Working Paper on Social-Ecological Resilience SeriesNo. 2012-015
The Importance of Sweet Potatoes in Rural Villages
in Southern Province, Zambia
By

Hidetoshi MIYAZAKI, Yudai ISHIMOTO and Ueru TANAKA
Research Institute for Humanity and Nature
March 2012

Vulnerability and Resilience of Social-Ecological Systems
RIHN Research Project E-04

Research Institute for Humanity and Nature (RIHN)Inter-University Research Institute Corporation, National Institutes for the Humanities

大学共同利用機関法人 人間文化研究機構
総合地球環境学研究所

Working Paper on Social-Ecological Resilience SeriesNo. 2012-015

The Importance of Sweet Potatoes in Rural Villages
in Southern Province, Zambia
By

Hidetoshi MIYAZAKI, Yudai ISHIMOTO and Ueru TANAKA
Research Institute for Humanity and Nature
Kyoto, Japan
E-mail: miyahide@chikyu.ac.jp
March 2012

Vulnerability and Resilience of Social-Ecological Systems
RIHN Research Project E-04

Research Institute for Humanity and Nature (RIHN)Inter-University Research Institute Corporation, National Institutes for the Humanities

大学共同利用機関法人 人間文化研究機構
総合地球環境学研究所

Abstract
Stable maize production and increased productivity are important for improved foodsecurity in Zambia. Because most farmers cultivate maize under rain-fed agriculture,
however, a maize monoculture is vulnerable to drought or excessive rainfall. Increasing thediversification of crops and crop varieties is therefore important to achieve food security inthe face of a changing climate. The sweet potato is an important secondary food in Zambia
and has great potential both as a crop for consumption and as a source of income. The aim of
the study was to determine farmers’ familiarity with sweet potato varieties and their features
and to clarify production and consumption patterns in a rural area in Southern Province,
Zambia. Field studies and farmer interviews were conducted at three sites. Farmers in the
study area planted sweet potato in both the rainy and dry seasons, but sweet potato production
varied between planting seasons and among the three study sites. As a group, farmers wereable to identify a total of 22 sweet potato varieties, but many farmers were not able to identify
a single variety, and only 10 of the 22 identified varieties were actually cultivated in the study
area. Sweet potato production was much greater at one site. Further study of some households
at this site indicated that sweet potato tubers were consumed about twice a week, mostcommonly for breakfast. Consumption was highest during and immediately after the harvest
and then gradually decreased. Sweet potato leaves were rarely consumed. Annual sweet
potato sales per person generated sufficient income at this site to purchase enough mealiemeal (a local staple food) to feed 7.4 adults for a year.

Key words: Food security, Crop diversification, Food consumption, Cash income, Tuber
crop

要約

ザンビアにおける食料安全保障を改善するためには、安定したメイズ生産と生産性の向上が重要である。しかし、多くの農民は天水農業下でメイズを栽培しており、メイズに偏重した作付けは干ばつや過度の降雨に脆弱である。したがって、気候変動に直面しながら食料安全保障を成し遂げるには、作物の多様性を増すことが重要となる。サツマイモは自家消費用食料、ならびに世帯の現金収入源として大きな可能性があるといわれている。そこで、本研究では、ザンビア南部州農村地帯の 3 サ
イトにおいて、サツマイモ品種についての農民の知識を理解すること、また、サツマイモの生産と消費を明らかにすることを目的とした。
サツマイモは雨季、乾季ともに栽培されているが、その栽培割合は季節間、サイト間で異なっている。農民へのインタビューの結果、22 種類ものサツマイモ品種があることが判明したが、彼らの多くは 1 種類も回答することができなかった。また、確認された 22 種類のうち栽培されていたのは 10 種類に過ぎなかった。調査した 3
サイトのうち 1 サイトでは、特にサツマイモ生産が盛んにおこなわれていたが、そのサイトでのさらなる調査の結果、サツマイモの塊根は主に朝食として利用されており、1 年間の全食事を通じてみると、1 週間に 2 回程度消費されていた。消費は収穫直後に最も高く、徐々に減少した。サツマイモの葉は、ほとんど消費されていな
いこともわかった。サツマイモ販売による売り上げ額は高く、１年間当たりの売り上げで大人 7.4 人分の主食（メイズの粗挽き粉）を購入できることがわかった。

