“c\--‘.v .‘..‘., _i ,?qj-& ~n~e;&~~6,‘j&. R%se&ti f&&+., :.._ ?L2 .ji . ..#: ..,

c’ , P.O. Box 933, Manila, Pl-$pines ‘,.-“;...i-. ~+2-“; :*: ‘5

._ -J-it: ‘.J :‘?\<;‘,T .‘:a. ..‘I ;:;:zt:* ‘. ,; ‘:;‘::.‘, j .:” ,‘- .*:*:.r Z(, ;. ;,i iii ,‘.’ - < .‘I- -y;.--.:;“.f ,

‘^ ., _I. ..i- _: . . . . :- . f. -y -_,’ -‘I... (

_ ,‘::a ., -. ;.7Lc,;. :irr. Ta ;; ;s 3: ji?y --;-. -1 ‘f’I c-s - 17, ‘-.‘,A .L( .z:; -, ,L’..-r,‘i ! ., i .~. -,- i i. { _ i: _.- ,yz

,..--, 7 p (... :. : ,., ‘I, - c “‘<. .-... ‘;, ., _ .“...: .( : I.” -.; ..- -,: -,:,,,:., ,i I’. ‘;-, ;-,,; > - .._ ,__ “..‘.7-.:1 -7 x .- ;<. <; !: ,.,... -. . : INTRODUCTION. 1 .-” c c ,:;‘. !,

:: - . ;c-.-‘T;T :. - _ ..:__ TK& ‘kxistence- of an” agr&o-hi<-@&ntial f$ BGA “in‘.rice’, Eultivatibn was recognized in 1939 by De, who attribl’i&l the natural fertiiity’of tro&aI ridefields to biological nitrogen-fixation (BNF) by those organisms. Since then, long-term fertility expgriments and nitrogen-fixation measurements i%.k d’onfi;med the -.. -- ._.. _^_ -._ ____ ,__--._ l_l .- ._._.I_. ‘, importance of BGA and other nitrogen-fixing organi;;; in mamtalnmg a moderate but constant rice production in fields receivi$ no nitrogen iertilizer .

i The importance of BGA in rice culture.was magi $ear_jn -the literature revi%’ by, R+ef‘Bnd Kulasooriya (1980) ; which in$u$$zi~.,‘~>ny repotis of rice:fields.bej~ng ma”ipulated to maximize blue-giee~~,.,~igal.‘ni~~ge~~~~,~~ion. mostly by the addition of dried inocula. H~$$.Gr;;‘~~ti~~~~~ t@& reports lack- . ,- ‘,V> _ y$< ‘.‘+-; : “.(A ed detailed documentation of methods and results;and,a.mqre-f-ecent fzCview (R;ger, 1g8g) takes a cautious view when ~~;~~~~~ii;;~~~~~~~~~~~cebt ear,ier

-?.A’* res&aich...- ..I . . . . . . w>-.w..2;*. .2” -.,, :,. p .., ..;,.~“,-:;~~:,..-,~:a ._( ,I . ..” . ..- . l.l..“. ;;” .‘.i-!i: ,... :. , j t.2. :,!A.*.‘<... - ,4 r,.:,,:,$.$: ,a.. _- a%?, 2 .:,5’ ,y”. .&yz 2’. _ -,;” i$ .: .~,. f- : t ,

Fords Documentaire ORSTOM Cote : &bA 6 Ex: 4

' * I

1 - 120 BNF Associated With Rice Proauction - 4

Nitrogen Contributiori Es t imated from Biomass' Measurements *

Reported standing crops of BGA in ricefields range from a few kg ha- ' to 0 . 5 t ha-' dry weight (aw) (Roger et al., 1987a). However, values express- e d as fresh weight (fw) or dw ha-' give little information on the agronomic significance of the biomass because of the wide range of dry matter (0.2514%) and ash (31-71 96) contents in field-grown BGA (Roger et al., 1986b). Nitrogen in one ton fw of BGA averages 1.2 kg but may vary from 0.1 kg to 4 kg. Assuming a maximum biomass of 0.5 t dw ha:' and using average ash and N values obtained for field samples (Roger et al., 1986b), the pbtentia! average contri of a BGA bloom isabout 15 kg N/ha. I-

1 summarizes 400 biomass measurements performed weekly in 65 plots on the IRRI farmwhen BGA were visible. In most cases, biomass contained a few kg N ha- ' (median: 4 kg N/ha). The highest value was 17 kg N ha-'. -

Available data indicate that: (1) a visible growth of BGA usually cor- responds to less than 10 kg N ha-'(2) a dense bloom may correspond to 10-20 kg N ha-', and (3) values were higher onlfin experimental microplots or'in soil-based inoculum production plots (Reddy and Roger, 2988; Roger e t al., 1985a).

Nitrogen contribution by BGA is the result of nutrient turnover of the

Assuming that all carbon input in the floodwater and surface soil is through nitrogen-fixing BGA (which is an obvious overestimation) and using an input of 0.6 t C ha-' per crop (Saito and Watanabe, 1978) and an average C/N ratio of 8 (Roger et al., 1986b), the maximum contribution of nitrogen-fixing BGA could be 75-kg N ha-l per crop.

~ I - -

- 1

standing biomass, for which no data are yet available. u

C o u n t s (no) 707 . I

' .

60 I ............... ~ ......................................................................................

50

40 . _

30

20

ló

O 2 1 < - 7 - 9 11 13

S t a n d i n g b i o m a s s of BGA Fig. 1 : Dtstribution of 400 es g crop of BGA in 65 plots on the IRRI farm

. > r -

F

Nikpgep, _fixation by: BG A. ,h~as. been-.mos t freq tent I y: estim at ed by. acetylene i redgclng, aqtiyity (ARA) meas,ur.ements.'~Estimaïes published before:l980. vary:: fr.om, afew toA80 kg N..ha; "and. average. 2-7 kg.ha5.r perkcrop in plots where,; no.-BG& werq,.i.noc,ul$ed .(Roger _and, Kulasoo-riya~,,1980) & 5. ,J:<;.J

.-:,i: .Figure.2 % . .> presents the~distrib1~tio11..o_f:180: estimatesBf the aver pm~cycle;.i,n,~experim,ental. plots at:. IRRLLSixtyl plots -received. n o j izer, 60 received 55 kg N ha-' as broadcast .urea, and 60 receiv-

ed 55 kg.N ha-' as deep-placed uiea.: Àssuming.an acety1ene)N''Fafio'bf '4;"

h - l) . Va1Ues';ange from 0:2Yo;5O-$g N ha- 1 'perf 9.5). Avejage values per treatment are 2 4 . q N-ha-l in,cZntrol plots, 8 kg in plots with broadcast urea, and 12 kg in plots where nitrogen was deep-placed

BNF.expressed-in ."i.?, --CI,... .... kg N ha- l <.-,.; percrop-is ,-._ - about-lllo

. i r .1 .u , . . _--. _.__ -_u_--

~_._-_ -----_XI.. _-_----I ,. . . . . . -_ r, ,.*,.,.? ,. ~

. - ... :. i . . z ... ... - .. .., , ,*..

c z - Counts CnO-)' . -- "..> . .

.."_ .+_, -... . ..................................................................... ...........-...... v ............. .......................

.... . . . . .y< - ..7-_. ... ,-ai.!. c y - :

................................................................................................................................ - '. . ,~ -::., ,.,.-

.I__._I___.,_-._.._ I_-.^I^ ....-..-.̂ __I--. . .- _I_ -- .I ---- I ............................................................................................... r:....>.:.:..2 .............

...

, " . . . _i

. , i- " ' '

* Unpubl. data. Each value is the average of estimates in 60 plots. Each estimate is the average of 9 to 13 measurements during the crop cycle using composite samples of 8 soil cores.

J

122 BNF Associated With Rice Production

Utilization of BGA Nitrogen by the Rice Plant

Rëcoverymof BGA N by rice (Tadle 2) varies from 13 to 5 0 % , depending on the nature .,,.:.-.it of I the ...-...., material :..- .. (fresh ._ ...... versus,dried) ,.th.e method of, applicati,on, and thipresence Ór 'absence of soil fauna (Grant, '1985c Tirol et al., 1982;'Wilson et al.; 1980a)- Ricë use of nitrogen of the BGA biomas; is more efficient-whén 1

the biomass is incorporated into the soil. Recovery was highest with fresh BGA incorporated into-a- soil depleted of fauna (Wilson et .al., 1980a): Recovery was lowest with dried. BGA applied 'on the su'rface of a soil rich in tÙbihcid': worms (Tirol et al.', 1982), which reduce the recovery of algal niGogen Gy rice by making more ssil nitrogen available throughmineralization' (Grant; 1985a) :

. . .- z c - ,"..

. . . . ... I . . * - 7 .. , - -

- . - . I , .,. ,

._ t _. ..-:-. -

Table_2~,Availability of nitrpgen,from - !,GA. to rice: I ;.. 7'.L:- . , --s <f. ' ::: ; $-< ,.i :.

. . . .; -. . . . . . . . - f . . . . . .

* . applied.;-:; y;. . :J: . - . - * . . . . . .

, . . .

fresh 37 52 ' ' ? pot Wilson et al., 1980 dw 14 28 - Pot .Tirol et 4.,:1982 f

Tirpl~et_a1.,1982 , ~ ......... ~ -= -^__ + --field ,-̂ 23 23

38' I - pot Tuo1 et al.. 1982 LI dry _....- fresh . -

24< 4 4 ,

25 30 . . . :. . . . . . . . . . . . . . . . . . . . -" . . . . . . . . . . . . '7985 .........

. . . , . . . . . . 19 s... ....

fresh '

dry I - 35-40

36 .2 . . . . . . . . . . . . . . . . . . . . 24.6 . -.

, . Average .

'After Roger et al. (1987a).

