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CASSAVA RESEARCH AND PRODUCTION

Dr. T. Gebremeskel. Agricultural Economist Farming Systems Program Dr. S.K. Hahn. Program Director Root and Tuber Improvement Program Dr. D.S. Ngambeki. Consultant Dr. H.C. Ezumah. Agronomist Farming Systems Program Dr. A.M. Almazan. Biochemist Food Technologist

2 - 8 March. 1986 UTA - UNICEF CONSULTATION ON PROMOTION OF HOUSEHOLD FOOD PRODUCTIOI\l AND NUTRITION International Institute of Tropical Agriculture ibadan . Nigeria


Cassava Research and Production Perspective on Africa

Tesfaye Gebremeskel S.K. Hahn D.S. Ngambeki

H.C. Ezumah A.M. Almazan


I.

Importance of cassava in African countries

Cassava is an important food crop in sub-Saharan Africa (SSA)* In the last 10 years, SSA accounted for an annual average of 39 percent of total world production for cassava and for 52 percent of the total area used for its production. From 1975 to 1984 SSA used about 4.2 percent of its arable land annually for cassava production. In comparison, 8 percent was used for maize and 2 percent for r ice dud ng the same per iod (FAD, 1985). Cassava's importance is directly related to its role as a subsistence crop for the rural population and it is very well suited for this purpose. Farmers in developing countries usually do not have good provisions for food storage. As cassava can be left in the ground for a long time after it matures and it does not have to be harvested all at once, it assures farmers of a constant supply of food throughout most of the year without storage problems. This has particular s ignif icance for the "hungry season" which is a common feature of African agriculture. In southwest Nigeria, for example, up to 70 percent of the cassava produced on the farm is used for home consumption (Akoroda et a1., 1985), Forty-six percent of the world's consumption of cassava is in SSA. Average annual consumption for an individual in the last 10 years was 116 kg as compared to 23 kg for South America and 21 kg for the world. However, there is a great deal of variability by subregions as well as by country. For example, annual individual consumption in the last 10 years was 423 kg for Zaire and 115 kg for Nigeria (see Table 1). Cassava is an important source of energy for the of SSA. Individuals in Africa received 350 calories cassava in the last 10 years. For some countries the considerably higher (see Table 1). The corresponding

*Countries

population a day from figures are figure for

included in SSA together with their subregional groupings are as folows: SAHEL- Cape Verde, Chad, Gambia, Mali, Mauritania, Nigeria, Senegal, and Burkina Faso; WEST AFRICA Benin, Cameroon, Ghana, Guinea, G. Bissau, Ivory Coast, Liberia, Nigeria, Sierra Leone, and Togo; CENTRAL AFRICA- Central African Republic, Congo, Gabon and Zaire; EAST AFRICA- Burundi, Ethiopia, Kenya, Rwanda, Somolia, Sudan, Tanzania, and Uganda; SOUTHERN ~FRICABotswana, Lesotho, Madagascar, Malawi, Mozambique, Namibia, Swaziland, Zambia, Zimbabwe, and Angola. The classifications are for the convenience of the authors and do not reflect any implications, political or otherwise.


2

Table 1.

Countries of sub-Saharan Africa with the highest per capita consumption of cassava and the highest average daily per capita calorie intake from cassava 1975-84

Country

--Per-Capita-consumption-- Calorie(kg/yr) cal/day

----------------- --------

-----

-----

---- -------

I.

Zaire

423

1277

2.

Congo

359

1084

3.

Central African Republic

337

1018

4.

Gabon

271

818

5.

Tanzania

243

734

6.

Mozambique

242

731

7.

Angola

215

649

8.

Liberia

159

480

9.

Benin

158

477

10. Togo

154

465

II. Ghana

145

438

12. Madagascar

124

374

13. Nigeria

115

347

14. Guinea

114

344

15. Burundi

98

296

16. Rwanda

96

290

--

-- -

-----Source: FAO Computer printouts, 1985


3

South America is 69 calories and the figure for the world is 64 calories. There are many countries in SSA where cassava leaves are important as a vegetable, representing over 60 percent of all vegetables consumed. If this is taken into account the contribution of cassava to caloric intake would have been much higher. Although cassava provides a large portion of the calorie requirements for the people of SSA, its protein contribution is minimal. However, cassava is rarely eaten alone. It is always eaten with other side dishes consisting of vegetables, meat, or fish. On the farm, it is grown as an intercrop and intercropping in SSA has several important objectives (Norman, 1976). One major objective is the provision of a continuous supply of food in combinations that are nutritionally well balanced. There are many types of intercrops (see Ezumah et al., 1986) but the most common cassava intercrops are: cassava/maize: cassava/groundnut and cassava/maize/vegetables. Table 2 shows the crop combinations and the nutrient yields per hectare of these intercrops. For comparison, Table 3 shows the nutrient content and yield per hectare when the crops are grown on their own. It can be seen from Table 3 that cassava tubers contain a lot of calories and they are rich in vitamins Band C. But they are low in protein and lack vitamin A. A look at Table 2, however, shows that some of the deficiency is counterbalanced by the alternative crop mixtures. When intercropped with maize the protein output is more than tripled: when mixed with groundnut it is more than doubled, and when intercropped with melon, maize and okra, protein output is increased by more than four times and vitamin A is added. In countries where the leaves are also eaten the level of output of all these nutrients is much higher and vitamin A, which was lacking in the crop systems is available. Cassava is a subsistence crop in most SSA countries, but because of strong demand for processed cassava in urban areas of such countries as Zaire, Cameroon, Ghana and Nigeria, there is also brisk internal trade for these processed products in most of these countries. A recent study conducted in southwest Nigeria estimated that farmers sell 30-40 percent of their cassava output each year, which accounts for up to 50 percent of their total farm cash income (Akoroda et al., 1985). However, SSA does not play any role on the international market for cassava. Even trade within the region is insignificant and is restricted to illegal trade around the border areas.


4

Crop

1.

Coabirt..~'oll

....,

.it.t:lDlit

1•• ..,••

e •••v.

..ttb e •••• v. 1... " ••

... i .... C. . . . . . '

tidel U./ .. ,b

1:1.21

'7.02

J.n

11414.00

Ul.ID

1150.70

2"".70

'OS). ,0

'.00

11.10

11.711

".70

10.tO

Ul.OD

22.10

U5.10

'H.1D

'''.,0

Calorie heel/bale

4 •'rot..ll1 10

e" ... }

• lOt

CarbotaydratA (g/ba) • 11)' Vit_in ~

tlv./b.) • La· Vit. . . in.

Cag/ba) & lOt Yh . . h C (~/ba) • 104

11.