キーワード：食料安全保障, 作物多様化, 食料消費, 現金稼得, 塊根作物

1. Introduction
About 75 percent of farmers in Zambia engage in small-scale farming, with an average farm sizeof 2 ha (VAM Steering Committee Zambia, 1998). Most of these farmers cultivate maize, which is astaple food in Zambia, and stable maize production and increased productivity are important for foodsecurity. Because small-scale agriculture is predominantly dependent on rain-fed cultivation, a maize
monoculture is vulnerable to factors such as flooding and drought. Increasing diversification of crops
and crop varieties is therefore important to achieve food security in the face of a changing climate(Cotter and Tirado, 2008). As a result of structural adjustments and economic liberalization carriedout in the early 1990s, crop diversification has improved. Zulu et al. (2000) found that the cultivatedarea of crops excluding maize increased from 1993 to 1998, including that for cotton, groundnuts,
cassava, and sweet potato. Production of groundnuts, cassava, sweet potato, and tobacco also
increased during this period. Jayne et al. (2007) found that cassava, groundnut, and sweet potato
productivity all increased with the introduction of improved varieties in the early- to mid-1990s, so
crop varieties also need to be considered when undertaking crop diversification.
The sweet potato is an important secondary food in Zambia and other countries in southern
Africa (Kapinga et al., 2005). In addition to its important role as a food crop for self-consumption, it
has great potential as a source of income for farmers (Rees et al., 2001). Therefore, it is important tounderstand the production and consumption of sweet potatoes in rural Zambia, but there is little
published information on the area under cultivation or how the crop is utilized at the household level.
The aim of this study was to determine farmers’ familiarity with sweet potato varieties, the featuresof these varieties, and to clarify production and consumption patterns of sweet potato in several ruralvillages in Southern Province, Zambia.

12. Study Area
The study sites were located in Southern Province, Zambia (Fig. 1), which is in thesemiarid tropics and has an average annual precipitation that ranges from about 600 to 900 mm(Yatagai, 2011). The rainy season occurs from November to April, and small-scale farms in the area
are used to cultivate maize under rain-fed conditions. The elevation gradually increases from theLake Kariba shore to the highlands, and the three sites were located in the lower terrace near Lake
Kariba (Site A), the middle of the escarpment (Site B), and the upper terrace of the escarpment (Site
C). Sites A and B each consisted of two villages, and Site C had one. The sites’ agro-ecosystems andsocial structures were different because of differences in rainfall amount, temperature, andvegetation. All residents of the sites were of Tonga ethnicity, but Site A and B residents belong to the
Gwembe Tonga and Site C residents to the Plateau Tonga.

BatokaSite C
Bbaamp market

Site B

Site A

Maamba0

Figure 1 Study sites in Southern Province, Zambia

25km

3. Crop Distribution
3.1 Crop calendar
Planting and harvesting dates were determined though group discussions at each site.
Figure 2 shows the crop calendar for all three sites. Farmers plant maize at the beginning of the rainyseason in November either by dry planting, where they start planting by hoe after the first rain, or byusing an animal-drawn plow after the first several rains. They usually plant other crops (e.g.,
pumpkin, sorghum, pearl millet, and beans) mixed in with the maize at the same time. When theyfinish planting maize, they begin to plant other crops in other fields. Some “green” maize isharvested in March, and the remaining maize is harvested after it dries in the fields. The dried maize
is used to make ground maize meal, usually beginning in the end of April. The sowing time for dry
season maize differs between Site A and Sites B and C. At Site A, planting takes place from the endof February to the beginning of March, but at Sites B and C, it goes from the end of August to
October. Other crops are also grown during the dry season. The dominant dry-season crop is okra at
Site A and sweet potato at Site C. Vegetables such as cabbage, tomato, and rape are planted ingardens at all of the sites. They are planted in March or April by farmers with suitable fields, suchthose near riverbanks or dambo (shallow wetlands). Some of the farmers continuously grow andharvest vegetables to sell, particularly at Site C.
Nov

Dec

Jan Feb Mar
Rainy season

Apr

May

Jun

Rainy season maize /sorghumJul

Aug Sep
Dry season

Oct
Planting
Harvesting

Dry season maize
Site A Cotton
Okra / beans etc.
Dry season okra /garden vegetables
Rainy season maize /sorghum
Dry season maize
Site B
CottonSite C
Sweet potato / okra etc.
Dry season sweet potato/ garden vegetables