O t h e r Possible Effects

The best known effect of BG from BNF, but other effects have been rep2rted. BGA may prevent the growth of weeds, (Subrahmanya-n et al., 1965). They increase soil organic matter con- tent and its aggregation, which might be of special interest for restoring soil structure for an upland crop after rice (Roychoudhury et al., 1983). Excretion of organic acids by BGA might increase phosphorus availability to rice (Arora, 1969). Presoaking rice seeds in BGA cultures (Jacq and Roger, 1977) or field

(Aiyer et al.'! 1971) was reported to decrease sulfide injury in soils subject to sulfate reduction processes detrimental to rice.-

Theie have been many claims that soaking seeds or growing seedlings with BGA - _ _ l _ l _ l cultures - can ---- benefit rice - - - plagsby pjoducing plant growth reguJat0i-s (PGR) . Roger and Kulasooriya (1980) cite 11 references where the additive I

effects of BGA inoculation in the presence of nitrogen fertilizers were hi&-

. -

-- -

effect of a PGR produced by the i 2 E i

-7 -1

.’

P.A. Roger 123 _I -&“:- . _, i 5 _I ,. . ;: -r-s’i::*,:j te.r.-ci---.-dr; r&~;.,.L.P~s ,: , ‘ “‘c-l. -F-r: -‘,=I ‘<I’ ‘.‘.? 4.) .;‘~.;‘:i;,La.L~‘ _*! ..- L, 4. . _

. o&i&& hi&y hjipbth-ekai: Mote direct:evjden’cebf PGR e,ffkct$ has come,?; p$&riijl fi&the trkathent bf rice.s’eedling.4 ihrith aJgalkculttire~,o,rYtheir;exY1:~ tr&C R$& <nd’&&&oriJa (1986) cite 12 referencei reporting that presbakf- i ing of seeds or seedlings in BGA cultures or extracts had some of the folk-wing.- effects: : ehhanced: getmination;C fdster.. growth; eqriy~-Feedljng _ rec?<yery; rhizbgen&k‘effect; ‘prolonged tilleKing; stimulated ,yegetaUvp grp@h; _a?$ in;: i crease in length and number of.ears, in-number of grains per_ ear,-and,i4:weigh!- $ and prbiein’content of the grain’s. Hoti$er,:when 13g.qn‘iaigai strai~~.~~oiated,; from-sit& iti Africa. (n&ail kitefik4ds), were, t.ested (q++c,d-,and Reye-q$i:,- . ‘-I*_l.. 1987) for their effects on rice gern$nation and growth, 70% had a nFg_at!v_e si effect on iermin&ion a‘nd only 21.%,a stimui~tsrsc.ef~e~~;~~a.~.y,-~~o~~o~~.~ain~. __ had & &gativei effe&‘~i:; -;;:te --r-- 1, !!2 :) ‘r e . L’:+z _ lat~-s2~xs~~ss -.kJ..i~ g;&$ 5is:j ‘?,z i-$cyTs;ta

alms As fiointed out bjl Metting:??d-.Pyp!e, (Mettjng.~an4Py~e,1~~8_~~ ,. the sT numkrous reports of algal PGR.showed,pp_definitive_st~~y,Ir?,wl?jc~ ~.+~~~o&&‘~::;

., -=.. *;..

PGR was isolated and characterized. jg${p:i’-j - , j&$1, ;-a:;zlt ;...,..,‘>~~:~~ -ii $si’y . c ~-----+‘~---.-----~~ 7 Q +. : : c 0 r; _ 7;: --;z” ( .;

” -* ;z - .._ r.:y.: -, &A, Potential Estimated from.I&%%latibS ExperimWi’< j 3 ,-: - irs ,’ ..tz >. 77. I -?----?1--? p ..-.. ,.+w...-..L -. .-.-.d_7.-.L:; i :,! $ $.;. __ The effe&‘s”on rki yield of soil inokuiation by BGA were first r&&ted by -, Wataq.$k et al: (1951) : a 25% increase in .a qoorly diained @field ink&lafed : ,,., , ‘,‘,

; I with ToJ~pothiix’~~~~~~~Several putho!: reporied i&r&& tie11 aye; 200%’ ‘. ‘I .. frbm’ p6f kals ‘(Singh; -296~~~ ;Sbridara Rao ei‘ki., 1963). Sut@&tint’ &&k~~~‘F d-C ,’ i have indicated much io~~~‘&~ea~~s~$ field than in’tot trials, even khere comparative studies have b&?$ade .(Huang, ‘1978). Possible caus’es for ’ “.’ ,: ̂ “ overestimated effects of BGA inocuiafiph.iF p,<t _e)cperiments include the &ong:;:.-. reduction of grazer populations (dry s&I:‘dep’ieted‘?f fauna, is usually uskdj t ’ i-s climatic disturbances, and a mechanical kffkt +the pot wall, where BGA . may .grdLv profi&y’. ’ 2 ‘. .‘Ai”,$h-<; : -:

Studies on BGA inoculation have been disco;itl~~~~~~~~~a~an, buf’s&&: L cjuentiy have been pursued in India and a few other count&. Iiiocul~ have mostly been derived from laboratory-grown strains, following th.2 ekJy.Studies .:: .: I,

- w’ith.TTtenuis in Japan (Watanabe,-1961).--- Y~.,--..-,c,m~i rY [; z:[;$The interest generated in BG+, in Icdia led in 1977I in the Ail-India door-

dineted Project in ‘Algae, whichUi$&v~d the% prGd&&n, distributioz, and testing of soil-based inocuia‘ k gdd! F&&k i&ekI?& the results give details ofnp~~$<~~i ‘A&j.& (\je;;kai&&fisfi! 1972 itid 1981ay! ~~~~~~~~ ‘ge p&pgied;

f$ii$ &$bf St&iris is&tdd’&iginaii~ from ricefieidk?md’Qroivn in shallow,

.1

124 BNF Associofed With Rice Producfion - -d~,y’s.: :.

addition of 20-30 kg ha-l. N, provided phosphorus fertilizer is added (Sharma and Gtrpta;‘ 1983). Reports on field experiments availabke to Roger and Kulasboriya,(1980) showed thatbn the average, algal inpcul,ation causes

.5

14.5%.‘relative increase in ,grain yield, corresponding to 475_kg grain ha;‘:. per-crdlj;:-s’ K. ’ :, ; ‘3::. ._,... z *. ‘,: . : - .. , ‘21 ~_ 5 r -* .: .L ;.L ._. _:. ., ., ,,,

L-y. Hdwever‘a recent review, considers 260 experiments reported between :, 1980 and 1987; and shows a lower. average yield increase of about 300 kgdha..\ (8.5%) in inoculated’plots.~The f -test of Student-Fischer.for paired samples,-*

’ (ddf &‘258_; t-s ‘L 1.734) shows no significant difference in average yield,bet-, we& ino&lated and’noninoculated plots at p =’ 0.05 (The.level of significance. is 0.084:): J. ‘iA? ’ -: ,:“:. .--: ; :5 _.. L;,.i-7 1::. i :- “\:“~i c;;; ,, ‘_ ‘. ;-;’ .‘:: i I- .-.l ; / :, : i

:“c lFigu?es 3”aiid 4-and i‘able 3 present the’ahalysis of a bibliographic corn:;. pilaiion ,ofr.field data (634 experiments) reporting yield: values in. both .a :. nonino&lated co&of &id ttiec’orresponding inoculatedtreatment at the same fertilile? IeCel: The intercept of the’regression curve with the y:axis has,a value. ‘field ]n inoculated plot (kg/ha) ‘* .b’ : : ‘“:“:.r:~ :‘: :: b_i.: - .j ::,c.“. I ‘,. ,

3 ‘““1 .T . . ,, a._ ‘...Y.. . . . . .:

.‘i;’ 1. -’ .. ” - *

_ __ i.“- 1.7 ‘_ -

,;- _-.’ ‘: __ ‘: .: -.. 7 -. !._. ,.,, ;:- :, :. . . ,,, .:‘-, ^ ,- .., :. .-, . . 4

