Renewctble Agriculture ond Food 5j',rrenr,r.' 22(4): 297 306 doi: I 0. 1011 lS11 4217 050700 I 895

Organic banana production inEcuador: Its implications on blackSigatoka development and plant-soilnutritional statusMaria Jimenezl'", Lieselot Van der Veken2, Heleen Neirynck2, Helga Rodrguez1,Omar Ruiz1, and Rony Swennen2lEscuela Superior Politcnica del Litoral Centro de lnvestrgaciones Biotecnolgicas del Ecuador,Guavacuil. Ecuador.2l

^s^,^r^,,, ^+ T"^^i^^LquvaLU,y v, ,,up,uol Crop lmprovement, Division of Crop Biotechnics, Catholic Universty of Leuven,Leuven, Belgium..Corresponding author: mjimenez@espol.edu,ec

Accepted 6 April 2007 Research Paper

AbstractBlack Sigatoka, caused by the leaf fungus M),c'o.sphoerella.lijiensi.t Morelet, is a major cclnstrajnt to banana productionaronnd the world. In EcLrador, the biggest banana-exporting country in the world, this clisease has become increasinglyaggressive. This has resulted in more ftingicide irpplications, which have si-enificantly incrcased costs in production and forthe environrnent. Consequentiy, rnany bananr growers have shitied to organic plodr.rction, which produces greater econonlicretLurrs as a result ofhigher sale prices. In addition, plodLrction costs are lower as no firngicides ale appiied. These organicbrnrnas receive sr-rbstrntial anoLrnts of organic products. This stLrdy describes the blrck Sigatoka disese rnd nr.rtlieut statusin an organic banana plantation and comp:rres it with a conventionally l'eltilized and lirngicide-trerted plantation. BlackSigatoka syt'l"lptoms were evrlllated ir.r the vegetative and flowering st:rges under both production conditions nd in vitroconditions. Univariate and mr-rltivariate descriptive statistics wee used to rnalyze the parzrrneters. Disease syrnptons weremore severe in leaves tiom the organic lield than in leaves fi'om the inolganic fre1d. bLrt the nr-rtrient statLrs (soil and foliar')did not diffel between the two farms. Banana plants fi'om the organic farm had 12 l'rnctional lerves rt flowering and eightfunctional ieaves at harvest. Average banantL yields were over .10% lower for orgrLttic versus inolsunic ntrnugetuent;however, the average price receivecl fbr organic bananlLs wlrs (rvcl two tinles higher. Profit-cost analysis has shown that theorganic banana farm was substantially more profitable than the inorganic one ciuring the time period analyzed. These rcsLrltsindicated that bananas cirn be grown commercially withoLrt firngicides, ancl the lower prodnctivity levels are compensatetl byhigherprices of organic fmits in international markets. ln addition. orglnic production has beneficial impacts on social anclenvironmental issues.

Keywords:banana,b1ackSigatoka'diseasesyII-lpi0Irrs.Iiqtliciarrdsolidbio.f'ertiliorganic production

lntroductionIn Ectrador 14'7.282ha-near1' 0.67c of Ecuador's lands11-g used for banartt cultivrtion. Comrnercial brnanaproduction takes place chiefly on the rlluvial plains of thecoastal lowlands in the provinces of l-os Rios, Guayas anclE,l Oro. About 10-l2Vo of all ecclnomically actir'.- peoplcin the country obtain some benefit from banana production.At presently, there are 5871 producers of banana anil

plrntain. [Jnlike banana prodLrctiot.t in othe exportingcountries, production in Ecuador is not in the hinds ofmultinaLional conrpanies cultivating large areas. Instead,80% of the total export prodr:ction cornes fLont growersmiiintuining areiLs sl.naller tl.ran 30 hat.

Illack Sigatoka, caused by the ascomycefe Mvcosphaer'ellrt

.fi.iiensi,y. is a major econonric constraint on bananaplocluction bec:ause it reduces the phcltosynthetic area andconsequently reduces fruit filling and induces prenttture

t 1007 Canlbridge University l)ress

298

fruit ripening". Yield losses_range from 30 to 1007cwithout tlngicide applicationso''.