5616.00

~l . .

In.DD

'1i.U n./b,)

~;!l~~:l ',-o".ill

• U· 1,!bIIl

• 10" Carbohydrat.e

(v/bal • l~' Vituin l

'7.tO

t.tO

'.10

CaSlaY, 4 ,rOliruSn\l.t 1100 •

561'.00 17.00

2'0.00

21.tO 'Z •• OD

u) plant. PO' bect.are' ',02

loU

2100.00

151.20

)U.tCl

24U.IO

H21.1O

t.1D

U.20

16.70

K.JO

31.50

22.S0

13. fO

521. )D

1\."1

'0'7.'0

1111/110.) • 10·

Sil.,OO

5.].10 5615.1)0

Wit.-ill • ';oIIplu

lag''''' • 10'

11.00

t.40

n.lo

22.le

27.20

{ag/ha) .. 10·

411.00

210.00

11.1Cl

424.1D

102.10

Wit&lllin C

Hi.

e.s.ava .. Melon .. MIIiae ... 0_ ... liald U:/_I Calorie

11.11

'.02

feal/nal 'rotein '9fha' • 19"

1140.00

15i,20

nlJ.)O

50.'0

t. Zil

217 •. )D

SO)!..50

1.50

11.2<:

1l.S,tl

Z.)~

G.4\>

fJ •• t}

~'.~t

1,/bal • Ie·

196,'0

" "

231.50

1.'0

1.)0

n.j..2l1

65). '0

32.'u

32.90

5,fiU.'O

OL

'.B

3.2.

