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Hoang Kim , Pham Van Bien and R.H. Howeler

Director, Hung Loc Agricultural Research Center (HARC); Leader of National Program of Cassava Breeding and Dissemination; Secretary of National Root Crops Program.

Director, Institute of Agricultural Science of South Viet Nam (IAS); Coordinator of National Cassava Program.

CIAT Cassava Asian Regional Program, Dept. Agric, Chatuchak, Bangkok, Thailand

International fund for Agricultural Development (IFAD)
Rome, Italy

Institute for Agricultural Science of South Viet Nam (IAS)
Ho Chi Minh City, Viet Nam

Centro Internacional de Agricultura Tropical (CIAT)
Cali, Colombia

The objectives of the study are:

To analyse the past and present situation of cassava in Viet Nam, with a view to describing the lessons learned from past development interventions and their implications for a strategy of future investment in cassava research and development


Cassava plays an important socio-economic role as a secondary crop in Viet Nam. In the north the crop is an important source of food and feed at the household level; in the south mainly as a source of cash income. In South Viet Nam cassava is predominantly used as a raw material for processing into a wide range of products, both at the household and small-scale processor level, generating employment in the rural sector.

Over the last seventeen years (1980–1997) the total area of secondary food crops has decreased, especially for sweet potato and cassava, while the maize area increased. Cassava has declined in the last seventeen years because of its relatively low profitability (low yield), low (or fluctuating) demand, price fluctuations and marketing problems. Soil fertility problems are also important. Processing is constrained, especially by raw material supply fluctuations and quality. The potential for processing technology is significant.

Cassava yields can potentially increase through the development of improved varieties; appropriate fertilizer use; intercropping or the rotation of cassava and beans; erosion control; weed control by mechanical or chemical means; and by more efficient crop management (especially labour). Cassava product marketing efficiency can be significantly improved by better information (price) and management of marketing systems.

Cassava varietal dissemination in Viet Nam has made rapid and consistent progress. The Viet Nam Root Crops Program, in cooperation with CIAT, has recently (1993–1996) selected and recommended two new cassava varieties: KM 60 and KM 94. In South Viet Nam the new cultivars are now planted on a fairly large acreage, already generating additional economic benefits of about five million US$, which is shared by processors, production organizers and small farmers according to their size of operation. In North Viet Nam, the total economic scale is much smaller; yet, little by little the new cultivars are spreading widely; here the additional cassava yields are converted into additional pig sales per family. It appears to be the most equitable contribution of crop breeding. Cassava, with the immediate possibility of yield increases, will play an increasingly important role as an income generator to upland farmers in Viet Nam.

Principal experiences in linking cassava R&D activities in Viet Nam include:

  1. Establishment of the Viet Nam Cassava Research and Extension Network (including advanced cassava farmers, researchers, extensionists, managers of cassava research and development projects, cassava trade and processing companies);

  2. The conducting of on-farm research, demonstration trials and farmer participatory research (FPR); and

  3. Ten mutual link-up activities (10Ts).

Six essential conditions for a successful cassava R&D program include: Materials, Markets, Management, Methods, Manpower and Money (6 Ms). Viet Nam now has favourable conditions for cassava development. However, other problems should be taken into account: price fluctuations and unstability of the market; crop competition; varietal degradation; varietal mixtures and genetic erosion; soil fertility degradation and erosion; high labour requirements; lack of financial resources and facilities from the government to support the cassava technology transfer work (while cassava farmers are very poor, especially those living in the midlands and mountainous regions where root and tuber crops are important food crops).

During the coming years the cassava planting area in Viet Nam will not be increased, but will remain within the range of 200 000 to 300 000 ha. However, cassava yields will increase by the adoption of new cassava varieties and more intensive cultural practices. On-farm research and transfer of technology for cassava production are key factors for cassava development. They are an important bridge linking science with production. Another top priority is to link small cassava farmers and processors to regional and international growth markets of cassava starch-based products by expanding existing cassava market, process and products analyses in Southeast Asia. This will serve as a basis for developing an action plan for integrated R&D of cassava production, processing and marketing.


Cassava sustains the lives of an estimated 500 million people in Africa, Latin America and Asia. The crop has a great potential for food security, not only at the family but also at the community as well as at national levels in many countries. Cassava has many advantages compared to cereal crops, in terms of drought tolerance, pest and disease resistance, adaptation to poor soils and an indeterminate harvest period. This is an ideal crop for emergency situations, such as during war or natural disasters (FAO, 1996).

Cassava processing at the household level is an important income generator in poor rural areas, particularly for women, not only-in Africa but also in Latin America and Asia. Cassava contributes to economic diversity and creates opportunities for development of other processing industries: for example, the cassava industries in Thailand and Brazil as well as in several African countries on a smaller scale (FAO, 1997).

Viet Nam ranks thirteenth in cassava production in the world. The average annual cassava production during 1993–1995 was 2.37 million tonnes and in 1996 it was about 2.50 million tonnes. However, Viet Nam is the fourth in export of cassava products in the world, after Thailand, Indonesia and China. The annual cassava export volumes averaged 30 thousand tonnes during 1992–1994 and increased up to 150 thousand tonnes in 1997. The Viet Nam cassava industry is still largely underdeveloped and the export volumes are small; however, it has potential, and the sector has been attracting foreign investments to the country for starch and MSG processing, particularly in South Viet Nam, since the early 1990s.

The International Fund for Agricultural Development (IFAD) is an agency that has funded research, field experiments, multiplication and dissemination of cassava varieties in Africa and Latin America. IFAD is developing a global research strategy for cassava in order to enhance global cassava research and development and exploit the potential of this crop for food security, income generation and development of cassava-based industries, including feed, food, paper, textile, alcohol and medicines. This process requires the close collaboration among governments of cassava growing countries, IFAD, cassava research institutions, donor organizations, non-government and private organizations.

The report: “Status of cassava in Viet Nam: Implications for research and development in the future” is a case study of Viet Nam to help formulate a global cassava research and development strategy by IFAD. The objective of this study is to analyse the past and present situation of cassava in Viet Nam, with a view to describing the lessons learned from past development interventions and their implications for a strategy of future investment in cassava research and development.