In Ecuador the disease was reported in 1987 inCavendish plantations near the nohern coastal provinceof Esmeralclast. From there, the clisease spread rapidlythroughottt the country and affected all bananrL grou'ingareas. Since then. black leaf streak has been controlled withcontact and systemic fnngicides, ancl with mineral oilsprays. Disease forecast systems based on climatic data arerarely nsed. Also, the behavior of the fungus towardsfungicides has not been evalurted by farrners so farE.Chemical control is based on erlternating syster.nic fungi-cides (benzimidrzole, triazole, morphoiine and strobilurin)and contact fungicides (chlorothalonil rnd mancozeb).Dr-u'ing the past 10 years, the number of fungicide cycleshas increased dramatically in Ecr-rador. This is mostprobably due to a reduced sensitivity of M,

.ftjiensis towardsfungicides of the propiconazole gr:oup'.

Because of environrnental concerns regarding heavypesticide use and soil degradation, many banana growershave shifted towards organic production. In such systemsnutrients come from large amounts of organic matter,animal manule and rock phosphatc. Key practices in thisproduction system include the application of products oforganic origin, soil management that stimulates bio-logical activity, improved drainage, balanced nLrtlition,and removal of Sigatoka-infectecl lelves"'. Today. over5000ha of bananas have been certified as ot'ganic inEcuador, whereas many trrore are in the process oftransition towards organic production.

Since black Sigatokr is sr-rch an aggressive airbornefungus, especially ln large banana plantations consisting ofCavendish varieties only", it is puzzling to note that sornany farmers in Ecuador adopt a fungicide-free productionsystern. Thus the main aim of this study is to describethe specific agronomic practices of the organic productionsystem while proving the presence and evaluating theaggressiveness of fungal isolates from organic (OR) andinorganic (IN) farms. F-uture aims foctts on understandingwhy black Sigatoka is not devastating organic bananroroduction.

Materials and MethodsGeographical situation and clmatccharacteristicsTwo neighboring farms (7km apart fiom each other)were selected: one farm receiving only inpr.rts of organicorigin and products rpproved for olganic agriculture, andhenceforth crlled the OR frrrn, and a frrm receivinginorganic fertilizers and fungicides, hereafter called the INfarm. Both fums wee located in the Gr-rayas province(southern coast of Ecuador), nelr the viliage of Taura(2'18'00'5, 19'42'00"W). The close proximity was essen-tial for conducting r compalative study on black Sigatoka

M. Iimenez. et al.because we'Lther conditions (such as tempertture. urollntof rainll and sunshine) influence fLrngal developrnentrr.

Based on 1O-year averages, weather data for this areawere as tbllows: maxintunr temperatrue 30.6"C; nlinimun-ttemperature 20.4"C; annual rainfall 842mm; and relativehumidity 80.60lo''. The rainy season lasts fiot'n Januaryuntil Nilay, and the dry season fron .Tnne until December.

General facts about the OR and lN f armsThe OR f am covered i96ha cLrlrivated wirh the Cavendishcultjv'Lrsrl Willirn-rs (40E). Valery (40%), Gand Naine(107c) and T:rura (107o), r locrl Cavendish selection. Plantdensity varied between 1450 and 1500planrsha-t. Theplantation was at least 10 years olcl and was initially treatedwith srnthetic fertilizers and pesticrides. Eight years ago,there nrr,'licer re2c,'l The OR farnl no lonoer trr,',1"'..t''pesticides against black Sigatoka. Presently black Sigatokainfected leaves were pruned and nutrients were appliedthrorigh solid bio-fertilizers and liquid bio-fertilizers(l.BFs). Annual yields varied fiom ll00 ro 1500 boxesha'' yr - ' depending on the geographical distribution of thedifftrent plots within the frrm.

