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Urban cassava markets
Urban cassava markets The impact of fresh root storage
W. Janssen and C. Wheatley
The authors explain how although fresh cassava Is important In rural nutntlon, its importance in urban areas IS limited and declining In Colombia, the third most important cassava-producing country In Latin America, both the structure of the marketing channel and consumer preferences are considered m explammg this difference The principal factor hmiting urban market volume and demand is identified as the rapid root post-harvest deterioration which necessitates high margins to cover marketing risks Appropriate storage techniques which overcome this problem are evaluated and their possible positive impact, through reduction of marketing margins, on retail and farmgate prices and on urban consumption IS estimated A strategy for storage technology adoption IS discusSSd
Keywords markets
Cassava. Colombia urban food
Mr WIllem G Janssen IS a Cassava Economist wllh the Centro lnternacional de Agncultura Tropical, Apartado Aereo 67-l 3. Call, Colombia Dr Christopher C Wheatley IS Postdoctoral Fellow in cassava utlllzatlon at CIAT ‘FAO, FAO ProductIon Yearbook FAO, Rome, 1982 *J H Cock, Cassava a basic energy source in the tropics , Snence, Vol218. pp 755-762 ?bfd % 0 Dtaz, and P Pinstrup-Andersen, Descrrpclon Agro-economlca de/ Proceso de Produccron de Yuca en Colombra, CIAT, Call, Colombia, 1977 ‘R R Tejada and W Moscoso, Resumen estudio perdidas post-cosecha en yuca en la RepublIca Dommlcana 1 Semrnano Sobre la Reducc~on de Perdrdas PostContinued on page 267
0306-9192/85/030265-13$3
00 0
Cassaba with
the major
IS
a total
which
quaIltIes
root
producton
crop ot the Latin
of 31 6 mllllon
enable
It to yleld
American
tonnes
dell
In
lowland
tropics
’ It has setera
1981
m the marglnal
enwronments
chnracterlstlc of many troplcal regions rspeclally m areas of poor dnd/or low ramtall ’ The roots have no period of absolute maturity can be harvested
oler
Llgorous
of
nature
Integration tropical hectare.
a tlmespan cassa\d
growth
mto the associated
The crop does. hobtever. of only 1% ot fresh IteIght. Increases
tr‘msport
and If necessary -’ The
months
makes
cropping
It especially
systems Important
agriculture Despite a relatIveI> this IS e\enlv spread throughout
has a low cost of productlon
\\hlch
ot several
high lahour the growth
per calorie
at farm
SOIIS
level
suitable
tor
m small-scale
requirement per period ’ Cassava (Table
1)
ha\‘e some dlsdd\antages a protein content a moisture content of between 60 and 70% costs
and a very
short
post-harvest
storage
life
This IS due to a rapid phq’slologrcdl deterloratlon of the root and can lead to ler! high losses \\lthln two or three days of harvest The losses habe been estimated at 1-l to 759, ’ Cdssaba still constitutes
an Important
America.
suppl>rng
hoHe\er
suggest that this proportlon
part of the hum,m
7 % of total calorie
requirements IS
decreasing
diet m Latin
In 1971 ’ Data do. (Table
2)
Between
1971 and 1981 world cassaba production Increased bv 24% but tell bv 12”” rn Latin America (Table 2) During the same period. yearI> populdtron Increases averaged 2 96” o m Latin America. le per capita cassa\a production decreased by 21%. compared with a -lo0 decrease tar potatoes nnd a 4”0 Increase for we (Table 1) The role of cassn\a as a calorie source has thus been decllmng during the last 10 iears wth other crops, especldlly we. expanding to take Its place Fresh
root
consumption
of cassd\a
comprises
about
17”,,
of total
Latin Amerlc‘in productron. including Brazil. and about No0 excluding Brazil The remdmder IS used for starch flour. animal teed or alcohol productlon 1 Current evidence suggests that fresh cassava consumption IS declmrng rapIdI>, due to tHo main factors a decrease In consumption per capita m urban areas (Table 3) and the r,jpld mlgratlon from rural regions to urban centres (Table 1 and 5) Cassaka consumption IS falling in urban products
areas because (Table 6)
1985 Butterworth & Co (Publishers) Ltd
of Its Increasing
price
relatrbe
to that
of other
265
Table 1 Direct production (US dollars per hectare)
costs
of rice,
potatoes
and cassava
Potato
lrrtgated race
Sources For nce CIAT Annual Repori CIAT Call. Colombra 1981. for potalo Flores ef al Costos de Produccron de Algunos Culfwos Documento de Trabafo ICA-Bogota Colombra 1979 for cassava CIAT Cassava Program Internal Document mrmeograph CIAT Call Colombra 1983
I
83 473
81 289
335 502
93 88
Total costs
661
1 394
551
of
20 000 1 400 000 007
2 560 913 206 0 26
Total costs 100 000 kcal
72 4
Total cost-labour 100 000 kcal
60 6
22 000 2 398 000 0 03
99 6
23 0
65 78
1093
0 42
0 27
0 34
rice and potatoes on a global and Latin Amenca basis. 1971 and 1961
II
World Area (thousands hectares)
Cassava
185 108 74 93 201
Tofar cosfs 1OOg protern
Table 2 Area, yield and production of cassava,
m 1981
Machrnery Labour Water Seed Other Inputs
Yreld (kg) Yield (kcal) Tolal costs per kg
Note The table consrders only dwect costs not land Data are skghtly brased rn favour of cassava because of Its longer growing cycle entarlrng higher land management and caprtal costs These costs can be estrmated at approxrmately US8100 per crop lor nce US8180 for potato and US$173 for cassava
m Colombia
Yield (kg ha-l)
Production (thousands tonnes)
of
I
Latm America Area (thousands hectares)
of
Yield (kg ha-l)
Production (thousands of tonnes)
1971 Casaava Rrce Potato
10 836 134 148 22 294
9 438 2 304 13 140
102 248 309 096 292 945
2 597 6 581 1 127
13 788 1 706 8 189
35 808 11 224 9 229
1981 Cassava
14 054
9 055
127 161 (24%)” 413 785 (34%) 256 978 f-124.1
2 734
11 569
8 220
1 896
1 046
11 261
31 631 f-1200) 15 586 1398 I 11 779 (28%)
Fkce Potato
144 915
2 855
17 861
14 387
Note a Growth over 1O-year penod grven In parentheses Source
FAO ProductIon
Yearbooks
FAO Rome 1972and
1982
Table 3 Consumption of fresh caasava consumption par head (kg/year)
Bolrvra (1972)a Brazrl (1975) Colombra ( 1970) Cuba (1978) Domrnrcan Republrc (1975) Ecuador (1974) Paraguay (1976) Peru (1978) Venezuela (1975)
in Latin American
countries,
total urban and rural
Rural
Urban
Total
170 112 350 30 0 42 3 31 0 1800 183 27 4
54 27 16 5 124 20 0 60 35 0 56 50
153 63 20 4 188 33 1 190 110 1 110 98
59
11 4
Note a Year of estrmate rn parentheses Total Source
Table 4 Latin America
Source lnteramencan Bank IDB Washrngton DC, 1981
266
19 1
Lynam and Pachrco op crt, Rel 7
Annual Reporf
1960 absolute Percentage 1981 absolute Percentage Yearly growth
rural, urban and total population.
1960 and 1961
Rural population
Urban population
Total population
101 611 000 504 114067000 32 7 0 55%
100 142 000 49 6 235 139 000 67 3 4 15%
201 753 000 1000 349 206 000 100 0 2 65%
FOOD POLICY August
1985
Table 5 Colombia
rural, urban and total population,
8 957 000
Percentage
Development Bank SoUrCe lnleramerlcan Annual Report IDB, Washmgton, DC 1981
Percentage Yearly growth
Cassava Fllce Potato
21 9 -15%
287-290
“J Marriott, B 0 Been and S Perkins. The aetiology of vascular dlscolouratlon In cassava roots after harvesting assoclatlon with water loss from wounds , Physlologja Plantarum, Vol 44, 1978, pp 38-42
FOOD POLICY August
1985
26 665 000
78 1
1000
4 5%
2 1%
and price of cdssava, rice and potatoes in Call, 1976-62
Per capita consumption (IWear) 1970
Per capHa consumption (kg/year) 1962
Percentage change in consumption
Percentage change in price
274 33 2 27 9
128 378 56 6
-533 138 1029
210 160 -4 3
deterioration
Among
and tuber
the troplcal
such a restricted Conbnued from page 265 cosecha de Productos Agrrcofas en ef Area de/ Canbe y Amenca Central. Santo Domingo, RepublIca Dommicana 1979 pp 1-7, D G Coursey and R H Booth The post-harvest phytopathology of perishable tropical produce , Rewew of Plant Pathology, Vol 51, 1972, pp 751765 Janssen, unpublished data, CIAT. Call, Colombia 6J Lynam, Options for Latin American countries In the development of Integrated cassava production programs’, in Development Studies Centre Monograph No 11, Australian National University, 1978 7J K Lynam and D Pachlco, Cassava In Latin America, current status and future prospects’, mimeograph. CIAT. Call, Colombia, 1983 ‘R H Booth, Storage of fresh cassava (Manhot esculenta) I Post-harvest deterioration and its control Experrmental Agncufture, Vol 12, 1976. pp 103-l 1 1 ‘/b/d, C C Wheatley, Studies on cassava (Man/hot esculenta Crantz) root postharvest physlologlcal deterioration’, PhD thesis, London University, 1982 “‘Booth, op nt, Ref 8, J E Rickard. Biochemical changes Involved In the postharvest deterioration of cassava roots , Troprcal Soence, Vol 23, 1981 pp 23% 237. Wheatley. rbrd “Booth, rbrd R A Noon and R H Booth, Nature of post-harvest deterioration of cassava roots , Transactrons of the Bnbsh Myco/og/cal Sooely Vol 69, 1977, pp
1000
20 832 000
Cassava post-harvest
remarkably consumption
17213000
48 0
5 833 000
Table 6 Change in consumption
Source P Plnstrup-Andersen and N de Londono. Estudro de Consum/dores de la Cwdad de CalI CIAT. Call Colombia 1971 Nora de London0 personal communlcatlon 1963
8 256 000
520
1981 absolute
Total population
Urban population
Rural populatlon
1960 absolute
1966 and 1961
root
post-hxbest
crops
cdssdia
IS umque
life ’ The deterlordtion
m havmg
m qudhtv
cdn be
fast sometlmes roots become unacceptable for human wthrn 21 hours of harvest. although a 2-I to 72 hour period
IS more usual ’ Cassava hds a short post-harvest hte because ot the development blue-black plgmentatlon m the kdscular tissues ot the storage accompamed b\ dewcatIon cells These comhlne to gl\e appearance.
very
harvest,‘”
of the parenchvmal (starch contdmmg) the roots an unwholesome hlach or brown
unsatlsfactor)
These plgmentatlon changes rn the root
cooking
qudhtles
harvesting deteriordtion
and which
tirst
require
oxygen
appears
,md handling significdntl)
The can.
