 | Roots 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.) |
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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). |
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Note: |
n.a. = Data not available. |
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a Whole tubers, cut tubers, or botanical seed. |
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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. |
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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
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Average annual growth rate, |
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 |
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Nigeria |
2.67 |
3.2 |
0.30 |
0.20 |
0.20 |
0.18 |
0.50 |
0.40 |
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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 |
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India |
1.30 |
5.1 |
0.15 |
-0.05 |
0.55 |
0.45 |
-0.10 |
-0.30 |
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Thailand |
0.63 |
5.4 |
-0.05 |
-0.10 |
0.40 |
0.25 |
-0.10 |
-0.25 |
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China |
0.72 |
5.6 |
-0.05 |
-0.15 |
0.45 |
0.35 |
-0.20 |
-0.35 |
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Source |
IFPRI IMPACT, June 1998. |
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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. | |
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