The report includes chapters on:

  1. Cassava production in Viet Nam

  2. Cassava processing and marketing

  3. Main problems in cassava production and consumption

  4. Recent progress in cassava research and extension activities

  5. Lessons learned from cassava development

  6. Implications for future cassava research and development in Viet Nam


2.1 Soils, topography and climate

Viet Nam is a humid tropical, long and narrow country, located between latitudes 8.5° and 23.5° North and longitudes 102° and 110° East. The narrowest part is only 40 km wide. Toward the east lies the sea and towards the west the Truong Son Mountain range. The terrain is highly varied and tends to slope down towards the sea. This results in marked differences in soils and climatic conditions between regions. Because of this topographic and climatic heterogenuity the country has been divided into seven more or less homogeneous agro-ecological zones (Figure 1), i.e. the north Mountainous Region (which includes the Northern Highlands and Midlands), the Red River Delta, the North Central Coast, the South Central Coast, the Central Highlands, the Southeastern Region and the Mekong Delta.

The soils of Viet Nam are closely associated with its topography. The mountainous and hilly areas of the northern and central part of the country are mainly Ultisols with some Oxisols in the more tropical regions of the south (Figure 2). Large areas of Inceptisols are found mainly in the Mekong and Red River deltas as well as along smaller rivers and near the coast. The more recently developed Entisols are found mainly along riverbanks and along the coast. By overlying the cassava production map on the soils map, it is possible to estimate the area of the various soil orders on which cassava is grown. Thus, it was estimated that in Viet Nam about 66% of cassava is grown on Utisols, 17% on Inceptisols, 7% on Oxisols, 4% on Alfisols, 3% on Entisols and 2% on Vertisols (Howeler, 1992). The soil pH generally varies from 4.5 to 6.0. (Pham Van Bien et al.,1996)

In North Viet Nam about 68% of the cassava growing area has a rocky soil, while 18 and 12% have clayey and sandy soils, respectively. Rocky soils are prevalent in Ha Son Binh and Ha Bac provinces. Cassava is grown mainly in areas with ondulating and hilly topography. About 89% of cassava in North Viet Nam is grown on these kinds of soils (Pham Van Bien etal,1996).

Figure 1

Figure 1. Cassava production areas in seven agro-ecological zones in Viet Nam in 1997. Each dot represents 1 000 ha cassava.

Figure 2

Figure 2. Soil map of Viet Nam. Adopted from FAO World Soil Map by R.H. Howeler.

In South Viet Nam most cassava soils are sandy in the Central Coastal area and in the Southeastern Region, while rocky soils predominate in Gia Lai-Kon Turn and are also common in Dac Lac province. The cassava growing areas in the provinces of the Central Highlands have a similar topography. In the Central Coastal Region and in the Southeastern Region, cassava is grown mainly on white-grey soils or coastal sandy soils. These regions are flat, soils are poor in nutrients and not suitable for rice cultivation. The cassava growing area in this type of soils accounts for more than 70% of the total cassava area of the south. In the Mekong Delta, cassava is not very important. However, cassava grows well on acid sulfate soils of the Mekong Delta under conditions of high nitrogen (N), potassium (K) and organic matter (OM) application. Cassava is not seriously affected by aluminum (A1) toxicity when grown in these soils. Due to these marked differences in cassava soil characteristics, research in the north should concentrate on erosion problems and soil fertility enhancement, whereas in the south research on cassava soil improvement and conservation by using intercropping systems is of highest priority (Pham Van Bien et al.,1996).

The climate varies substantially between regions (Figure 3). The northern part of the country has a subtropical climate with low winter (15°C) and high summer (29°C) temperatures. Most rain falls during the summer months of May to September, but during the winter months of January-March there are many rainy days with almost constant drizzle, resulting in a low number of sunshine hours, In the south, however, the climate is tropical with relatively small fluctuations in monthly temperatures (25–29°C). The rainy season is about one month delayed compared with the north, but total rainfall is similar. The dry season in the south is more intense, due to an almost complete lack of rain during 5–6 months. In the Central Coastal Region total rainfall is high, but it is poorly distributed with very heavy rainfall from September to November and a long dry season of 7–8 months (Nguyen Van Thang, 1996).

2.2 Cassava growing areas

Table 1 shows that in Viet Nam agriculture, food production plays the most important role, accounting for 98% of annual crop area (over 8.2 million ha). Flooded rice is by far the most important, having an area of 7.09 million ha and a production of about 27.65 million tonnes in 1997. Other food crops are grown on 1.17 million ha, with a production of 2.60 million tonnes in rice equivalents (General Statistical Office, 1998). The main food of the Vietnamese people is rice, which accounts for 88–95% of daily food intake. But this varies among regions. Other food crops include maize, sweet potato and cassava. These subsidiary food crops are very important, because they supply not only food for humans but also feed for animals, and serve as raw material for the food industry (alcohol, maltose, cakes, sweets, noodles, etc). Cassava is a major raw material for the food industry.

Cassava is among the four most important crops in Viet Nam. It occupies an area of about 238 700 ha (Table 1). The crop is grown in almost every province (Figure 1), especially in Son La (15.2), Thanh Hoa (14.4), Quang Nam (12.4), Gia Lai (14.0), Kon Turn (11.2), Nghe An (10.9), Binh Dinh (10.8), Quang Ngai (10.5), Phu Tho (8.6), Hoa Binh (8.6), Yen Bai (8.2), Lai Chau (8.2) and Ba Ria-Vung Tau (7.7 thousand ha) provinces (General Statistical Office, 1998).

Figure 3

Figure 3. Agro-climatic map of Viet Nam. Adapted from Agro-climatic map of SE Asia. Source: Huke, 1982.

Table 1. Production of principle crops in Viet Nam in 1997.

CropArea ('000 ha)Yield (t/ha)Production ('000 t)
Food crops   
Rice7 091.23.9027 645.8
Sweet potato267.46.141642.5
Annual industrial crops   
Sugarcane251.145.5111 428.2
Perennial industrial crops   
Rubber329.4 180.7
Coffee (beans)270.0 400.3
Cashew (nuts)250.0 120.0
Tea (dry)81.7 52.3
Pepper7.7 10.7

Source: General Statistical Office 1998

Cassava production has not been stable, as indicated by the decline in planted area from 437 000 ha in 1980 to only 238 700 ha in 1997 (Figure 4). This decline occurred throughout the country, but particularly in the southern part of South Viet Nam, where cassava had to compete with more valuable crops. Cassava is grown mainly by small farmers, but there are several state-farms of over a thousand hectares in the country.