In order to Increase the storage deteriordtion must be pre\ented mlcroblal mentation
and
d bitter
taste
reactlons are the result of complex ph)srologlcal tissues. which are lnltlated \flthln a fe\\ hours of ‘I Hence
moisture
tissues acts to accelerate the deterlordtlon reactions tihere moisture loss IS most rapid. are therefore deterloratlon
ot a root
a\oldancr b)
Itselt.
of root reduce
loss from
root
I’ Areas of damdge. the re_glons where ddmdge the
by caretul
lncldence
ot
life ot cdssaba roots this physlologlcdl However there IS a subsequent
deterioration conslstmg of general rotting and tissue ferwhich develops m roots stored tor longer than tour to seten
days In some \ia\s symptoms can be similar to those of physlologlc,il detenoratlon since the bdscular pigmentation can dlso occur but i\lth different dlstrlbutlon in the pathogens mvolled m rotting the mlcroorgamsms root rnterlor
d
root tissues Estdblishment of the root IS aided bj the presence of d&image gl\lng
eas! access to the starch and sugar substrates
of the
At present this mrcroblal deterloratlon IS rarely a problem since root acceptablllt) IS Imarlably dftected precIousI\ b\ phvslologlcal detenoratlon It this latter were prevented, however. a method for controlllng this mlcroblal problem would be necessxy Control of one Hlthout the other would hardlq Improve root storage life over the present one to three days
267
Effect of deterioration
on cassava root marketing
Currently no storage methods are used In the marketing ot fresh cdssdva roots In Colombia The rapid deterloratlon which occurs In the pre\alhng post-harvest ambient conditions effectlkely makes cassaba storage lmposslble Roots must be consumed within two days ot hane\t In the case ot urban markets.
often distant from the producing
regions
roots hnbe to be handled within a \erv short time to reach the consumer before deterioration becomes wslble There IS a substantial risk to the N holesalers sold This
and retailers
necessitates
wholesaler. transferred
that roots ~$111deteriorate
a close
mtepratlon
of
betore the1 can be
producer.
Intermediary.
retailer ,~nd consumer. so that the dally demand cdn be bachwards down the marketing channel to the producer
Because of this reverse demand
Integration
of the marketing
channel.
the followmg descrlptlon UIII work trom retailer to producer In Colombl,l ret;lllers often hats estabhshed contacts \\lth salers
For example
the retailers
rather smdll quantities
In the Atlantic
ot roots - around
whole-
coast region trade In
50 kg of roots per day - and
travel dall) to the wholesale market to purchase this quantity I’ This IS because (a) the\ do not want to risk being left with unsold pen\hable roots. (b) the! must make many smJl transactions ench day and (c) they are dispersed throughout the to\\n In order to tacllltate shoppIng bv housewl\rs A higher percentage of cdssd\a than of other crops IS sold In local nelghbourhood markets despite the hlpher price found for CSS‘I\~ compared \\lth large central markets (Table 7) Although retailers attempt to mlmmlze the rlsh ot hd\lne casbava lett at the end of the dav them
The\
were
the time I’
For
deterloratlon
In tact. left with unsalable them.
structure I_lrban wholesalers
cassavd usually
IS
buy their
unsold
a serious problem
deteriorated
a risky
diaries without ha\mg to leale the toHn smdll volumes ot roots per day (around
IS
product
cassa\a
with
from
tor
roots 14% of a high cost
rural
Interme-
These wholesalers also handle 2000 hg m the Atlantic Coast
region of Colombln) A \\hole5aler who buys 1000 kg a day and sells to retailers In 50 kg lots must mahe 30 transactions a da! These transxtlons dre made In the early morning allowclng the retailer to sell the cassavd during the remainder of the ddy This. together with the risk of haling unsold root> etfectlvely prekents him from Increasing the quantity of roots handled Often wholesalers HIII arrange tuture purchases and hx prices Hlth rural lntermedlarles who then organize producers’ hanests to obtam ‘%assava Economics,CIAT. unoubllshed survev material. CIAT. Call. Colombia 1983’
’ 4lbrd
the
required
hno\\ledge agreement
qu;rntltk
Thev
offer
prices
to farmers
based
on the
that the price with the wholesalers IS already agreed When IS reached between Intermediary and farmer the harvest IS
Table 7 Percentage of total volume of cassava, potatoes and nce sold m neighbourhood shops and in the central market place m Cartagena, Colombia, 1973, compared with their pnce in each location Neighbourhood
Note
a Prices
in US$
Source CEIMA. Estudro de/ Mercadeo Ahmenfos. CEIMA Bogota Colombia 1973
268
de
shop
Central market place
Commodity
Percentage sold
Price/kg”
Percentage sold
Price/kg
Cassava Rice Potato
46 32 39
0 15 0 25 023
50 57 55
0 13 0 25 0 23
FOOD
POLICY
August
1985
lrrban Table 9 Characteristics
of the wholesale sector of Cucuta, 1973
Number of employees
Buying frequency (days)
Average purchase (tons)
Trade per wholesaler per month (tons)
Always buy at same supplier (percentage)
27 10 13
13 7 16 11
341 66 25
76 140 75
37 5 0 100
Wholesalers
Source CEIMA Estudio de/ Mercedeo Ahmentos. CEIMA Bogota Colombia 1973
de
Grams processed products Potato Plantalticassava
cassar a marhets
usually arranged for the followmg day. although sometimes longer-term agreements are made when demand IS guaranteed Thus It IS clear that many people are mvolked m makmg small transactlons a feature which lnevltahly Increases prices (Table 8) Another factar contributing to high prices IS related to the risk wholesalers the day
and retailers
deterroration
face of hd\lng
roots left unsold at the end of
could make them unmarketable
the next day
In order to avoid this traders WIII tend to order less than they expect to sell on an average day Suppliers will be faced with an mtermedlate demand actually lower than the final consumer demand and will deliver a restrlcted market
amount
of cassava onto
the market
will thus be much less likely than undersuppl!
Oversupply
In the
and consequently
dally prices above equlhbrmm level will be more IlkrIb than prices below equlllbrlum level (Figure 1) This mechanism also holds at the level of the rural Intermediary cover his guaranteed sales and able to hanest
he will harvest a sufflclent amount to more It IS possible that he UIII not be
110
a sufficient quantity of roots to meet this target (eg mhen SuPPlY
Demand Non
rerlimdf.wche rural mermedlw
of
Wholesalerdemand
Wholarlw dernrnd mdUctlon -I
Demand transfer
SuPPlY tramfer
Conrumor
demand I” equllibrwm
Figure 1 The demand fresh effects
cassava
in
mechanism
Colombia
and
of its
on prices
Effectlvs SU~@V to ccmUmer
Mvkat clwnnel mechrmsm Effect of mukm channelmechanism
The upward arrows represent demand that IS transferred, downward arrows are the actual amount of supplled cassava Starttng from consumers’ demand In equlllbrium. demand transfer decreases gradually and eventually less cassava than actually demanded reaches the consumer This causes a price above the equiltbnum level a F $ = price elasticity of demand = percentage percentage
FOOD
POLICY
change In demand change In price
August
1985
TOUI market tumover lower than equlhbrwm
Total market turnover hi#wr thm equilibnum
Mtiet agmX~cwld rlther be better or WOM off wnh ltmmd rupplv
Marlwt w(r better off With limitad supply
269
l’rbun
CUSS~L a rnarkrrs
harvests
get delayed)
but he WIII neler
When the price elastlclty of demand - 1 to 0. a restrlctlon of marketed
harvest
more
than
the needs
for cassava tails wlthln a range ot bolurnes leads to higher mane!
turnovers favourmg the marketmg agents they get more money for less work Cassava price eldstlclty hns been estimated at -0 8 and -0 06 ” Indicating that market restrlctlon tavourlng traders could Indeed he occurring
in Colombia
Deterlordtlon thus puts pressure on the supply to be below the equlhbrlum level Prices Increase as a result. leaving traders with extra profits This mechanism also explains why. while market prices are high. many farmers do not start growing more cassd\d If the! Integrated into the market channels via the rural lntermedlarles be unable
to sell their
The negatl\e
produce
effects of deterloratlon
the marketing
channel
are not they ~111
on the fresh market
are twofold
has to be fast movmg and ldbour Intensive
and
the high risk Involved \%clth this crop dlmmlshes the quantities marketed and causes price rises As d result the marketing margin tor cdssa\a IS berg high, approxlmatelv tin,4 retail price The
US$O 30 a hologram. retall margin comprises
le 609/o or more ot the US$O 17 to 0 30 the
wholesale margln US$O 03 to 0 06 and the assembly-agents margin US$O OS to 0 1’ Transport costs account for less than W’O of the total margin For potatoes a slrnllxly bulky product produced slmllar SIZS a marhetlng margin of only 36% was calculated a hologram
In Colombld
Advantages In the rural
during
1%
and disadvantages areas
cassavd
can often
at tarms ot at US$c) 13
I’
for consumers be
stored’
simply
by harvesting
plants only when required In the town. however. where consumer5 must buy and eat cassava on the same day. the high cassaca shopping frequency that this necessitates leads to Increased consumer purchasing costs because ot the often large distances between home and marketplace These
storage
and
market
characterlstlcs
strongly
Influence
the
sultablhty of cassala for consumption by rural and urban societies This IS shown In Table 9, where the relatlbe advantages and disadvantages of cassala
for rural and urban consumers ha\e
been compared
with
those
ot rice and potatoes bv asslgnmg values to 10 consumer demand factors Cassava is a very attractive crop for rural subsistence communities, It 15L Fl Samnt, L Was M C Duque and C Sere, ‘Food consumption patterns in Colombia - a cross-sectional analysis of the DANE-DRC1981 Household Survey Trends m C/AT Commodities, 1984, pp 31-63, CIAT. Call, Colombia, D Pachlco, W G Janssen and J Lynam, Ex ante analysis of new technology A comparison of cassava for the feed and fresh markets In Colombia’, Agncultural Systems, Vol 11, 1983, pp 131-142 I60 E Van der Zaag and D Horton, POtal Productron and Utrlrzatron m World Perspechve w& Special Reference b the Troprcs and Sub-Troprcs, mimeograph, CIP. Lima. Peru, 1983, 41 pp j7FA0. Food Balance Sheets, FAO. Rome, 1980
270
has a low price
and productlon
costs (see Table
1). ease of association
with other crops and year-round avallablhty The deterloratlon problem IS not severe m rural areas since roots can usually be left unharvested until required for Immediate local consumption The low nutritional due to the poor protein content IS only a problem when additional protein sources are absent The avallable data on nutntlon rn Latm America suggest that this IS not the case I7 In the urban marhet. however the rapid perlshablllty of the roots becomes a major dlsad\antage because of the risk of large losses m value
storage, wholesalers dnd retailers need high marketing margins. which result In the roots being elpenslve for urban consumers Low cassava production costs are completely outweighed by the higher marketing costs The supply ot roots ma) also vary throughout the year as storage to even out fluctuations m supply and demand IS lmposslble Fmally. the
FOOD
POLICY
August
1985
Table 9 Comparison of the different characteristics self-producing and urban-purchasing communities
Charactenstics
Note a In rural socletles thus means produchon costs especially cash expenses In urban areas 11 refers to the retail pnce ‘As regards mterand mlxed croppmg planting and harvest times and spread of labour needs through crop cycle c Different ways In which It can be Incorporated ways the crop can be Inlo a meal “Different processed e Size of mlmmum purchase unil The scale used was 5, good not appkable
1 bad na means
Source Cassava Economics CIAT Consumpbon Survey m fhe Attantrc Coast Regton of Colombra unpubkhed data 1983
of cassevs, rice and potato in both rural
Casseva
Rural Rice
Potato
Cassava
Urban Rice
Potato
5
3
4
3
5
3
2
4
4
2
4
4
4
2
3
na
na
na
3
4
2
3
4
3
2 4
3 4
2 3
3 1
5 4
4 3
na
na
na
1
5
3
3
3
3
3
5
4
4
4
4
4
4
4
5
3
4
na
na
na
3
5
3
2
5
3
PrIcea Composltlon (nutnhonal quality) ProductIon” flexiblllty Combmatlon In the dlef Avallablhty through year Penshabllity Acqulslhon COSU effort Waste In preparahon Faclllty of preparahon Ultkation posslbllltles’ Mmimum size of consumphon/purchasee
rapld perlshabihty means that consumers must make frequent small purchases and still risk a conslderable hkehhood of deterloratlon before consumption
As a consequence
of rapid deterloratlon
cassava
IS
more
expensive than either rice or potatoes rn urban areas (Table 10) The urban consumer regards purchase ot cassava as mvohmg considerable effort
and risk
Thus while
cassava IS out performed areas All
the
above
factors
cassava consumption
It
well adapted
IS
to rural consumption.
by almost all other major foodstuffs contribute
to explalnmg
per head found between
m urban
the difference
In
rural and urban areas
For rural consumers who do not produce cassava themselves the situation IS Intermediate they still tace the high margm and the risk of deterloratron. but to a more limited extent since marketing shorter and quicker The emphasis placed Third-World populations
channels are
on cassava m helping to feed expanding based heavily on Its productlon propertles.
