Cover Image
fechar este livroRoots and Tubers for the 21st Century - Trends, Projections, and Policy Options. 2020 Vision for Food, Agriculture, and the Environment. Discussion Paper 31 (IFPRI, 2000, 72 p.)
Ver o documento(introduction...)
Ver o documentoForeword
Ver o documentoAcknowledgments
Ver o documento1. Introduction
Ver o documento2. Trends in the Use of Roots and Tubers
Ver o documento3. Trends in the Supply of Roots and Tubers
Ver o documento4. Baseline Projections of Production and Use
Ver o documento5. High Demand and Production Growth Scenario
Ver o documento6. Roots, Tubers, and the Environment
Ver o documento7. Conclusions and Recommendations
Ver o documentoAppendix: Supplementary Tables
Ver o documentoReferences

Appendix: Supplementary Tables

Table 24 - Main agronomic characteristics of principal roots and tubers

Characteristics

Cassava

Cocoyam (tannia)

Potato

Sweetpotato

Taro (cocoyam)

Yam


(Manihot esculenta)

(Xanthosoma nigrum)

(Solanum tuberosum)

(Ipomoea batatas)

(Colocasia esculenta)

(Dioscorea spp.)

Growth period (months)

9-24

9-12

3-7

3-8

6-18

8-11

Annual or perennial plant

Per.

Per.

Ann.

Per.

Per.

Ann.

Optimal rainfall (centimeters)

100-150

140-200

50-75

75-100

250

115

Optimal temperature (°C)

25-29

13-29

15-18

>24

21-27

30

Drought resistant

Yes

No

No

Yes

No

Yes

Optimal pH

5-6

5.5-6.5

5.5-6.0

5.6-6.6

5.5-6.5

n.a.

Fertility requirement

Low

High

High

Low

High

High

Organic matter requirement

Low

High

High

Low

High

High

Growable on swampy, waterlogged soil

No

No

No

No

Yes

No

Planting material

Stem

Corms/cormels

Tubersa

Vine cuttings

Corms/cormels

Tubers

Storage time in ground

Long

Long

Short

Long

Moderate

Long

Postharvest storage life

Short

Long

Long

Short

Variable

Long

Sources:

Derived from D. E. Kay, Root crops, London: Tropical Products Institute, 1973, as presented in Horton (1988).

Note:

n.a. = Data not available.

a Whole tubers, cut tubers, or botanical seed.

Table 25 - Raw material characteristics of roots and tubers


Aroids

Cassava

Potato

Sweetpotato

Yam

Dry matter (%)

22-27

30-40

20

19-35

20-42

Starch (%FW)

19-21

27-36

13-16

18-28

18-25

Total sugars (%FW)

2.0

0.5-2.5

0-2.0

1.5-5.0

0.5-1.0

Protein (%FW)

1.5-3.0

0.5-2.0

2.0

1.0-2.5

2.5

Fiber (%FW)

0.5-3.0

1.0

0.5

1.0

0.6

Lipids (%FW)

0-1.5

0.5

0.1

0.5-6.5

0.2

Vitamin A (µg/100g FW)

0-42

17

Trace

900

117

Vitamin C (mg/100g FW)

9

50

31

35

24

Ash (%FW)

0.5-1.5

0.5-1.5

1.0-1.5

1.0

0.5-1.0

Energy (kJ/100g)

390

607

318

490

439

Antinutritional factors

Oxalate crystals

Cyanogens

Ylycoalkaloids

Trypsin inhibitors

Alkaloids, tannins

Starch extraction rate (%)

n.a.

22-25

8-12

10-15

n.a.

Starch grain size (micron)

1-12

5-50

15-100

2-42

1-70

Amylose (%)

3-45

15-29

22-25

8-32

10-30

Maximum viscosity (BU)

n.a.

700-1,100

n.a.

n.a.

100-200

Gelatinization temp. (°C)

68-75

49-73

63-66

58-65

69-88


Source:

Wheatley et al. 1995, Bradbury and Holloway 1988.

Note:

n.a. = Data not available. FW = fresh weight; µg = microgram; mg = milligram; BU = Brabender units; kJ = kilojoule.

Table 26 - Key IMPACT parameters for selected countries and regions


Average annual growth rate,
1993-2020

Income elasticities of demanda



Cassavab

Potato

Sweetpotato and yam

Countries/region

Population

Income

1993

2020

1993

2020

1993

2020


(percent)

Brazil

1.12

3.2

-0.08

-0.18

0.40

0.30

-0.10

-0.25

Nigeria

2.67

3.2

0.30

0.20

0.20

0.18

0.50

0.40

Central and Western Sub-Saharan Africa

2.70

3.8

0.10

-0.05

0.40

0.38

0.30

0.20

Egypt

1.56

3.2

0.05

-0.15

0.40

0.25

0.10

0.00

Turkey

1.24

4.5

0.00

-0.20

0.35

0.20

0.10

0.00

India

1.30

5.1

0.15

-0.05

0.55

0.45

-0.10

-0.30

Thailand

0.63

5.4

-0.05

-0.10

0.40

0.25

-0.10

-0.25

China

0.72

5.6

-0.05

-0.15

0.45

0.35

-0.20

-0.35

Source

IFPRI IMPACT, June 1998.

a Estimates for the baseline scenario.

b These figures are for cassava and other roots and tubers such as taro. For developing countries, cassava alone accounts for over 97 percent of the total.