The IN thn.n consisted of 87.5 ha of the cultivarWilliims. Plant der.rsity was 1l50plantsha-r. This planta-lion was about 15 ye:rrs old rnd annr-ral yields were 2100boxesha-'yr-'. Black Sigatoka wrs controlled by bothprotectant (calbamates. cl.rlorothalonil) and systemic (tria-zoles, benzimidazoles. morpliolines rnd strobirr-rlins) fungi-cides with seven or more fumigation cycles per year.Weeds were controlled with glyphos:rte every six to eightweeks in the rainy season and every l0 weeks in the dryselson. The banana fertilization consisted ofzl00kgh ' Nnlosrly from nrea, 600 kg ha I K, 80 kg ha I Mg. 2 kg ha I

, t-Zn e,ntl 1 kg he ' B sprcad over lJ application cycles withina year.

Generalfacts relating to LBFsLocal micro-organisms (LM). The growth mediurn for

micro-organisms consisted of boiied rice (1-50g) and 400m1of r mixtr.rre o1' sugarcane molrsses (40 liters). fish merl(27kg), NaCl (6809) ancl water (80 liters). This nrixtr.u'cwas boiled, put into small containers covered by a nrosquito net and placecl near trees borclering the banana field.

After 21 days, Lrnidentified miclo-organisms wereharvested. Sinrultaneonsly another suqarcrane molasses-fi shnteal-NrCl wirter mixture was maclc and transferred to a500 liter tank. Fiftl' to seventy pots with micrcl organismswere transferred to the big tank immediately and werehermeticall1, sealed. Micro-organisms were mLrltiplied bytransfen'ing -50liters of the aw material to another tank(500 liters), where 20 liters of slrgrrcrne ruolasses wereadded to 430 liters of wlter. The tank wrs ihen hermeticallysealed lbr 7 days, afte which it was re:idy fol use in thepreparation of the LBF.

LBF preparation. The LBF was a femrented solulionprepared l'roln raw materirls used in the OR farm. The

Organic banana production in Ecuador

production of the LBF was based principally on freshcow dung (a0kg), sugarcane molasses (4 liters), soybeansand bean leaves (10kg), burned rice husks (lOkg) andLM (Aliters from the diluted LM tank). A 200 liter tankwas filled with water. and the mixturc was left to fermentunder anaerobic conditions.

Once the fermentation process was finished, ancl prior tothe foliar application, each tank of 200 liters was enrichedwith the following micronutrients: MgSOa (0.9-1.3kg),H-rBO3 (0,9-l.3kg), ZnSOa (0.9-l.3kg), CLrSO (0.9-1.3 kg) and MnSOa (0.9-1.3 kg.. In the case of LBF for soilapplication, the emiching with K and P wis done post-felmentation and with the following qLrantity per 200iiterstank: 3.2-6.4kg of KzSOa and 3.2-6.4 kg of phosphoricock. After 60 days of anaerobic frlnentation, the LBF wasused as foliar or soil fertilizer. The LBF was sprayed onthe leaves with a motorized backpack sprayer at a rate of3litels of pr.rre bio-feltilizer diiuted in 17liters of waterha-' week-'. The soil LBF was applied weekly through theirrigation \ystenr at 100 litcrs ha-r,

For approximately I year six samples were collectedfrom the organic banana plantation to analyze the nutrientcomposition of the liquid products used as a main alter-native in the management of black Sigatoka ciisease.Methodology for the chemical characterization is explainedbelow,

Experiment one: black Sigatoka in vitrodevelopmentThirt, randoinly selected plants in theil vegetalive attdgenerative growth stage were twice selected from the ORand IN fhrms, during both rainy and dry seasons. Thedisease development was measured in fr.rlly extended leaves1-6, leaf I being the youngest leaf emergeclr't. In thelaboratory, an incubation medium was prepared withbacto agar DifcorNl (4gl-') aclderl to clistilled water anclsterilized for 25 min at 121'C and l5 psi. Benzimidazole at50ppm was added to the Petri dish with a sterile syringe(Millex t -GP 0,22 gm) under sterile conditions. Leaf discs(5 cm2) with the upper leaf surface on the medilrm wereincubated under continuous light (4000 + 200 LLrx)

^t26'Cfor 30 days approximately'. For each leaf disc. symptomdevelopment was recorded as: Stage 1: small whitish oryeliow specks (less than I t.nm long); Stage 2: nlnowreddish-brown or dark brown strerks. generally 2-5 mmlong; Stage 3: streaks of 20-30 mm length; Stage 4:coalescing strerks brordened to a brown spot; Stage -5:elliptical black spot, usually surottnded by a yellow halo;Stage 6: center of the spot dry. and clear grey, surroundedby a well-defined blacl< border"'.