The yield of cassava in Viet Nam has been increasing slightly, but is still very low. Yields gradually increased from 7.5 t/ha in 1980 to 9.0 t/ha in 1992; it was about 8.3 t/ha in 1997. There are few provinces harvesting over 10 t/ha of fresh roots, even though there were many demonstration plots which produced over 30 t/ha in Dong Nai, Binh Phuoc, Tay Ninh, Ha Bac, Hoa Binh and Vinh Phu provinces. Very low yields are obtained mainly in the North Central Coast, the South Central Coast and the Red River Delta (Hoang Kim and Pham Van Bien, 1996).

2.3 Cassava cultural practices

Land preparation: Cassava land preparation methods vary among agro-ecological regions. On the sloping soils of the mountainous regions of both North and South Viet Nam, most cassava fields are plowed once, while in the Red River Delta and the North and South Central Coastal Regions they are plowed twice. Especially in some cassava areas under intensive cultivation, such as in Son La, Hoa Binh and Quang Binh provinces, many farmers plow their cassava fields up to three times. After plowing, most of the farmers harrow their land once in the south, once or twice in the north, but three to four times in Son La, Hoa Binh and Quang Binh provinces. However, more than half of all farmers in both North and South Viet Nam do not harrow their fields at all, but plant directly after plowing or manual land preparation. Nearly all tillage for cassava is done by hand or with animals. Only in some provinces of South Viet Nam (Lam Dong, Tay Ninh, Binh Duong, Binh Phuoc and Dong Nai) cassava land cultivation is done with tractors. According to cultural traditions of each region, farmers plant cassava on ridges or on the flat. In both North and South Viet Nam about 50% of the cassava area is planted on ridges and 50% on the flat. However, large differences exist among provinces, with farmers in some provinces, like Hai Hung, Son La, Hoa Binh and Quang Nam, planting predominantly on ridges, while those in Gia Lai, Kon Turn, Dac Lac, Ha Giang, Tuyen Quang and Bac Thai planting predominantly on the flat (Pham Van Bien et al., 1996). However, in production and experimental plots the two different cassava planting methods did not show any significant difference in yield. The ridge planting seems to be more suitable in heavy soils or on light grey and sandy soils which are poor in nutrients. On relatively good soils, flat planting may produce higher yields due to better land use.

Figure 4

Figure 4. Cassava area, production and yield in Viet Nam from 1976 to 1997.

Planting time: The planting time is variable, depending on local climatic conditions and cropping patterns (Figure 5). Generally, farmers plant cassava either at the beginning (first or second semester) or at the end (4th semester) of the rainy season. In the provinces of the North Mountainous Region and Red River Delta, the planting is done from February to April, when soil moisture increases due to spring rains. However, the low temperature in February is a limiting factor, so in many areas cassava planted in March produces better growth and higher yields. In the North Central Coastal Region, planting usually starts at the end of the year (November–December), while in the South Central Coast and the Central Highlands cassava planting is generally done in the first semester; the harvest takes place from August to October before the height of the rainy season, which may cause flooding. In the Southeastern Region, cassava is generally planted in the second semester, at the beginning of the rainy season (April–May), but in Tay Ninh province most cassava is planted at the end of the rainy season (October).

Stake preparation and storage: Almost in every region farmers use their own cassava stems for planting. Only a few buy their stakes, mainly the medium- and large-scale farmers of Tay Ninh and Khanh Hoa provinces. Stake quality also influences cassava growth and yield. At the cassava harvest, long stems of 10 to 12-month old plants, free of diseases and insects, are selected to cut stakes. The duration of stake storage varies from <1 to >12 weeks, depending on the harvesting time and the time of planting the next cassava crop. In the provinces of the North Mountainous Region and the Central Coastal Regions many farmers plant stakes taken from cassava stems harvested during the previous month. But in parts of the North Mountainous Region, in the Red River Delta, in the Central Highlands and the Southeastern Region cassava stakes are normally stored 5–12 weeks before planting. If it is necessary to store stakes for a long time, most farmers place stems, tied in bundles, in a vertical position in a shaded area under trees, or cover the stems with leaves to keep them fresh and viable. Under conditions of reduced sunlight and low temperature of the north, some farmers store stems horizontally in an open field and still maintain good quality. However, the majority of farmers in both North and South Viet Nam store stems in a vertical position in the shade (Pham Van Bien et al., 1996).

Figure 5

Figure 5. Cassava cropping times in eight agro-ecological regions of Viet Nam. Dotted lines in diagram indicate the earliest or latest harvesting dates of cassava (from Cassava Production Survey, 1990/91). Map indicates isotherms for the temperature during January, as well as the rainfall distribution in various locations (adapted from Khi Hau Viet Nam, 1987).

Planting method: Most farmers in Viet Nam plant stakes horizontally (76% in the north, 68% in the south). This planting method is suitable mainly on poor soils with thin surface soils. This method maintains adequate moisture in the stakes for sprouting and for root development at the early stage. Vertical planting is used by farmers of a few provinces, such as Quang Binh, Quang Nam, Da Nang and Lam Dong, where the planting is done at the end of the wet season with heavy rain and high moisture content in the soil. In many regions, mainly in the Central Coastal Region and the Central Highlands, farmers plant stakes in a slanted position to combine the advantages of the two previous planting methods. In a slanted planting position, cassava has a relatively good root development, it can take full advantage of the soil depth and generally produces high yields, especially in areas where the surface soil is deep. Slanted planting is done mainly in Quang Nam, Da Nang (71.0% of farmers), Quang Binh (72.5%), Nghe An, Ha Tinh (45.9%) and Lam Dong (40%).

Plant population and spacing: Cassava is planted at various spacings depending on the region. Most of the farmers use a spacing between rows of 50–100 cm and between plants in the row of 50–100 cm. In some provinces, farmers adopt a wider spacing (in the North Mountainous Region and the Central Highlands) due to a thicker surface soil layer. In contrast, in some provinces, such as Ha Bac, Tay Ninh, Quang Ngai and Song Be, a closer spacing (50 × 50 to 100 × 50 cm) is used because of poor soils. Therefore, the cassava plant density in these provinces increases up to 20 000–25 000 plants/ha, whereas in Ha Giang, Tuyen Quang, Cao Bang, Bac Can, Lang Son, Dac Lac, Lam Dong and Khanh Hoa a plant density of less than 15 000 plants/ha is generally used.