Figure 2. Crop calendars for the study sites.
3

3.2 Spatial distribution
We measured the size of all cultivated fields at the three sites in the 2008_09 rainy and2008_09 dry seasons with the aid of hand-held GPS units (Garmin etrex, Garmin Ltd., USA) . Rainyseason fields were measured from March to April/2009. Dry season fields were measured from
August to October/2009. There were 80 households at Site A, 39 at Site B, and 95 at Site C. Table 1
and 2 show the crop distribution for each crop as a percentage of the total cultivated area for each of
the sites in the rainy and dry seasons, respectively. As noted previously, some other crops are usuallyplanted with maize in the same field. In these cases, the entire planted area was considered as theprimary crop, which was determined by the field’s owner.
Maize is the dominant crop grown during the rainy season, but there were many othertypes of crops planted, ranging from 9 at Site C to 11 at Site B (Table. 1). The percentage of area
under maize cultivation exceeded 70% at Sites B and C and was more than 45% at Site A, which
also had a large amount of cotton (44%). Site C had the largest percentage of land devoted to sweet
potato cultivation (20%). Other crops included sorghum, cowpea, sugar cane, sunflower, andgroundnuts, but none was larger than 5% of the total area at any site. Clearly maize dominated theplanted area, but the farmers planted a variety of crops.
At Site A, the predominant crop was okra in the dry season, followed by maize and garden
vegetables (Table. 2). At Site B, maize predominated, but sweet potato and vegetables each had a
25% share. At Site C, maize was planted on 90% of the total area and garden vegetables on theremaining 10%.

4

Table 1. Crop distribution in the rainy season for Sites A, B, and C. The values are the amount ofcultivated area for a given crop as a percentage of the entire cultivated area for that site.
Maize Cotton Sorghum Sunflower Groundnut Cowpea

Sweet
Sugar
Cassava
Bananapotatocane

Okra

Green Garden
Orchard Othersbeans vegetables

Total

Site A

45.7

44.2

4.2

0.0

0.0

0.4

0.5

0.0

1.4

0.0

3.2

0.1

0.1

0.0

0.1

100

Site B

87.5

1.3

2.2

2.0

0.4

0.5

1.4

0.0

0.02

0.4

3.8

0.0

0.3

0.0

0.0

100

Site C

69.6

5.9

0.8

0.0

1.5

1.3

20.5

0.2

0.0

0.0

0.0

0.0

0.1

0.1

0.0

100

Table 2. Crop distribution in the dry season for Sites A, B, and C. The values are the amount ofcultivated area for a given crop as a percentage of the entire cultivated area for that site.
Maize

Sweet
BananapotatoOkra

Green Garden
Othersbeans vegetables

Total

Site A

35.7

0.0

0.0

56.0

0.0

8.3

0.0

100

Site B

41.2

25.7

2.7

0.3

0.6

24.9

4.6

100

Site C

89.4

0.7

0.0

0.0

0.0

9.9

0.0

100

3.3 Sweet potato production
Sweet potato was planted in both the rainy and dry seasons in this area. In the rainy season,
20% of the cropped area at Site C was planted with sweet potato, but the amounts were muchsmaller (<2%) at Sites A and B (Table 3). Similarly, a much larger percentage of households planted
sweet potato at Site C than at the other two sites. In the dry season, Site B had the greatest
percentage of land used to cultivate sweet potato (25.7%) as well as the highest percentage ofhouseholds (17.9%). There was almost no production of sweet potato at the other sites during the dry
season. Clearly, sweet potato production varied by both site and growing season. On average, 30%of households planted sweet potato on 8.3% of total cultivated land during the rainy season.

5

Table 3. Sweet potato production by area and number of households who planted sweet potato at thethree study sites

Site A
Site B
Site C
Total

Rainy season
Area (ha)Households (No.)
0.5
(0.5)
1
(1.3)
0.9
(1.4)
5
(12.8)
22.0 (20.5)
59(62.1)
23.5
(8.3)
65
(30.4)

Dry season
Area (ha)Households (No.)
0.0
(0.0)
0
(0.0)
0.5 (25.7)
7(17.9)
0.1
(0.7)
1
(1.1)
0.7
(2.6)
8
(3.7)

The numbers in parentheses represent the percentage of the entire cultivated area for that site.