:.. ;. 60*0-;1.:::~;.~‘8db0

’ Data from Aiyer etaI:;-1972;‘Alimagno ,a_nd Yoshida,, !975; ,-Beri,and Meelu, >983: f3h:uiya: 19@l;,Bh_uiyaet.al., JVF+; Cha?drattqr ef all_lV83;Gaur,and Sir@, 1983;-G(a~t~et’al.~~ \V85;, t+!ssa,e! al.. 1979; Indian,Agncu!tural Resea;ch,$sitit>te, jV78 and.1980; Jagannathan and: Kannaiyan, 1977; Jal’$&i Rao‘et’;IlG i977:‘Jhb et al.; 1965: Kannaiyan!.‘l98la, 1981b; 1985. a&1986; Kannaiyan and’Gb‘“indaraja~~~1982; K*dnnalydn et al:; 1980; Kannaiyan et ali; 1982; Ko$shi: 2nd ‘Seiiio, 1961; kkdholitar et al;;: 1973: Pant&i& and Gonzales,.l~?76:.pateliet al:: 1984; P&i; 1980: Ram and Ratidt.,1984; Ram et al., 198% Re_ddy et al:. 1986: Re!da,nj,. 1963, and 1965;~Roychp~~h~ry et.al., 1983;-S~n,kgram et a!.. 1967; Sr$$ a$f~Islam, IVy;Sjngh,’ 198: pn~d21V8?;T$i~as~n, an.. Ponnayya,.l978,; Subraman! et al.; 1980; Venf%&aman; 1975:’ ,-;;. 1 i,,:, It”,jf;ts )‘> !f:<*i,-’ .’ f 12. . T I I ,.-.-, . 4 ,,,I ._.i 0. 1:9+X,7 and 1980.. , ,_a / ‘. 3 I :i;: .I., ‘Y,

~~~i?..?,,~~,!r,i:i’r,c, 8. . i- -’ .-. ;,. ;: ‘,Z ,’ _..- ;- )“L~ I_ ,I ,.:.y; ; I.

c.ne I :: . 9 ,: / ‘* _ .” ‘.-r;i .,. . . )(S.. ..I I_ I~?--, t: ,S‘, ., ._ . ;7 : &: *

-/ -” ‘.‘: - .,. -. ,.rY :..-. c,..; :r : ,-_ ,.,. .,. *p ” :-

P.k. Roger i25 L.

60

40

20

\.., np-, r----i .c ;.::: :_. : &,I!::: ,j’ Ii .% ‘. i.2 ~15 <.;; . :*.:I ;; i ..-; -, i,, -Y,: $’ ,‘.’ ::;,+“: ; . . Fig.“;jl‘bk~~~~~‘of’abSol;;e Geld differenies b&w& in&ul&d~~lo3‘and &&%I~. Bl%&&id“.‘ ’ compilation. ’

. ‘: “_ _. _ ,: : ,:.;

* Data fr,om Aiyer et al.. 1972: Aliniagno,.and Yoshida:1975: Beti and Meelu, 1983; Bhuiy& .:’ 198?;;+yiya.et al., lYF4: Chandrakar et al.,,1983; Gay,r:and S@; 1983; GrantpI al., l.q85*;,,! Hamissa ei al., 1979; India; tigricult~~al RearFh.1.nsti!utd, 1978 and 1980; Janannathqc and Kan’$%; i977; ja’lapathi RaGei al.‘, 1977; Jha et61.. 1965; Kanbaiyan, 1981a. 1981b. 1985 ” and.1986; Kahriaiyaii ind Goitind$afi; 1982; Kannaiyan et dl.; i980; Kannhiyan et el;;,‘1982; ‘* Konishi and S&b, 1961: Mudholkar et al., 1973; Pantasticb and Gonzales,’ 1976; Pate1 et al.,‘. -. 1984;~~ill~,ii,~198~;Ram and Rawat, 1984; Ram et al.,.1985,: Reddy et al., 1!+6; Relya@.. .. and 1965; Roychoudhury et al., 1983; Sankaram et al., 1967: Sarkarsnd Islam, 1984; Sing!: I 1981 and 1982; Srinivasan an4,Ponnayya, 1978: Subramani et $.; 1980: Venkaiarar@F, 1975, 1y77 anb 1y80;: .?:...

r .(, . .- __ ,. I . _ : ,_ .’ -7

i ‘:5,‘:;.: ,-., : :‘i5t .-., - 1 k.‘ - _,, , * ;-. 4: ,‘- /I’ l.;“. ,_.. 1, .y;-.i ::.x _,l * _.,,_ : :;: .;:,t’:. -1 ,l *._ r! - : __,. .-. I.“.-.,’ I’:‘ i: .“Z.. ::. ..; I.“‘;: Ta -:““:<-,,‘: ., - ?.7;‘R

of 3,+0 kg,grain ha:’ _.. >._, 4: ! a?$ !hq.differenceln yield between, inoculated- a+ FO~-~~!~ trol plot; is almost independent of the ;ield of the co&&l (fig: 3). .Stati.st,i~6!C,z ..i”.. 1 _, . . .- .- - _ . . ,__ ...I _.i ~j -. analysis (Table 3). shows a very ,large v+.abilit_y, of Jhe,, ci$fer_encs ji$eld bet- .-... - _, .z.. -” _ .,. _ . j ‘” * _ _ / .,I. i“ . ~ .a ween inoculated and nonlnoculated plqts,, $6 sp,~e~surp~ging_eytreim_e..,v.aiues.;l .: ..r--4, .._ . ../.-._ I. )). . I” ._ _ . and 9 $c&$ent of..variation of more than 100%. fiverag< ci~f~r~~cejs,~~~ ;:L ..I .,.I... VW j,., .._ ( c _,,*. . ..*s I kg grain ha-2 ,. Howe_vTr, a v~y dis_syrnetrical,.~i~!ograSn:!Figi,P). and a:stan;,-..,. , .^,. -.,/ .I. It .LII dard d&&&L’ci~~~ to “ihe mean (Tadle 3) indicate a-!gg-nqrmal, distribut‘ionp :. of the. data.*Therefore; the median (25.7 kg :b+;tlJ

,<, (..l, iv /..: ..-_,-, ..:,d -+“. ,;: “... ^L. S”. .‘l*. ~ d - ^,_.. “. ,_, -..L. ., . _. @ a better, index s 5” ._ ‘-“*..“” I l.. of. the

avqagg $&f.~qf, i.noq&t@~, ,that $5 .??a?,. ?: . ::‘. il:‘;sL1l :--.- 2rLI ,r::,+e,..212 ; C>, . I, ’ .;;IJhe t-test .of Student-Fischer for paired samples..($df 4 63,i $ T,~;J 3;$&, ., -.A4 “.. . .._.I.. -.- ~-_- _I _._- _. . ._ . ..r I.. I

sho-~?,q statistically,signjfi~+~difference in ave_r?ge, yie_ld:~~;ween~~~ocu!?~ed-i~l ,. ..-.. D_ I. “.-, .~ (3??? h/~a!,.L~d Wnpcuk~e~ .W~%-d.ha!.p!~ts at e ,c%.,Q,!~ ~ow~~e~~:, J only 17.96 of the experiments report a statistically significant difference bet-

. .

i

126 BNF Associoted With Rice Production '

-

Tab le 3: Statistics of absolute and relative yjeld differences between inoculated plots and controls. Bibliographic compilation *

Difference between control and inoculated I "

Statistics

Absolute Relative (kg ha - l ) (96)

Number of observations 634 - 634 Maximum 3700 168.2 Minimum Average Median Standard deviation Coefficient of variation

1984; Bhuiya et al., 1984; Chandrakar et al., 1983, Gaur and Singh,-1983; Grant e t al., 1985; Hamis4a e,t al., 1979, Indian Agricultural Research Insbtute, 1978 andJ980; Jagannathan and 1

Kannaiyan, 1977; Jalapathi Rao et al., 1977; J h a et al., 1965;,Kannaiyan, 1981a. 1981b, 1985 and 1986; Kannaiyan and Govindarajan, 1982;J(annaiyan et al., 1980, Kannaiyan et al., 1982: Konishi and Seino, 1961; Mudholkar et al., 1973; Pantastico and Gonzales, 1976; Pate1 e t al., 1984; Pillai, 1980; Ram and Rawat, 1984; Ram et al., 1985, Reddyet al., 1986; Relwani, 1963 and 1965; Roychoudhury et al., 1983; Sankaram et al., 1967, Sarkar and Islam, 1984; Singh, 1981 and 1982; Snnivasan and Ponnayya, 1978; Subramani et al., 1980; Venkataraman, 1975, 1977 and 1980

ween inoculated plots and controls. This indicates that (1) the response to algal inoculation varies, (2) the response is small, and (3) the experimental error is larger than the response. The most common design for BGA inoculation experiments has been 4 X 4 m plots wjth four replications, which usually gives a coefficient of variation higher than 10% and a minimum detectable difference of 14.5% (Gomez, 1972) larger than the average yield increase reported after algal inoculation.

Another impoqant aspect of the statistical analysis of BGA inoculation experiments refers to the experimental design to compare an inoculated treat- ment receiving nitrogen fertilizer with a noninoculated treatment receiving an additional 25 'or 30 kg N. ha-': If the yields in both treatments do not significantly differ; the authdrs conclude that the effect of BGA is equivalent t o the application-of 25 or 30 kg N ha-1. This design should not be used because it doesnot peimit the testing of yield response at thë-additional level of nitiogen. In addition, wi'th such 'a design, concluding that twd values are '

not siignificantly'diffërent requires p > 0.95 whereas most a 0.05: ivhi'ch is ekoneöus:

1 * When herpreting data from the iiteratúre, it should also be kept in mind that, probably, unsuccessful trials were "often not reported: When they were rnehioEed, it was usually withbufquantitative data that could explain the possi- ble ie6son for failure? Fdr' example, a report of a multilocation trial in India

'-

_ I , .

ing the 22 sets of data presented, "the *: - _ . I

8

P.A. Roger 127 .1_ 3 : ‘,i ,-: :,..: pi __, I . .- . - :, i ,.

results from many other locations . . . were not received because of the failure of multiplying BGA at these locations.” -j c “- ; ,I:‘ ; “: ., 7 r- _ ? ‘. .& QC Avai)able~data~sh~owCthatU a!gal inoculation can incre&e~r$e Geld but its I.. -_

L ; effects often seem to;% erratic .a.nd li-rn~m;iltediwhich, mayL.exelainthe’ farmers limited.adoption of ,algal inoculat&n~: A st.~dy.of,!t~-e!ec~~no_milcs of BGA.. use -, 6:. .- by:,4.0, farmers in. Tamit, Nadu. @iv. of.,‘Madras,:. 1982) found no significant I ::‘...~;.r;.ir. I, ‘:.. ..:.<.-< difference in the average pera hectare cost of cultivatro-nz.between ;croPsSus!ng i .‘.:.Y. i.: ($247) ,and not using ($246) B&AL,b,uf, t.te average return of @GA-utili?ation ,:’ 1, I’& CL’. “+&.,‘. ;,;., ..-

;-was, only. $&[-ha.. When’ askedI$vheth,er, BGA had ~~~“p~.~~.d.~~ld,,.~nly five . ..I.. _.,. ““a, . :.out of 40 farmers respond+ p~~iti~~~~.‘~~m~~s~~~~~~~~~~~ers not usi,“, BGA, -...C_L -. -_ : ;ez:.,*. i.. ->“. c ‘fo’ur were unaware of the technology’, two’were awareti$ ~~b,r+Y~<or.$r&.get any inocu,lu_m,,_an,d_!;qur!sajd they were not. convinced-of the yi’eld-rncreasjng

’ ;‘Guai!t? of the hae: :‘; -- .z; L111.:L,;;::7>.‘:, i ‘1. “- .z..,. ._.*_ ,-,:rri. . .1: ,, ‘. .i

./ .,.. 1 ,-.. -, - . . <., : .-.‘,I& :. .I,..:FL.L .,F;i;i ,F+..; i ;si,r?r:T2zJ.,i