Fertilization: Cassava grows rather well on poor soils but to produce high yields the crop requires a large amount of nutrients. To maintain high yields it is necessary to maintain the fertility of the soil. Otherwise, with time, soils will become poorer and cassava yields will decrease. In some provinces of the Red River Delta and the Central Coastal Regions farmers apply 5–7 tonnes of manure per hectare. But in other areas the amount of manure applied is generally much lower (less than 2 t/ha). Fertilizer N is applied to the cassava fields at a rate of 0–50 kg N/ha; highest rates are applied in the provinces of the Red River Delta, the South Central Coast and the Southeastern Region, especially in Tay Ninh. The average K application rate for the whole country is only about 19 kg K2 O/ha. However, a higher rate of 30–90 kg K2 O/ha is used in Ha Bac, Hai Hung, Ha Son Binh and Tay Ninh provinces. A rate of 50–100 kg K2 O/ha is generally needed to replace the K removed in the root harvest. Due to the abundant availability of single superphosphate in the north, P is applied to cassava at a fairly high rate of 15–30 kg P2 O5/ha in some provinces of the North Mountainous Region, in the Red River Delta and in the North Central Coast. A similar P rate is also used in Tay Ninh province of the Southeastern Region. However, in other parts of the North Mountainous Region, the South Central Coast and the Central Highlands, P application rates are very low. In general, chemical fertilizers are applied to cassava fields at low rates. Due to a lack of resources, farmers usually apply fertilizers only to other crops. When the cassava price fluctuates and their income from cassava production is not stable, they can not afford to apply large amounts of fertilizers to cassava. Thus, the application of nutrients to cassava soils in the form of animal manure and through intercropping with grain legumes can play a significant role in increasing cassava yields and maintaining soil fertility.

Weeds, diseases and pests. Weeds cause a decrease in cassava yield by competing for light, water and nutrients, especially in the rainy season and at the early growth stage. Weed control is done up to four times, mainly by hand, using a hoe. Most farmers weed two-three times during a crop season. Due to the high temperature all through the year in the south, the number of weedings in that region is slightly higher than in the north. The last weeding is done when cassava is about four months old and the crop canopy completely shades the ground. No herbicides are used to control weeds in cassava fields.

Diseases and insects are not very important in cassava and no serious damage to cassava production has been reported. Most farmers do not report the presence of any insect pests in cassava. Only mites are reported to damage young cassava plants in the Central Coastal Region of the north, but the area affected is limited. The principal cassava diseases are cassava bacterial blight (caused by Xanthomonas manihotis) and Cercospora leaf spot (caused by Cercospora sp.).No good control means are available except the use of clean planting material and resistant varieties. A study in 1968 in Viet Nam reported 19 diseases on cassava caused by different pathogens, but none are of economic importance.

Intercropping: In the north, cassava is generally planted in monoculture. After many years of cassava monoculture, soil productivity is often reduced due to erosion and nutrient exhaustion, resulting in a decrease of cassava yields. Cassava-based intercropping systems in the north occupy less than 10% of the area, while in the south, this area reaches 30–40%. In Binh Thuan , Ninh Thuan, Gia Lai, Kon Turn, Dac Lac and Dong Nai provinces, the area under intercropping with cassava is as high as 70–90%. Generally, maize, groundnut, black bean and mungbean are used as intercrops with cassava. Besides these, cashew nut, fruit trees, vegetables, soybean and winged bean are also intercropped with cassava, but to a lesser extent. Although we can show the good effect of cassava-based intercropping systems on soil conservation, most farmers are concerned only with the economic aspects of the intercropping systems.

Harvesting: Harvesting time is an important factor affecting cassava yield. If the farmer harvests too early, cassava is still young, and the starch content and yield are low. In areas where cassava is grown for fresh human consumption, farmers harvest from six to seven months after planting up to complete maturity (at 11–12 months). When cassava is consumed as boiled fresh roots, farmers in some areas harvest cassava at less than 6 months after planting. However, the majority of cassava is harvested after 10–12 months, especially in the south, where the processing of cassava into different products requires a high starch content in the roots (Pham Van Bien et al., 1996).

2.4 Socio-economic conditions

Cassava farm characteristics: In line with several other Southeast Asian countries, farm size in Viet Nam is small and does not vary much among locations. But, cassava farms in the Southeastern Region are on average double the size of those in North Viet Nam. Cassava area per farm for all of Viet Nam is small as well, and average 0.27 ha, with extremes for the Southeast (0.85 ha) and the North Mountainous Region (0.20 ha), as can be seen in Table 2. When farms are classified according to size, 31.6% of the sampled farms are smaller than 0.6 ha, 35.5% are between 0.6–1.05 ha, and the remaining 33% are (slightly) larger than 1.05 ha (Pham Thanh Binh et al., 1996).

Cassava production costs and revenues: The total variable cost of cultivation in 1991 was about US$154/ha (Table 3); at an average root yield of 12.4 t/ha, the production cost would beUS$14.1/t fresh roots (Table 4). Gross income is US$326/ha. Net income is US$173/ha. Gross return to labour is US$1.16/mdays (Table 5). On average, labour accounts for 61% of cassava production costs. In some regions, like the Red River Delta and the North Central Coast, this may be as low as 49.5 and 57.3%, respectively. In other zones, like the Central Highlands, this may be as high as 80.6%. The average labour requirement is 204 mdays/ha (Table 6). The data shows that on average, significantly more labour is required in the north (322 mdays) than in the South (175 mdays), with a large variation among different provinces. The second largest cost item is fertilizer, constituting 15.6% of total production cost for the whole country, 19.0% in the north and 11.8% in the south (Figure 6). In the Southeastern Region (Dong Nai, Song Be, Ba Ria-Vung Tau, Tay Ninh and Ho Chi Minh city) the main cassava crop season constitutes the planting in May and harvesting from November to April, and the secondary crop season of planting in October and harvesting from August to January. The (approximate) monthly fresh root output distribution for the Southeastern Region: Jan 14%; Feb 14%; Mar 15%; Apr 12%; May 4%; Jun 2%; Jul 2%; Aug 3%; Sept 6%; Oct 8%; Nov 11% and Dec 12%.