4. Farmer Familiarity with Sweet Potato Varieties
We were not only interested in the types of crops grown, but also in the varieties ofsweet potato grown. To clarify the farmers’ familiarity with sweet potato varieties, weinterviewed the household head or spouse at all households at the three sites from August to
September in 2009. Interviewees were asked about the number of varieties they were familiar with

as well as their features, including time to maturity, tuber size, color of the tuber skin, taste, pest
tolerance, and drought tolerance. A total of 77 households were interviewed at Site A, 38 at Site B,
and 82 at Site C. Demographic data for the interviewees are presented in Figure 3. The male tofemale ratios for respondents who reported their age were 35 to 30, 17 to 16, and 43 to 22 at Sites A,
B, and C, respectively.

The numbers do not match the total number of households because we wereunable to obtain age information for a few households at each site.

4.1 Number of varieties identified
Distributions of the number of identified sweet potato varieties for each site are shown in
Figure 4. In the figure, a “0” means one of two things: the farmer knew there were different varieties
but could not name them or the farmer was totally unfamiliar with any variety of sweet potato.
Farmers at Site C consistently could identify the most varieties, whereas the majority of farmers at

6

Site B could not identify a single variety and many could not do so at Site A as well. In fact, every
farmer at Site C could identify at least one variety. The average number of sweet potato varieties
identified by males was 0.9 at Site A, 1.4 at Site B, and 4.5 at Site C. A similar trend was observed
for females (1.2 at Site A, 0.5 at Site B, and 4.1 at Site C). The overall site averages were 1.1 at Site

80 - 89
70 - 79
60 - 69
50 - 59
40 - 49
30 - 39
20 - 29
10 - 19
0-9
no dataAge (years)

Age (years)

C (p<0.01).

010Site A

20
30
40
Responses (%)

80 - 89
70 - 79
60 - 69
50 - 59
40 - 49
30 - 39
20 - 29
10 - 19
0- 9
no data

80 - 89
70 - 79
60 - 69
50 - 59
40 - 49
30 - 39
20 - 29
10 - 19
0-9
no data

50

0

0

10

Site B

20
30
40
Responses (%)

Age (years)

A, 0.9 at Site B, and 4.4 at Site C. There were significant differences between Sites A and B and Site

Male

80 - 89
70 - 79
60 - 69
50 - 59
40 - 49
30 - 39 20
10
20 - 29
10 - 19
0-9
no data50

Female30010Site C

40

50

20
30
Responses (%)

40

80 - 89

6

5

5

4

3
2
1

0

60 - 69
50 - 59
40 - 49
30 - 39
20 - 29
10 - 19
0- 9
no data

4

3
2

0

1

Site A

25

50

Responses (%)

75

100

6

Male

5

Female

4
3
210

20

30

40

50

1
0

0
0

Varieties (No.)

6

Varieties (No.)

Varieties (No.)

Figure 3. Demographic characteristics (age and sex) of interviewees
at Sites A, B, and C.
70 - 790Site B

25

50

Responses (%)

75

100

0

Site C25

50

75

Responses (%)

Figure 4. Distribution of the number of sweet potato varieties identified by farmers at each site.

7100

4.2 Varieties and features
4.2.1 Identified varieties
The varieties of sweet potato identified and the distribution of the responses are presented
in Table 4. A total of 22 varieties were identified. Apart from the major varieties, there was a large
number of minor sweet potato varieties at each sites; Kalyabalumi, Kalembula, and Mandala at Site
A, Kalyabalumi and Mandala at Site B and Kalyabalumi, Kalembula, Muvuba Chacha, Simpa
Ubone and Fwaka. There were 12 varieties identified by farmers at Site A, 13 at Site B, and 6varieties at Site C. The varieties identified by farmers were very different among the three sites.
Only three varieties, Kalyabalumi, Kalembula, and Muvuba Chacha, were known at all three sites.
Mandala, Kapiri, and Ndindinkuni were identified at Sites A and B. The remaining 16 varieties wereidentified only at one site. Two of the varieties commonly noted at Site C were not mentioned at
Sites A or B. Ministry of agriculture, Zambia recommended the following improved sweet potato
varieties: Lukulu, Lukusashi, Lunga, Mulungushi, and Kalungwashi FoDiS (2009). None of thesevarieties was mentioned by a single farmer at any site, which means that these improved sweet
potato varieties have not yet been introduced in this area.