Experiment two : black Sigatoka diseasedevelopment under greenhouse condtonsThe expeliment was repeated two tiines. Eich time. 80micropropagated Cavendlsh plantlets (Wiliiams variety)were established in a sreenhouse at 28'C and L)67a relative

299

humidity. Eight weeks after pot planting, planrs wereinocr-rlrted with 1r ylro conidia of M. Jtjiensls (3 < l0lconidia ml-t) isolates from each farnr. Three differentmedia were used to produce in vif ro conidia from mono-sporic colonies (both fronr the OR ancl IN farms). Potatodextrose agar (4c/o) DifcorNl was used for colony growth for7 clays'at 26"C-- and in complete darkness. 'fhen, colonieswere transferred to a mycophil medium for 20 daysr"rnder the rbove-mentioned conditions. Cclnidiophores wereinduced by transfeming small pieces of myceliLrm to V8sporulation medium (pH ) Conidia were produced aftel 7days at 26'C and with continuous light (4000 t 200 Lux).

The disease in the greenhouse wls lueasured accordingto Alvarrdo et a1.". which is a l.nodificrtion of rhe scalepresented by Fullerton und Olsenl8, rs follows: 0: leafsynlptoms absent; 1: reddish flecks on lower lerf surface,no synlptoms on the upper surface; 2: regulzrr or iffegularcircular spots on the lower lerf surface, no synlptonts onthe upper sr-rrface; 3:legLrlar or difTused light brown circulrrspots on the upper leaf snrface; .l: blacl< or brown circularspots. possibly with a yellow halo or chlorosis of adjacenttissr.rcs, on the r.rpper leaf surface, areas of green tissnesonretinres present; 5: black spots with dry center of graycolor and the leaf completely necrotic.

Experiment three: black Sigatoka disease andnutrtonalsfaus under f ield conditionsDuring 2003 and 2004, 80 banana plants of 2 m height wererandomly chosen per scason (rainy lncl dry) in the OR andIN farms. Iror cach plant, leaves number 3 ancl 4 wereevaluated weekly for l0 weeks for black Sigatoka symptom

300

E,c

z

E,!

o

oo

al

E

c

c

'trE

E

.E!

!

[1

a

L

Z

L

at

,

L

r,-ffr)lrr\ rs

N@.d o-;.=ts.74x c;1 ?; xcoF-=Lq

uOtr

,FEc,?E

O

F*'.O=

&i

M. Jimenez et ctl.on the

-Q-f.rcial Methtds o.f Anah'.ris of AOAC Int.erttutirntl-''. Soil sanrples were processed by Mehlichextraction, whereas foliar samples werc treated by wet,acid digestion. Nitrogen was analyzed by the Kjeldahldigestion procednre for plant tissue.

Stati'stical AnalysisThe valiables were clrssified ir.rto two types: discretevariablcs fbr the clise ase symptoms, and continuonsvariables such as nlrtrient content or yield per farm andthe daa of area nnder a cnrve of index disease evolutionduring evaluation time, Univariate clescriptive sratisticswere applied for the estimation of central tendency parameters such as averages, and dispersion parameters suchas standard deviation ar.rd coefficient of variance (CV).Multivariate descriptive statistics were used fbr analyzingsilnilrities between the nlrtrient content over time in bothfums. The soil nutrient content ()ver tlre wrs analyzed byhieruchical chrster rnalvsis usinil the Ward method rndEuclidian distrnce.