. ..- -.. . r>::. , *... r..:.t.: t’ :;r,- .:.:‘:~.$./ ., -. in_ ‘c,.,;. >:-. -yw-t’( :.r.r,:$- $:y e+..;c: Iti: 7- h+rtebrates like cladocerans,,copepods; ostracods, mos&,to larvae and Snails I i’,. . :*. .:;:.j;;s.;:f, ark, common, grazers ,of‘ algae, in ricef+!c&+ ,,Their I,d&elopment reportedly “.Ld’ -, prevented the. establ+ment of in&& (Hi&no et ai.i’i955’; Watanabe et a!. , 1955) and car&d algal blooms to disappear (irenka~~;ama,n,~,l96lj: Recent studies confirm that gr&ing is a major hmiting facfo&r’BGA g%wth (G&t

.’

.L

et al., 1983; Grant et al., 1985; Wilson et al., 1980 b) > Jngestion rates of Heterocypris determined in. uitro by. Grant.and ,co&&ed~@,GA consumed by a field population (87.00.mm2) totalled’187 g N.ha-1. day-i[4j-or 73.kg fi algae ha-1 ‘. ‘da;-1 or i9 kg N ha-1 . crop-r. In microplot (0.5 m*) ex- periments, nitrogen accumulation at the soil surface increased by one to three- a?d-a-half times when gr,tiers were controlled (IRRI, 1986). ‘:y;- ;-

A trend among nitrogen-fixing BGA is that strains forming muc$aginous colonies (Aphanothece, Nostoc, Gloeotrichia) are less susceptible to grazing than strains that do not form such colonies (Grant et al:; 1985).~?hkrefore, grazing has a selective effect on BGA. Plate counts (Roger et al:; 1987) &OW-

ed that’genera forming mucilaginouC&lonies were dominant in m&e than 90% of 102~studied~soil~~~hile other genera were present’ in many. soils but were rarely do?ii’lnant. This’may indicate that grazing leads to the dominance of m~~agin%s BGA, whichire usually less active in BNF (Grant et al;, 1985; Antarikanonda .et al., 1982). I

iz. __ <I 7” : -

~howhorus 1 ..i’ $ 5 LuX cq:- :_ s ;+ L ;, .j g* “$-i 2 z &> 2 &< Phosphorus’is o&n-a limiting factor fey BGA growth as shown by aipositive

; correlation between available phosphorus and.the abundance of BGA i;;” rice $*,i’ I i ‘2 soils and experiments demonstrating that pl%phorus application stimulates BGA growth and photodependent BNF (Roger and Kulasooriya, 1980;

128 BNF Associated With Rice Production

-

Nitrogen Fertilizer

Roger and Kulasooriya (1980) list seven references reporting that nitrogen fer- tilizer inhibiied BGA growth in ricefields, but alsö suggest that inhibition in situ might not be as,marked as that in vitro. Studies at IRR1 (IRRI, 1987 and 1988) show that broadcasting ure-a strongly inhibited photodependent acetylene- reducing activity (ARA) in about 75% of 60 cases, while in others, a signifi- cant ARA was recorded (Fig. 5). The negative correlation between photodepen- dent BNF and rice yield (Fig. 5) indicates that a significant ARÄ developed

nitrogen applied) was low. hoculation experiments at various levels of nitrogen fertilizer also show

inconsistent trends. Some authors observed a more or less marked decrease of the effects of BGA inoculation when nitrögen_fertiljzer was applied (Indian Agricultural Research Institute, 1978; Gaur and Singh, 1983; Kannaiyan and Govindarajan, 1982) while others report a similar effect of BGA inoculation at all levels of nitrogen applied ¡an Agricultural Research Institute, 1978;

A trial at 22 locations in India (Pillai, 1980) showed: (1) a better average effeci i f BGA inoculation without nitrogen fertilizer (310 kg grain ha-') that when 25 k i N ha-' was applied (190 kg/ha) (Table 4) but a t both levels the

itrogen application when . . . nitrogen efficiency (k

- , - * . Jalapathi-et al., 1977). - . % -

Yield (tiha) 1

y = 5.356 - 0 . 0 0 7 ~ '

R = 0.70

1 ':

I ' 3 1

,. - , . . * _ ~, ;. . , . , , . c . . ,. .__ " \ " : . - - - . . _ .

Fig. 5: Rice yield and averagephotodependent N2-fixing activity during the crop cycle in plots with urea broadcast aî 80 kgN/ha (unpubl. data)

' P.A. Roger 129'

Table 4. Average effect of nitrogen fertilizer and BGA inoculation. dn. yield in 22-Sit.es from,,a

. .

muhilocation trial, calculated from Pillai (1980)

- .

. -1 '+ . . ...

130 gNF Associated with Rice Production

- - RECONSIDERlNG.BGA INOCULATION - . - Ïi!¡ recently, almost all studies on the agronomic use of BGA have emphasiz- ed algal inoculation with foreign strains selected in the laboratory. This arose (mm the earlier belief that nitrogen-fixing BGA were not normally present in many ricefields. Recent results show that nitrogen-fixing BGA are probably EbiquitÓus in rice soils and foreign strains inoculated in a soil rarely establish. Therefore, research on BGA inoculation should pay attention to agrjcultural pt-actices to alleviate factors limiting BGA growth and inoculum quality.

Occurrence of Nitrogen-fixing BGA in Rice Soils Early qualitative surveys reported a limited occurrence of nitrogen-fixing BGA in rice soils (Venkataraman, 1975; Watanabe, 1959; Watänabe and Yamamoto, 1971). However, quantitative studies during the last decade show- ed the consistent presence of nitrogen-fixing BGA, frequently at high densities, in soils under rice cultivation (Table 5). In published data (Table l), the average value is 1.5 x 105 CFU 9-1 dry soil (median 2.0 x 104). A quantitative study (Roger et al., 1987) of 102 samples of rice soils'from the Philippines, India, Malaysia, and Portugal showed that heterocystous BGA occurred at densities ranging from 102 to 8x lo6 colony-forming units (CFU) cm-2. The abun- dance of heterocystous forms showed a positive correlation with pH and available P content of soils.

BGA seem to be either ubiquitous inrice soils or, at least, much more frequent than estimated in earlier qualitative studies.

I Inoculation versus Alleviating Limiting Factors

. *

w

-.- - - -- I -- - -

~

œ.

*.

_ - -

The growth of nitrogen-fixing BGA in ricefields is most commonly limited by low pH, phosphorus deficiency, grazing, and broadcasting of nitrogen fertilizer.

. Cultural practices tha! alleviate the limiting factors might be sufficient in some cases to allow the development of agronomically significant nitrogen-fixing blooms of indigenous strains.-

" Liminglis knavn to favor growth (Roger and Kulasooriya, 1980; Watanabe and Cholitkul, 1982) but is rarely economicalty feasible.

Phosphorus application. Many laboratory experiments have demons- trated that phosphorus application stimulates photodependent BNF and BGA growth (Roger and Kulasooriya, 1980), especially in acid soils (Cholitkul et al. , 1980); Wilson and Alexander, 1979). However, reported efficiency (2-3 g N g P-l) Cholitkul et al., 1980) is low. Split application was shown to be more efficient than basal application (IRRI, 1986). Recent studies by Bisoyi and Singh (1988) provide detailed information on the effect of phosphorus on BGA production. Phosphorus increased both BGA biomass and its nitrogen conteni. Split application was more efficient than -basal application. 17.4 kg P ha-' increased yield (dw after two weeks) by 2.5, 3.5, and 5 times with Aulosira, Aphanothece, and Gloeotrichio, respectively. Biomass produc- tion was maximum at 17.4 kg P/ha and decreased at higher phosphorus

" _

r - '

I

,

!

J

~ , - ..

132 BNF Associated With Rice Producfion

values. Highest yield (900 kg dw/ha or 30 kgN ha-’ in 15 days) was obtained with 17.4 kgN ha-] applied in three splits (O, 5, 10 d) using an in- digenous inoculum of fresh - Aulosiro (60 kg dw ha-’) containing 2 kg N.

Grazer control. Field measurements of ARA, and BGA and grazer abun- dance showed that suppressing ostracods with insecticides stimulated BGA growth and BNF (Grant et a1.,1983; Grant e ta l . , 1985) even when insec- ticidal action was limited to a few weeks (Grant et al., 1985). When snails were present, insecticide applicaiion wàs ’hot suffic.ent to ensure BGA growth. Grazers can be economically controlled by pesticides of plant origin (Grant et al., 1983) and by seasonaldrying:

Deep placement of nitrogen f;3rtilizei, The study of different methods of nitrogen fertilizer application o$ the algal flora and photodependent BNF has shown that surface broadcast appli;ation of nitrogen fertilizer; which is widely practiced by farmers, not only inhibits photodependent BNF (Table 1) but also favors the growth of green algae, which increases the pH o? the floodwater and causes fertilizer losses by ammonia volatilization (Fillery et al., 1986). Fer- tilizer deep placement, in contrast, decreases N losses by volatilization and reduces the inhibitory effeh of N fertilizer Òn BGA (Table 1) (Roger et al., 1980).