8

Table 4. Sweet potato varieties identified by farmers at the study sites
Name
Kalyabalumi
Kalembula
MuvubaChachaMandalaKapiriNdindinkuni
Sikamamba
Kayuwi Yuwi
Chilima Boofu
Bbwaki Bbwari
Kacharn
Libingi
CarrotKabikkagoko
Katukatu
KayuyuLukkanga
Lutembwe
Namukkolo
Simpa Ubone
Fwaka
Kasimpa
Bayanga

Site A
Rate (%)
19 (15)16 (12)Site B
Rate (%)
24 (9)
5 (2)Site C
Rate (%)
100 (82)
72 (59)

1

(1)

8

(3)

74 (61)25 (19)12 (9)
9 (7)
9 (7)
4 (3)
3 (2)
1 (1)
1 (1)
1 (1)

18
5
3

(7)
(2)
(1)

3
3
3
3
3
3
3

(1)
(1)
(1)
(1)
(1)
(1)
(1)
95 (78)76 (62)
1(1)

The rate is the percentage of households that identified a particular variety relative to the total
number of households interviewed at that site. The rates do not add up to 100% because somehouseholds identified more than one variety. The number of households is given in parentheses.
They do not add up to the total number of households because some households identified more than
one variety.

4.2.2 Features of the varieties
Figure 5 summarizes responses for the following features of the six main varieties of sweet
potato: maturation time, tuber size, color of tuber skin, taste, pest tolerance, and drought tolerance.

Maturation time
There were great differences between Sites A and C for Kalyabalumi, Kalembula, andMuvuba Chacha, and Site B was intermediate between the two for these varieties. There were also
differences between Sites A and B for Mandala, Kapiri, and Ndindinkuni. The identified maturation9

times increased from Site A to B to C. These differences may be the result of differences in theagro-ecosystems of the sites, for example, temperature or rainfall amount.
Tuber size
Sites A and C again showed notable differences and Site B was intermediate between thetwo for the first three varieties. There were also smaller differences between Sites A and B for thelast three varieties. Except for Kalyabalumi, tuber size increased from Site A to B to C.
Color of tuber skin
Except for Muvuba Chacha and Ndindinkuni, the identified tuber skin colors were very
similar for each variety. Kalyabalumi, Kalembula, and Kapiri ranged from white to yellow andMandala from white to orange. See Figure 5 for the color variations for Muvuba Chacha andNdindinkuni.
Taste
Mandala, Kapiri, and Ndindinkuni each generated consistently negative taste comments(normal taste). Kapiri generated contradictory comments, ranging from tasteless to sweet. The othervarieties had only positive comments such as good, sweet, and sweet and soft.
Pest tolerance
Pest tolerance comments were inconsistent between varieties and among sites. Overall,
40% of responses indicated the varieties were low tolerance and 36% that they were tolerant.
Drought tolerance
At Sites A and B, Kalyabalumi, Kalembula, and Muvuba Chacha were thought to be
tolerant to drought, but they were not considered to be tolerant at Site C.

10

100%

Responses (%)

80%
60%
Late
40%

Medium

20%

Early

0%
Site A Site B Site C Site A Site B Site C Site A Site B Site C Site A Site B Site A Site B Site A Site B

Kalyabalumi

Kalembula

Muvuba Chacha

MandalaKapiriNdindinkuni

Maturation time

100%

Responses (%)

80%
60%
Big
40%

Medium

20%

Small

0%
Site A Site B Site C Site A Site B Site C Site A Site B Site C Site A Site B Site A Site B Site A Site B

Kalyabalumi

Kalembula

Muvuba Chacha

MandalaKapiriNdindinkuni

Tuber size

100%
White

Responses (%)

80%

Cream white

60%

Yellow

Orange

40%

Pink
20%

Red
Purple0%Site A Site B Site C Site A Site B Site C Site A Site B Site C Site A Site B Site A Site B Site A Site B
Kalyabalumi

Kalembula

Muvuba Chacha

Color of tuber skin11

MandalaKapiriNdindinkuni

Brown

100%

Very Sweet

Responses (%)

80%

Sweet and Soft60%

Sweet and good

Sweet

40%

Good and Soft20%

Normal taste
Good

0%
Site A Site B Site C Site A Site B Site C Site A Site B Site C Site A Site B Site A Site B Site A Site B
Kalyabalumi

Kalembula

Muvuba Chacha

MandalaKapiriTastelessNdindinkuni

Taste

100%

Responses (%)