Inferential strlistics-analysis of variance (ANOVA) andthe centrai iirnit theorern-were applied to cotltpue the leafnutrient content from experimental site versus LCV, byhypothesis contrast where Ho: F = LCV verslrs Hr:$>LCV. The -test was used for analyzing the yields,income and profit data. and by Levene's test the equality ofvariances was proved. All data were analyzed by nrnningSPSS version I I and MINITAB l3 for Windows.

Results and DiscussionYields, incomes and profts at OR and lN farmsOver a 5-yenr period. banana yields for the IN farnraveraged 40.9 t ha- I yr-1 which was 690lo greater (P = 0.01 )than the 21.2tha-' yr-' for the organic farm (Table l).However, prices over the 5-year period for the organic frr-ritaveraged over two times that of conventional fruit (6.9versus 3,1 dollars per bclx) resLrlting in gross product salesthe same or higher: on the OR farm (8735 versus 6757dollarshr ryr' '; P=0.025). Hence on in annual basis theIN farm wls more productive than the OR firm (Table 1).However, :rs organic frr-rit fetches much highel prices, thelower yield in the OR farnt was more thrn compensated.Therefore, rn average 167c higher net profit (3485 versus14.57 doliars hit-' yr-'; P = 0.023) was crlculrted in the ORfarm compared to the IN frrm dLrring 2001-2005.

Nutrient compostion of LBFThe nutient composition of the LBF was monitored oveL tperiod of 10 nionths (Table 2). The high CV (fron 77.4to 241.57a) indicated that the nrinerrl cor.nposition of theLBF vuied sLrbstantially during the year. This wis notsr"uprising since the LBF wrs tuade from locally availablematerials that aiso varied during the year2s'26. Moreover,the quantities o[ rhe dift-erent materials used for the

Organic banana production in Ecuador 301Table 2. Nutrient composition of LBF samples plepared and applied on six clitl-erent ciates by fbliar appiication in the OR tann.

Samples

Elements Mar-03 Sep-03 Oct-03 Nov-03 Jan-04 cv (qa)

N (rotal)

1339.0395s.02634.0

912.02623.0

5927.0

93.51.5

293.38.t)0.6

38.2

10.760 i .-s

49.435.989.5

r030.2

0.90.02.50.10. I1.6

3693.21252.82291 .11022.43'754.3

r023.0

180.20.6

239.32.93.75.9

99 r.636-57.51864.3871.0

3055.2

r548.-5

229 50.8

169.16.73.3

1034.5

144.0l1 .61'l .482.388.6

140.0

I 13.485.0'7'7.4

I 04.5123.324t.5

PK

MoNa

SiCuFeZnBMn

Nlacronutrients (mg 100g r dry material)10.1 B7.5 808.368.6 5808.8 7258.334.3 3004.8 3 165.8r9.8 1550.7 1685.046.2 4944.9 6873.3Macronutrients (mg l-r fresh)

'112.9 637.0 26 r 0Micronutrienfs (mg 100 g-r drv material)

0.50.0.o0.20. I

I 1.9

494.1 607.-s1.5 1.2

253.',7 226.1ll.0 r7.84.1 10.41,5.3 6134.2

() ?oac0

Incubation time (days) at leaves number'l-6Figure 1. Black Sigatoka (BS) syrnptoms evolution cluring 28 clays on ii r'lo cultured lelf ilise s ol floweling plants. Leaves l-6 wereint-ected durine the rainv season in an OR ancl IN falm.

fermentation process were not well controlled. Table 2shows that macronutrients like K, Na and Ca andmicronutrients such as Fe, Si and Mn wet'e present in thelargest quantities.

Black Sigatoka development under in vitroconditionsLeaf discs of brnana leaves l-6 were collected fl'omvegetative growing and flowering plants in the organic trndinorganic fields. Black Sigatoka symptollls ttnder in vifroconditions were trrore pronounced in leaf discs frol.u theOR farm than in leaf discs froll the IN frrm, both in plantsin the vegetative growing stage (data not shown) andin the flowering stage (Fig. 1). The pattern of black

Sigatoka synrptonr evolution was sin'rilar for all leaves, inboth f-arms and at both plant stages. However, differences insymptonl evolution in the OR and IN farms were morepronounced in the ffowering plants and with increasingleaf age.