While the effectiveness of those practices in increasing BGA growth and/or ARA has been established, n o experiment has yet qubntified the relative contribution of the increased BGA dctivity and the directAeff ect of the practice’ to yield increase, when some was observed.- ‘

z -- f -

Why Inoculate - . - - The ubiquity of heterocystous BGÁ in rice soils does not imply that inocula- tion is not needed. There seem to be no data to support the claim by Agarwal (Agarwal, 1979) that the introduced BGA can establish themselves almost per- manently if inoculation is repeated for three to four cropping seasons.

Inoculation might be useful because the accumulation of phosphorus by the propagules of the BGA inoculum (produced with high levels of phosphorus) gives them an initial advantage over the propagules of the most often phosphorus-deficient indigenous BGA (Roger et al., 1986b). This is likely t o be more important in the case of those species that surviJe dessication as whole filaments, aC akinetes (spores) are apparently characterized by a high phosphorus content (Whitton, 1987) and so are unlikely to differ much whatever their source.

Since spore germination is photodependent (Reddy, 19t$3), inoculated propagules applied on the soil surface might germinate better than indigenous propagules -mixed with the soil.

The effect of inöculation is likely to be much more important where there are marked seasonal Fhanges in &e us: of land, such as when an upland crop is grown before rice or after a lbng dry fallow: Under such‘ circumstances, the natural BGA population density may be low at the beginning of the subse- quent rice season, leading to a lag of several weeks before it makes a signifi- cant contribution to nitrogen fixation.

,a, 1,s : , . . , ( ‘. ,‘.T.

_

oculum production do not include tests of composition and vrabrlrty. Re&ritY studies show that the density of colony-forming units-of nitrogen-fixing strains in soil-based inocula may vary fro-m’ 103 io:iO~/g’dti’+md~cdmprise ‘an‘: averdgell3W‘ of the total algae (Roger et al:, 1987) :.,r 1 A,.; .; ,_ :,-..YL::;‘;Z>;‘C -...

t>-Ttik’stiidy ‘of the ratio-of indigenous heterocystous BGA. in,.192 soi.!! to heterb&.lbus BGA‘coritained in 10 kg (recommended dose).of 22 soil-based inocula’shotied that in 90% of the cases, indigenous BGA were more abun.-. : dant than BGA-in the inoculum: In 59%. otthe casesi the rati~of_indigeno,~s.r;, BGA 16’ inoculatkd:BGA-was higher than 100 (Roger.etlal;,;;1~87_...;;I,,~.,,

.“The low contentjn BGA propagules’of the inoculum.niight~ be_one or,,, the’reasons for the failure of inoculation; “i 2% :Y:; .:y) -7: :,=~;:~iz;;~~n~z ,r:;;;u3iC

ii’ _** il -. . E . k-t t :. fq..‘;K r a -2 ‘ -r.::’ .;,ri -.“I 7.t xs;i .z ,; I . ; t-3 .fl &.zT5” +:; :.r ?-,.-,~, .i c.- _I ‘ .

lnd’.B~n~~~,~~.~~~rains yer:F? Foreign Strains : .- ,,‘.. ; !

.L ,-.- -t -- .-.f. :.*, “-3 . ^ ry..,;2.“,y *;i ;;y- _. Most.,alg~~~lizationtfials have’been carriedSTout using. inocula developed from, “a- :_ ..: ...I ,;: 7-b .‘Z’

.’ a mi~t-&e~pf !a&rator$culturas; but:almost nonk’$:th.e p,ublished i$c,u@o’~~~, :t .. jl 5: experiments have paid a~ntioh:t;;=~~e’establishrne’~~“~f mocul&d strains. .k ‘,

The first quantitativesfudy to establish”th’e fate of strains .&bse&en~“to” ,.: inoculation is that of Reddy and Roger (1988). In this study, the fate of five laboratory-grown heterocystous strains representtrig 75%bf the ifio&lum wasJ5 studied for one month in.l-m2 plots of five different soils. During.the month- ;Z following inoculation, the inoculated strains multiplied to some- extent in all-., soils, but rarely dominated the indigenous BGA.: They did so only when the- I growth of indigenous nitrogen-fixing species yas poor or after the population of indigenous species declined. The soils were dried at the end, of the perjod ,_:T 2~ and then resubmerged together. with neem- (Azodirchta indica) to control C,’ grazers:.Two of the inoculated strains did not reappear, but one (Aulosiya jer- ,. tilissima) ddvelopedpn agronomically significant bloom on two soils.,In all the. : ,.:> soils control of grazers by neem combined,with phosphorus ,application per:, mitted the.establishment of nitrogen-fixing blooms;-but in 23 of the.25 corn--,. binations tested: blooms were of the*indigenous.strai,ns,.,~.: . ,!:: ::-.: ;‘.., :

.qln a recent study of the effect of phosphorus on BGA production, Qsoyi Y!: and Sigh. (1988) found no effect of inoculation with foreign strains,~where.as ;il inoculationtiith jndigenous strains increased inoculum productionby moreJtll than .I0 times. as compared with a noninoculated plot;:! :II’ .+ >,.+:i ,Zi,,:iZ,Tpt.p-

+A similar. observation’:was made by Reynaud, and..Metting (1_988)-v~ho,.,, studied the e’stablishment of 23,strains in an irrigated soil-and found-that,t,he.:i 1 only. strain: that significantly developed:was a local isolate,,toJVostoc,~ ::<:i:: i._

Ii;‘ft&ds ivith’giich natural flora it seems likely that’other strains usually.:-! will rapidljr’Soutgr’oui populations~detived from the’origirial laboratory isolates. Where f&mers i‘&Sre$se~ their inocula in shalloti trays or’ponds;. it is probable :sl that strains present in the added local soil may outgrow the original isolates even before inocula are added to the fields.

-J

134 BNF Assocjoted With Rice Production

Available data are not enough for drawing definite conclusions but clearly cr:qqest that the potential of inoculating ricefields with an inoculum produced j;,,m the soil to be inoculated should be tested whenever inoculation ex- :.cqjments are conducted.

(yied Inoculum versus Fresh Inoculum

In inoculum production plots, we usually observed easier establishment of the &:ae when a fresh inoculum was used (unpubl.). Bisoyi and Singh (1988)

ined the highest BGA biomass in an inoculum production plot (900 kg dw ha-’ or 30 kgN ha-l-in 15 d) with 17.4 kgP ha-’ applied in three splits (O, 5, 10-d) using an indigenous inoculum of fresh Aulosira (60 kg dw/ha) containing 2 kg nitrogen. Such conditions are quite different from what has been currently recommended for field-inoculation. In experiments where in- oculum corresponded to 0.126 kg N ha-’ (about 4 kg algae-dw ha-I) , net nitrogen yield ranged from 1.6 to 5.5 kg N ha-’ and averaged 3.3 kg N ha-’ , m

densjty might be more effici n a dry soil-based inoculum to promote the growth of an early bloom of nitrogen- fixing BGA which-is more efficient to provide nitrpgen to the current crop. The feasibility of such a technology has to be studied.

Does the Super-strain Exist? Since the identification of BGA as Cyanobacteria, significant progress has been made in their genetics, including, from an applied point of view, the transfor- mation of Anacystis for herbicide resistance studies (Golden and Haselkorn, 1985). One can speculate on the possibility of selecting or designing more ef- ficient strains for field inoculation.

Efforts have been made to select strains with especially high nitrogen- fixing ability. Screening of a range of strains obtained from enrichment cultures has provided strains that are fast-growing in the laboratory (Antarikanonda and Lorenzen, 1982; Huang, 1983), but there is yet some evidence that such strains will not perform equally well in liquid culture under laboratory condi- tions and in situ. It seems unlikely that an introduced strain will survive long in competition with the natural flora, unless there is a simultaneous change in the environment, which gives it a competitive advantage. In fact, most fast- growing strains, with doubling time of five to 12 hours, belong to the genus Anabaena, have short filaments, and do not form mÜcilaginous colonies (An- tarikanonda and Lorenzen, 1982; Huang, 1983). Such strains are very suscep- tible to grazing. A laboratory screening of 12 strains of six genera and the study of their establishment in the field showed that strains with high specific activity under laboratory conditions did not establish in the field (Huang, 1983).

A further use for selected strains might be the production of inocula resis- tant tÔ pesticides. It is clear that the growth and activities of BGA are affected

~ -..

Fresh inoculum applied at a hi