0.12

Carbohydrat.e

~~~~~~ = 10· \'l tatr.in IInlO/bll ) r illlg/t•• )

"l t.".; ---~-

._--

~---

I!

:01""1.,,

:I:

l.t·

I.U

1 ... •

321.60

~

2:0: • S6H.

..

211(; .

"

-.---.~--.- - -.~------~------.

0.2(.

0.25

D.H

11.2L1

2L'0

5.50

321.10

t07.10

-----------

Co!.tr;b~tjo~. 0: r... :rienl frcII. c:ar~.\.·. l~It.\·e~ lc tot .. l 01 ClOp .,p't~rf'!: n Jq:":i"II.Tl"j~ilr. "r,d 1li'." 30;111 h"r ... ",a.;loPd .1 2 ~r>d ~ • "o,,",-hl. 1nt"'n"aJ"

blH'C or casi..\.'" ~'J~)o 910"'" .~on", ~1,,1C! i . 10r

&

CO!!..,'>" am:

q!~:.m"·.ut

)'lltlc data .rt; trOT L\l'tiJ.t";,·,

l!=lf!>.ot.l.,,~~

aft f",r: t"l'orcu, l!hL

c \.lu,,~ fe: T,~~ti,,~·. fe' lO~ C; ~';;"~f ;'>CI~lcr. (flf: "'~. ~lt.l;ll cr':'H'~'~ 110r fl.~t •. ';~t-~~ .'_Tt C(.r.\·~T:"C ,_ ~ ' H tI~~UI:f ,· .... I.C t.J 1I1~'t'f'lYlT'~ rallS t')- p .. :ctnt e05't.·, "c:t.c-r,. Fe,! C"a!llO·... it IE (;i J.oClCt-r,"•.


'"

3

Iten

t

leaves

c •••ava

..alle

Nelon

aJc..ra

Groundnuts

1014.5

13.6

315.3

8.0

2.7

41.9

0

16.2 to 16.9

20.2 to

1.3 to 1.405

151.2

29.6

10.3

199.6

14.3 to 14.9

1.512

23OC.5

11.2

210

0

·1.6

13.5 to 14.0

0.72'

10.5

1l.5

0

0.7

33.3

2.96

551.3

5616

7.3

0

1.02

0

•••

0

581

2.0

33

448.2 to 466.5

12.0

280.'

25.0

6.0 Carbohydrate 9

21.1

451.9

l'.7Z

C•••• v. tuber.

Nutrient content and yi.ld of aa.a .elected food crop. in 8ub-.aha,a Africa planted in pure atand.

~ield

4

10

.utri.nt contentl 100 9 of edib1a

I~/b.. l "

Vit. C

(~/h&) " 10 4

Vito B cOIIpl ...

Vito " (ill/ha)

(g/ha) " 10

Carboh.ydrAte

II 10 4

Protein (g/ba)

II 10'

Calorie (cal/ba)

Nutrient (t/ba)

~&bl.

A.

B.

10.0

19.0

150

portion

2.0

71

0

1.2

363 0.7

4.0

0

1. 75

25

28

37.0

1000

2.46

0 Table.

153

0

0.48

0

Calorie

Vito " iu

0.10

50.0

Prot.ein 9

Vito B c0llp1." '"9

30 a.a

Vito C 1119 --Source


6

The average total value of cassava production ~n SSA during the last 10 years was approximately US $4.8 billion. In most of tropical Africa the role of women in agriculture is greater than the credit given to them. They playa dominant role in all of the activities from cassava production through marketing. Studies done in Nigeria have estimated that while their labor contribution to production can be as high as 70-90 percent of the total, they are fully involved in its processing and marketing (see Table 4). However, despite the fact that processing is labor intensive (Jones and Akinyele, 1976), the value added through processing (and hence income to processing women) is quite low (Oyewole et al., 1986). Farmers attach a great deal of importance to cassava because of its ease of production, its ability to perform very well undeI marginal soil and dry weather conditions, the flexibility it offers in terms of planting and harvesting and its availability throughout the year. These important characteristics are discussed later in this document.

â&#x20AC;˘ Average annual production during the last decade (FAO, 1985) valued at US $ 70/ton. (Horton et al., 1983 for value/ton)


7

Table 4

..

Percentage labor input contribution of females and .ales in cassava production and processing activities

IInambra

Bendel

Cross River

Benue

Approx. Average for Nigeria

Oyo

Activity F

M

F

M

F

M

F

M

F

M

F

M

Field preparation

20

80

60

40

25

75

30

70

35

65

34

66

Planting

90

10

80

20

75

25

70

30

70

30

77

23

Weeding

90

10

100

75

25

90

10

75

25

86

14

Harvesting

80

20

90

75

25

BO

20

60

40

77

23

Processing

100

100

100

100

100

100

Storage

100

100

100

100

100

100

Marketing

100

100

100

100

100

100

Overall liver age

83

17

90

10

10

79

21

81

Source: Anthony Ikpi, 19B6, University of Ibadan.

19

77

23

82

18


8

II.

Environment and Ecological Requirements of Cassava Production

Cassava is a crop which is produced over a very wide range of climatic conditions extending from Mozambique in southern Africa to Senegal in the west (Figures 1 and 2). Within this range cassava can grow at altitudes of up to 2000m but slowly. It gives relatively low yields at altitudes above l400m (personal communication, Abaka-Whyte and Alvarez, 1986). Cassava yields are low in cold climates and it does not tolerate frost. The ideal climate a ~arm, moist atmosphere where the temperature ranges from 25 C-29 C. Optimal rainfall for cassava ranges from lOOOmm to l500mm a year and should be well distributed. However, it is highly drought tolerant and does reasonably well even where rainfall is as low as 500mm. Some varieties also do well in areas where rainfall can be as high as 5000rnrn per year (A-As-Saqui, 1983).

JS

The best soil for cassava cultivation is light sandy loam of medium fertility with good drainage; it tolerates a wide range of pH levels. It does not do well in poorly drained or clay soils. Cassava roots rot easily in water logged soil and if the roots do not receive good aeration. In general cassava can grow and perform well on soils where other crops would not be productive.


9

--

...-'~ """ ......

........

--.

LEGEND , ••••• '" TROPICSt.;UBTROPICS ".. /

SUMMER /

WINTER

~

NORMAL

, ... .... '"

INTERMEDIt.TE

_

HIGH

I

1HIGH

RAINrALL

ISOLINE ISOLINE

ALTITUDES/COLD TEMF AL T ITUD ES /COO" TEMP

(:;:::::::::; vERY SUITAB L E

(::.> '<:-l

SUIT AB L E

~~I

Mt.'!GINALL Y

L.-------.JI

NOT

5 UITt.B L E

SUITAB L E

Fig . 1

~ENERALIZED

RAINFED

AGRO- CLIMATIC SUITA31L1TY

CASSAVA

PRODUCTION

ASSESSMENT

FOR


10

MAN IOC IN AFRICA tCl om".d d ,m ,but lOf'l aoo..rr 1950

Fig. 2 . Distribution of cassava in Africa . Source: Jones, W. O., 1969.


11 III.

Agronomic and Cultural Practice

Within the cultivated species of cassava, Manihot esculenta, there are a large number of cultivars wherever the plant is grown. In general, all of the cultivars can be classified into two broad categories, sweet and bitter, on the basis of their cyanogenic glucoside levels. The sweet varieties usually have lower glucoside content and are normally harvested earlier than the bitter varieties. As was pointed out earlier, cassava is commonly grown as an intercrop in traditional agriculture. It is usually the last crop to be planted before the land is returned to fallow (Onwuama, 1978; Okigbo, 1977; Ezeilo, 1978; Ezumah and Okigbo, 1980). Planting may be on tilled or untilled soil. If the soil is in good condition and is well drained, cassava is planted on flat land. On poor soils it is grown on mounds or ridges. (Hahn et a1., 1979). The cuttings are planted either vertically, at an angle, or horizontally. If planted vertically or at an angle, two-thirds of the cutting is buried below ground; in horizontal planting, the whole cutting is buried below the soil surface. Generally plants from longer cuttings produce more but lack of supply usually prohibits using longer cuttings. If cassava alone is grown, the usual plant spacing is 50-200 ems by 50-200 cm between plants, but this depends on soil fertility and cultural practices. When intercropping, wider spacings are used. In areas where the soil is depleted because of short fallow periods, farmers use higher plant populations to make up for yield losses. Like all other crops, cassava needs good moisture during its establishment phase. Therefore it is good to plant during the rainy season. However, when it is intercropped, farmers adjust the planting time to dovetail with the planting times of associated crops. Most traditional farmers generally do not weed cassava fields but weed once or twice at early growth stages until the cassava canopy fully develops (Onochie, 1975; Akobundu, 1980). Some farmers, however, do weed cassava two or three times during its season - the first one month after planting, the second two months after and the third, three months after planting. Weeding is done using hand tools.