3.1 On-farm cassava processing and sale

Cassava on-farm utilization can be divided into auto consumption (human and animals), further processing (and sales) and sales of fresh roots. In Viet Nam (Table 7 and Figure7) more than one third is consumed on-farm (12.2% for human consumption and 22.4% for animal feed) and the remainder is on-farm processed (16.8%) or sold as fresh roots (48.6%, mainly for processing). The amount of fresh roots that is sold can go to various destinations: 1) to local starch processors; 2) to the local market, where it is sold directly to consumers; and 3) to large starch factories through several middlemen and assemblers. The price of cassava fresh roots fluctuate markedly in Viet Nam. It depends mainly on the price in the international market and somewhat on domestic demand. The price was high in 1995 (500 VND/kg fresh root) but decreased in 1996 (220 to 320 VND/kg) and increased again in 1997. In October, 1997 the fresh root price at the Vedan factory - Dong Nai province - was 400 VND/kg (US$ 33.9/tonne). The fresh root price in the Central Coast Regions and Central Highland (180 to 250 VND/kg) is generally lower than that in the Southeastern Region (220 to 320 VND/kg). In remote areas the price can be very low (120 to 220 VND/kg) due to transportation problems.

Table 2. Characteristic of surveyed households in Viet Nam, 1991.

IndicatorUnitNorth Viet NamSouth Viet NamTotal Viet Nam
North Mount. RegionRed River DeltaNorth-Central CoastSub-TotalSouth-Central RegionCentral HighlandsSouth-Eastern RegionSub-Total
Number of households surveyed 287961024852731002205931 078
Number of provinces surveyed 52294331019
Average cassava areaha0.
Small size farm (< 0.6 ha)%47.7440.8615.6939.6339.7816.0010.5525.0031.60
Medium size farm (0.6–1.05 ha)%41.1144.0951.9643.9836.1525.0020.6428.5535.50
Large size farm (>1.05 ha)%11.1515.0532.3516.3924.0959.0068.8146.4533.00
Private households%64.6979.1795.0573.9191.2196.00100.0095.2285.59
Cooperative households%35.3120.834.9526.098.794.000.004.7814.41
Experience of farmer <3 years%0.7013.547.844.741.830.0010.914.894.82
Experience of farmer 4–5 years%2.796.253.923.715.138.809.557.255.66
Experience of farmer 6–10 years%17.4215.6321.5717.9416.4844.0031.8226.8122.82
Experience of farmer > 10 years%79.0964.5866.6773.6176.5648.0047.7361.0566.70
Average pigs/householdhead2.662.272.792.611.932.541.701.952.25
Average cattle/householdhead1.481.422.531.691.381.280.621.081.36
Average chickens/householdhead26.4816.9920.0523.257.8111.1810.409.3415.60

Source: Pham Thanh Binh et al., 1996

Table 3. Cassava production costs (US$/ha) for total cropping cycle by province and region and Viet Nam in 1991.

CodeProvince/RegionTotal costLabourMaterialsFertilizerAnimal powerTractorPackingOtherLand rentCreditImplement
ANORTH VIET NAM179.69107.3112.7834.609.720.343.250.266.820.614.00
INorth Mountainous Region154.65101.839.9826.985.640.
04Ha Giang + Tuyen Quang138.7989.649.2624. 5.20
08Hoang Lien Son128.21107.600.355.400.590.003.270.995.410.004.60
09Bac Thai134.22126.331.351.490.660.
11Vinh Phu169.1770.6620.1947.5017.121.097.530.
12Ha Bac201.07118.8618.5460.862.490.
IIRed River Delta224.83111.3615.1963.1912.570.000.150.4212.043.016.90
14Ha Son Binh217.36102.6315.7754.4916.760.000.200.5615.953.907.10
15Hai Hung245.29137.5313.4889.320.
IIINorth Central Coast207.82119.0618.4930.2418.630.833.660.0814.590.142.10
19Nghe An + Ha Tinh202.07110.0916.0926.1221.360.635.650.0019.130.003.00
20Quang Binh216.53132.4022.0636.3814.581.110.700.217.840.350.90
BSOUTH VIET NAM133.0982.1612.4815.819.581.240.361.927.720.021.80
IVSouth Central Coast146.5785.1110.1322.5512.770.160.781.7110.460.002.90
23Quang Nam + Da Nang147.9388.939.9428.8813.070.000.842.612.660.001.00
24+25Quang Ngai + Binh Dinh162.98102.4210.2521.2815.060.001.640.508.930.002.90
27Khanh Hoa148.1878.766.3615.0014.530.000.070.0926.470.006.90
28Binh Thuan + Ninh Thuan127.9970.1913.5124.328.730.590.523.435.400.001.30
VCentral Highlands131.84106.236.821.276.583.
29Gia Lai + Kon turn103.5657.1410.230.0014.710.000.000.0321.430.000.02
30Dac Lac90.3281.642.160.173.600.860.000.001.890.000.00
31Lam Dong166.52143.077.442.454.
VISoutheastern Region116.6967.4718.0014.006.971.710.013.054.520.060.90
32Binh Duong + Binh Phuoc89.7966.446.935.475.342.
33Tay Ninh156.4154.5239.7035.3314.112.810.003.686.230.030.00
34Dong Nai108.8576.4711.425.983.462.750.024.674.180.001.90
 TOTAL VIET NAM153.8493.4212.6224.229.840.831.651.177.310.282.70

Note: US$1 = 7 000 VND

Source: Pham Thanh Binh et al., 1996

Table 4. Cassava production costs (US$/ton fresh roots) for total cropping cycle by province and region in Viet Nam in 1991.

CodeProvince/RegionTotal costLabourMaterialsFertilizerAnimal powerTractorPackingOtherLandCreditImplement
ANORTH VIET NAM15.338.431.193.700.840.
INorth Mountainous Region9.836.370.641.780.370.
04Ha Giang + Tuyen Quang8.155.270.541.410.240.000.390.
08Hoang Lien Son10.128.500.030.430.
09Bac Thai6.686.
11Vinh Phu14.255.961.704.001.440.090.630.000.430.000.00
12Ha Bac9.965.890.923.
IIRed River Delta21.2811.281.346.690.690.
14Ha Son Binh17.708.521.314.251.390.
15Hai Hung24.8614.051.389.
IIINorth Central Coast14.907.651.602.641.460.
19Nghe An + Ha Tinh9.973.161.191.941.580.050.420.000.420.000.21
20Quang Binh19.8412.142.023.341.340.
BSOUTH VIET NAM12.928.431.081.150.950.
IVSouth Central Coast14.938.721.032.291.300.
23Quang Nam + Da Nang14.708.840.992.871.300.
24+25Quang Ngai + Binh Dinh19.2112.081.202.511.780.
27Khang Hoa12.436.610.531.
28Binh Thuan + Ninh Thuan13.417.361.422.550.910.060.050.360.570.000.13
VCentral Highlands14.5311.080.850.
29Gia Lai + Kon tum15.318.451.510.
30Dac Lac10.759.720.260.020.430.
31Lam Dong17.5315.070.780.260.420.630.000.000.300.000.07
VISoutheastern Region9.305.511.371.070.560.
32Binh Duong + Binh Phuoc8.296.140.640.510.490.
33Tay Ninh9.613.352.442.170.870.
34Dong Nai10.
 TOTAL VIET NAM14.128.431.132.420.890.