I i?.; ‘. : ,....._. advers-e~y..by..,~o,rne. commonly used p~stj~d’es”(PQhhy;’ ].985)i’_A strain of .2- _.2_S,l_ GLeocopsa was reported by S’ingh‘et al..(i986) to be-highly’resistani to the herbidides’bachete and Basalin,~,whereas Nostoc muscorum was’ouite, se& sitiief Rep&iid ]+&io;y ~c&N~ with increasing ..ldvels of pesticide led to increased”~esistance’df three. nitrogen-fixing strains to, four fungicibes.and :“VW~ “-.: ::‘j insecticide$‘ [Sharma a,~-~~~~~~r,~398_1),~_Artificiall~.’~n~~c’~~.mutants resistant, ” . -, , ..I:, j !;?:E;‘.’ :. ‘. :’ to, B$ox-h_qve,been pbtaine$ foL,t,two N&t& &ins,$nd 6ther.imutants rests-., tant,jo ,Carb.aryl, Zineb and Mancozeb ha’;8 beenobtai$d-(,P?dh y, 1985). Most studies.on oesticid,e folerance..i,n z$GAl’hjv.e be$laboratory:ba&d. Data. &:-.I i ..c . . ..z+..! .L, 1.” j.LyLz j- 7.-Z i- -.--a-. .=,.. $ edTMdLrectly on, f_ield ~$$er,vations and assays on ,strains.of particular s$%cies’taken from sites with a known’pesticide history ~~,“~,-P.~~,.ff~itd~rstand:w~~~~~~~ i L % 3’ ? . .d*- ,*l’. : / ^ _ _. . ‘, , , sr?o~-Bc4;~-~i!y,ac-~u~~.gen~~,c toleran,$e for pestrcrdes .ur$,er fiekj condi$ons~.:

Biological engineering on BGA_is c$ently Ii&&d to ‘u.nicelltilai: strains’ _ -&‘3‘ :; _, ‘I;-‘.) .7-T’ “‘-CL 19.1 7 ._. that are morphologically,~ physiologically, and:ecologrcally~very,,different from’ . . 1.. _.., the nitrogen:fixi& &rains consider&l foi’~~i;tuliit~n~,~itkfields~~~~~~~~1 i,.,:.,: _ i ~ I . -. .’ j _. _. .,. r2 __ t : ,.<:) (,

L Probably,super nitrogen-fixing RG~‘can’be~seie&d ~‘designed‘and’ I ‘; ” ._. ,:-.y... . . .& ‘5.c.‘. ‘_l,.. -- < - / a; ;, : _ . . -~..~-.,-.~,. gro,w~,!?~test tubes bui‘ ihe characteristics that will enable them to syrvive,, ._ i-.-. :.-.J.L’; ,” _.:;_ : ‘ . ,,T. ee - develop,,and fix,gitrogen as.programrneb~~,~d~~el~~;;r;e &$l lar&$“&known.‘ The i,m,rqe$ate. need is for a, be@r* ,under$anding ‘ioB,GA~Zol~&~~.i$ F.5’ I./ I. ..I __ . . a Jong term,.genetic. %en,gineering, may also~cdntribute to t,h$ “r:oo$ic use of &A; - __ 1 ._,,,:I ,;; ‘;-; ““:;: ” -.‘:’ -‘.

.: L :::; . r;<.,-.. :;. I ., i :>,I : ‘: .:y;:.‘:<,, :: _- -,; : : : . . .;r,-,.,:z .,. . . . . _ .. ‘*’ * - : j 0; _ - ,’ :- ; .; .;,.-;., I. _,, .‘:-

CONCLUSION.- .,. -“,

,;. ._. c t;-;. .; I ..‘Lt In’ ricefields,’ BNF in general and BGA in particular have been the most effi- . , cient systems in sustaining production in low-input, nonintensive traditional. cultivatiori[. It is possible to influence the amount of nitrogen fixed by BGA i. in many ricefields. One of the ways is by inoculation, a method which is . I &.&tjmes effectjv&. ‘.:>- r ” ‘... *1 . : : I. - :,

In general, BGA have less potential in terms of nitrogen fixed than 3, legumes or Aiblla (Roger and Watanabe;- 1986) but inoculation, ‘when suc- cessful, is a low?ost technology with a cost-to-benefit ratio far more favorable than thaf of green manure (Venkataraman; 1981b). Numerous-experiments indicate‘that, when‘successful; BGA inoculation of ricefields may increase grain yield’. byl$OO-450 kg ‘hafr~~‘per~crop;. but its effects :.seem‘ erratic. and, limited. Cultural practices to enhance the growth of indigenous or inoculated, BGA“are known, but’their’ efficiency” and, economic: viability ‘have’to:,be defermii&d‘d. .: ,,) ~5 *“; ;z?h Y; .I 1:. ‘T,;‘ ‘: a-a~*,~;.,J~ ,‘;-,;, -.J; c:r-$ -z-,‘I”“’ -” It 2. : 4 j,j. * _‘:I t3 f.r;,-3 ““i.‘+ Be&& knowledge- of factors that‘allow BGA to establish and.,bloom in’ricefields is limited; BGA inoculation is co’nducted on a trial-and-error basis. Ndii7ethod for estimating the cl&&of success’of ino’culatioilin-a given agro-. ec’osystem‘is ‘avaiiable. It‘rnay explain. why algal inoculation is practiied in on?

.’ I$~~a’limited hectaiage i< som,e:Indian states’and possibly in. Burma,. Recent ,,. j studies show that: (1.1 l&-fixing BGA are present in ricefields at a much higher rate than was previously thought, and [ZJ foreign strains’rarely establish. Idkn-

tifying and alleviating limiting factors in fields where BGA are present but do not bloom might sometimes be enough to make use of their potential. They are also a prerequisite for establishing inoculated strains.

Many of the studies‘on algal,ization have been uncritical. They most ofte’n appeared to be concerned only in grain yield and to lack‘any, interest in the microbia) and ecological processes that might influence this. The dearth of quan- _ titatjve’studies on the fate-of inoculated st;ains-has hindered the evaluation’ of algaliz,at~bn studies. A prerequisite for any progress in BGA technology is’ ttie a&$t&r~of ex$+-rental design and measurement that all& interpreta- tion of ‘yield data.‘They in&de! [l] experiments over-‘sever@ crops using ex-. pe&er$‘design~ .thaj:ret~~~!atijticai analysis, 121 qtialitiative and qi%ntitaiive analysis of B~GA’@opulations in the %I a&d-the inoculum; [3] chemicalanalysis qf,the~soil~, 14) ie.;iordof major rlimatic $&mete&, [5j ‘esti;tlation‘of tlie’algal. biomass d,uring’,the.~r$p’ ar$if if ‘&sib&, its”mtrogerilfixing activity,-,and [6]’ _,...” p ., *.- ). ,, record’of visual observatibns impo~rtant for,4naersianding”thC; resulis.[grazer popiriatid~s;:rice’ pe~~~,-in~id~nce’of ~e;.&,~eic,.j .“‘!“.’ I&’ ‘1 :. ‘,‘I 1”: L

L “The e&t tb’which’algblizat&r W’iil ~~entuallypr~;e’tvbrthwhile will de- pend ,on,jocai, c~~~~;i;5tan~~~:“~i~~‘~~~~o~se’js likely to-be ‘most.evident in non-‘ acidic~soil&ith ‘moderateto hi&r phos&rus’ availability where nitrogen fer- tili<er isnot broadcast: In’oculatidn is iesseff%ient in-the presence’bf broadcast nitrogen fe&zer, .t%t’stili Vmay ~nc&%.e”r~c&‘yiekl~ Agrosyste’ms with-“a long .,_ -:_, ,. dry falloti ‘or an’u&nd~<rop before’& might he especially responsive-to in- ’ . .;y )*. ‘, -;.-, _, (: ,. - , ,, oculatron because of a low rncrdence of grazers &d a l&e; indigenous densi- ty of viable propagules of BGA after the dry period.

Available information is not sufficient for a definite conclusion but sug- gests that research priority should’ be on: ‘_

.I l] identifying the major characteristics of rice ecosystems responsive to BGA inoculation, 8’ ‘.“ ~.. _. .i’

21 comparing the relative efficiency of indigenous strains versus foreign strains, and ,. hi

31 comparing the relative efficiency of dry inoc&m and that of fresh inoculum.: , : :. i

:. BGA have a potential in low input farming systems where ,fer&zer’is ._ not available or affordable; however, they are, unlikely to *be. an” exclusive nitrogen source for producing high ,yields. Therefqre.an. jmpprtant, aspect .of their possible use is integrated nutrient management.-4 conce!n in recent high-, input, intensive rice cultivation is the sustainability of the high yield and. the possible: environmental-.impact< of crop .-intensification, -co.nsidering that regardless of the quantity,of chemical nitrogen fertiiizer,applied, rice obtains most of its nitrogen from the soil. Knowledge in this aspect is still limited, but the importance of the photosynthetic aquatic,biomass and its BG.A compo- nent in maintaining the fertility of rice soils under intensive-cultivation has been, recognized. (Golden and Hdselkorn,7 1985): However,, the. agronomic poten- ., tial of, BGA- is. currently underutjlized, and benefits from. the’ intentjonal)use of BGA are far less than their spontaneous,contribution to:the nitrogen fertility

’ : ir>.,,. t. .- . ../ , _ “2 - , _.I < : ,: ‘.Y. ‘.I;..? ; I _ ;-: : I,, ’ c-s *“: i-y: __ .-,, . r. 2 I 7.i: ,..,.:. ‘-2, , ’ :-; ,$ ,i_ ,_ ‘;‘:; ;.* ._-, 3’ ‘,e:“;: _’ 1’. ,I ‘.‘_ .-;‘,’ jl, ,,: ,. ‘? : ; _.*’ _a-,: .:

--_

-,

.

Subramoney. Madras Agricultural Journal 58(5):.405,-407, 1971.

- “..A q.-‘.“,u’,‘.-_. e.... ___., IC I - i:cj &qp#>i; I[ :;!:.‘-, >,:+“n . . . . -,.& .*‘” ,> :,,i;f,,,6r,:,.Lo .2 ;&‘-. (,1_? ;:

Aiy_er, R.5.: S. Salahudeen and’G S Venkataraman; Indian Journal Agricultural Science 52(5): -- _-..I./ ..-‘-2 ._ _ -_( / -, c. . .ljd ,.,._... * ..I . . . ,_ . x ._ 1 L +So:333;. 1,979. .:.;. .j$” :-. c.~;2rr-l.“:l..‘~~ ;,; ~+.:.$.: Z.f< t‘s: r L:’ L.% .:-‘p ‘1 .z ,.“l,:,:r., ,; *’

Alimagn, B,.V., and T.:,~o~hi,d?:;~~~~lipp~ne Ag+u!!urist 591344): 30-9.0, :lQ75. ~, ,,-+:z,Tt. Antarikanonda, P. and H. Lorenzen. Arch Hydro@o!,,Supp!. -63(!); 5377.0, .!98&;. -+ Araragi, ‘M. an,d-BL Tangchen?. -.?oif,%~%c~~Planf Nutr$ion 25(3):,297;309, 1979. ,;,, ,f;L-.,. :, ..? . . . . . . .r. y,l_.h Arora, S.K. Rise 18(2): 135-138, 1969. -5’ 1 2