12 The best time to harvest cassava tubers, depending on the cultivar, is around seven to 12 months for the sweet types, and 12 to 18 months for the bitter. Harvesting is less strenuous if done during the rainy season. Once the cassava tubers are harvested they cannot be kept unprocessed for more than three days. Cassava leaves can be harvested at regular intervals and depending upon the frequency, root yield mayor may not be affected (Lutaladio and Ezumah, 1981).


13 IV.

Technology. Productivity. Cost of Production and Value

Cassava has many characteristics suitable for the conditions that prevail in developing countries. Most farmers in many SSA countries make their living by cultivating small parcels of land that are either of poor quality or are not very well suited for the production of other crops. Cassava does well under such conditions and plays an important role in providing the necessary food and employment to the farm family. Because cassava can be harvested at any time. it allows farmers greater flexibility in the use of their scarce labor which leads to greater efficiency in overall farm activity. Cassava production requires relatively very little input. Cost of production in roots and tuber crops such as yam and cocoyam is strongly associated with the cost of planting materials because the planting material is the edible output. Cassava. on the other hand, is propagated through stem cuttings which does not cost much. It requires no chemical inputs such as fungi,cides, insecticides or pesticides because most cultivars are aggressive toward some insect pests and weeds (A-As-Saqui. 1983; Hahn et aI., 1979). It can still produce some yield even after attack (Coursey and Haynes, 1970). Cassava does not require fertilizer as much as other crops especially on newly cleared land. On poor soils, however, it can respond to nitrogen, lime, and potassium applications (IITA, 1981. 1982). Cassava's ability to suppress weeds and its minimal cultural requirements result in little labor input for its production. This, coupled with high yield (see Table 5) results in the highest cassava output per unit of labor, with 60kg for each man day (MO) as compared to 30 kg and 40 kg per MO for yam and cocoyam, respectively (Knipscheer and Wilson, 1981). Cassava production has many advantages: It can be produced in sections of the farm where other crops cannot survive; it can be grown after the main crop when rainfall is usually not sufficient for another second crop; it is compatible with and can be grown with many other crops resulting in a higher total energy output for each unit of cropped area (see Table 6), total energy input and man hour expended than would have resulted if the same resource was used for a cereal monocrop (Okoroji and Obiechina, 1985) or a cereal based cropping system (Chandra et al.,1976).


14

Table 5:

----

Average root crop and cereal grain yield, prices, and gross return/ha in developing market economies - - - - - - - - - ---- -- - - -

~-------

~

Yield

Price

Gross return

(t/ha)

US$/t

US$/ha)

---~~-

Potato

-

- - - -- ---- --------

11.0

142

1562

9.7

163

1581

13.4

89

1192

Cassava

9.0

70

630

Cocoyam

4.8

123

590

Rice

2.2

170

374

Wheat

1.5

148

222

Maize

1.5

119

179

Sorghum

1.0

123

123

Yam Sweet potato

Source: Prices from D. Horton et al., 1983 and yields from FAO computer printouts, 1985.


15

Table 6

Top ranking food crops in terms of dry matter production/ha and edible energy in developing market economies Dry matter production

Rank

----

Energy

Crop

T/ha

------

-------

production

MJ/Ha/Day *

Crop

------

1

Cassava

3.0

Potato

216

2

Yam

2.4

Yam

182

3

Potato

2.2

Carrots

162

4

S. potato

2.1

Maize

159

5

Rice

1.9

Cabbage

156

6

Carrots

1.7

Sweet potato

152

7

Cabbages

1.6

Rice

151

8

Bananas

1.5

Wheat

135

9

Wheat

1.3

Cassava

121

10

Maize

1.3

Eggplant

120

------ ------ -

----

-------- --

Source: D. Horton et aL, 1983

*

1 megajoule

= 238.66

calories

----

--


16 The cost of producing cassava is low relative to the other root and tuber crops. It is estimated to be within the range of US $100-200 per hectare, which is about a third of the production cost for sweet potato and one-tenth of that for cocoyam and yam (Horton et al., 1983). In comparison, the cost of production of open pollineated maize is approximately half of that of cassava. The cost of production for rice exceeds cassava production cost by 15 percent. Gross return per hectare is around US$600, which is less than that for yam and sweet potato but greater than that for cocoyam (see Table 5).


17

v.

Major Areas of Cassava Production in Sub-Saharan Africa

Cassava ranks first among the root crops (yarns, sweet potato and cocoyam) in total production. In the past decade (1975-84), an average of nearly 47 million metric tons (MT) of cassava were produced a year on seven million hectares (see Table 7). This accounts for 61 percent of all root and tuber crops produced annually during the same period. In comparison, the average annual production of maize and rice during 1973-82 was 13.51 million MT and 4.3 million MT, respectively. An average of 13.1 million hectares were allocated annually to maize and 3.02 million hectares to rice during the same period (see Table 7). At least 33 countries in Africa produce cassava but 65 percent of the total area planted is accounted for by five countr ies - Za ire (27 percent) 1 Nigeria <17 percent) 1 Mozambique (8 percent); Tanzania (7 percent), and Uganda (6 percent). However, 11 countries had an average of over 100,000 hectares planted to cassava annually for the period 1975-84 (see Table 8).


~

Table 7.

AreA ('ODD

Area, production and yield of cassava, maize and

rice, Airica

1975-84

,

change

O.H

1965-74

Yield (MT/HA)

,

6795

change

6464

1975-84

2.20

1965-74

Production ('OOMT)

U~)

, 46905.20

chAru)e

37631. 40

1975-84

1.70

1965-7'

6902.47

-----~~~----

5821. 21

CASSAVA

Africa

-u.81

0.92

7217

D.24

4942 7826

6364

3.32

.508 1.60

6214

7576

0.25 16198.00

2.24

5435

640,

541.33 13199.28

14724.6

3.51

6470

527.71 2.41

un).3

8503.7

2.26

-0.66

2244.5

1.99

5988.8

5792.00

109.5'

1763.24 2313.6

0.18

5420.2

117.05

w. 1894.67

1122.44

2.36

Sahel

C. Africa. UOL 95

1060.4

1963-72

13507.5

1973-82

2.83

change

1352

laO)

1963-72

1430

1031

1973-82

0.56

D. ;n

Africa

B. Africa. 837.7

-0.1

S. Africa

change

10,180.6

0.08

,

----1973-82

2.56

H19.0

------

change

1963-72

13.105.5

4,282.1

,

10144.9

-0.48

, MAIZE

3.019.7

printout., 1985

3167.0 comPQ~er

RICE

Source; FAO


19 Table 8:

Countries that have over 100,000 hectares planted to cassava in sub-Saharan Africa, 1975-84, and their average annual per capita production

Country

Area (000 Ha)

Annual per capita cassava production (kg)

1975-84 l.

Zaire

2.

Nigeria

3.

1965-74

1975-84

--iS79.7------ 474--

------

460

1153.0

162

256

Mozambique *

575.2

290

182

4.

Tanzania

485.0

263

288

5.

Uganda *

431. 4

113

107

6.

Cameroon *

338.9

105

91

I.

C. Af r icCQ Republic

298.3

411

396

8.

Madagascar *

272.4

176

192

9.

Ghana

238.8

180

161

10.

Ivory Coast *

208.6

101

92

11.

Angola *

126.0

278

92

12.

Guinea

86.1

126

127

13.

Rwanda

41.4

79

101

144

134

Africa

---

-----

--