Note: US$1 = 7 000 VND

Source: Pham Thanh Binh et al., 1996

Table 5. Cassava production costs and revenues in Viet Nam, 1991.

CodeProvince/RegionGrowing cycle
Production cost
Farmgate price
Gross income (US$/ha)Net income
Gross return to labour
ANORTH VIET NAM10359179.6914.5424.10350.44170.750.950.98
INorth Mountainous Region10343154.6516.2623.62384.05229.401.481.12
04Ha Giang + Tuyen Quang10307138.7917.0222.86389.08250.291.801.26
08Hoang Lien Son9343128.2112.6522.85289.08160.871.250.84
09Bac Thai13375134.2220.1423.58474.92340.702.541.27
11Vinh Phu8295169.1711.8522.18262.8393.660.550.89
12Ha Bac10406201.0720.1625.91522.31321.241.601.28
IIRed River Delta9393224.8311.4724.86285.1060.270.270.72
14Ha son Binh9377217.3612.0324.30292.3675.000.350.77
15Hai Hung10442245.299.7825.61250.525.230.030.57
IIINorth Central Coast10371207.8212.4524.99311.18103.360.500.84
19Nghe An + Ha Tinh11315202.0713.4925.71346.87144.800.721.10
20Quang Binh10455216.5310.9024.29264.7348.200.220.58
BSOUTH VIET NAM11215133.0910.6128.41301.43168.341.261.40
IVSouth Central Coast10248146.579.9526.14260.10113.530.771.05
23Quang Nam + Da Nang10272147.9310.0627.14273.05125.120.851.00
24+25Quang Ngai + Binh Dinh11289162.988.4727.14229.9066.920.410.79
27Khanh Hoa10232148.1811.9125.70306.06157.381.061.32
28Binh Thuan + Ninh Thuan10201127.999.5424.30231.31103.820.811.15
VCentral Highlands13191131.848.5432.42276.90145.061.101.45
29Gia Lai + Kon tum10136103.566.7632.86222.11118.551.140.63
30Dac Lac1018790.328.4032.88276.23185.912.061.48
31Lam Dong15221166.529.4930.71291.49124.970.751.32
VISoutheastern Region10185116.6912.3727.92345.37228.681.961.87
32Binh Duong + Binh Phuoc1017888.7910.8227.85301.36211.572.361.69
33Tay Ninh10142156.4116.2827.67450.48294.071.883.17
34Dong Nai10217108.8510.8428.33307.07198.221.821.41
 TOTAL VIET NAM10280153.8412.3626.41326.39172.551.121.16

Note: US$1 = 7 000 VND

Source : Pham Thanh Binh et al., 1996

Table 6. Average labour utilization in cassava production in Viet Nam, 1991.

CodeProvince/RegionTotal mdaysHiredFamilyExchange
per hamdays%mdays%mdays%
ANORTH VIET NAM3225717.5726381.6830.75
INorth Mountainous Region3004715.5625083.3341.11
04Ga Giang + Tuey Quang2975317.7624482.1510.09
08Hoang Lien Son2464116.8319278.05135.12
09Bac Thai3083611.6127288.3100.00
11Vinh Phu3018026.4222273.7500.00
12Ha Bac53411421.3442078.6500.00
IIRed River Delta4147518.2533881.6400.00
14Ha Son Binh3736016.1631383.9100.00
15Hai Hung65016425.2648674.7700.00
IIINorth Central Coast3187824.6224075.4700.00
19Nghe + Ha Tinh2706323.2220776.6700.00
20Quang Binh45112126.9332972.9500.00
BSOUTH VIET NAM1754525.5812772.5731.85
IVSouth central coast2966321.2723278.3810.35
23Quang Nam + Da Nang46814430.7532268.8020.48
24+25Quang Ngai + Binh Dinh46111224.2534975.7000.00
27Khanh Hoa2082713.1617985.0610.78
28Binh Thuan + Ninh Thuan3258124.8424475.0800.08
VCentral Highlands2324519.2718178.0262.71
29Gia Lai + Kon Tum2064923.7915776.2100.00
30Dac Lac1804122.6012770.56126.84
31Lam Dong2814616.2323182.2141.56
VISoutheastern Region1313930.098967.9431.97
32Binh Duong + Binh2407330.5916669.1710.24
33Tay Ninh904145.614651.1133.28
34Dong Nai1622616.2413281.4842.28
 TOTAL VIETNAM2044723.0615475.4931.45

Source: Pham Thanh Binh et al., 1996

Table 7. Relative shares (%) of on farm cassava utilization in Viet Nam, 1991.

CodeProvince/RegionHuman ConsumptionAnimal feedFurther processedSoldTotal on-farm consumedFurther processed and sold
ANORTH VIET NAM19.1034.907.0039.0054.0046.00
INorth Mountainous Region15.4039.406.5038.7054.8045.20
04Ha Giang+Tuyen Quang22.6042.908.8025.7065.5034.50
08HOang Lien Son18.7038.4014.7028.2057.1042.90
09Bac Thai11.6040.201.1047.1051.8048.20
11Vinh Phu37.9046.9010.504.7084.8015.20
12Ha Bac6.9030.807.5054.8037.7062.30
IIRed River Delta22.0023.803.4050.8045.8054.20
14Ha Son Binh21.7022.903.7051.7044.6055.40
15Hai Hung29.7032.300.3037.7062.0038.00
IIINorth Central Coast27.5028.8011.2032.5056.3043.70
19Nghe An + Ha Tinh23.9031.1013.0032.0056.0045.00
20Quang Binh39.2021.805.3033.7061.0039.00
BSOUTH VIET NAM6.7013.7024.4055.2020.4079.60
IVSouth Central Coast10.9019.4040.0029.7030.3068.70
23Quang Nam + Da Nang14.9032.700.0052.4047.6052.40
24+25Quang Ngai + Binh Dinh31.1022.100.0046.8053.2046.80
27Khanh Hoa4.805.5071.0018.6010.3089.70
28Binh Thuan + Ninh Thuan12.9051.800.1035.2064.7035.30
VCentral Highlands2.1012.2032.7053.0014.3085.70
29Gai Lai + Kon Tum3.6015.500.0080.9019.1080.90
30Dac Lac1.6010.4048.7039.3012.0088.00
31Lam Dong0.4011.1044.9043.6011.5088.50
VISoutheastern Region5.2011.808.8074.2017.0083.00
32Binh Duong + Binh Phuoc5.1017.2026.4051.3023.3077.70
33Tay Ninh0.800.000.0099.200.8099.20
34Dong Nai5.9011.803.9078.4017.7082.30
 TOTAL VIET NAM12.2022.4016.8048.6034.6065.40
Figure 6
Figure 7