IS
but these are outwelghed m urban communities by the marketing problems of fresh roots caused by post-harvest deterioration In the last two decades urbamzatlon
has continued
at a rapid rate m Latin America
(Table 2). hmltmg the mcentlbe to improve cassava cultlvauon for rural commumtles and reducing the advantageous Impact of Improvements Nofe ’ Pnce calone of nce or potato dlwded by pncekalone of cassava OCalones of nce or potatokalones of cassava Sources Lynam and Pachlco op cut. Ref 7 for pnce data For consumptton ligures for Brazil Esfudro Nacronal da Despesa Famrkar, SecretarIa de Planeamlento da Presldencla da Republlca. RIO de Janeiro, 1977 lor Colombia ECIELstudies Broolungs Insbtu\e Washmgton. DC 1978. for Peru P Lizard0 de las Casas Moyas A Theorehcal and Appked Approach Towards the Formulatron ol Attemahve Agncutturat Sector Poke/es ,n Support of the feruvran Agncutturat Plannfng Process PhD thesis. Iowa State Unlverslty. IA, USA 1977, for Venezuela, Longtenn Forecasts of the Supp/y and Demand of Agncuttural and Lwestock Products In Venezuela, Consejo de Bienestar Rural Caracas Venezuela, 1985
FOOD
POLICY
August
1985
Table 10 Relative price and consumption casssva in several Latin American countries
of potatoes
and
rice
Potato Relative price. Braz113 Reclle Sao Paul0 Colombia Barranquilla Bogota Peru Lima Venezuela Caracas
In comparison
with
Rice
Relative consumptior+
Relative price
Relative consumption 130 1150
3 19 2 15
106 8 18
0 66 0 35
1 51 0 85
063 306
0 65 043
57 7 18
1 41
754
0 66
27 0
1 16
1 08
0 20
2 93
271
Lkbrzrr cuw~u murhrrs since the rural suhslstence populations are relatively declmmg An Improvement m the productlon potential of cassaba can only habe a limited Impact on Its urban consumption as a fresh root since only 35”” of the fmal urban price reaches the producer To increase the role of cassava m the nutrrtlon of the urban population of Latin America. a more direct and effective strategv would be to develop a solution to the problem of cassa\a root deterioration In this manner. the marketing margin could be dlmm,shed to the urban consumer
and the attractiveness
of fresh cassala roots
increased
Prevention of post-harvest
root deterioration
There are three aspects to the solution ot the deterloratlon problem One concerns the storage condltlons which prebent the appearance of physlologlcal detenoratlon. the second m\olves the lnhlbltlon of rmcroblal growth and subsequent root rots which can develop during storage and the third relates to the correct handling and selection of roots before storage with the aim of avoiding damaged roots which WIII not store
It IS essential
e\en
for relatively
short-term
storage ot onlv
one week. that all three of these factors are taken mto account Together. they should not add greatly to the costs of marketing and should be simple producers funds
to carry out with mmlmal
capital
of cassava tend to be small farmers
costs because the
with limited
access to
Some high-cost, high-technology storage processes have been developed for cassava which could be useful In the hmlted sphere of export markets. where the high product price would permit higher storage costs Examples of this are paraffin \hax coating of roots developed by IIT In Bogota, Colomblalx and freezing of peeled. parboiled root pieces for supermarket sale However. it there IS a desire to Introduce root storage into the normal fresh operating m Colombia. a simple. Before damage
conslderatlon caused
during
of simple hanest
root marketing chain low-technolog) method storage and
methods,
handling
must
the questron
and mlcroblally-induced
ot
be considered
however effective the storage method may be If broken roots are used the result will InvarIably be poor Both physlologlcal
ds presently IS required
deterloratlons
or damaged tend to be
Initiated at points or regions of Injury and subsequentlv spread to the rest ot the root When roots are separated from the plant, two points of injury are necessarily made one at the distal and one at the proximal end In addition. the bark IS often damaged After harvest. careful handling of roots IS crucial Frequently. roots are piled up mto heaps m the field - sometlmes even thrown, not placed bark easily becomes damaged as roots rub against each other An
The
Improved harvesting and handling process. In which roots were not subjected to the more damaging practices. would be a simple way of reducing the incidence of both types of deterioration without the use of costly Inputs. as well as reducing losses due to broken, damaged roots which dre currentlq unmarketable The percentage of roots suitable for
1B~E Zapata and H Rlveras, Preservaclan de la yuca fresca’, I/T T~c~o&/K+.VOl 115, 1978, pp 9-20. Bogota. Color&la
272
storage would also be increased who are prmclpally subsistence TradItional cassava cultivators. farmers producing cassava for their own c&sumptlon. avoid the deterioration problem by harvesting a few plants at a time as needed Where root storage IS required after harvest. the usual practice IS to
FOOD POLICY August 1985
rebury
the roots m a trench.
unrehable
coverlng
because of the dependence
them with so11 This
on local envlronmental
IS
rather
condltlons
and does not seem to be In wldespread use I9 In a TDRIKIAT project this reburlal method uas Improved through the use of a straw lining. ventilation pipes and a drainage ditch This worked well In less extreme tropical climates. but when temperatures Inside the -field clamp’ structure exceeded 10°C. losses from mlcroblal rotting were conslderable “’ The method has not been adopted on d commercial basis. because In addition to rts relatrke unrellabllq. It does not solve the problem transported
of marketing
fresh cassaba. since roots cannot be
during storage
The rebunal. or field clamp. method relies tor Its success on the natural wound repair processes which the root Itself mltlates gILen the right condltlons namely high temperature (higher than 30°C) and high relative humrdlty (higher than SS’%) ‘I The root lays down a protectrbe barrier over any Injured tissues. effectlbely preventing moisture loss and air entry Into the root This takes approximately fl\e days dnd completely Inhibits the mltlatlon of the reactions producing physlologlcal detenoratlon. as well as provldmg a barrier against pathogen access to the starch substrate however,
of the root Interior
be completely
effective
This curing process cannot.
If the amount of damage
IS
too gredt
hence the Importance of root selectlon prior to storage Unfortunately the condltlons needed to obtain tast curing are also fa\ourable for the growth of mlcroorgamsms Despite the phvslcal barrier laid down over damaged areas. post-hat-lest root rots can rapidly develop
A method of controlling
any method m which root curing The prevention of physIologIcal used m the development technology Inputs which marketing “J S Ingram and JR 0 Humphrres, Cassava storage a revfew’, Troprcar Saence. Vol 14, 1972, pp 131-148, JE Rlckard and D G Coursey, Cassava storage. Part I, storage of fresh cassava roots , T;op/ca/ Sc/encey Vol 23, 1981, pp l-32 20R H Booth Storaae of fresh cassava (Manhot escufenta), II Simple storage techniques’, Expenmental Agrrcufture, Vol 13, 1977, pp 119-128 * ’ /b/d *‘/b/d *%I H Booth, T S de Buckle, 0 S Cardenas, G Gomez and E Hervas, Changes n quakty of cassava roots during storage’, Journal of Food Technology, Vol 11, 1976, pp 245-264 24D D Oudlt, Polythene bags keep cassava tubers fresh for several weeks at ambient temperature , Journal of the Agncultural Society, Trrnrdad and Tobago, Vol 78, 1976. pp 63-66, J C Lozano, J H Cock and J CastaAo, New advances In cassava storage’, n T Breckelbaum, A Bellottl and J C Lozano. eds, Proceedmgs of the Cassava Protecbon Workshop, CIAT, Call, Colombia, 1978, pp 136-142, CIAT. Annual Report, CIAT, Call. Colombia, 1982 *% C Wheatley, unpubkshed matenal
FOOD
POLICY
August
1985
smce.
used deteriordtion
be integrated
Into
bv root curing has been
of two simple storage systems with lowdo seem to be suitable for fresh cassava
unlike
the previous
possible during transport In the first system,‘”
this must theretore IS
systems mentioned.
and marketing
storage
IS
operations
roots were stored In wooden
boves pached with
moist sawdust or other locally available materials Roots could be stored successfully for from SIX to eight weeks and were ot an acceptable quality for both human and animal consumption
” They did, however,
hate a slightly sweeter taste caused by a breakdown of the root starch to sugars However transport costs are relativeI> high since box and packing material must also be transported suitable for high-value export markets onl)
This
method
appears
More recently. trials of roots stored m plastic bags ha\e proLed successful ‘-l The microclimate inside the bdg IS Ideal for root curing the roots themselves
rapidly generate sufficient
er. a fungicide application growth of microorganisms
heat and humidity
prior to storage If no applications
rot only five to seven days after harvest
Ho\\ev-
IS
necessary to Inhibit the are mdde roots begin to
Ot course.