While in the generative plant growth stage blackSigatoka in leaves 5 and 6 reached about stage 5 in theOR fann after 28 days incubation. it eached only stage 3in the IN farrn (Fig. 1). In the vegetative growth stage,black Sigatokr was ajso more pronoLrnced in the OR farlnthan in the IN fann bLrt diff'erences were smalle (scores 2and I for lerf

-5 after 28 days' incLrbation for the OR andIN fanns respectively (data not shown). The symptomevolution in the vegetative growth stage did not showany differences, br-rt were significantly different in the

Leafnumber

ORMean + SB

INMean + SE

f.Test(P value)

302

Table 3. Black Sigatoka sylrptoms accumulation (area under thecurve) in six Ieaves fi'om banana plants in therr genelatire strge rnrun OR rnd lN l'arm t = 50 pe lerl'rnd pel lhrnrt.

M. Jimenez et al.were tnonitored on rnicropropagated plints grown Llndergreenhouse conditions. I)isease symptoms werc sinrilar tothose observed in the fielcl on mature plants fbr conidiaoriginating fronr both farmsrr. -fhe clisease developmentgenerated by both isolates was similar regardless of theorigin of the conidial snspension during each evaluationtime (Fig, 2). ln addition. in vitro characterization of bothisolates showed similarities in the olgan's development(data not shor.vn).

Black Sigatoka disease and nutritional statusunder field conditionsIn brth growine seasons, black Sigatoka clisease symptomswere nrore pronoLrnced in the OR farm than in the IN farm(Fig. 3;, and the accurnulation of the disease svmptoms inleaves 3 and 4 confirnrerl significant differences beiweenOR and IN farms in relatirn to the season (data not shown).'fhis was attributed to the fact that black Sigatoka was keptnncler control in the lN farnr by fi'equent fungicideapplications. In the OR frrnr however, the fungus was notcontrolled by fungicides, but leuves received LBF on aregular basis. This conclusron is sr-rpported by other

. t llilltl1()fs'- - -.Disease severity wzrs ;rlways lowest in the IN tarm during

any plant growth stage. indiciting good cheurical controi(Table ,l). This resulted in a significantly higher number ofstanding leaves in the IN frrm at any growing strge exceptflowering. Despite the better Sigatoka control in the INfarm. the Sigrrtoka seenrecl to have been adeqr"rately con-trolled in the OR farn'r. Incleed, at han,esting 8.5 functionalleaves rvere observed. while 6 7 functional leaves are

I2345

20.3 + 1.7tltf a f

29.6 + 3.135.2 + 2.838.3 + 3.539.7 + 5.i)

9.0 + 0.710.-5 + 0.914.1 + 1.415.6 + 1.221.4 + L420.8 + 2.0

0.000*0.000r,0.000'i0.000!'0.000r'0.000*

Significant drfferences at cx, = 0.05.

generative gfowth stage between the OR and IN falnrs(Table 3).

These esults coresponded to synptom developrnentunder field conditionsl:2t. The lo*er infection level in theIN fun was attribllted to fungicide residlles. The incrersein black Sigatoka development sllges wls linked to leal'age and plant stage. This might be caused by the lower'nutrient status of the leavesls 3l when aging leaves exportnutrients to younger leaves and the developing bunch.The translocation of nutrients lrom the older to the yoLrngerpllnt tissLle could also contribute ro higher diseaseclevelopment2.

Black Sigatoka disease development undergreenhouse condtonsIn order to elinrinate environmental effects and the possibleeffects of differcnt M, /ijiensis isolates. disease symptonrs

Days of evaluation per fungus isolate

Figure 2, Black Sigatoka (BS) symptoms evaluation over 60 days on micropropagated banana plants -Qrown in the greenhonse and

inoculated with a M. .lijiensis conidirl sr-rspension tiom an OR and IN fattn.