Beri, V. and.O:P.-Meelu. Fertilizer Neu~s 28(11):,33-38. 1983:, :,:? :.I_ .:L: ~ “‘I.:” ~1;:. ‘,, .;, _ Bhuiya, Z.H. In: Cment Perspectiyes-in Nitrogen Fixption: A.H. Gibson and W.E. Newto! (eds.)! ”

Australian. Academy of Science, Canberra, p,: 498, 1981. i, ic.l.;, : ’ ::. : ;rj.. , I . . . . Bhuiya, Z.H. kx,Proceedings,o.f~~lena~ional Symposium/Wo$shop on Nitrogen-and @uiron.;.:

menf, K./k. Mailk et a). teds.), Nuclear Institute for Agriculture. and Biology, Faisalabad.:,: Lahore, pp: 339-344, 1984. ; +-.: ..I .!, : -(. r ;: :,, _,. .-. ’ u xI ,_.,., -z-,:s;

Phuiya; A.H.;A.K.M,.‘Nurul Islam., M.A. Hashem, Z.N. Tahmida Begum and M.M. Rahman.:; Bangladesh Journal Agriculture g(2): 47-51, 1984.,,> _ ., ,., ,,-, _).: ; .-;

Bisoyi,:R.N. and P.K. Singh, Biology and Fertility 01 Soils 5: 338+3,1988.

.i...-: c ., ; . ; I, .;-.

Chandrakar, B.S.. K. Singh and G. Ram. Oryza 20: 69-71. 1983. .,..: 1.’ :

Cholitkul, W.. B. Tangcham, P. Sangtong and I: Watanabe. Soil Science Plant Nutrition 26: :291-299,..1980..-: ,:-: ,,; ._.-,- .,‘- ; : ; A- G. <. ,>! : , 1- -_ . . ;

De, P.K. Proceedings R. Sot. Lond. i27B: 121-139, 1939. . ._. . ;” *‘; Fillery, I.R.P.; P.A. Roger and S.K. De Dana. Soil Science Society American Journal5d: 86-91, I._

1986. if,:: , :. ‘:-. I -..:.: z-1. *>. ,).’ .‘_,i L< . ..( s>> ‘;.c ‘,:, :..: :, Garcia, J.L.‘, M. Raimbault, V. Jacq., G. Rinaudo and P.A. Roger. Reu. Ecol. &of. Sot. 11(2):,.

169-185, 1974 (in French). :. ;i + .,: I ,~ ..:z, \.:.s “,:.+%3 .::. .;+ .;, : ;‘.-> r.: ? .;!.: _. ~~ Gaul. A.C. and R: Singh.~Feriilizerflews 27(2),,z 87-97; 1983, (Cited by Ben and Meeju, 19B3):.;: Golden, S. and R. HaseIko& Science 229: 1104-1107, 1985. iy.3 f Gomez. K.A. Techniquesfor Field Experiment tuith Rice,.lRRI, Manila, Philippines, p&46, 1972,;:: Grant, I.F. Seegers Soils Biology and Biochemis~ry.17: 559-563, 1?85a.-,,,,.l; .; -; ..r.el.::,,l Gram, I.F., E. Egan and M. Alexander, Hydrobiojogy ?06:L1_99120Li: 1983..Tc ,+. ‘,; .L.:-~ ;c::’ Grant, I,F.,.P.A.. Roger and I.:.Wa!anabe,Biqlogy andiertility,.ol.Spils 11,: 61:72,- 1985.. r..i+: Hamdi, Y.A., A.N. Yousef, S. @&a~$, A. AlTai.and M.S.D.,.AlBaquari Soil Ecol. Bull lStocl$tolmj

,;.26~:,110~115,.197~.-: :’ > I, -1 r. ie,~:,,. ,:: ,“-, yc. 5 .i;t.>e:. :.‘. : iIn:. !:i:::;: ‘t.! ..A ? .a>2.ns Hamissa, M.R., M.S. Khadr and A.Y. Gad. Agric. Res. Reu. (Egypt) 57(g): 2?3:2!1,,,1979. Hirano.:.T,;, K:.Shiraiqhi and K. Nakano. Shikokq Nogyo,$hikenjo Hokoku-2;# 121- 137;<1?55,::

(in Japanese). .y.TF;. ! y.,:: ;. “? ,=;7tI;:-.., -s .+,.-id ,;.r,:;; z.y .x. Huang, C.Y. Bol. Bull. Acad. Sin,. 19(l): 41-52. 1978. Huang, T-C. National Science Council Monthly ROC ll(6): 521-526, 1983. Indian Agricultural Research Institute, New Delhi, India. All India Coordinated Project on Algae

Annual Report /1977-1978), p. 72, 1978.

3

Y '

138 BNF Associated With Rice Product ion . .

Indian Agricultural Research Institute, New Delhi, India. All India Coordinated Project on Algae

'IERI, Annual Report for 1984. Manila, Philippines, 1985. IR.RI, Annual Report for 1985. Manila, Philippines, 1986.

IRRI, Annual Report for 1987. Manila, Philippines, 1988. Jacq , V. and P.A. Roger. Coh. ORSTOM, Ser Biol. 12(2): 101-107, 1977 (in French). Jayannathan, R. and S. Kannaiyan. Adutburoi Rep. l ( 1 2 ) ; 130-131, 1977. Jalapati Rao, L., A. Venkatachari, W.V.B. Sundara Rao and K. Raj Reddy. Current Science

Jha, K.K., M.A. Ali, R. Singh and P.B. Bhahacharya. Indian Society SoilScience 13(3): 161-166,

Kannaiyan, S. Annomaloi Uni. Agri. Res. Ann. 11: 86-95. 1981a. Kannaiyan, S. Nitrogen Conservation in Rice Soils by Blue-green Algae. INSFFER Training Course

Kannaiyan, S.,Algol Biofertilizer for Lowland Rice. Centre for Advanced Studies in Agricultural

Kannaiyan, S. Annomoloi Uniu. Agri. Res. Ann. 11: 86-95, 1986. Kannaiyan, S. and K. Govindarajan. (Eng) Notl. Acod. Sci. Lett. (Indib) 5(4)1 117-1_19, 1982. Kannaiyan, S., K, Govindarajan and H.D. Lewin. In': Proceedings of Notional Workshop on Algol

Systems, C.V. Seshadd et al. (eds.), Indian Soc. dt Biotechnology & Shui AMM Murugap- pa Chettiar Research Centre Pub.,'Madras, pp. 21-24, 1980.'

Kannaiyan, S:, K. Govindarajan. H.D. Lewin and G.S. Venkataramän. Madras Agnc. J . 69:

Kobayashi, M.. E. Takahashi and K. Kawaguchi. Soil Science 104: 113-118, 1967: Konishi, C. and K. Seino. Bull. Hokuriku Agric. Exper. Sta. 2: '41- 136, 3961. Matsuguchi, T. and B. Tangcham. Trans. 10th Ini. Congr. Soil S c i 9: 180-188, 1974. Metting, B. and J.W: Pyne. Enzyme ond Microbial Technology 8(7) : 385-448. 1986. Mian. N.H. and W.D.P. Stewart. Plant on¿ Soil 83: 363-370, 1985. Mudholkar, N.J., M.N. Sahay and C.R. Padalia. Indian Joumol Agronomy 18(3): 232-284, 1973. Padhy, R.N. In: Residue Reuiew u 95, Gunther (ed.) , Springer Verlag. pp. 1-44, 1985. Pantastico, J.B. and J.L. Gonzales and P. Kalikasan. J . Biol. 5: 221-234. 1976. Patel, S.R., S.K. Shrivastava and B.R. Chandravanshi. International Rice Reseorcb Newsletters

Pedurand, P. and P.A. Reynaud. Plant ond Soil 101: 235-240, 1987., Pillai, K.G. Biofertilizers in Rice Culture. Problems and prospects for large scale adoption. AlCRlP

Ram, G.. B.S. Joshi and B.S. Chandrakar. lndion Farmer Times 3(9): 18-19, 1985. Ram, G . and A.K. Rawat. International Rice Research Newsletter 9(6): 25, 1984. Reddy. P.M. Arch. Hydrobiol. Suppl. 67: 299-304, 1983. Reddy, P.M. and P.A.'Roger. Biology and Fertility of Soils 6: 14-21, 1988. Reddy; P.M., P.A. Reger, W. Ven

Relwani, L.L. Agriculture Reseorch'New Celhi 3(3):' 181, 1963. Relwani. L.L. Current Science 34: 188-189, 1965: Reynaud, P.A. and B. Metting. Biol. Agric. ond Hort. 5t 197-208, 1988. Roger, P.A. In: Microorgonisms thof Promote Plant Productiuity, J.O. Dawson and P. Dah (eds.);

Roger, P.A., I.F. Grant and P.M. Reddy. Blue-green Algoe in India: A Jrip Reporf'. IRRI, Manila,

Roger, P.A., I.F.'Grant, P.M. Reddy and I. Watanabe. In:.€fficiency of Nitrogen Fertil&m for ' '

Annual Report (1979-1980/, p . 126, 1980.

IRRI. :A~nual Report for 1986: Ma,nila, PhilippiFes, 1987. . . . ..

46(2): 50-51, 1977. . . . . . .

1965. ' ' . ' . . . . ~

t , .

. Handout, IIRI, Manila, Philippines, 1981b.

Microbiology, Tdmil Nadu Univ:, Coimbatdfe', p. 24,' 1985 -.- . '

, I ; .a. , . ' - '- ' ' . '

. , , . . , , . , . , , . ._.. .... ' ' 1-5, 1982.

. :

.. ' '

9(3): 25, 1984.

Publication No. 196, 1980.

. , -

I . .

and I. Watanabe. Philippine Agriculturist 69 (4b): 629-632, ,

. , . _ , . . . . " , . _ 1986. . . f . . .

~

Martinus Nijhoff/W. Junk Publishers, The Hague, 1989 (in press):. ' i . .' .

Philippines, p . 93. 1985a: . " . ' .

, . .. Rice. IRRI. Manila, Philippines, pp. 43-68, 1987a . I . 1. : : . , i

8 , .

, i .I

. , . . . . _- ,. i I 2 "

., . , - . . -

I’ ,.,_ 0 .., - : .-. ,_ i’ , ,^, 7 . P.A.,eoger 139 .I

_ : -. ; .,i I I 1: ._ :

i; 1pg. I I (‘. - , (’ ‘.‘. /_ . , I I _ _ 7 . f’, : : “ . ; ;. ,,’ Roger, P.A.; S.A. Kulasoortya, A.C. T&l and’E.5. C&we;). &~j&f~oii5fi 137_142,“;‘$8d. Roger! P.&, S, Santiago-Arda;les, P!M. Reddy and I.~Watanabe, Biojosy on,$ ~e+ifY oj 80’1s -;

5: 9thio5. 1987. ‘- .,j i._ Roger, P.A., S. Santiago-Ardales and I. Watanabe. Philipp. A&c.‘691 589-598, 1986.‘;- ., Roger, P.,A.,.A: TFO), S..Arda)es and l:Wat,anabe. Biology o~dF&fltfy ?fS$s 2:. 131-146. !9el ., Roger,‘P.A. and I. Watanabe.‘Feriilizer Research 9: 39-77, 1986. ,, J ;. r. ;: ..’ Roy9houdhury, P ,,-. G.R. Pillai,,,S.,L. pandey, G.S.R. Krishna Murtl.and.G.S.:Venkataramanr, ., ,_. .

Soil Tillo~e Research 3: 61-66, 1983. Saha, K.C. and L.N. Mandal. Journal Indian Society Soil Science 27(4): 470-477, 1979. Saito, M. and 1. Watanabe. Soil Science Plant Nutrition 28(3): 427-440, !978. Sankaram, A., M.J. Mudholkar and M.N. Sahay. Indian JournolojMicrobiology 7(1/2): 57-62,

~, 1967..:, :,-.-i.i I _,._ _: 1 ‘-> ;.k2 :. .. ,-: . A::. ,...,. i -, .: ..> . ;+I; ; : -.z-;:;” : ,.- -c’L~. :; f:; Sarkar, N.I. and M.S. Islam. in: Proceedings .of lnternotional Symposium on Soil rest Crop

.Response Correlqfion Studies, M.A. Mannan et al. (eds.). International Society of Soil Science Publications; Dhaka, pp. 269-273; 1984.,:; :’ I w,s,.:;a-i _ i b:‘, x.=~i~’ ::.,:;‘.z: :.-.: :,

Sharma and Gaur. Internotional Joumol Ecology ond Enuironmentqf Science 7: 117.- 122, 1981. Sharma. B.N. and R.S. Gupta.-Phykos 22: 176-179, 1983.. : .::! -‘c .,I, A. : ;‘I’. Singh, A.L.. and P.K,- Singh. Proceedings Indian Academy of Science (Plant Science] 96(2):