80%
60%
Low
40%

Medium

20%

High

0%
Site A Site B Site C Site A Site B Site C Site A Site B Site C Site A Site B Site A Site B Site A Site B

Kalyabalumi

Kalembula

Muvuba Chacha

MandalaKapiriNdindinkuni

Pest tolerance

100%

Responses (%)

80%
60%

Low
40%

Medium

20%

High

0%
Site A Site B Site C Site A Site B Site C Site A Site B Site C Site A Site B Site A Site B Site A Site B
Kalyabalumi

Kalembula

Muvuba Chacha

MandalaKapiriNdindinkuni

Drought tolerance

Figure 5. Sweet potato features identified by farmers at each site: (a) maturation time, (b) tuber size,(c) color of tuber skin, (d) taste, (e) pest tolerance, and (f) drought tolerance.

124.3 Planted varieties of sweet potato
Eleven households (14% of all households interviewed) planted sweet potato at Site A, 11(29%) at Site B, and 54 (66%) at Site C. These numbers include farmers who intercrop and use
mixed cropped fields. The planted varieties at each site are presented in Table 5. Only 10 of the 22
identified sweet potato varieties were cultivated, five at Site A, six at Site B, and five at Site C. The
number of varieties planted differed between the sites. Most households planted only one variety at
Site A, whereas about 90% of households at Site C planted multiple varieties and 20% of them
planted five.

Table 5. Varieties of sweet potato planted at the study sites
Name
Kalyabalumi
Kalembula
MuvubaChachaMandalaKapiriNdindinkuni
Chilima Boofu
Kabikkagoko
Simpa Ubone
Fwaka
Not known

Site A
Rate (%)
27 (3 )

Site B
Rate (%)
73 (8)
9 (1)Site C
Rate (%)
100 (54)
20 (11)31 (17)

36
27
18
9

(4)
(3)
(2)
(1)

27
9
9

(3)
(1)
(1)

9

(1)
89 (48)31 (17)

9 (1)

18

(2)

The rate represents the percentage of households that cultivated a given variety relative to the total
number of households that planted sweet potatoes at each site. The rates do not add up to 100%
because some households planted more than one variety. The number of households growing thevariety is given in parentheses. They also do not add up to the total number of households for thesame reason.

4.4 Simpson’s diversity index
Simpson’s diversity index was calculated from the results for sweet potato varieties
identified by farmers and for those actually planted (Table 6). Site C’s values were much higher forboth sets of results. Although farmers have knowledge of many varieties of sweet potato at Sites A
13and B, their knowledge of the varieties varied widely at both sites.

Table 6. Simpson’s diversity index for sweet potato varieties identified and planted by farmers at the
study sites

Sweet potato varieties known by farmer
Planted sweet potato varieties

Site A
0.086
0.015

Site B
0.069
0.034

Site C
0.324
0.148

5. Home Consumption and Sales
In this section, we examine household consumption of sweet potatoes and their use asa cash crop, both of which can enhance food security. Because Site C farmers were much morefamiliar with sweet potatoes, we focused on selected households at Site C.

5.1 Household consumption
Boiling the tubers of sweet potatoes in a small amount of water is the most common
cooking method in this area. The boiled tubers are sometimes dried for storage and later rehydrated
and mashed to make a dish called bupapa. Sweet potato leaves are sometimes fried and used as aside dish accompanying nshima, which is a staple food in Zambia made from a ground maize flour
called mealie-meal. Only two varieties are used for this purpose, most commonly Kalembula andoccasionally Kalyabalumi. Kalyabalumi leaves were said to have a slightly more bitter taste thanKalembula leaves.
We collected self-reported data from six Site C households on household consumption ofsweet potato tubers from May 2009 to April 2010. The respondents noted the number of times they
ate the tubers for breakfast, lunch, or supper inconsecutive two weeks a month during this period.
From these data, we calculated the average monthly frequency of consumption (Fig. 6). On average,14

sweet potato tubers were consumed about once every 3 days, but as can be seen in the figure, thefrequency peaked in May 2009 and decreased to almost nothing in March 2010. Sweet potatoes weremost commonly served at breakfast as a main dish, and they were almost always boiled. When they
were served at lunch and supper, they were served with nshima or other side dishes. In total, sweet
potato tubers were consumed at 12% of all meals during the study period. Sweet potato leaves wererarely consumed throughout the study period, possibly because of the attributes of the varieties
grown in the area, primarily Kalyabalumi and Simpaubone, the leaves of which are not considered tobe suitable for consumption.