--.

-- ---

Source: FAO computer printouts, 1985

â&#x20AC;˘

Countries not considered for proposed IITA/UNICEF Project


20

VI.

Production and Yield Trends

World cassava production increased at an annual rate of 2.41 percent in the last two decades. Eiqhty-one percent of the increase is accounted for by area increase. The averaqe annual rate of increase in production decreased from 1.92 percent durinq 1965-74 to 1.78 percent durinq the last 10 years primarily because of a slight decrease in area (see Table 7). The largest increase in world cassava production during the last 20 years took place in Asia. The qrowth was stimulated by a strong European demand for cassava as a substitute for qrain in animal feed production. The average annual rate of increase for the period was 5.84 percent and the rate of increase was actually higher durinq the second decade. Most of the increase in the first decade is attributable to higher yields and most of the increase in the second decade was due to area increase. The production of cassava in SSA increased at an annual rate of 2.2 percent, from 37.6 million MT in 1965-74 to 46.9 million MT in 1975-84 (Table 7). Among the root crops only yam achieved the same growth rate. However, 77 percent of the increase is accounted for by area increase for cassava but only 44 percent for yam. The average rate of increase in cassava production in SSA decreased from an annual rate of 1.66 percent in the first decade to 1.48 percent durinq the second (Table 9). In comparison, the production of maize in SSA increased from 10.2 million MT in 1963-72 to 13.5 million MT a year during 1973-82. This is equivalent to a 2.8 percent rate of increase a year. Rice production increased at an annual rate of 0.08 percent during the same period. Changes in cassava production in SSA var ies from subregion to subregion. According to Table 10, a large percentage of the increase took place in East Africa rollowed by Central Africa. The smallest increase occurred in the Sahel. Most of the increase in production in East Africa was due to substantially higher yields. In Central Africa, most of the increase was due to an increase in area. In Southern Africa there was a decrease in yields and in the Sahel there was only a 0.25 percent increase in production because of a decrease in area.


21

Table 9:

Rate of change in cassava production, in percent.

Region

Area

Production

Yield

1965 - 84 World

1.95

2.41

0.46

Africa

1. 70

2.20

0.49

South America

0.57

0.80

1.38

Asia

3.60

5.84

2.23

1965 - 74 World

1.69

1.92

6.23

Africa

1.66

1. 66

0.00

South America

1.68

0.46

1.22

Asia

1. 79

4.01

2.22

1975 - 84 World

1.54

1. 78

0.24

Africa

1. 48

1. 48

0.00

South America

0.92

1. 49

0.57

Asia

3.44

4.57

1.13

Source: FAO Computer printouts, 1985.


22

Table 10:

African countries that have expanded cassava production rapidly during 1975-84, percent change

Area

---------- -- -

.

Production

Yield

-- ------- -

Cape Verde

2.45

9.74

7.28

Nigeria

2.25

8.00

5.75

Rwanda

4.62

5.69

1.07

Mali

2.26

5.63

3.36

-2.61

4.24

6.85

Burkina Faso

2.02

3.48

1.46

Madagascar

3.96

3.47

-0.49

Somalia

2.49

3.04

0.55

Ivory Coast

1.13

2.93

1.29

Uganda

3.67

2.58

-1.09

Zaire

2.29

2.37

0.07

Tanzania

----------West Africa

2.41

1.60

-0.81

East Africa

0.18

3.51

3.32

Central Africa

1. 99

2.24

0.24

S. Africa

2.36

2.26

-0.10

-0.66

0.25

0.92

Sahel

- - - ------- Source: FAO computer printouts, 1985


23

Data presented in Table 10 show the rates of change in production, area, and cassava yield, for the last 10 years for countries of SSA that have expanded production rapidly. It is interesting to note that the list includes countries that are relatively dry I namely, Mal i, Burkina Faso and Somalia. Average annual per capita production of cassava in SSA countries decreased from 144 kg in 1965-74 to 134 kg in the last 10 years (see Table 8). Production has increased during the last decade but it was more than offset by increases in population. Only three countries (Nigeria, Tanzania and Madagascar) out of the 11 largest producers in Africa registered increases in per capita production of cassava.


24 VII

Cassava Production and Utilisation Constraints

The major biological constraints in cassava production are disease and pests. The most Pfedominant are: cassava mosaic (CMD) and bacterial blight diseases, and anthracnose while the most serious pests are the mealybug (CM) and green spider mite (CGM). Sources of resistance for the diseases and the two pests have been identified and incorporated into susceptible but high yielding clones and populations (Hahn and Kyser, 1985). IITA has developed two control methods over the last few years resistance breeding and biological control. After a four year study the Africa-wide Biocontrol Project has identified a wasp (Epidinocarsis lopezi) as the most promising natural enemy in lowering populations of CM to the subeconomic level (IITA, 1984). There are two groups of socio-economic constraints: those that relate to its poor image and those related to its nigh water content. Two factors contribute to cassava's poor immage, prussic acid and low protein content. Cassava is generally regarded as a low quality food crop because of this problem, which could be overcome through the development of alternative forms of utilization. People should be taught that the nutritional level of cassava based diets could be balanced by consuming cassava with other food items that provide the nutrients it lacks. It should also be pointed out that cassava leaves are rich in protein, vitamins and minerals and that they can be eaten as a vegetable, as is done in many countries. Studies have shown that cassava varieties contain cyanide, ranging between 4.8 to 8.9 mg per 100g of edible portion of fresh weight. A combination of peeling, grating, fermenting, dehydrating, sundrying, frying and/or boiling is necessary to reduce the hydrogen cyanide content to safe consumption levels (Figure 3). Such processing is labor intensive and can become a constraint when attempting to introduce cassava into new areas without providing the proper processing methods. Cassava tubers require a lot of storage space and their transportation is difficult and expensive because of their bulk. Also, once cassava is harvested it begins to deter iorate after three days. All of these problems are associated with the high water content of cassava tubers. Preliminary work at CIAT and IITA has indicated that storage life can be extended by minimizing injury during harvest.


III

N

i

11

Pi

TCIfaI HeN

~

~12

!In._

HCN(mQ/lC>OQ fr.ttI weq.tl

25 20 10 10 ~

o1

Pfoc:eu

V

\/I

r~Md m

D PeeIecI GrOltCI

,v Oehy4rQII<I

X

CQUOVC

IX

Y Flrmenttcl tor I clay VI Flrmenttcl for 2 gay. VII Si-* VIII Fried I)( Oven- drIII:I X S-'(Gc!rll

VII

XI CaaiItd (EbeI)

VII

Fio- 3. Ef fact d trodiIioIld processinQ of four varieties of

XlI

tuberous roots

in the prtIpOrotion of QOI'i,on totol and free c~ content at each respeclillfl UOQt fA prOCftSinQ. Source: HoM S.K.,1983.


26

However the best way to extend storage life and to reduce transportation costs is to process cassava into products such as gari, depa, chikwange, etc. that are popular in many SSA countries.


27 VIII.

Recent advances in cassava researcb in Sub-Sabaran African countries