It
IS
necessarv to
ensure that any funglclde used does not leave toxic residues In the interior of the root although this IS unlikely gilen the thickness ot the peel layer Given good control of the mlcroblal rotting problem, storage times of two to three weeks with losses of less than 5% or only 1% after one week. are readily obtainable ” Roots maintain a fresh appearance both internally and externally altered. although there
IS
and taste and texture after bollmg are not a tendency for roots to taste sweeter after
273
Supplv old SuPPlY new
more than two \\eeks ot storage ns the root sugar content Increases slIghtI) Neither the amount of roots pached per bag. nor the hag thickness or colour has any etfect It IS. however. Important that roots should be packed within phvslologlcal deterioration etfectlve
Root
treatment
for this deadline Demand
three hours of harvest to start and curing and packing
A longer delay allows thus not completeI\
IS
must be carried
out In the tleld
to be met
Plastic-hag storage has adbdntdges pre\louslk It IS the best adapted marketing
system
kilogram) flexlhlllt!,
and chemicdl treatment ot the marketing chain
With
oler for
the additional
the other methods mentioned Integration Into the current
costs of plastic
bags (US$O 01 d
(USQJ 01 d kllogrdm) 15 great11 Improved
storage time made teaslble by this method 1s more ellmlnate the prohlems ot marhetlng fresh cassd\~~
the trddltlonal The tHo Meek
than
adequate
to
Expected benefits from cassava storage technology
1
bI1
’
Dmand old
OUllllllV
Figure 2 Effects of successful detenoratlon research on socloeconomlc benefits (I) Decrease in the marketing margin and subsequent shift of supply function traditional case of socloeconomlc benefits
(II) Increase In the willingness to pay because of improved quality and decrease in the marketing margin and subsequent shift of supply function non-traditional case of socioeconomic benefits
Ellmlnatmg
deterioration
the storage
technology
First. the pressure IimItation ot traded storage technology traders can transfer
ot cas5aLa In the tresh market discussed
ahoae
HIII basIcall\
marhetlng
the cost ot commerclallzatlon \\III decrease Thus back the fIndI demand at a lower cost and assummg
margin
for
cassavrl
maxImum reduction of this marhetlng 1JS$O 13. close to the mdrhetlng margin but non-perlshahle
use ot
on the market channel for quick handling ‘lnd Lolumes HIII be relle\ed As d consequence ot
open access to cassavd trading the marketing margin should lead to Increased consumption (see Figure :(I)) 1982 the
through
have two etfects
crop)
Taking
\\as
would tall This In Colomhla In
US$O 30 a kilogram
mxgm \\ould be to of potatoes (a slmllarlq
Into account
A about bulk\
the cost ot the developed
storage techniques (estimated at US$O 02 a kilogram) lahour costs It would be more reasonable to s\pect
plus \ome extra margins bet\\een
US$O 18 and 0 73 Second Improbed
the quality of cassatd as a consumer commodlt! WIII he It deterioration can be prevented a constant a\allablhty In
the marhet place IS more edsll] guaranteed The risk of perlshablhtg at home \\III be small and no special Items like refrigerators ~111 be needed Waste due to deterloratlon de\eloplng between to store cdssa\d purchase
and tood preparation
will be reduced
Purchasing
costs \\III tall
since the necessltv to hub fresh roots e\erj da! UIII disappear In this cassaba Hould become a more nttractl\e toodstuff for urban \\ay consumers \\ho would be wllhng to pas more tor It (Figure I) Although
almost
of ‘1 product
all research
tends to Influence
but also the qunllt!.
estimates
not only
ot this effect
the avaIlabIlIty are rare
Consumer \\llhngness to pa] more for storable cassa\d IS dltflcult to measure et mte because ot the highly abstract nature ot the question and the dlfhcult!, for the consumer fall In costs on cassaba consumption
of making ‘1 reliable estimate ot the Instedd three different Lalues ha\e
been estimated for the Increase In the ullhngness to pay (WNP) a zero Increase. ImplyIng no gro\\th In the WNP (le the benefits calculation In Its tradltlonal torm). a US$O 05 a hologram Increase. equal to a 10’0 Increase In WNP. and a US$O 10 Increase. equal to a Wb increase m WNP The modest US$O 05 Increase IS probably the best of these estimates The benefits
274
of successful storage
technology
FOOD
were estimated
POLICY
August
with
1985
surplus
economic
people
theory
were hvlng
deterloratlon
”
In
1982 III Colombia
m towns of over
could
The consumption
almost
100 000 people.”
have conslderable
effect
15 mllhon
% here reduction
on the marhetmg
of cassava In these towns
was estimated
ot
margm
at 10 kg per
capita (40% down from the 1970 estimate) The price elastlcltv of demand was estimated at -0 88. the average ot the tao v,jlues mentioned before Values of 0 S and 1 0 for the price elastlcq of supply were assumed ” Other assumptions were linear demand and supply functions. a perfectly elastic suppI> of marketing ser\lces and a parallel shift In final demand and supply function through the apphcatlon of storage technology With these assumptions and using the method of Freebairn.
Davis
technology
for the fresh market
and 28 mllhon 26M Curry, A Murphy and A Schmidt, The concept of economic surplus and 11s use In economic analysis , The Economic Journal, Vol 81, 1971, pp 741-799. R D Wllllg, Consumer’s surplus wlthout apology’. The Amencan Economic Review, Vol 66, 1976. pp 58S597 27F N M Hulsbosch, Colombra, Koninklijk lnstltuut Voor de Tropen Amsterdam, 1981, 77 pp 28A Pastore A oferta de productos agncolas no Brazil , Pesqursa e Planelamento Vol 1, 1971, pp 171-234 *%V Freebairn S Davis and G W Edwards, Dlstnbutlon of research gains In multistage production systems , Amencan Journal of Agncultural Economrcs, Vol 64, 1982, pp 39-46
and
Edwards.‘”
per year (Table
the
Prices
between
US$O 45 and US$O 39 a kilogram
level)
Farm-level
consumer
In Latm America times greater than
level
prices would
to between US.%0 29 and prices at farm lebel)
successful
storage
be between
US$ 19
areas would Increase from 11. Projected consumption
capita) retail
the
ot
would
11)
Consumption per head m the urban to between 11 3 and 12 3 kg (Table at
benefits
of Colombia
\bould
tall
(Table
increase
trom
10 kg per
US$O 17 to
11 Projected
prices at
from an aLerage
US$O 17
LJS$O 2-I a kilogram
(T,lble
as a whole fresh consumption that In Colombia alone The
11, Projected
of cassava IS seven Import,mce of rural
versus urban consumptron IS similar to that of Colombia (Table 4) A rough estimate of total benefits for Latin Amerlcd of cassava detenoratlon
research
between Colombia
then
should
be seven
times
the figure
for
Colombia.
US$133 and 189 mllhon per year If the assumptions hold for Latin America m general
Table 11 Effect of successful cassava-deterioration
made
research m Colombia
Price elaatwly of supply 05 Margin decwaes to 0 18 023
Pnce elasklty of supply 10 Margm decreases to 0 16 023
Expected benehts (mrhon US&year) Wlllmgness to pay (WNP)
0 +lO% +20%
1669 27 42 36 35
1074 1669 27 42
19 17 27 99 3731
consumer benefits = 59 7% producer benefrts = 40 3% Propcted
W’W
COnSUmptlOn
+o + 10% +20%
per Caprta (present consumptfon 11 29 11 a2 1235
1064 19 17 27 99
consumer benefrts = 74 6% producer benellts = 25 2%
= 10 kg)
10 76 11 29 I 1 82
11 60 1226 1293
1094 11 60 1226
0 38 039 041
0 42 043 0 44
0 20 021 023
0 19 020 0.21
Projactad prrces at retart level (present retarl prrce = lJS$O 47) (WNP)
+o + 10% + 20%
0 40 0 42 044
043 045 047
Pro)ectad prrces at farm level (present farm puce = U.S$O 17) W’JP) Note Most reasonably to be expected values are underlmed
FOOD POLICY August
1985
to +10?6 +20%.
0 22 0 24 026
0 20 0 22 024
le
for
Urban ~(US~LYI marhers
Strategy for increasing
urban availability
of cassava
Previous sections of this paper show that storage technology could hale conslderable Impact on the urban fresh cassa\a market Another. production-onentated (yield mcreasmg) strategy \\ould also be eypetted to habe Impact on cassaba consumption In urban area\ Yield Increases of 679/o were estimated to benefit Colombia bq approxImateI! US$5 mllhon per year “’ An addmonal benefit of around US.V mllllon would be produced m the ammal feed market Thus. the expected value of storage technology could be four to hve time\ that ot productlonorientated technology In Colombia In order
to compare
technological
the relative
strategies.
to be assessed
advantages
of these two different
the cost of their successful Introduction
Basically.
two major
cost components
needs
can be dlstlng-
unshed the research cost of deslgnmg appropriate technology and the cost mvolved m the actual mtroductlon of this technologv In the speclflc region under conslderatlon Development of appropriate technology for yield-IncreasIng research requires the ldentlflcatlon of high-yleldmg, good quality cassava varletles Integrated m a package of agricultural prepardtlon. fertlhzatlon and weed control) yleldmg cassava varletles
1s highly complex,
lty ot the dlfterent varieties The technological package IS therefore because of the generally programmes
A simple
given the reglonal speclflc-
development a long-term
poor development practical
practices (such ds ldnd Identlflcatlon ot highof dn appropriate actlvltv especIalI\
ot natlonal cassava research
storage
method
hag already
been
developed and tested. with only mmor factors (such as bdg size and optimum harvest procedures) still to be determlned Storage technology has given stable
results over different
emlronments.
except
for the
socloeconomlc factors m\olved Thus. from d resenrch pomt ot view reglonally-adapted storage technology ~‘111be tar easier to develop than productlklty Improvements Once appropriate forms of technology have been developed and tested. lntroductlon mto the target region can commence Since almost e\ery
Latm American
ful agricultural
developing
extension
servlce,
country operates a relatively successthe adoptlon ot adequate lmproced
productlon technology can occur through alread! estabhshed channels ConsIderable evperlence with the lntroductlon of agricultural lmprovements IS dvallable.
suggesting that such new productlon
technology
w11l
be dlssemmated rather easily though perhaps slowI!, to the user To Introduce storage technology however new adoption strategies must be used The technology hds to be accepted by small farmers dnd trdders Whereas the hrst group can be reached through the extension serklce. traders might be dlfflcult to approach Thev are Lery rarely dctlvely Involved m development programmes ,Ind are otten SUSPICIOUS of dn> Instltutlonal actlon However. their adoptlon of storage technolog! WIII crItIcally depend on the acceptance of stored cclssdla b> the fmal consumer For the flnal consumer,
30Pach!coet al, op at, Ref 15
276
storage technology m pla\tlc bags WIII change At present consumers are used to the appearance of the product purchasmg unpacked cassava often cut open as an mdlcatlon of an undeterlorated state Adoptlon of storage technologv WIII necessitate purchase of roots m a plastic bag. preferably Intact Consumers dlso have to become aware that storage of cassava at home IS possible If roots
FOOD
POLICY
August
1985
are kept mslde the bag (bags must be resealed after removal of part of the contents) The coordinated
and simultaneous
demonstration
and mtroductlon
of
storage technology to farmers, traders. retailers and consumers will be necessary The use of consumer panels wtll enable the acceptablhty of stored roots to be judged and WIII provide a means of makmg consumers product’ In-store experiments ~111sene the same On-farm demonbtratlons ot the purpose for traders and retailers storage technology WIII enable farmer interest to be gauged Com-
aware of this new
mumcatlon
between
the different
test groups
will
be Important
m
ensuring that the technology IS adopted (traders WIII be aware ot consumer wllllngness to buy and of farmer ~lll~ngncss to supply stored roots) InformatIon
must also reach the general
urban consumer.
prohabl>
through the use of leaflets dnd the mass media this WIII have marked slmllarltles with a commercial product-release campaign rather thdn the usual low profile market structure directed
of mo\t development projects. normall} dlrected to improvement Personnel resources WIII ha\e to be
mto non-traditional
experience Thus, although
technology
areas where government development
and testing
lower for storage research than for productlon and market acceptablhty might well be shorter comparable
costs WIII be higher than for production
with normal
Industrial
mstltutlons
research.
costs will
product-adoption
be
the extension
The mtroductlon technology.
lack
lead time
perhaps
being
lead time of two
years 31 Improvements m storage technology will have d greater Impact on the urban avallablllty of fresh cassava than HIII productlon-orientated technology The marketing approach required to achieve the adoption of this storage technology demands the use of uncon\entlonal development
3’P Kotler, Markebng Management Analysis, Plannmg and Control, Prentice Hall, Englewood CMfs, NJ, USA, 1976
FOOD
POLICY
August
1985
models
Subsequently.