Organic banana production in Ecuador 303

Leaf 3 (!) and leaf 4 (ffi)OR-RainY

M,W WWWWMlMiw w w,ffi.,W W'W W W W:'W W iwa W 1M, tffi)W W"'W W JW W1922293643

lN- Rainy

6

4

2

60oao

ur

4:i2' ^* ,W

o iW,',M !'W iW1 B 15 21

"&wlffis0 61

@ .ffi ,ffiffi ffi YttW',W,WlW

15 21 28 36 s0 6'1 68

OR-Dry

lN-Dry

19222936W{:,Mpr43 50

4,I

2", ffit iW

^ ffiru t$&j\) ' '-"1BEvaluation tme (days)

Figure 3. Black Sigatoka (BS) symptoms evolution in leaf 3 and leaf 4 in an Oll and IN falm during the rainy and dry seasons.

Tatrle 4, Standing leaves and black Sigatoka severity (7c) in brnana plants at ditlerent glowth stages in an OR and IN f-arm (r =.50 plantsper growth stage).

Plant growth stage

Vegetativc F-lowering Harvest

Parameters Mean + SE

28 36

Number of standing leaves per plantLeaf area with black Sigatoka symptoms (%)

Number ol standing leaves per plantLeaf area with black Sigatoka symptottrs (%)

Numbel of standing leaves per plant (OR versus IN)Leaf area with black Sigatoka symptoms (7) (OR versus IN)

I 1.9 + 0. t362.9 + 0.21 1

13,03 + 0.1360 + 0.017

0.000x0.000'l

OR12.5 + 1.t933.3 I 0.333

INt3.4 + 0, t7 t

0 + 0.015ANOVA (P value)

0.()00'k0.000'k

8.5 + 0. r576.3 t 0.'137

9,7 t 0. 1651.2 + 0.1.53

0.-5-59 ns0.000*

' Significant differences at cx = 0.05.ns = not significant at s. = 0.05.

considerecl adequaters. Hence, black Sigatoka in the ORfarm was properly controlled, avoiding serious yield losses.

For bananas little is known about optimal nutrientrequirements in relation to disease resistance. Unpublisheddata from Mendez et al., mentioned by Romero3a, revealthat N and K imbalances favor black Sigatoka develop-ment. Results in Uganda show that the intensity of blackSigatoka disease has a highly significant relationship withfrctors sucl.t as organic nltter content in the topsoil andamounts of Ca and Mgro in the soil. Deficiencies in Ca andP content predispose the plant to fung;r1 rnd bacterialinfection35. Black Sigatoka severity can be reduced if soil

f'ertility and organic matter are hieh, sLch as in backyardsthat collect household refttse-'o.

Since both farms received nntrients in clifl'erent ways, thesoil nutrient status was evaluated. Both the OR and INfarns had the same nutrient content (Table 5) except forZn, which was significantly higher in the lN f'arm. On theother hand, higher electrical condLrctivity (EC) va[ies insoil fronr the IN farm n.ray result front the continttotts ttseof synthetic fertrlizers and subsequent nitrification of urei.

AIso. rnrcro- and rrieronLLtrient content in leaf 3 ofbanrna plants frorn OR and IN frrms wrs simjlrr, ind allnutrient requirentents were those recol-nrlended for banrna

304

Table 5. Soil parameters and nlrtricnts fl'our OR and lN tmsM. Jimenez et t.

prodr-rctiour7 r8. N{oleover. the leaf nutient content fuonlOR and IN farms was separately compared with thelanana l-CV. ln the OR farm the concentrations of K(StDev = 0.12) and Fe (StDev = 7) were significantlyhigher (P = 0.05), as was B (StDev = 1,05) in the inorganicfalm (Table 6). Yet soil nutrient clata over a 5-year periodclearly show that soils in both farms can be separatelygroLrpcd (data not shown),

ConclusionsCavendish plantations are reported to depend on syntheticfungicicles to remain prodllctive where black Sigatokadisease occrirs. However, present results indicate thatbananas can be grown commercially without flngicidesin FicLrador. Indeed in an OR farm under study an average

tlI)r(r(iLrctlvrt) ol l.{ t trt yr wir\ r'c( ()r'decl. wrth iLn iLVcragcof 8.5 fLrnctior.ral leaves, and 6.3a/c drsease severity ntharvest.