A large set of improved technologies on various aspects of cassava production and processing is currently available both at international agr icul tural research centers and within national agricultural research centers in Africa. For instance at IITA, achievements have been made in varietal improvements, in terms of yield, disease and pest resistance, rapid multiplication and disease-free germplasm storage and exchange techniques plus biocontrol of major cassava pests. A number of cassava varieties of the TMS series, namely 50572, 30555, 50395, 30001, 91934, 4(2)1425 and Kinuani have been developed at IITA. These varieties are adaptable to a wide range of agroclimatic zones. They have a maturity period of seven to 12 months after planting and give yield ranging between 15 to 30 tons a hectare under normal soil and climatic conditions. They are resistant to the major cassava diseases such as the cassava mosaic disease and cassava bacterial blight (IITA, 1983). Although most of these varieties were developed before the outbreak of cassava mealybug and cassava green spider mite, varieties TMS 30572, 30555 and 50395, recover faster at the onset of the rains, from CM and CGM attack. Varieties TMS 91934 and 4(211425 have moderate resistance to CM and CGM attacks. IITA cassava varieties give high dry matter content of up to 30 percent. Variety TMS 30001 has low hydrocyanic acid (HCN) and gives gari and quality flour which can be mixed up to 30 percent with wheat flour for baking biscuits, bread and cakes. Even though the other IITA cassava varieties have high cyanide levels this can effectively be removed through processing by fermenting and sun drying. All IITA cassava varieties give good field establishments and develop good canopy which help to smother weeds. Studies in Nigeria have shown that farmers in Rivers State ranked IITA variety TMS 30211 first for its quality of gari and fufu and its low branching ability which gives good ground cover and controls weeds (Ezeh, 1980). Farmers in Oyo and Ogun states prefer cassava variety TMS 30572 and TMS 30555 because of their high yielding ability, low branching ability and early maturity (Nigerian Accelerated Food Production Program (NAFPP), 1978: Akoroda et al., 1985).


28 Expertise and techniques for rapid multiplication and disease-free germplasm for storage and exchange are also available at IITA. These include tissue culture and virus indexing techniques which are very effective in producing disease-free materials and germplasm for storage and distribution (IITA, 1980). Cassava mealybug and green spider mite were first reported in Africa respectively, by Hahn and Williams in 1973 and by Nyiira in 1972, and have since become a threat to cassava production in almost all SSA countries. IITA is obtaining promising results from its biological control trials on CM using natural enemies introduced from Latin America". Mealybug predators have been released in a number of countries such as Nigeria, Zaire, Guinea Bissau, Ghana, Congo, Rwanda, Malawi, and Zambia. All biological control trials are being carried out with the cooperation of national governments and under the auspices of the Organization of African Unity's (OAU) scientific, technical, and research commission. Agronomic studies indicate that the optimal plant population of cassava is 10,000 plants a hectare planted on mounds or on ridges. Cassava should be planted at the onset of the rains using stem cuttings of 20 to 30 cm long. Highest sprouting, 84 to 92 percent, occurs 26 to 27 days after planting and tuber formation begins 40 to 70 days after planting (IITA, 1979, 1982). Canopy ground cover normally takes places at about 120 days after planting. Therefore, at least two cr i tical weedings are required-one at four to five weeks after planting and the second at 16 to 18 weeks after planting. Cassava can be harvested by digging out the roots and the period of storing fresh cassava tubers can be prolonged somewhat by avoiding tuber damage at harvest. When the soils are soft, harvesting can be done by using a cassava lever or by pulling the cassava stump by hand after cutting off the cassava plant (IITA, 1982) â&#x20AC;˘ varieties with low cyanide content (less than 10 gm/100 9 of fresh wt.) are generally low yielding as compared to cassava varieties with high cyanide content (more than 20 mg/lO 0 9 fresh wt. ) . A number of IITA improved varieties have been distributed to almost all cassava producing countries through national research programs. Before the 1960s, many African countries either did not have separate roots and tuber programs or neglected research on roots and tuber crops altogether. Currently, countries such as


29 Nigeria, Cameroon Zaire, Sierra Leone, Liberia, Ivory Coast, Ghana, Central African Republic, Tanzania, Rwanda, Uganda and Mozambique operate these programs within the national research setup or have designated a group of scientists and a research station to roots and tuber research activities. For instance, in 1974 Zaire started the cassava improvement program (PRONAM). It was established by an agreement between the Zairean Government and the IITA. The program has released one improved variety which has been rapidly multiplied on a large scale and distributed to many farmers. The Zairean cassava program has now been expanded with the help of external finance and IITA technical assistance. A large number of Zairean scientists also have been trained through IITA. Nigeria has the National Root Crops Research Institute (NRCRI) at Umudike, which focuses on cassava and yams. The National Accelerated Food Production Program (NAFPP) and the Nigerian National Seed Service (NSS) have received, multiplied and distributed IITA improved varieties to farmers. IITA varieties have spread to all the southern states through efforts of the NAFPP, NSS, various agricultural development projects, State Ministries of agriculture and by selected farmers. In Ghana, IITA improved cassava clones TMS 30572, TMS 4(2)1425, TMS 30395, TMS 30001, TMS 42025 and TMS 60142 were assembled at Pokuase, a plant quarantine station near Accra, for evaluation since 1983. So far, varieties TMS 4(2)1425, TMS 30395 and TMS 30001 have been picked as suitable for the preparation of Ghanaian fufu and TMS 30572 and 30555 for gari. Multiplication and distribution of the promising clones to farmers are now going on at Weija Irrigation Scheme near Accra and in the Volta Region Agricultural Development Project. Moreover, the Crops Research Institute Station at Ohawu, in the Volta Region, has been screening cassava since 1978 from IITA seeds. Recently, the government has created a national committee on root and tuber crops and this committee together with IITA, organized the Third West African Root Crops Symposium held in Ghana in 1985. A large number of IITA improved cassava clones have been introduced and promising clones have been identified both in Rwanda and Tanzania. National root crop improvement programs in some African countries have made considerable progress both in their cassava breeding and biological control research activities. Some countries such as Nigeria, Cameroon, Zaire and Rwanda have obtained more promising results in cassava research than others, because of IITA's cooperative programs with financial support from several donors. However, many African countries lack qualified personnel, research facilities and financial support, and/or their researchers suffer from scientific isolation.


30

IX.

Effects of Urbanization in SSA on Pood Crop Production