Jleld
related
technology.
uhtch
has a
longer lead time. WIII further Improbe tresh cassava supplies at reduced costs In urban areas A combmatlon of these two- complementary research and development strategies should maxlmlze the contrlbutlon of fresh cassava to Improved
urban nutrltlon
277
W. Janssen and C. Wheatley
The authors explain how although fresh cassava Is important In rural nutntlon, its importance in urban areas IS limited and declining In Colombia, the third most important cassava-producing country In Latin America, both the structure of the marketing channel and consumer preferences are considered m explammg this difference The principal factor hmiting urban market volume and demand is identified as the rapid root post-harvest deterioration which necessitates high margins to cover marketing risks Appropriate storage techniques which overcome this problem are evaluated and their possible positive impact, through reduction of marketing margins, on retail and farmgate prices and on urban consumption IS estimated A strategy for storage technology adoption IS discusSSd
Keywords markets
Cassava. Colombia urban food
Mr WIllem G Janssen IS a Cassava Economist wllh the Centro lnternacional de Agncultura Tropical, Apartado Aereo 67-l 3. Call, Colombia Dr Christopher C Wheatley IS Postdoctoral Fellow in cassava utlllzatlon at CIAT ‘FAO, FAO ProductIon Yearbook FAO, Rome, 1982 *J H Cock, Cassava a basic energy source in the tropics , Snence, Vol218. pp 755-762 ?bfd % 0 Dtaz, and P Pinstrup-Andersen, Descrrpclon Agro-economlca de/ Proceso de Produccron de Yuca en Colombra, CIAT, Call, Colombia, 1977 ‘R R Tejada and W Moscoso, Resumen estudio perdidas post-cosecha en yuca en la RepublIca Dommlcana 1 Semrnano Sobre la Reducc~on de Perdrdas PostContinued on page 267
0306-9192/85/030265-13$3
00 0
Cassaba with
the major
IS
a total
which
quaIltIes
root
producton
crop ot the Latin
of 31 6 mllllon
enable
It to yleld
American
tonnes
dell
In
lowland
tropics
’ It has setera
1981
m the marglnal
enwronments
chnracterlstlc of many troplcal regions rspeclally m areas of poor dnd/or low ramtall ’ The roots have no period of absolute maturity can be harvested
oler
Llgorous
of
nature
Integration tropical hectare.
a tlmespan cassa\d
growth
mto the associated
The crop does. hobtever. of only 1% ot fresh IteIght. Increases
tr‘msport
and If necessary -’ The
months
makes
cropping
It especially
systems Important
agriculture Despite a relatIveI> this IS e\enlv spread throughout
has a low cost of productlon
\\hlch
ot several
high lahour the growth
per calorie
at farm
SOIIS
level
suitable
tor
m small-scale
requirement per period ’ Cassava (Table
1)
ha\‘e some dlsdd\antages a protein content a moisture content of between 60 and 70% costs
and a very
short
post-harvest
storage
life
This IS due to a rapid phq’slologrcdl deterloratlon of the root and can lead to ler! high losses \\lthln two or three days of harvest The losses habe been estimated at 1-l to 759, ’ Cdssaba still constitutes
an Important
America.
suppl>rng
hoHe\er
suggest that this proportlon
part of the hum,m
7 % of total calorie
requirements IS
decreasing
diet m Latin
In 1971 ’ Data do. (Table
2)
Between
1971 and 1981 world cassaba production Increased bv 24% but tell bv 12”” rn Latin America (Table 2) During the same period. yearI> populdtron Increases averaged 2 96” o m Latin America. le per capita cassa\a production decreased by 21%. compared with a -lo0 decrease tar potatoes nnd a 4”0 Increase for we (Table 1) The role of cassn\a as a calorie source has thus been decllmng during the last 10 iears wth other crops, especldlly we. expanding to take Its place Fresh
root
consumption
of cassd\a
comprises
about
17”,,
of total
Latin Amerlc‘in productron. including Brazil. and about No0 excluding Brazil The remdmder IS used for starch flour. animal teed or alcohol productlon 1 Current evidence suggests that fresh cassava consumption IS declmrng rapIdI>, due to tHo main factors a decrease In consumption per capita m urban areas (Table 3) and the r,jpld mlgratlon from rural regions to urban centres (Table 1 and 5) Cassaka consumption IS falling in urban products
areas because (Table 6)
1985 Butterworth & Co (Publishers) Ltd
of Its Increasing
price
relatrbe
to that
of other
265
Table 1 Direct production (US dollars per hectare)
costs
of rice,
potatoes
and cassava
Potato
lrrtgated race
Sources For nce CIAT Annual Repori CIAT Call. Colombra 1981. for potalo Flores ef al Costos de Produccron de Algunos Culfwos Documento de Trabafo ICA-Bogota Colombra 1979 for cassava CIAT Cassava Program Internal Document mrmeograph CIAT Call Colombra 1983
I
83 473
81 289
335 502
93 88
Total costs
661
1 394
551
of
20 000 1 400 000 007
2 560 913 206 0 26
Total costs 100 000 kcal
72 4
Total cost-labour 100 000 kcal
60 6
22 000 2 398 000 0 03
99 6
23 0
65 78
1093
0 42
0 27
0 34
rice and potatoes on a global and Latin Amenca basis. 1971 and 1961
II
World Area (thousands hectares)
Cassava
185 108 74 93 201
Tofar cosfs 1OOg protern
Table 2 Area, yield and production of cassava,
m 1981
Machrnery Labour Water Seed Other Inputs
Yreld (kg) Yield (kcal) Tolal costs per kg
Note The table consrders only dwect costs not land Data are skghtly brased rn favour of cassava because of Its longer growing cycle entarlrng higher land management and caprtal costs These costs can be estrmated at approxrmately US8100 per crop lor nce US8180 for potato and US$173 for cassava
m Colombia
Yield (kg ha-l)
Production (thousands tonnes)
of
I
Latm America Area (thousands hectares)
of
Yield (kg ha-l)
Production (thousands of tonnes)
1971 Casaava Rrce Potato
10 836 134 148 22 294
9 438 2 304 13 140
102 248 309 096 292 945
2 597 6 581 1 127
13 788 1 706 8 189
35 808 11 224 9 229
1981 Cassava
14 054
9 055
127 161 (24%)” 413 785 (34%) 256 978 f-124.1
2 734
11 569
8 220
1 896
1 046
11 261
31 631 f-1200) 15 586 1398 I 11 779 (28%)
Fkce Potato
144 915
2 855
17 861
14 387
Note a Growth over 1O-year penod grven In parentheses Source
FAO ProductIon
Yearbooks
FAO Rome 1972and
1982
Table 3 Consumption of fresh caasava consumption par head (kg/year)
Bolrvra (1972)a Brazrl (1975) Colombra ( 1970) Cuba (1978) Domrnrcan Republrc (1975) Ecuador (1974) Paraguay (1976) Peru (1978) Venezuela (1975)
in Latin American
countries,
total urban and rural
Rural
Urban
Total
170 112 350 30 0 42 3 31 0 1800 183 27 4
54 27 16 5 124 20 0 60 35 0 56 50
153 63 20 4 188 33 1 190 110 1 110 98
59
11 4
Note a Year of estrmate rn parentheses Total Source
Table 4 Latin America
Source lnteramencan Bank IDB Washrngton DC, 1981
266
19 1
Lynam and Pachrco op crt, Rel 7
Annual Reporf
1960 absolute Percentage 1981 absolute Percentage Yearly growth
rural, urban and total population.
1960 and 1961
Rural population
Urban population
Total population
101 611 000 504 114067000 32 7 0 55%
100 142 000 49 6 235 139 000 67 3 4 15%
201 753 000 1000 349 206 000 100 0 2 65%
FOOD POLICY August
1985
Table 5 Colombia
rural, urban and total population,
8 957 000
Percentage
Development Bank SoUrCe lnleramerlcan Annual Report IDB, Washmgton, DC 1981
Percentage Yearly growth
Cassava Fllce Potato
21 9 -15%
287-290
“J Marriott, B 0 Been and S Perkins. The aetiology of vascular dlscolouratlon In cassava roots after harvesting assoclatlon with water loss from wounds , Physlologja Plantarum, Vol 44, 1978, pp 38-42
FOOD POLICY August
1985
26 665 000
78 1
1000
4 5%
2 1%
and price of cdssava, rice and potatoes in Call, 1976-62
Per capita consumption (IWear) 1970
Per capHa consumption (kg/year) 1962
Percentage change in consumption
Percentage change in price
274 33 2 27 9
128 378 56 6
-533 138 1029
210 160 -4 3
deterioration
Among
and tuber
the troplcal
such a restricted Conbnued from page 265 cosecha de Productos Agrrcofas en ef Area de/ Canbe y Amenca Central. Santo Domingo, RepublIca Dommicana 1979 pp 1-7, D G Coursey and R H Booth The post-harvest phytopathology of perishable tropical produce , Rewew of Plant Pathology, Vol 51, 1972, pp 751765 Janssen, unpublished data, CIAT. Call, Colombia 6J Lynam, Options for Latin American countries In the development of Integrated cassava production programs’, in Development Studies Centre Monograph No 11, Australian National University, 1978 7J K Lynam and D Pachlco, Cassava In Latin America, current status and future prospects’, mimeograph. CIAT. Call, Colombia, 1983 ‘R H Booth, Storage of fresh cassava (Manhot esculenta) I Post-harvest deterioration and its control Experrmental Agncufture, Vol 12, 1976. pp 103-l 1 1 ‘/b/d, C C Wheatley, Studies on cassava (Man/hot esculenta Crantz) root postharvest physlologlcal deterioration’, PhD thesis, London University, 1982 “‘Booth, op nt, Ref 8, J E Rickard. Biochemical changes Involved In the postharvest deterioration of cassava roots , Troprcal Soence, Vol 23, 1981 pp 23% 237. Wheatley. rbrd “Booth, rbrd R A Noon and R H Booth, Nature of post-harvest deterioration of cassava roots , Transactrons of the Bnbsh Myco/og/cal Sooely Vol 69, 1977, pp
1000
20 832 000
Cassava post-harvest
remarkably consumption
17213000
48 0
5 833 000
Table 6 Change in consumption
Source P Plnstrup-Andersen and N de Londono. Estudro de Consum/dores de la Cwdad de CalI CIAT. Call Colombia 1971 Nora de London0 personal communlcatlon 1963
8 256 000
520
1981 absolute
Total population
Urban population
Rural populatlon
1960 absolute
1966 and 1961
root
post-hxbest
crops
cdssdia
IS umque
life ’ The deterlordtion
m havmg
m qudhtv
cdn be
fast sometlmes roots become unacceptable for human wthrn 21 hours of harvest. although a 2-I to 72 hour period
IS more usual ’ Cassava hds a short post-harvest hte because ot the development blue-black plgmentatlon m the kdscular tissues ot the storage accompamed b\ dewcatIon cells These comhlne to gl\e appearance.
very
harvest,‘”
of the parenchvmal (starch contdmmg) the roots an unwholesome hlach or brown
unsatlsfactor)
These plgmentatlon changes rn the root
cooking
qudhtles
harvesting deteriordtion
and which
tirst
require
oxygen
appears
,md handling significdntl)
The can.