Consumption frequency (%)

100
90
80
70
60

All meals

50

40

Breakfast

30

Lunch

20

Supper10
0

Figure 6. Monthly household consumption frequency of sweet potatoes for selected households at
Site C. The values are the monthly average percentage of meals at sweet potatoes are
consumed.

5.2 Sweet potato sales
Vegetables and other commodities are sold by farmers at a roadside market near Site C.
The Bbaamp market opened in the mid-1990s after economic liberalization and is located on themain road between Batoka and Maamba (Fig. 1). Many farmers sell products, including sweet
potatoes, to passengers on buses and other vehicles. We collected self-reported data from a sample of
13 women from 12 households, including the six households discussed in Section 5.1, from May
2009 to April 2010. The respondents reported the frequency and monetary value of sweet potato
15

sales inconsecutive two weeks a month . From these data, we estimated the average monthly sales
frequencies and average monthly income per household (Fig. 7). The sweet potato harvest began in
March, and the tubers were sold from March to September. The frequency of average monthly sales
peaked in July at 9 days per person. The average monetary value of the monthly sales fluctuatedfrom 0 to 270,000 kwacha (ZKW) per person and peaked in August. The average annual income was
ZKW 1,140,000 per person, which is equivalent to USD 248 (USD 1 = ZKW 4,600 as of September2009). The weekly average price of mealie-meal per 25-kg bag from May 2009 to April 2010 was
ZKW 50,000 at the nearest town (Sinazeze). Therefore, sweet potato sales were equivalent to 22.8
bags per person. Using the FAO (1992) estimated mealie-meal consumption rate of 418.6 g perperson per day, we calculated that the average yearly sales of sweet potatoes per person was

12

300

10

250

8

200

6

150

4

100

2

50

0

0

Sales income(1,000 ZKW)Sales frequency(/week/household)sufficient to purchase enough mealie-meal to feed 7.4 adults for a year.

Frequency
Sales

Figure 7. Average monthly sales frequency and income from sales of sweet potatoes for selectedhouseholds at Site C.

16

6. Conclusion
This study clarified that farmers planted sweet potatoes in both the rainy and dry seasonsin the study area, but production varied between the seasons and among the sites. Many Site C
farmers planted sweet potato in the rainy season, and the area of cultivation was the largest at thissite. Dry-season planting was most common at Site B, but the dry-season fields were much smaller
than the rainy-season fields. Overall, farmers could identify many sweet potato varieties, but they
did not plant all of the varieties identified. Although Sites A and B had more crop diversity innumber of varieties planted, Site C had a larger Simpson’s crop diversity index value than either Site
A or B.
Sweet potato was not a primary crop at Sites A and B, but it was important at Site C.
Further study at this site indicated that boiled sweet potato tubers were consumed about twice a week
on average and were most commonly eaten for breakfast. The leaves were rarely eaten. Sweet potato
sales generated sufficient income at this site to purchase enough mealie-meal to feed 7.4 adults for ayear. From these results, we conclude that the sweet potato can play a large role not only inhousehold consumption but also in enhancing food security by providing a source of income.