The urban populations in West Africa become larger and increase in density per unit area as one moves from the Savannah, through the forest to the coast. Of course the larger the populations, the greater the demand for food supplies. Cassava and yams are grown mostly in the mid-belt and the southern forest zone. The urban centers in northern Guinea and Sudan Savannah zones have a higher demand for sorghum and millets which are the traditional staple foods there. However, studies conducted in northern Nigeria, Benin and Senegal indicate that demand for cassava and yams is increasing partly due to (al immigrants of forest zone origin, (bl decline of soil fertility and occurrences of drought in the semi-arid zone that have greatly affected the production of the traditional cereal crops (Fisk, 1978; see also p. 22 and Table 101. In eastern and southern Africa, the urban population is concentrated along the railway lines, near lakes and rivers and on high plateaus. In the last 20 years, with the development and concentration of industrial activities in urban centers, coupled with the difference between urban and rural wage rates, many African countries have experienced an exodus of the young from rural areas into urban centers in search of employment. This , has affected food production and supplies in many ways. Firstly, the urban-rural migration of young men and women has deprived the rural areas of the labor that is needed for agricultural production. Secondly, the phenomenon has accelerated the rate of urbanization and created a large demand for food supplies. Thirdly, the aged farmers that are left in the villages using traditional production methods find themselves unable to maintain the productivity of the land and to perform all farming activities. This, coupled with the poor marketing infrastructure, has caused food shortages in urban areas. Governments addressed this problem by importing food grain and flour which in turn discouraged farmers from producing traditional crops such as roots and tubers, sorghum, millet, etc. Meanwhile the population density on the land was increasing at a faster rate, shorter fallow periods became more common and soil fertility maintenance became more difficult. After 1974, many African governments realized the importance of being self-sufficient in food production. They no longer could afford to import or to produce grain using expensive


31

fertilizer and other technologies. So they turned to their agricultural sectors to feed their burgeoning urban population. Farmers responded by cultivating their land more i ntensi vely which in a short time resulted in reduced soil productivity and agricultural output. As the soil became depleted, and could not support more demanding crops such as yam, maize, rice etc, farmers began growing cassava whicn can produce reasonable yield even in marginal soils.


32

x.

Governaent Policies Affecting Cassava Production in SSA

Throughout recent history, countries of sub-Saharan Africa have done very little to encourage the production and utilization of cassava. Prior to the 1960s agricultural research emphasized only export crops such as cocoa, oil palm, coffee, cotton, tea, sisal, tobacco, groundnuts and rubber. Cassava was introduced into SSA during the late 19th century to serve only as a security crop. At that time it was not considered an important food crop. After independence, most governments followed similar policies because they needed foreign exchange to finance large-scale development schemes. When this did not work, and they came to realize the importance of being self-sufficient in food production, they turned their attention to the grain crops and not to the traditional staple foods like cassava (Coursey and Haynes, 1970). The situation is still the same in many SSA countries. Most of them do not allocate money for roots and tuber research as much as they do for research on cereal grains (see Figure 4, for example). Current agricultural policies of most countries of sub-Saharan Africa include subsidies on important inputs such as fertilizers that are used primarily in the production of cereal grain. In most cases, the use of such inputs increases yield and improves the relative economic advantage of cereal grains over cassava and other root and tuber crops. Under such circumstances, farmers are forced to shift out of the production of staple foods and into the production of cereal grains. Several scholars (Byerlee, 1985, Delgado and Miller, 1985) have pointed out the alarming upward trend in wheat (and rice) consumption and imports in developing countries including those in sub-Saharan Africa. This trend is happening when food production per capita is decreasing in the region. The major cause for the increase in cereal grain imports are government policies that have kept the price of wheat and rice lower than the price of the traditional staple foods. This had a profound effect on production and consumption patterns. Farmers in most SSA countries are already faced with increased production costs because of uncontrolled inflation. When this problem was compounded by decreased demand for their products most of them either quit farming or decreased producing staple food crops such as cassava. At the same time, consumers in urban areas are increasingly being drawn to wheat bread and rice because of their lower relative prices and the ease and convenience of using them.


33

CFA ( in thousand) 100

-Rice

90

80 -Groundnut

70

60

50

- Maize

40 - Cowpea

30

20

-Sorghum

Yams.

Millet

â&#x20AC;˘

Cossava

10 bsweet potato

Cocoyom

0

0

40

80

120

160

200

240

280

Production, MT ( in thousand) Fig. 4. Relationship of government spending for research and production of selected crops in the Republic of Benin, 1983.

320


34 Studies have determined that up to 20 percent of cassava flour can be substituted for the wheat flour used in bread without affecting the final product. Yet no effort is being made by processors to use cassava flour. The major reason for this is that the use of cassava flour does not offer any advantages to the processors, as government subsidizes the price of wheat flour. Most SSA countries maintain exchange rates that are artificially high. As a result of this policy imported grains are cheaper than domestic food staples such as sorghum, millet, cassava and other root and tuber crops in most of these countries. The effect of this on production and consumption of these staples is obvious. Because food shortages have become a chronic problem in many countries of sub-Saharan Africa, food aid programs have assumed important roles in the economies of such countries. In most cases, such programs have made a positive contribution but they also have had negative outcomes such as the introduction of new food habits at the expense of traditional staples. Recently the governments of a number of countries such as Nigeria, Cameroon, Zaire, Rwanda. Ghana and others have established research programs that are directly concerned with research and development of root and tuber crops. Many other countries have yet to do likewise.


35 References A- As -Saqui, M. 1984. The potential of cassava in optimizing small farm productivity in Liberia. Proceedings: Sixth Symposium of the International Society for Tropical Root Crops, eIP, Lima, Peru 21-26 Feb., 1983. International Potato Center, 1984, 199-203. Abaka-Whyte, J. 1986.

Plant Breeder, IITA, Cameroon.

Akobundu, 1.0. 1980. Weed control in cassava cultivation in the subhumid tropics. Tropical Pest Management, 26 (4), 420-426. Akoroda, M.O.; Gebremeskel, Tesfaye, and Oyinlola, A.E., 1985. Impact of IITA cassava varieties in Oyo State of Nigeria, Unpublished Report, IITA, Nigeria. Alvarez, M.N. 1986.