In order to Increase the storage deteriordtion must be pre\ented mlcroblal mentation
and
d bitter
taste
reactlons are the result of complex ph)srologlcal tissues. which are lnltlated \flthln a fe\\ hours of ‘I Hence
moisture
tissues acts to accelerate the deterlordtlon reactions tihere moisture loss IS most rapid. are therefore deterloratlon
ot a root
a\oldancr b)
Itselt.
of root reduce
loss from
root
I’ Areas of damdge. the re_glons where ddmdge the
by caretul
lncldence
ot
life ot cdssaba roots this physlologlcdl However there IS a subsequent
deterioration conslstmg of general rotting and tissue ferwhich develops m roots stored tor longer than tour to seten
days In some \ia\s symptoms can be similar to those of physlologlc,il detenoratlon since the bdscular pigmentation can dlso occur but i\lth different dlstrlbutlon in the pathogens mvolled m rotting the mlcroorgamsms root rnterlor
d
root tissues Estdblishment of the root IS aided bj the presence of d&image gl\lng
eas! access to the starch and sugar substrates
of the
At present this mrcroblal deterloratlon IS rarely a problem since root acceptablllt) IS Imarlably dftected precIousI\ b\ phvslologlcal detenoratlon It this latter were prevented, however. a method for controlllng this mlcroblal problem would be necessxy Control of one Hlthout the other would hardlq Improve root storage life over the present one to three days
267
Effect of deterioration
on cassava root marketing
Currently no storage methods are used In the marketing ot fresh cdssdva roots In Colombia The rapid deterloratlon which occurs In the pre\alhng post-harvest ambient conditions effectlkely makes cassaba storage lmposslble Roots must be consumed within two days ot hane\t In the case ot urban markets.
often distant from the producing
regions
roots hnbe to be handled within a \erv short time to reach the consumer before deterioration becomes wslble There IS a substantial risk to the N holesalers sold This
and retailers
necessitates
wholesaler. transferred
that roots ~$111deteriorate
a close
mtepratlon
of
betore the1 can be
producer.
Intermediary.
retailer ,~nd consumer. so that the dally demand cdn be bachwards down the marketing channel to the producer
Because of this reverse demand
Integration
of the marketing
channel.
the followmg descrlptlon UIII work trom retailer to producer In Colombl,l ret;lllers often hats estabhshed contacts \\lth salers
For example
the retailers
rather smdll quantities
In the Atlantic
ot roots - around
whole-
coast region trade In
50 kg of roots per day - and
travel dall) to the wholesale market to purchase this quantity I’ This IS because (a) the\ do not want to risk being left with unsold pen\hable roots. (b) the! must make many smJl transactions ench day and (c) they are dispersed throughout the to\\n In order to tacllltate shoppIng bv housewl\rs A higher percentage of cdssd\a than of other crops IS sold In local nelghbourhood markets despite the hlpher price found for CSS‘I\~ compared \\lth large central markets (Table 7) Although retailers attempt to mlmmlze the rlsh ot hd\lne casbava lett at the end of the dav them
The\
were
the time I’
For
deterloratlon
In tact. left with unsalable them.
structure I_lrban wholesalers
cassavd usually
IS
buy their
unsold
a serious problem
deteriorated
a risky
diaries without ha\mg to leale the toHn smdll volumes ot roots per day (around
IS
product
cassa\a
with
from
tor
roots 14% of a high cost
rural
Interme-
These wholesalers also handle 2000 hg m the Atlantic Coast
region of Colombln) A \\hole5aler who buys 1000 kg a day and sells to retailers In 50 kg lots must mahe 30 transactions a da! These transxtlons dre made In the early morning allowclng the retailer to sell the cassavd during the remainder of the ddy This. together with the risk of haling unsold root> etfectlvely prekents him from Increasing the quantity of roots handled Often wholesalers HIII arrange tuture purchases and hx prices Hlth rural lntermedlarles who then organize producers’ hanests to obtam ‘%assava Economics,CIAT. unoubllshed survev material. CIAT. Call. Colombia 1983’
’ 4lbrd
the
required
hno\\ledge agreement
qu;rntltk
Thev
offer
prices
to farmers
based
on the
that the price with the wholesalers IS already agreed When IS reached between Intermediary and farmer the harvest IS
Table 7 Percentage of total volume of cassava, potatoes and nce sold m neighbourhood shops and in the central market place m Cartagena, Colombia, 1973, compared with their pnce in each location Neighbourhood
Note
a Prices
in US$
Source CEIMA. Estudro de/ Mercadeo Ahmenfos. CEIMA Bogota Colombia 1973
268
de
shop
Central market place
Commodity
Percentage sold
Price/kg”
Percentage sold
Price/kg
Cassava Rice Potato
46 32 39
0 15 0 25 023
50 57 55
0 13 0 25 0 23
FOOD
POLICY
August
1985
lrrban Table 9 Characteristics
of the wholesale sector of Cucuta, 1973
Number of employees
Buying frequency (days)
Average purchase (tons)
Trade per wholesaler per month (tons)
Always buy at same supplier (percentage)
27 10 13
13 7 16 11
341 66 25
76 140 75
37 5 0 100
Wholesalers
Source CEIMA Estudio de/ Mercedeo Ahmentos. CEIMA Bogota Colombia 1973
de
Grams processed products Potato Plantalticassava
cassar a marhets
usually arranged for the followmg day. although sometimes longer-term agreements are made when demand IS guaranteed Thus It IS clear that many people are mvolked m makmg small transactlons a feature which lnevltahly Increases prices (Table 8) Another factar contributing to high prices IS related to the risk wholesalers the day
and retailers
deterroration
face of hd\lng
roots left unsold at the end of
could make them unmarketable
the next day
In order to avoid this traders WIII tend to order less than they expect to sell on an average day Suppliers will be faced with an mtermedlate demand actually lower than the final consumer demand and will deliver a restrlcted market
amount
of cassava onto
the market
will thus be much less likely than undersuppl!
Oversupply
In the
and consequently
dally prices above equlhbrmm level will be more IlkrIb than prices below equlllbrlum level (Figure 1) This mechanism also holds at the level of the rural Intermediary cover his guaranteed sales and able to hanest
he will harvest a sufflclent amount to more It IS possible that he UIII not be
110
a sufficient quantity of roots to meet this target (eg mhen SuPPlY
Demand Non
rerlimdf.wche rural mermedlw
of
Wholesalerdemand
Wholarlw dernrnd mdUctlon -I
Demand transfer
SuPPlY tramfer
Conrumor
demand I” equllibrwm
Figure 1 The demand fresh effects
cassava
in
mechanism
Colombia
and
of its
on prices
Effectlvs SU~@V to ccmUmer
Mvkat clwnnel mechrmsm Effect of mukm channelmechanism
The upward arrows represent demand that IS transferred, downward arrows are the actual amount of supplled cassava Starttng from consumers’ demand In equlllbrium. demand transfer decreases gradually and eventually less cassava than actually demanded reaches the consumer This causes a price above the equiltbnum level a F $ = price elasticity of demand = percentage percentage
FOOD
POLICY
change In demand change In price
August
1985
TOUI market tumover lower than equlhbrwm
Total market turnover hi#wr thm equilibnum
Mtiet agmX~cwld rlther be better or WOM off wnh ltmmd rupplv
Marlwt w(r better off With limitad supply
269
l’rbun
CUSS~L a rnarkrrs
harvests
get delayed)
but he WIII neler
When the price elastlclty of demand - 1 to 0. a restrlctlon of marketed
harvest
more
than
the needs
for cassava tails wlthln a range ot bolurnes leads to higher mane!
turnovers favourmg the marketmg agents they get more money for less work Cassava price eldstlclty hns been estimated at -0 8 and -0 06 ” Indicating that market restrlctlon tavourlng traders could Indeed he occurring
in Colombia
Deterlordtlon thus puts pressure on the supply to be below the equlhbrlum level Prices Increase as a result. leaving traders with extra profits This mechanism also explains why. while market prices are high. many farmers do not start growing more cassd\d If the! Integrated into the market channels via the rural lntermedlarles be unable
to sell their
The negatl\e
produce
effects of deterloratlon
the marketing
channel
are not they ~111
on the fresh market
are twofold
has to be fast movmg and ldbour Intensive
and
the high risk Involved \%clth this crop dlmmlshes the quantities marketed and causes price rises As d result the marketing margin tor cdssa\a IS berg high, approxlmatelv tin,4 retail price The
US$O 30 a hologram. retall margin comprises
le 609/o or more ot the US$O 17 to 0 30 the
wholesale margln US$O 03 to 0 06 and the assembly-agents margin US$O OS to 0 1’ Transport costs account for less than W’O of the total margin For potatoes a slrnllxly bulky product produced slmllar SIZS a marhetlng margin of only 36% was calculated a hologram
In Colombld
Advantages In the rural
during
1%
and disadvantages areas
cassavd
can often
at tarms ot at US$c) 13
I’
for consumers be
stored’
simply
by harvesting
plants only when required In the town. however. where consumer5 must buy and eat cassava on the same day. the high cassaca shopping frequency that this necessitates leads to Increased consumer purchasing costs because ot the often large distances between home and marketplace These
storage
and
market
characterlstlcs
strongly
Influence
the
sultablhty of cassala for consumption by rural and urban societies This IS shown In Table 9, where the relatlbe advantages and disadvantages of cassala
for rural and urban consumers ha\e
been compared
with
those
ot rice and potatoes bv asslgnmg values to 10 consumer demand factors Cassava is a very attractive crop for rural subsistence communities, It 15L Fl Samnt, L Was M C Duque and C Sere, ‘Food consumption patterns in Colombia - a cross-sectional analysis of the DANE-DRC1981 Household Survey Trends m C/AT Commodities, 1984, pp 31-63, CIAT. Call, Colombia, D Pachlco, W G Janssen and J Lynam, Ex ante analysis of new technology A comparison of cassava for the feed and fresh markets In Colombia’, Agncultural Systems, Vol 11, 1983, pp 131-142 I60 E Van der Zaag and D Horton, POtal Productron and Utrlrzatron m World Perspechve w& Special Reference b the Troprcs and Sub-Troprcs, mimeograph, CIP. Lima. Peru, 1983, 41 pp j7FA0. Food Balance Sheets, FAO. Rome, 1980
270
has a low price
and productlon
costs (see Table
1). ease of association
with other crops and year-round avallablhty The deterloratlon problem IS not severe m rural areas since roots can usually be left unharvested until required for Immediate local consumption The low nutritional due to the poor protein content IS only a problem when additional protein sources are absent The avallable data on nutntlon rn Latm America suggest that this IS not the case I7 In the urban marhet. however the rapid perlshablllty of the roots becomes a major dlsad\antage because of the risk of large losses m value
storage, wholesalers dnd retailers need high marketing margins. which result In the roots being elpenslve for urban consumers Low cassava production costs are completely outweighed by the higher marketing costs The supply ot roots ma) also vary throughout the year as storage to even out fluctuations m supply and demand IS lmposslble Fmally. the
FOOD
POLICY
August
1985
Table 9 Comparison of the different characteristics self-producing and urban-purchasing communities
Charactenstics
Note a In rural socletles thus means produchon costs especially cash expenses In urban areas 11 refers to the retail pnce ‘As regards mterand mlxed croppmg planting and harvest times and spread of labour needs through crop cycle c Different ways In which It can be Incorporated ways the crop can be Inlo a meal “Different processed e Size of mlmmum purchase unil The scale used was 5, good not appkable
1 bad na means
Source Cassava Economics CIAT Consumpbon Survey m fhe Attantrc Coast Regton of Colombra unpubkhed data 1983
of cassevs, rice and potato in both rural
Casseva
Rural Rice
Potato
Cassava
Urban Rice
Potato
5
3
4
3
5
3
2
4
4
2
4
4
4
2
3
na
na
na
3
4
2
3
4
3
2 4
3 4
2 3
3 1
5 4
4 3
na
na
na
1
5
3
3
3
3
3
5
4
4
4
4
4
4
4
5
3
4
na
na
na
3
5
3
2
5
3
PrIcea Composltlon (nutnhonal quality) ProductIon” flexiblllty Combmatlon In the dlef Avallablhty through year Penshabllity Acqulslhon COSU effort Waste In preparahon Faclllty of preparahon Ultkation posslbllltles’ Mmimum size of consumphon/purchasee
rapld perlshabihty means that consumers must make frequent small purchases and still risk a conslderable hkehhood of deterloratlon before consumption
As a consequence
of rapid deterloratlon
cassava
IS
more
expensive than either rice or potatoes rn urban areas (Table 10) The urban consumer regards purchase ot cassava as mvohmg considerable effort
and risk
Thus while
cassava IS out performed areas All
the
above
factors
cassava consumption
It
well adapted
IS
to rural consumption.
by almost all other major foodstuffs contribute
to explalnmg
per head found between
m urban
the difference
In
rural and urban areas
For rural consumers who do not produce cassava themselves the situation IS Intermediate they still tace the high margm and the risk of deterloratron. but to a more limited extent since marketing shorter and quicker The emphasis placed Third-World populations
channels are
on cassava m helping to feed expanding based heavily on Its productlon propertles.