147-152, 1985. l.t..;~.~‘-L...~: 1. ~ -&, -T.-q .y*-.; --,--q-y .-;: ;--.~-..;‘. -* Singh, P.K. in: Currenf ~erspecfiues in Nifrogen Fixation. A.H. Gibson and W.E. Newton (eds.); ..

p Australian Academy of Science; Canberra, p. 12. 1981.,.. : _ i . . _ 7.. L-. ; . Singh, P.K. Indian Forming 32(7): 3-22, 1982. /~ _. . : ‘. , Singh, R.N. Indian Council of Agrfculfuro~ Research, New Delhi, p: 175. 1961. ,.. _.I . _ Singh, R.P., R.K. Singh and D.N:Tiwari. Plant Prof. Q. l(3): 105-102, 1986. ..- .;:..-..’ Srinivasan, S. Aduthurqi Rep. l(4): 29, 1977*.’ .: .:..:‘L c rx.*‘~_. - -. : :: : ej :. ....’ :iz: Stin/vasan. S. Aduthoroi Rep. Z(11): 135. 1978. f_ : -: ,i _, i ‘t.1 . ,.. Srinivasan, S:and J.H.S. Ponnayya. Blue-green Algae OS c Biojetilizer, Tamil Nadu Experience;

Fertilier Association of India Seminar, New Delhi, 1978.. -. . . . . :.: .’ Subramani et al. Cited from Bert and Meelu. 1983. ‘. ., . Subrahmanyan, R.. L.L. Relwani and G.B. Manna. Proceedings lndion Academy Science 62B: +

252-277, 1965. .-., :_>‘. Sundara Rao, W.V.B., S.K. Goyai and G.S. Venkataraman. &rent Science 32: 366-36;:1&3.

* ..’ i i . . %’

Suzuki, T. JARQ 2(l): 8-12. .1967. .: . ..rl’ ‘.fL 3. ; _‘, .a..-- 1 -3 _ I,.. :’ ., ,t _,_ r” Tirol, A.C., P.A. Roger and 1. Watanabe. Soil Science Plonf Nutrition 28: 559-570, 1982. University of Madras. Blue-green Algae us c Source of Bjo-jenj/jzers in ?%onjouur Districf-Tamil ~

Nodu. Res. Stud. No. 74 of the Agric. Eton Res. Center, Multigr., p. 79, 1982. . . Venkataraman, G.S. Science Culture 27: 9-13, 1961.. s :,;, .:., .I : .!> -. ‘. :.. ‘:i., .“,‘:,i’ _ Venkataraman. G.S. Algol Bioferfilirers and Rice Cultiootion. Today and Tomorrow’s Printers:

.Faridabad (Haryana), p. .75.- 1972:-,,?. . .i=fr :, 2 r- ..;:, .,. .t- ,- :*‘:“.‘P’ 11, :,. f :, Venkataraman, G.S. In: Nitroien .Fixotion by Free-living Microorganisms. IBP No. 6, W.D.P;

,.Stewart (ed.). Cambridge University,Press, pp. 207-218, 1975: ..” .; , II 1:,._ .,.:I.. Venkataraman, G.S. In: Proc. h’ofl. Symp. Nitrogen Assimilofion ond Crop Productiuify, Hissarc

pp. 132-142, 1977. I .;‘,.:i;“:g.:.~.~ ,*;, ,, C’...T...y.’ :;. : ;. .:. ej .: 3. Venkataraman,. G.,S. In: Nitrogen and Rice,. IRRI, Manila,.Philippines, pp..311-324. 1980.: : Venkararaman;-G.S. FAO~.Soij.Bull. no 46, p. 102. 1981a, :; .: :!. :, . . . .; “_“; ,,. *-‘I. Venkataraman,.,C,.S. ,Current.Scie~ce,5.0(2): 94-95; ,1981b.,/ (;: ~:...:,.~;,., .., r) i:’ ..-. -.; *I Watanabe; A.: Journal General Applied +yobiology.5> 21r29, 1959:‘. ?. ,. .! ., ,L L”j. ;‘:: ii; Watanabe,. AI Sfud,Rokugowo Inst., Tokyo ,9: 162- 166,- 1961L:I.:r..* : ; : ...,c.:--.. .:_,:* :.. Watanabe, A., R. Ito and T. Sasa. Journal General Applied Microbiology Ir 137- 141.* 1955.: Watanabe. A., S. Nishigaki and C. Konishi. Nature 168(4278): 748-749, 1951..1. . “,,, : :‘ ,:: Watanabe, A. and Y. Yamamoto. Plonf ond soil. Special Volume: 403-413, 1971.

140' BNF Associated With Rice Producfion

Watanabe, I. and W. Cholitkul. In: Internofional Symposium on Distribution. Chorocteristics ond Utilization of Problem Soils. Tropica1,Agriculture Research Center Japan, Ibaraki, pp. 2 1 9 ~ 2 2 6 .

Watanabe, I., S.K. DeDatta and P.A. Roger.-ln: Advances in Nitrogen Cycling in Agricul&d

Whiiton, B.A. In: Surviual and Dormmoncy o/ Microorganisms.' Y. Henk (ed.) J,ohn Wiley and '

Wilson, J .T. and M. Alexander.'Soil Scie&e.Am&con Journal 43(4): 936-939. 1979: Wilson, J.T., D.L. Eskew and M.R.~Habte.~SOiI Science Society o/ Americdn JOumoI 44:

Wilson; J.T.. S. Greene and M. Alexander. Sb;./Biology and Biochemistry 12: 237-240, 1980b.

....... .. . . . , . 1982,

. .. 1 : . _ b , ,. . : . , ' Ecosysfems, 1 9 8 8 (In press)." .' .i ' .

. - . ' _ . I . . Sons Inc.. pp: 109-167, 1987. .

. . . _ . 3 , - , <- . , . . - 1330-1331, 1980a.

. .:. # . "- ,.. ; . , . . . . . . I i . - !.. : . " . . . . - - .

, . . . . I" .. -:-: ~ . I, .,. '.. . . . . D l s c G s s l o N s . . . ; ; . . . . . . .. , , . I

.. , ~ . . . ,.. . . . . . . .1 . , . -,. . , - . . . _ - . _ _ Q: G.B. Monno: A Suggestion. The priority of research on BGA should go for optimum ecological

. A: I-agree for giving priority to the characterization of environments respónsive to BGA manage- mentiinoculation. Howcder the estimation of the relative potential of foIsign and indigenous strains to establish'is very important if the'farmer does not produce inoculum in his field but ;:

requirement for desired manifestation irrespectively of native or inoculated BGA. .'. J. . . . '

is using an inoculum produced somewhere-dse'or'a'commercial inbculant.. . . . r .. '. in Aulosoria acclaimed good results. What is your view? -I . ! '

Q: R.K. Mishro: What is' the prospective of B.G.A. spraying on rhizosphere? Sen and Manda1 .

'A: I suppose you refer to lhe so called "auxinic effect" of BGA; My views and those'of other.. . authors are summarized injhe paper. Currently n o PGR has been isolated from a BGA and characterized. . . _

Q: Anonymous: Do you think the literature survey data you prekented is based towards positive : responses, because experiments 'with effect or negative response would not be published. ' i

A: Yes. When all results are negative, authors usually do not published their data. To my knowledge . there are only 3 papers reporting no effect of BGA inoculation. But in the literature survey .. presented in my paper there are some negative results obtained from multilocation trials where ,-

.~ , .

.. . . . . . . .

. - . - . . . . .-+. .

. , . . both positive and negative results i e r e recorded. ' ' I . . . ~

Q: Douid €skew: Does any one know what is the active bio-chemical principle in nim-cake? A: The main active ingredient in neem is azadirachtin. which act as an insecticide and antifedant

for algal grazers. Several studies on this topic have been publish by Grant and coworkers (see refs: in ttie paper..) . . . . . 7- . . . . . .

tal designs in case of field trials'on B-.G.A.? . . i I..

include a 'chapter on statistical analysis and experimental designs. . I . 7 .

t . . . . . Q: Anonymous: What is the type of statistical analysis technique being cmtemplated for expehen-:l

A: A booklet on methods for field studies with BGA is going to be published by IRRI and will

Q: What are the major characteristics of rice'ecosystem ¡ed for responsive to' B.G.A.<nocuIation?J .: 7.'. 7 . . ' ~

A: The environmental characteristics of ecosystems resp BGA inoculation 6ut alio to BGA management is certainly a key problem and little progress will be made in BGA utilization as long as we ha ie not answered this question. This requires multilocation trials. properexperimental designs and records of environmental data which have been traditionaliy '

Frdm'empiribl objervations, I expect neü6al to alkaline soils, in areas with high'incident l ight , . ') high temperature, and long dry fallowto be more responsive'to BGÄ management! ! ':

Q: G. Oblisomi: The performance of B.G.A.' inoculation is varying in different agrd-dknatic systems ' . in the state or region. Do yoÜ agree to take up indepth studies on the survival mechanism .' of the introduced B.G.A. inoculum (composite culture) and competitiveness over the native'.. (indigenous) B:G.A. strai

'

. . - '. ,.:. . . . . .

. . overlooked in inoculation experiments. ?, . .! : Y:.! - d

. "

~ -. : , ' -, ;; . . . . . . " . .. L.,'', ~ I l,.l.l A: Yes, yes, yes!' "'1 i I - - . -

,.. . . . c .- : . . . >" I ' .) ' :. ," ,,.. - . . - . . . .~ , * .

P.A. Roger 141

Q: S.K. Roy: To avoid any further confusion on the prospect of B.G.A. ¡nodat ion, there should be detail survey of the native B.G.A. flora as well as the agroecolt~~ical conditions prevailing in different locations. This will obviously guide us to plan the algalisation programme eHec-

'tively. The detection of efficient strains in some field should simply be followed by support . of nutrients particularly phosphorus and to allow the maximum growth and contribution to

the rice and the other subsequent crops. A:, I fully agree with your views. Besides P, which is obviously a key factor, attention has to be

paid to grazer control by economically feasible means handle with general pest management. There is a s o p e for pesticides of plant origin for such a p u p s e .