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Byerlee, D. 1985. Avoiding the wheat trap: how inappropriate pOlicies change dietary habits. Ceres 107, 20-25. Coursey, D.G. and Baynes, P.B. 1970. Root crops and their potential as food in the Tropics. World Crops 22, 261-265. Chandra, S.; Evenson, J.P., and De Boer, A.J. 1976. Incorporating energetic measures in an analysis of crop production practice in Sigatoka Valley, Fiji. Agricultural Systems 1(4), 303-311. Delgado, C.L. and Miller, P.J. 1985. Changing food pattern in West Africa: implications for policy research. Food Policy 10(1) 55-62. Ezeh,

W.O.A. 1980. NAFPP cassava/maize production recommendation: A socio economic survey adopted in six states of Nigeria. Management Conference, Port Harcourt, Nigeria.

Ezeilo, W.N.O. 1978. Intercropping with cassava in Africa. In Intercropping with Cassava. Proc. of International workshop, held at Trivandrum, India, 27 Nov. - 1 Dec., 1978, pp. 49-55; IORC - 142e.


36 Ezumah, H.C.I Hahn, S.K.I Okigbo, B.N., and Gebremeskel, Tesfaye. 1986. Root crops based farming systems research at IITA. Paper presented at Workshop in Farming Systems Research, ICRISAT, India, 17-21 February, 1986. Ezumah, H.C. and Okigbo, B.N. 1980. Cassava planting systems in Africa. In Cassava Cultural Practices. Proc. of workshop held in Salvador Bahia, 18-21 March, 1980. IORC, Ottawa. FAO, 1978. Report on the agro-ecological zones project, vol.l methodology and results for Africa, World Soil Resource Report, Rome, Italy. FAO. 1985.

Computer Printouts

Fisk, E.J;. 1978. The adaptation of traditional agriculture: socioeconomic- problems of urbanization. Development Center mono No.1l. The Australian National University, Canberra. Gebremeske1, Tesfaye, and Ngambeki, D.S. 1984. Socioeconomic perspective of roots and tubers in Tropical Africa. Paper read at the Eastern and Southern Africa Regional Crop Workshop, 10-14 December 1984, Kampala, Uganda. Hahn, S.K. 1983. Cassava research to overcome the constraints to production and use in Africa. In: Delange, F., and Ahluwalia, R. ed. Cassava Toxicity and Thyroid: Research and Public Health Issues. Proc. of a workshop held in Ottawa, Canada, 93-102. Hahn,

S.K. 1984. Tropical root crops, utilization, IITA, Ibadan.

their improvement

Hahn, S.K. and Kyser, J. 1985. Cassava: a basic Outlook on Agriculture 2:95-100.

and

food of Africa.

Hahn, S.K.I Terry, E.R.: Leuschner, K.: Akobundu, 1.0.: Oko1i, C., and La1, R. 1979. Cassava improvement in Africa. Field Crops Research 2, 193-226. Hahn, S.K. and Williams, L. 1973. Investigations on cassava in the Republic of Zaire. Report on Commiscure d'Etat a l'Agriculture, Republic of Zaire, pp.1-l2.


37 Horton, D.; Lyman, J., and Knipscheer, H. 1983. Root crops in developing countries. An economic appraisal. In Proceedings: Sixth Symposium of the International Society for Tropical Root Crops. CIP, Lima, Peru 21-26 Feb., 1983. International Potato Center. 1984. 9-39. IITA.

1979, 1980, 1981, 1982, 1983 and 1984 Annual Ibadan.

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Jones, W.O. 1959. Manioc in Africa. Stanford, Calif1 315pp.

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Knipscheer, H.C. and Wilson, J.E. 1981. Cocoyam farming systems in Nigeria. In: E.R Terry, et all eds. Tropical root crops: research strategies for the 1980's. Proc. of the First Triennial Root Crops Symposium of the International Society for Tropical Root Crops - Africa Branch, 8-12 Sep. 1980, Ibadan, Nigeria, 247-254. Lagemann, J. 1977. Traditional African farming systems in Eastern Nigeria. Weltforum Verlaz, Munchen, W. Germany.


38

Lutaladio, N.B. 1985. Planting periods and associated agronomic practices for cassava (Manihot esculenta Crantz) production in southern Zaire. Unpublished Ph.D Dissertation, University of Ibadan, Ibadan, Nigeria. Lutaladio, N.B. and Ezumah, B.C. 1981. Cassava leaf harvesting in Zaire. In E.R. Terry, ICA. Oduro, and F. Caveness, ed., Tropical Root Crops: research strategy for the 1980s. Proc. of the First Triennial Root Crops Symposium of the International Society for Tropical Root Crops - Africa Branch, 8-12 Sep. 1980, Ibadan, Nigeria. NAFPP, 1978. National Accelerated Food Production Programme (NAFPP), 1978 Annual Report, Nigeria. Norman, D.W. 1976. Developing mixed cropping system relating to the farmers environments. In J.B. Monyo, A.D.R. Ker, and M. Campbell, ed. Intercropping in Semi Arid Areas: Proceedings of a Conference held at the Faculty of Agriculture, Forestry, Veterinary Science of the University of Dar es Salaam. Morogoro, Tanzania, 10-12 May 1976. Nyiira, Z.M. 1972. Report of investigation on cassava mite, Monongchel1us tanagoa Bondar Kwanda Research Station, Kampala, Uganda, 14pp. Okigbo, B. N. 1977. Prel iminary cassava interp1anting tr ials. Paper prepared for the First National Cassava Workshop, Umudike, Nigeria. IITA, 20pp. Okigbo, B. N. 1978. Cropping systems and related research in Africa. Association for the Advancement of Science in Africa (AASA) Occasional Publication Series - OT 1. Okoroji, E.C. and Obiechina, C.O.B. 1985. Base for farm resour allocation in the traditional farming system: A comparative study of productivity of farm resources Abakalik area of Anambra State, Niger ia. Agr icu1 tur System 17, 197-210. Onochie, B.E. 1975. Critical period for weed control in ca in Nigeria. PANS, 21(1), 54-57. Onwueme, I.C. 1978. Tropical root and tuber crops. USA, John Wiley and Sons. 234p.

New


38

Lutaladio, N.B. 1985. Planting periods and associated agronomic practices for cassava (Manihot esculenta Crantz) Unpublished Ph.D production in southern Zaire. Dissertation, University of Ibadan, Ibadan, Nigeria. Lutaladio, N.B. and Ezumah, H.C. 1981. Cassava leaf harvesting in Zaire. In E.R. Terry, K.A. Oduro, and F. Caveness, ed., Tropical Root Crops: research strategy for the 1980s. Proc. of the First Triennial Root Crops Symposium of the International Society for Tropical Root Crops - Africa Branch, 8-12 Sep. 1980, Ibadan, Nigeria. NAFPP, 1978. National Accelerated Food Production Programme (NAFPP), 1978 Annual Report, Nigeria. Norman, D.W. 1976. Developing mixed cropping system relating to the farmers environments. In J.H. Monyo, A.D.R. Ker, and M. Campbell, ed. Intercropping in Semi Arid Areas: Proceedings of a Conference held at the Faculty of Agriculture, Forestry, Veterinary Science of the University of Dar es Salaam. Morogoro, Tanzania, 10-12 May 1976. Nyiira, Z.M. 1972. Report of investigation on cassava mite, Monongchellus tanagoa Bondar Kwanda Research Station, Kampala, Uganda, l4pp. Okigbo, B. N. 1977. Prel iminary cassava interplanting tr ials. Paper prepared for the First National Cassava Workshop, Umudike, Nigeria. IITA, 20pp. Okigbo, B. N. 1978. Cropping systems and related research in Africa. Association for the Advancement of Science in Africa (AASA) Occasional Publication Series - OT 1. Okoroji, E.C. and Obiechina, C.O.B. 1985. Base for farm resource allocation in the traditional farming system: A comparative study of productivity of farm resources in Abakalik area of Anambra State, Nigeria. Agricultural System 17, 197-210. Onochie, B.E. 1975. Critical period for weed control in cassava in Nigeria. PANS, 21(1), 54-57. Onwueme, I.C. 1978. Tropical root and tuber crops. USA, John Wiley and Sons. 234p.

New York,


39 Oyewo1e D.B.I Fapohunda B.M.T., Gebremeskel, Tesfaye, and Hahn, N.D. 1986. Cassava processing: techniques and processes, Unpublished paper. Socioeconomic Unit, IITA, Ibadan, Niger ia. Platt, B.S. 1962. Tables of representative value of food commonly used in tropical countries. London, England, Her Majesty's Stationery Off ice, Medical Research Council Special Report Series, 303.


CASSAVA RESEARCH AND PRODUCTION