IS
but these are outwelghed m urban communities by the marketing problems of fresh roots caused by post-harvest deterioration In the last two decades urbamzatlon
has continued
at a rapid rate m Latin America
(Table 2). hmltmg the mcentlbe to improve cassava cultlvauon for rural commumtles and reducing the advantageous Impact of Improvements Nofe ’ Pnce calone of nce or potato dlwded by pncekalone of cassava OCalones of nce or potatokalones of cassava Sources Lynam and Pachlco op cut. Ref 7 for pnce data For consumptton ligures for Brazil Esfudro Nacronal da Despesa Famrkar, SecretarIa de Planeamlento da Presldencla da Republlca. RIO de Janeiro, 1977 lor Colombia ECIELstudies Broolungs Insbtu\e Washmgton. DC 1978. for Peru P Lizard0 de las Casas Moyas A Theorehcal and Appked Approach Towards the Formulatron ol Attemahve Agncutturat Sector Poke/es ,n Support of the feruvran Agncutturat Plannfng Process PhD thesis. Iowa State Unlverslty. IA, USA 1977, for Venezuela, Longtenn Forecasts of the Supp/y and Demand of Agncuttural and Lwestock Products In Venezuela, Consejo de Bienestar Rural Caracas Venezuela, 1985
FOOD
POLICY
August
1985
Table 10 Relative price and consumption casssva in several Latin American countries
of potatoes
and
rice
Potato Relative price. Braz113 Reclle Sao Paul0 Colombia Barranquilla Bogota Peru Lima Venezuela Caracas
In comparison
with
Rice
Relative consumptior+
Relative price
Relative consumption 130 1150
3 19 2 15
106 8 18
0 66 0 35
1 51 0 85
063 306
0 65 043
57 7 18
1 41
754
0 66
27 0
1 16
1 08
0 20
2 93
271
Lkbrzrr cuw~u murhrrs since the rural suhslstence populations are relatively declmmg An Improvement m the productlon potential of cassaba can only habe a limited Impact on Its urban consumption as a fresh root since only 35”” of the fmal urban price reaches the producer To increase the role of cassava m the nutrrtlon of the urban population of Latin America. a more direct and effective strategv would be to develop a solution to the problem of cassa\a root deterioration In this manner. the marketing margin could be dlmm,shed to the urban consumer
and the attractiveness
of fresh cassala roots
increased
Prevention of post-harvest
root deterioration
There are three aspects to the solution ot the deterloratlon problem One concerns the storage condltlons which prebent the appearance of physlologlcal detenoratlon. the second m\olves the lnhlbltlon of rmcroblal growth and subsequent root rots which can develop during storage and the third relates to the correct handling and selection of roots before storage with the aim of avoiding damaged roots which WIII not store
It IS essential
e\en
for relatively
short-term
storage ot onlv
one week. that all three of these factors are taken mto account Together. they should not add greatly to the costs of marketing and should be simple producers funds
to carry out with mmlmal
capital
of cassava tend to be small farmers
costs because the
with limited
access to
Some high-cost, high-technology storage processes have been developed for cassava which could be useful In the hmlted sphere of export markets. where the high product price would permit higher storage costs Examples of this are paraffin \hax coating of roots developed by IIT In Bogota, Colomblalx and freezing of peeled. parboiled root pieces for supermarket sale However. it there IS a desire to Introduce root storage into the normal fresh operating m Colombia. a simple. Before damage
conslderatlon caused
during
of simple hanest
root marketing chain low-technolog) method storage and
methods,
handling
must
the questron
and mlcroblally-induced
ot
be considered
however effective the storage method may be If broken roots are used the result will InvarIably be poor Both physlologlcal
ds presently IS required
deterloratlons
or damaged tend to be
Initiated at points or regions of Injury and subsequentlv spread to the rest ot the root When roots are separated from the plant, two points of injury are necessarily made one at the distal and one at the proximal end In addition. the bark IS often damaged After harvest. careful handling of roots IS crucial Frequently. roots are piled up mto heaps m the field - sometlmes even thrown, not placed bark easily becomes damaged as roots rub against each other An
The
Improved harvesting and handling process. In which roots were not subjected to the more damaging practices. would be a simple way of reducing the incidence of both types of deterioration without the use of costly Inputs. as well as reducing losses due to broken, damaged roots which dre currentlq unmarketable The percentage of roots suitable for
1B~E Zapata and H Rlveras, Preservaclan de la yuca fresca’, I/T T~c~o&/K+.VOl 115, 1978, pp 9-20. Bogota. Color&la
272
storage would also be increased who are prmclpally subsistence TradItional cassava cultivators. farmers producing cassava for their own c&sumptlon. avoid the deterioration problem by harvesting a few plants at a time as needed Where root storage IS required after harvest. the usual practice IS to
FOOD POLICY August 1985
rebury
the roots m a trench.
unrehable
coverlng
because of the dependence
them with so11 This
on local envlronmental
IS
rather
condltlons
and does not seem to be In wldespread use I9 In a TDRIKIAT project this reburlal method uas Improved through the use of a straw lining. ventilation pipes and a drainage ditch This worked well In less extreme tropical climates. but when temperatures Inside the -field clamp’ structure exceeded 10°C. losses from mlcroblal rotting were conslderable “’ The method has not been adopted on d commercial basis. because In addition to rts relatrke unrellabllq. It does not solve the problem transported
of marketing
fresh cassaba. since roots cannot be
during storage
The rebunal. or field clamp. method relies tor Its success on the natural wound repair processes which the root Itself mltlates gILen the right condltlons namely high temperature (higher than 30°C) and high relative humrdlty (higher than SS’%) ‘I The root lays down a protectrbe barrier over any Injured tissues. effectlbely preventing moisture loss and air entry Into the root This takes approximately fl\e days dnd completely Inhibits the mltlatlon of the reactions producing physlologlcal detenoratlon. as well as provldmg a barrier against pathogen access to the starch substrate however,
of the root Interior
be completely
effective
This curing process cannot.
If the amount of damage
IS
too gredt
hence the Importance of root selectlon prior to storage Unfortunately the condltlons needed to obtain tast curing are also fa\ourable for the growth of mlcroorgamsms Despite the phvslcal barrier laid down over damaged areas. post-hat-lest root rots can rapidly develop
A method of controlling
any method m which root curing The prevention of physIologIcal used m the development technology Inputs which marketing “J S Ingram and JR 0 Humphrres, Cassava storage a revfew’, Troprcar Saence. Vol 14, 1972, pp 131-148, JE Rlckard and D G Coursey, Cassava storage. Part I, storage of fresh cassava roots , T;op/ca/ Sc/encey Vol 23, 1981, pp l-32 20R H Booth Storaae of fresh cassava (Manhot escufenta), II Simple storage techniques’, Expenmental Agrrcufture, Vol 13, 1977, pp 119-128 * ’ /b/d *‘/b/d *%I H Booth, T S de Buckle, 0 S Cardenas, G Gomez and E Hervas, Changes n quakty of cassava roots during storage’, Journal of Food Technology, Vol 11, 1976, pp 245-264 24D D Oudlt, Polythene bags keep cassava tubers fresh for several weeks at ambient temperature , Journal of the Agncultural Society, Trrnrdad and Tobago, Vol 78, 1976. pp 63-66, J C Lozano, J H Cock and J CastaAo, New advances In cassava storage’, n T Breckelbaum, A Bellottl and J C Lozano. eds, Proceedmgs of the Cassava Protecbon Workshop, CIAT, Call, Colombia, 1978, pp 136-142, CIAT. Annual Report, CIAT, Call. Colombia, 1982 *% C Wheatley, unpubkshed matenal
FOOD
POLICY
August
1985
smce.
used deteriordtion
be integrated
Into
bv root curing has been
of two simple storage systems with lowdo seem to be suitable for fresh cassava
unlike
the previous
possible during transport In the first system,‘”
this must theretore IS
systems mentioned.
and marketing
storage
IS
operations
roots were stored In wooden
boves pached with
moist sawdust or other locally available materials Roots could be stored successfully for from SIX to eight weeks and were ot an acceptable quality for both human and animal consumption
” They did, however,
hate a slightly sweeter taste caused by a breakdown of the root starch to sugars However transport costs are relativeI> high since box and packing material must also be transported suitable for high-value export markets onl)
This
method
appears
More recently. trials of roots stored m plastic bags ha\e proLed successful ‘-l The microclimate inside the bdg IS Ideal for root curing the roots themselves
rapidly generate sufficient
er. a fungicide application growth of microorganisms
heat and humidity
prior to storage If no applications
rot only five to seven days after harvest
Ho\\ev-
IS
necessary to Inhibit the are mdde roots begin to
Ot course.