This OR farm received orgrnic products made on-farmby fermentation of wrste prodllcts, which vary tremen-dously from application to appliciition. However. with in-organic fertilizers and fungicides, yield and black Sigatokacr.rntrol is higher (42tha-tyr"-r with 9.7 functional leavesand a disease sever:ity ct l.3uh at huvest). Compu-irtrveresults bofh it't viro and in the greenhouse showed thrt thcblacl< Sigatoka fringns of both farms inteacts in the sameway with plants from the OR ancl IN farms. Soil analysisshows no differences between the OR and IN f'at'ms except

IN

Mean + SEf-test

(P value)pHOM (c/o)EC (dS rn-')CEC(rneq 100 rnl t)

(mgkg-')NH+P

(meq 100 ml-')KCaMg1\a

(mgkg ')

CuFeZn

MnS

6.7 + 0.11.9 + 0.20.1 + 0.2

1f t+ f f

6.0 + 2.015.50 + 2.50

0.4+0. I14.1 + 0.76.7 + 0.30. l+0.0

8.4 + 0.752 9 + 12.8

4.6 ! 0.30.6 + 0.23.9 + 0.7

,16.0 + ,|5.3

6.4 + 0.1l. + 0.20.8 + 0.2

22.9 + t.5

0.12o.140.7-50.52

Nlacronutrients

-5.5 + 2.-512.5 + 0.5

0.6+0.tt3.8 + 1.38.2 + 0.00.t+0.0

0.210.860. r20.3-s

0.6 |1.000.019,r0.860.190.35

0.890.44

Nlicronutrients

9.2 + l.l052.9 + 14.0

7.-5 + 0.30.7 + 0.3.l s + | l

21.4 + 2.2

'i Significant difference at o. = 0.05.OM, organic matter; EC, clectrical concfi"tctivity; CEC. carionexchange capacrty.

Table 6. Nutdent concentration on a dry nratter basis in leaf 3 ol-banana plants from OR and IN farms an

Olganic banana prodnction in Ecuador

for Zn, yet cluster anrlysis over a 5-year period iillowed aclear separation between the OR and IN farms.

Leaf nutrient analysis shows that all plants had optimalnntrient amounts except for K and Fe in the OR f'arm. and Bin the IN farm. The fact that organic fruit costs twice asmnch as inorganic frnit means greater profits and makesorganic banana production a profitable agricultural system,Theretbre further research is needed to investigate whethcrthe Sigatoka disease in the OR farm is controlled dne to afungicidal action of the bio-f'enilizer rnd/or whether somenutrients or nutlitional brlance hrve rn effect on the plantdefense system.

Acknowledgements. This work was financed by VLIR (FlenrishInteluniversity CoLrncil, Belgium) by way of a grant gir,'cn toESPOL (Escuela Supelior Politcnica del Litolal, Ecuador). Ourspecial thanks go to Simon Caarte fbr allowing access to hsfield and Jose Ruiz and Albert Liptay tbl the criticrl readine.This wor*r is dedicated to Rodolib Maribona, who rnrtiatedbanana research at ESPOL, but passed away dr-Lring the courseof this work.

ReferencesI SICA, Servicio de Infblnacin y Censo Agropecualio del

Ministerio de Agricultura y Ganadera del Ecuador. 2004.Ilase de datos del IIT Censo Nacional Agropecualro. Onltnedocuments at SICA. Available at Web site: http://cna.sier.uor.ec/listado.htm

2 Carlier. J., Four. 8., Cauhl. F.. Jones. D.. Lepoivre. P..Mour-ichon. X., Pasbcrg-Cauhl" C.. and Ronero. R. 2000.Fungal disease of the foliage. In D. Jones (ed.). Disease ofBanana, Abaca and Ensete. CAB International. Wallingfix'd.UK. p. 37-99.

3 Mourichon, X., Peter. D.. and Zapater. M. 1987. Inoculationexpr'imentale de Mv