Figure 6. Relative cassava production cost shares in North and South Viet Nam in 1991. Source: Pham Thanh Binh et al., 1996.

Figure 7

Figure 7. Relative shares (%) of on-farm cassava utilization by agro-ecological regions in Viet Nam, 1991.
Source: Pham Thanh Binh et al. 1996.

3.2 Cassava fresh roots, dry chips and starch

Cassava consumption for animal production, both in fresh root and dry chips or flour form (both at the farm and by industry) accounts for most (73.1%) of the total cassava produced in Viet Nam. Cassava starch production is the second largest usage, representing about 20% of total production. Cassava in the form of fresh roots for human consumption accounts for 12.2%, as chips for export 4.9%, and for other home processing purposes (dry chips not included) 6.0%. Cassava starch processing generates the following products: a) wet starch; b) dry starch divided into three quality classes; and c) by-products, which are the peel, cellulose and latex. Only a small volume of high quality starch is processed on-farm. This is often further processed to upgrade quality and then further utilized (in other areas). The majority of starch is processed in rural and semi-urban villages and factories, or in semi-urban processing centers. (Pham Thanh Binh et al., 1996). In 1992, cassava dry starch was used for the following purposes: home consumption (56.9%), in food processing (35.6%), export and for several industrial purposes (7.4%), such as textiles, pharmaceuticals, cardboard, monosodium glutamate (MSG), glucose, maltose and plywood. The total demand for cassava roots for starch production (both wet and dry starch) was about 395 077 tonnes in 1992. About 20% of this was used for wet starch production, mostly for local processing into low quality noodles (Dang Thanh Ha et al., 1996). Recently, the cassava market situation has changed due to economic developments, but there are no available data.

3.3 Cassava starch-based products and consumption

Home consumption accounts for the largest share (about 40 000–45 000 t/year) of cassava starch usage. It is used to make different kinds of cakes and cookies, to fry meat and fish, and to make soups in the traditional Vietnamese diet. In the food processing industry, cassava starch is an ingredient used in bread making and for making rice chips; about 30% of total starch used is from cassava. Industries using cassava starch for food processing make a wide range of products and use mostly high quality starch. For making cakes, cassava starch is mixed with other starches from soybean, green bean and rice, as well as with wheat flour. About 25 000–30 000 t of cassava starch per year are used in this industry, currently the second largest starch user in the country.

Domestic production of MSG: The total amount of monosodium glutamate (MSG) used in Viet Nam is currently about 40 000 t/year. Most of it is imported from Japan, Taiwan and Singapore, and only a small amount is produced nationally. In the 1980s, Vietnamese companies produced MSG using cassava starch (75%) and by-products from the sugar industry (25%) as raw material. These companies used old technologies with very low conversion rates: 6 to 6.5 tonnes of cassava starch were needed to produce one tonne of MSG. Low conversion rates, low MSG quality and very high production costs made locally produced MSG unable to compete with imported MSG. Thus, many companies have ceased production or have attempted to modernize their technology by investing their own capital or through joint ventures with foreign partners. Since 1990, several foreign multinationals have started businesses in the MSG sector. In the early years, they all imported MSG to sell in Viet Nam. After conducting market research, they concluded that it was a viable option to produce MSG in Viet Nam rather than import it. Currently most of them have projects to invest in MSG production using local raw materials. First, they produce MSG using glutamic acid imported from the mother company, and at the same time conduct research on market potential and on market reaction to their products. Most of these companies believe that there is a very good potential for MSG production in Viet Nam. They are looking further into raw material availability, market environment, site selection and production organization, after which further construction will begin. The available raw materials could be cassava starch, by- products from the sugar industry, and other starch sources. Foreign joint-venture interest in the domestic production of MSG has currently led to the planned construction of four new MSG factories with a combined capacity of 35 000 to 40 000 t/year.

Cassava starch export: Before 1995, Vietnamese cassava exports were mostly in the form of dry chips and only a small quantity of cassava starch was exported. About 30 000 t of cassava chips are exported annually to the European Union (EU), and 10 000 t to Asian countries; only about 1 000 t of cassava starch and tapioca pearl are exported to neighboring countries. The export price of cassava chips (120 to 130 US$/t) to the EU is much higher than to Asian countries (70 – 80 US$/t). Because of the high export price to the EU, the price of locally used dry chips has increased and the export to Asian countries cannot compete. So, companies exporting chips to Asian countries have changed to invest in starch processing and in the export of starch or tapioca pearl. Since 1995, some foreign and Vietnamese companies have invested in cassava starch production in Viet Nam (Figure 8) with high production capacity, better technology and better export facilities. These investments have increased the opportunity for cassava starch production. In 1996, about 80 000 t of cassava starch were exported to Taiwan, and 20 000 t to other Asian countries; only about 30 000 t of cassava starch are used domestically. The export price of cassava starch to Taiwan is about 190–240 US$/t (FOB in Ho Chi Minh city, September–December 1996).

Glucose and maltose: The total quantity of cassava starch consumption in glucose production for Viet Nam is estimated to be about 1 800 t and for maltose about 40 t. To produce one tonne of glucose about 1.3 tonnes of cassava starch are required, while the production of one tonne of maltose requires about 1 to 1.5 tonnes of starch. Starch needs to be at least 90% pure for these two products. Glucose and maltose produced in this industry have further use in the pharmaceutical and food processing industries, on which depends their demand.