It
IS
necessarv to
ensure that any funglclde used does not leave toxic residues In the interior of the root although this IS unlikely gilen the thickness ot the peel layer Given good control of the mlcroblal rotting problem, storage times of two to three weeks with losses of less than 5% or only 1% after one week. are readily obtainable ” Roots maintain a fresh appearance both internally and externally altered. although there
IS
and taste and texture after bollmg are not a tendency for roots to taste sweeter after
273
Supplv old SuPPlY new
more than two \\eeks ot storage ns the root sugar content Increases slIghtI) Neither the amount of roots pached per bag. nor the hag thickness or colour has any etfect It IS. however. Important that roots should be packed within phvslologlcal deterioration etfectlve
Root
treatment
for this deadline Demand
three hours of harvest to start and curing and packing
A longer delay allows thus not completeI\
IS
must be carried
out In the tleld
to be met
Plastic-hag storage has adbdntdges pre\louslk It IS the best adapted marketing
system
kilogram) flexlhlllt!,
and chemicdl treatment ot the marketing chain
With
oler for
the additional
the other methods mentioned Integration Into the current
costs of plastic
bags (US$O 01 d
(USQJ 01 d kllogrdm) 15 great11 Improved
storage time made teaslble by this method 1s more ellmlnate the prohlems ot marhetlng fresh cassd\~~
the trddltlonal The tHo Meek
than
adequate
to
Expected benefits from cassava storage technology
1
bI1
’
Dmand old
OUllllllV
Figure 2 Effects of successful detenoratlon research on socloeconomlc benefits (I) Decrease in the marketing margin and subsequent shift of supply function traditional case of socloeconomlc benefits
(II) Increase In the willingness to pay because of improved quality and decrease in the marketing margin and subsequent shift of supply function non-traditional case of socioeconomic benefits
Ellmlnatmg
deterioration
the storage
technology
First. the pressure IimItation ot traded storage technology traders can transfer
ot cas5aLa In the tresh market discussed
ahoae
HIII basIcall\
marhetlng
the cost ot commerclallzatlon \\III decrease Thus back the fIndI demand at a lower cost and assummg
margin
for
cassavrl
maxImum reduction of this marhetlng 1JS$O 13. close to the mdrhetlng margin but non-perlshahle
use ot
on the market channel for quick handling ‘lnd Lolumes HIII be relle\ed As d consequence ot
open access to cassavd trading the marketing margin should lead to Increased consumption (see Figure :(I)) 1982 the
through
have two etfects
crop)
Taking
\\as
would tall This In Colomhla In
US$O 30 a kilogram
mxgm \\ould be to of potatoes (a slmllarlq
Into account
A about bulk\
the cost ot the developed
storage techniques (estimated at US$O 02 a kilogram) lahour costs It would be more reasonable to s\pect
plus \ome extra margins bet\\een
US$O 18 and 0 73 Second Improbed
the quality of cassatd as a consumer commodlt! WIII he It deterioration can be prevented a constant a\allablhty In
the marhet place IS more edsll] guaranteed The risk of perlshablhtg at home \\III be small and no special Items like refrigerators ~111 be needed Waste due to deterloratlon de\eloplng between to store cdssa\d purchase
and tood preparation
will be reduced
Purchasing
costs \\III tall
since the necessltv to hub fresh roots e\erj da! UIII disappear In this cassaba Hould become a more nttractl\e toodstuff for urban \\ay consumers \\ho would be wllhng to pas more tor It (Figure I) Although
almost
of ‘1 product
all research
tends to Influence
but also the qunllt!.
estimates
not only
ot this effect
the avaIlabIlIty are rare
Consumer \\llhngness to pa] more for storable cassa\d IS dltflcult to measure et mte because ot the highly abstract nature ot the question and the dlfhcult!, for the consumer fall In costs on cassaba consumption
of making ‘1 reliable estimate ot the Instedd three different Lalues ha\e
been estimated for the Increase In the ullhngness to pay (WNP) a zero Increase. ImplyIng no gro\\th In the WNP (le the benefits calculation In Its tradltlonal torm). a US$O 05 a hologram Increase. equal to a 10’0 Increase In WNP. and a US$O 10 Increase. equal to a Wb increase m WNP The modest US$O 05 Increase IS probably the best of these estimates The benefits
274
of successful storage
technology
FOOD
were estimated
POLICY
August
with
1985
surplus
economic
people
theory
were hvlng
deterloratlon
”
In
1982 III Colombia
m towns of over
could
The consumption
almost
100 000 people.”
have conslderable
effect
15 mllhon
% here reduction
on the marhetmg
of cassava In these towns
was estimated
ot
margm
at 10 kg per
capita (40% down from the 1970 estimate) The price elastlcltv of demand was estimated at -0 88. the average ot the tao v,jlues mentioned before Values of 0 S and 1 0 for the price elastlcq of supply were assumed ” Other assumptions were linear demand and supply functions. a perfectly elastic suppI> of marketing ser\lces and a parallel shift In final demand and supply function through the apphcatlon of storage technology With these assumptions and using the method of Freebairn.
Davis
technology
for the fresh market
and 28 mllhon 26M Curry, A Murphy and A Schmidt, The concept of economic surplus and 11s use In economic analysis , The Economic Journal, Vol 81, 1971, pp 741-799. R D Wllllg, Consumer’s surplus wlthout apology’. The Amencan Economic Review, Vol 66, 1976. pp 58S597 27F N M Hulsbosch, Colombra, Koninklijk lnstltuut Voor de Tropen Amsterdam, 1981, 77 pp 28A Pastore A oferta de productos agncolas no Brazil , Pesqursa e Planelamento Vol 1, 1971, pp 171-234 *%V Freebairn S Davis and G W Edwards, Dlstnbutlon of research gains In multistage production systems , Amencan Journal of Agncultural Economrcs, Vol 64, 1982, pp 39-46
and
Edwards.‘”
per year (Table
the
Prices
between
US$O 45 and US$O 39 a kilogram
level)
Farm-level
consumer
In Latm America times greater than
level
prices would
to between US.%0 29 and prices at farm lebel)
successful
storage
be between
US$ 19
areas would Increase from 11. Projected consumption
capita) retail
the
ot
would
11)
Consumption per head m the urban to between 11 3 and 12 3 kg (Table at
benefits
of Colombia
\bould
tall
(Table
increase
trom
10 kg per
US$O 17 to
11 Projected
prices at
from an aLerage
US$O 17
LJS$O 2-I a kilogram
(T,lble
as a whole fresh consumption that In Colombia alone The
11, Projected
of cassava IS seven Import,mce of rural
versus urban consumptron IS similar to that of Colombia (Table 4) A rough estimate of total benefits for Latin Amerlcd of cassava detenoratlon
research
between Colombia
then
should
be seven
times
the figure
for
Colombia.
US$133 and 189 mllhon per year If the assumptions hold for Latin America m general
Table 11 Effect of successful cassava-deterioration
made
research m Colombia
Price elaatwly of supply 05 Margin decwaes to 0 18 023
Pnce elasklty of supply 10 Margm decreases to 0 16 023
Expected benehts (mrhon US&year) Wlllmgness to pay (WNP)
0 +lO% +20%
1669 27 42 36 35
1074 1669 27 42
19 17 27 99 3731
consumer benefits = 59 7% producer benefrts = 40 3% Propcted
W’W
COnSUmptlOn
+o + 10% +20%
per Caprta (present consumptfon 11 29 11 a2 1235
1064 19 17 27 99
consumer benefrts = 74 6% producer benellts = 25 2%
= 10 kg)
10 76 11 29 I 1 82
11 60 1226 1293
1094 11 60 1226
0 38 039 041
0 42 043 0 44
0 20 021 023
0 19 020 0.21
Projactad prrces at retart level (present retarl prrce = lJS$O 47) (WNP)
+o + 10% + 20%
0 40 0 42 044
043 045 047
Pro)ectad prrces at farm level (present farm puce = U.S$O 17) W’JP) Note Most reasonably to be expected values are underlmed
FOOD POLICY August
1985
to +10?6 +20%.
0 22 0 24 026
0 20 0 22 024
le
for
Urban ~(US~LYI marhers
Strategy for increasing
urban availability
of cassava
Previous sections of this paper show that storage technology could hale conslderable Impact on the urban fresh cassa\a market Another. production-onentated (yield mcreasmg) strategy \\ould also be eypetted to habe Impact on cassaba consumption In urban area\ Yield Increases of 679/o were estimated to benefit Colombia bq approxImateI! US$5 mllhon per year “’ An addmonal benefit of around US.V mllllon would be produced m the ammal feed market Thus. the expected value of storage technology could be four to hve time\ that ot productlonorientated technology In Colombia In order
to compare
technological
the relative
strategies.
to be assessed
advantages
of these two different
the cost of their successful Introduction
Basically.
two major
cost components
needs
can be dlstlng-
unshed the research cost of deslgnmg appropriate technology and the cost mvolved m the actual mtroductlon of this technologv In the speclflc region under conslderatlon Development of appropriate technology for yield-IncreasIng research requires the ldentlflcatlon of high-yleldmg, good quality cassava varletles Integrated m a package of agricultural prepardtlon. fertlhzatlon and weed control) yleldmg cassava varletles
1s highly complex,
lty ot the dlfterent varieties The technological package IS therefore because of the generally programmes
A simple
given the reglonal speclflc-
development a long-term
poor development practical
practices (such ds ldnd Identlflcatlon ot highof dn appropriate actlvltv especIalI\
ot natlonal cassava research
storage
method
hag already
been
developed and tested. with only mmor factors (such as bdg size and optimum harvest procedures) still to be determlned Storage technology has given stable
results over different
emlronments.
except
for the
socloeconomlc factors m\olved Thus. from d resenrch pomt ot view reglonally-adapted storage technology ~‘111be tar easier to develop than productlklty Improvements Once appropriate forms of technology have been developed and tested. lntroductlon mto the target region can commence Since almost e\ery
Latm American
ful agricultural
developing
extension
servlce,
country operates a relatively successthe adoptlon ot adequate lmproced
productlon technology can occur through alread! estabhshed channels ConsIderable evperlence with the lntroductlon of agricultural lmprovements IS dvallable.
suggesting that such new productlon
technology
w11l
be dlssemmated rather easily though perhaps slowI!, to the user To Introduce storage technology however new adoption strategies must be used The technology hds to be accepted by small farmers dnd trdders Whereas the hrst group can be reached through the extension serklce. traders might be dlfflcult to approach Thev are Lery rarely dctlvely Involved m development programmes ,Ind are otten SUSPICIOUS of dn> Instltutlonal actlon However. their adoptlon of storage technolog! WIII crItIcally depend on the acceptance of stored cclssdla b> the fmal consumer For the flnal consumer,
30Pach!coet al, op at, Ref 15
276
storage technology m pla\tlc bags WIII change At present consumers are used to the appearance of the product purchasmg unpacked cassava often cut open as an mdlcatlon of an undeterlorated state Adoptlon of storage technologv WIII necessitate purchase of roots m a plastic bag. preferably Intact Consumers dlso have to become aware that storage of cassava at home IS possible If roots
FOOD
POLICY
August
1985
are kept mslde the bag (bags must be resealed after removal of part of the contents) The coordinated
and simultaneous
demonstration
and mtroductlon
of
storage technology to farmers, traders. retailers and consumers will be necessary The use of consumer panels wtll enable the acceptablhty of stored roots to be judged and WIII provide a means of makmg consumers product’ In-store experiments ~111sene the same On-farm demonbtratlons ot the purpose for traders and retailers storage technology WIII enable farmer interest to be gauged Com-
aware of this new
mumcatlon
between
the different
test groups
will
be Important
m
ensuring that the technology IS adopted (traders WIII be aware ot consumer wllllngness to buy and of farmer ~lll~ngncss to supply stored roots) InformatIon
must also reach the general
urban consumer.
prohabl>
through the use of leaflets dnd the mass media this WIII have marked slmllarltles with a commercial product-release campaign rather thdn the usual low profile market structure directed
of mo\t development projects. normall} dlrected to improvement Personnel resources WIII ha\e to be
mto non-traditional
experience Thus, although
technology
areas where government development
and testing
lower for storage research than for productlon and market acceptablhty might well be shorter comparable
costs WIII be higher than for production
with normal
Industrial
mstltutlons
research.
costs will
product-adoption
be
the extension
The mtroductlon technology.
lack
lead time
perhaps
being
lead time of two
years 31 Improvements m storage technology will have d greater Impact on the urban avallablllty of fresh cassava than HIII productlon-orientated technology The marketing approach required to achieve the adoption of this storage technology demands the use of uncon\entlonal development
3’P Kotler, Markebng Management Analysis, Plannmg and Control, Prentice Hall, Englewood CMfs, NJ, USA, 1976
FOOD
POLICY
August
1985
models
Subsequently.
Jleld
related
technology.
uhtch
has a
longer lead time. WIII further Improbe tresh cassava supplies at reduced costs In urban areas A combmatlon of these two- complementary research and development strategies should maxlmlze the contrlbutlon of fresh cassava to Improved
urban nutrltlon
277