17

References
Cotter, J. and R. Tirado. 2008. Food security and climate change: The answer is biodiversity A
review of scientific publications on climate change adaptation in agriculture Report
December.
FAO, 1992. Maize in human nutrition. Food and Agriculture Organization of the United Nations,
FAO Food and Nutrition Series. Rome (Italy). 160 pp.
FoDiS, 2009. Growing Sweet potato in Zambia. FoDiS Information Series Ministry of Agriculture
and Co-operatives / Japan International Cooperation Agency Food Crop Diversification
Support Project, September.
Jayne, T.S., J. Govereh, P. Chilonda, N. Mason and A. Chapoto. 2007. Regional strategic analysis
and knowledge support system for Southern Africa (ReSAKSS-SA). ReSAKSS Working
Paper No. 2, June, Trends in Agricultural and Rural Development Indicators in Zambia.
Kapinga, R., Tumwegamire, S., Lemaga, B., Andrade, M., Mwanga, R. Mtunda, K., Ndolo, P.,
Nsumba, J., Agili, S., and Serwadda. B. 2005. Development of farmer based seed systems
for healthy planting materials and increased sweetpotato production in East and Southern
Africa. Africa African Crop Science Conference Proceedings, Vol. 7, pp. 1169-1173.
Rees, D., Kapinga, R., Mtunda, K., Chilosa, D., Rwiza, E., Kilima, M., Kiozya, H. and Munisi, R.
2001. Effect of damage on market value and shelf-life of sweetpotato in urban markets of
Tanzania. Tropical Science 41, 1-9.
VAM Steering Committee Zambia, 1998 A comparative analysis of the vulnerability conditions ofrural Zambia. Prepared by the Food, Health and Nutrition Information System, Ministry ofAgriculture, Food and Fisheries Programme Against Malnutrition, Meteorological
Department World Food Programme, FEWS/USAID Vulnerability Assessment and
Mapping Report.
Yatagai, A. 2011. Interannual variation of seasonal rain fall in South Zambia. In Vulnerability and
Resilience of Social-Ecological Systems, FR4 Project Report, Edited By C. Umetsu,
Research Institute For Humanity And Nature, Kyoto, pp. 206-212.
Zulu B., J. J. Nijhoff, T.S. Jayne and A. Negassa, 2000. Is the glass half-empty or half full? An
Analysis of Agricultural Production Trends in Zambia Working Paper No. 3, Food
Security Research Project Lusaka, Zambia.

18

List of Working Paper

No. 2008-001

Moses Mwale, Synthesis of Soil Management Options for Better
Targeting of Technologies and Ecological Resilience under Variable
Environmental Conditions

No. 2008-002

Thamana Lekprichakul, Impact of 2004/2005 Drought on Zambia’s
Agricultural Production and Economy: Preliminary Results

No. 2008-003

Gear M. Kajoba, Vulnerability and Resilience of Rural Society in
Zambia: From the View Point of Land Tenure and Food Security

No. 2008-004

Lawrence S Flint, Socio-Ecological Vulnerability and Resilience inan Arena of Rapid Environmental Change: Community Adaptation to
Climate Variability in the Upper Zambezi Floodplain

No. 2008-005

Tetsuya Nakamura, The Livelihood of ‘Escarpment Tonga’: A Case
Study of One Village, Southern Zambia

No. 2008-006

Chihiro Ito, Re-thinking Labour Migration in Relation to Livelihood
Diversity in African Rural Area: A Case Study in Southern Province,
ZambiaNo. 2009-007

Matheaus Kioko Kauti, Rural Livelihood Security Assessment for
Smallholders Undergoing Economic Changes and Agro-Climatic
Events in Central Kenya

No. 2009-009

Gear M.Kajoba, Vulnerability of Food Production Systems of SmallScale Farmers to Climate Change in Southern Zambia: A Search for
Adaptive Strategies

No. 2009-010

Chileshe L. Mulenga, Resilience of Rural Households andCommunities to Economic Shocks, HIV/AIDS and Recurrent
Droughts: The Case of Households and Communities in the Mwami
Area, Chipata, Zambia

No. 2009-011

Bennett Siamwiinde Siamwiza, An Historical Analysis ofVulnerability and Resilience in a Semi-Arid Region of Zambia

No. 2009-012

Chewe M. Chabatama, Ecological Adversity and Food Supply inNorthwest Zambia

No. 2011-013

Elizabeth Colson, Resilience as a Way of Life in Gwembe Valley

No. 2011-014

Noriko Narisawa, Diversified Livelihood of Peasant Women in
Southern Zambia

No. 2012-015

Hidetoshi MIYAZAKI, Yudai ISHIMOTO and Ueru TANAKA, The
Importance of Sweet Potatoes in Rural Villages in Southern Province,
ZambiaVulnerability and Resilience of Social-Ecological Systems
Resilience Project Home Page: www.chikyu.ac.jp/resilience

社会・生態システムの脆弱性とレジリアンス
レジリアンスプロジェクトHP: www.chikyu.ac.jp/resilience

Research Institute for Humanity and Nature (RIHN)Inter-University Research Institute Corporation, National Institute for the Humanities

457-4 Kamigamo Motoyama, Kita-ku, Kyoto, 603-8047, Japanwww.chikyu.ac.jp

大学共同利用機関法人 人間文化研究機構
総合地球環境学研究所〒603-8047 京都市北区上賀茂本山 457-4

www.chikyu.ac.jp