Textile industry: Cassava starch is also used in the textile industry for sizing of cotton fabrics of all kinds. Currently this industry is using about 1 550 t of cassava starch annually. Other substituting starches are those from maize, wheat, potato and rice. In the past, some textile factories in the north of Viet Nam used corn starch, since this was available in the Red River Delta, while the supply of cassava starch was limited. Later they changed to using cassava starch when there was a sufficient supply. The starch quality satisfied their requirements and the price of cassava starch was lower than that of maize. Also, the government encouraged the use of cassava starch to substitute for that of other food crops used in industry. Currently, most textile factories use cassava starch in their production, since its price is lower than that of other starches and its supply is sufficient. In addition, cassava starch quality satisfies their technical requirements. At present, some textile factories have invested in modern weaving machinery with high production capacity and high weaving speed. This modern technology requires glue of a high quality, which is presently imported. This type of glue is made from starch and chemicals to obtain certain characteristics. Cassava starch could be used to produce chemically modified starch for this industry. It is expected that in the future chemically modified starch will be used in the whole textile industry, instead of using raw cassava starch. But cassava starch will still be used in small weaving factories and could be used for producing the new glue.

Figure 8

Figure 8. Cassava production and processing areas in Viet Nam. Each dot represents 1 000 ha of cassava in 1997. Source: Adapted from General Statistical Office and Projects under Promotion by State Committee for Cooperation & Investment (SCCI), 1998.

Glue for cardboard production and other purposes: Cassava starch is used as glue for the production of cardboard and other packing materials. In other countries, where cassava starch is unavailable, wheat flour and maize and rice starches are used for making cardboard. In Viet Nam, mostly cassava starch or flour is used, since it is available and has a relatively low price. Small cardboard producing units with simple technology use both cassava flour and starch, but in the modern cardboard factories only starch is used, since cassava flour cannot satisfy their technical requirements. This industry needs cassava starch with a high degree of adhesiveness and a purity of 90–92%; whiteness is not so important. In general, the starch produced in different processing centers satisfies these criteria. About 200 kg of cassava starch is used to produce five tonnes of cardboard. Currently, about 15 000 tonnes of cardboard are produced annually in Viet Nam using about 600 tonnes of cassava starch. The estimated consumption of cassava starch as glue material for other purposes, such as for use in offices, for packing etc., is about 50 t/year.

Plywood industry: Cassava starch is an ingredient used to produce industrial glue for plywood production, along with urea, formaldehyde and other chemicals. To produce one square meter of plywood about 0.46 kg of industrial glue is used, of which about 30–35% is cassava starch. Wheat flour and cassava starch are the two substituting materials. Because of its relatively low price, cassava starch is preferred. For the plywood industry, cassava starch needs to be pure (less than 5% of substance remaining after burning) have a pH value of 5.5 to 7 (not fermented starch), and must have less than 10% cellulose. As in the case of the cardboard industry, whiteness is not so important. With the current plywood production of about 700 000 m2, about 96 tonnes of cassava starch is used annually.

Pharmaceutical industry: At present, the pharmaceutical industry uses cassava starch in producing tablets and pills. Purity, whiteness and adhesiveness are the most important criteria in this industry and cassava starch produced using traditional technology generally does not satisfy these criteria. Starch is, therefore, bought from processing centers, after which it has to go through further processing to generate a starch that satisfies the requirements of the pharmaceutical industry. About 100 tonnes of cassava starch has been used annually in this industry. The reason for it using cassava starch instead of other starches, such as rice or potato starch, is that cassava starch is lower priced and there is sufficient supply. Also, the technology is available for using cassava starch in producing tablets and pills (Dang Thanh Ha et al., 1996).


4.1 Price fluctuations and instability of the market

The highest ranking constraints in South Viet Nam are large price variations, market (demand) problems and low profitability. This, to a certain extent, makes sense since southern farmers are much more market dependent than northern farmers. Low (or fluctuating) demand, which is strongly related to fluctuating prices, is a constraint for both northern and southern farmers. However, again, this constraint is ranked much higher in the south than in the north.

4.2 Crop competition

Sugarcane, rubber, coffee, fruit trees and cashew nut are competing with cassava, especially sugarcane. In the year 2000, Viet Nam expects to produce one million tonnes of sugar, 220–240 thousand tonnes of coffee, 180–200 thousand tonnes of rubber and 120–140 thousand tonnes of cashew nut. A total of 29 sugar factories and 52 cashew nut factories are operating to be able to reach the planned target. Rubber, coffee and fruit trees are receiving large investments from the Viet Nam government. Competition for land becomes a big problem for cassava production, especially in good soils and near cities.

4.3 Low yield potential and low genetic variability

Cassava varietal improvement greatly increased production, but the yield of cassava in Viet Nam is still very low (8 t/ha). There are few provinces harvesting over 10 t/ha of fresh roots, even though there were many demonstration plots which produced over 30 t/ha. However, the expansion of new cassava varieties resulted in the elimination of old varieties and this may narrow the cassava germplasm base. Although outbreaks of pest and diseases have not occurred, genetic diversity should be a priority in the cassava R&D program.

4.4 Soil fertility degradation and erosion

In Viet Nam, cassava is mainly grown in grey soils with low fertility and on slopes of 0–15%. Fertilizer application is very limited. Growing cassava continuously in a certain area is likely to lead to soil nutrient depletion, as not only the roots but also the leaves, stems and fallen leaves are often removed from the field; unless the nutrients in these plant parts are replaced, this will lead to yield reductions.

4.5 High labour requirements

In most cassava producing areas around the world, labour represents a major (40–70%) portion of cassava production costs. In the case of Viet Nam this also holds. Relative cassava production cost shares in North and South Viet Nam in 1991 show that on average labour accounts for 60.7%. The returns to labour are about US$0.86-1.43/day. If we assume that the average (rural) day wage is approximately US$1, depending on the proximity to urban areas where wages (opportunities) are higher, cassava cultivation in the south is on average a profitable alternative.

4.6 Constraints to cassava technology transfer

Two of the major constraints to cassava technology transfer in Viet Nam are: 1) lack of financial resources and facilities from the government to support the cassava technology transfer work. Although the Ministry gives some financial support and tries to create favorable conditions for the extensionists to transfer new technologies, this support is still inadequate; 2) farmers are very poor, especially those living in the midlands and mountainous regions, where root and tuber crops are important food crops. Few farm inputs are available for the application of new technologies for intensive farming of root and tuber crops. The farmers are willing to participate in extension programs, but the achievements of these programs depend greatly upon the suitability of the new technology to the conditions of poor farmers (Tran Van Son, 1996).

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