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Expanding the Competitive Edge in Diversified Markets

Clair Hershey2
Guy Henry3
Rupert Best4
Kazuo Kawano5
Reinhardt Howeler6
Carlos Iglesias7

1Background document prepared as part of the process of defining a global cassava development strategy, an initiative of the International Fund for Agricultural Development, and with participation of a broad representation of stakeholders in the cassava sector. A draft was reviewed in an Asian stakeholders' meeting in Bangkok in November 1998. The authors gratefully acknowledge comments and corrections of reviewers. Any remaining errors or omissions are the sole responsibility of the authors. March 2000.

2Consultant, 2019 Locust Grove Rd., Manheim, PA, 17545, USA. (Formerly Plant Breeder, Cassava Program, CIAT, Cali, Colombia.)

3Senior Economist, CIRAD-Amis, Rua Dr. Paulo de Castro Pupo Nogueira, 600 Campinas-Sao Paulo, CEP 13092-400, Brazil.

4Leader, Agroenterprise Development Project, CIAT, AA 67-13, Cali, Colombia.

5Professor, Kobe University Farm, Uzurano, Kasai-shi, Hyogo-Ken, 675-2103, Japan. (Formerly Plant Breeder and Regional Coordinator, CIAT Regional Office, Bangkok, Thailand)

6Soil Scientist, CIAT Regional Office, Field Crops Research Institute, Dept. of Agriculture, Chatuchak, Bangkok, Thailand.

7Maize Breeder, Weaver Popcorn Co., East Lafayette, Indiana, USA. (Formerly Leader, Cassava Project, CIAT, Cali, Colombia.)


Successful agriculture not only directly sustains its practitioners, but can also establish the foundations for broad-based development. This paper reviews the constraints and opportunities for improving the well-being of Asia's rural poor, by way of focusing on cassava, one of the region's most important food and industrial crops. Cassava production, processing and marketing has already contributed to considerable social and economic development in Asia, but the full potential is yet to be realized. The appeal of a substantial investment in the cassava sector lies in the efficiency and effectiveness with which some key economic and social goals can be met.


Cassava is a crop of the poor, and occupies mainly agriculturally marginal environments. These and other features endow it with a special capacity to contribute to food security, equity, poverty alleviation, and environmental protection.

In Asia cassava is emerging as a fully commercial crop entering diversified markets. This status defines an evolving and dynamic role in development for the region. Roots are converted into an array of products - human food as fresh or processed roots, starch and flour for food and industry, and animal feed. Rice continues a long tradition as the principal and preferred energy source in much of Asia, but where soils are marginal in fertility, and rainfall uncertain, cassava has a strong adaptive advantage. In this context, cassava serves as an ideal focus to achieve several key development goals. Improving this crop is a way to direct various benefits toward the poorest of rural populations, as well as contribute to broader economic development.

Cassava's role in food security has declined in post-Green Revolution Asia, but continues as a factor in times of political unrest, wars, food shortages, or other disruptions of normal food supply. On a country-wide basis, only Indonesia has moderately high consumption - about 50 kg per capita per year, in the form of a wide array of different food products. The rapidly growing on-farm use of cassava as animal feed in China and Viet Nam meets basic needs both of food security and income generation.

The capacity of the crop to provide income, and thereby alleviate poverty, is the principal attribute allowing cassava to function as a catalyst for development. The forces that enable and augment this central role are: a tradition of diet diversity, which expedites the success of new food products on the market; internal industry demand for starch and animal feed; and opportunities for export of pellets and starch.

The benefits of improving the cassava sector are generally skewed toward the lower income strata, thereby nudging the economic system toward a greater measure of income equity. However, mechanized production, while occurring slowly, is disproportionately displacing the labour of women. The trend toward larger centralized processing facilities is having similar effects where starch is the main commercial product. The cassava sector is not immune to the gender equity issues arising out of the modernization of agriculture and industry.

The links between cassava and environmental protection revolve mainly around implications of the large proportion of this crop grown in fragile or otherwise marginal ecosystems. Cassava's undeserved reputation as a crop that causes exaggerated soil degradation grew mainly out of the plant's ability to produce on poor soils, when most other crops would fail. Nonetheless, managing erosion is a critical need where cassava is grown on slopes and in light soils, especially during the first months before the canopy closes.

Cassava is a new crop in Asia, introduced from the Americas by Spanish explorers. Colonial rulers promoted it first as a famine reserve crop, and then as a source of starch for export

Disposal of waste products from processing is a growing environmental concern. The solutions lie in research on environmentally and economically sound waste management, by-product development, and reasonable but effective regulation. As processing plants become larger and more centralized, they are able to apply more resources to pollution control, especially through improved efficiencies of extraction and by-product utilization.


Spanish explorers probably first introduced cassava to Asia, through the Philippines, from its Latin American homeland. By the beginning of the 19th century it was widely distributed throughout tropical Asia. Cassava gained status as a famine reserve crop and as a raw product for starch production, especially in Indonesia and Malaysia. World War II disrupted starch trade, and in the post-war era, maize became the principal source of starch.

The region produces about 46 million tonnes of cassava on 3.4 million hectares (1999). In Southeast Asia it is fourth in production (dry matter basis) after rice, sugarcane and maize. Two-thirds of the total comes from Thailand and Indonesia alone. Seven countries account for 99% of the region's production: Thailand, Indonesia, India, China, the Philippines, Viet Nam and Malaysia. About 40% of cassava is used for direct human consumption, especially in processed form. Most of the remainder is destined for animal feed or processed for starch.

Trade policy has been instrumental in shaping cassava's role in the region. The most successful market evolved from policies that opened a niche for dried cassava in Europe's animal feed industry. Thailand's public and private sectors responded by supporting a vertically integrated system of production, processing and marketing, based on tens of thousands of small producers. From near zero in 1960, Thailand's exports of chips and pellets grew to over eight million tonnes annually in 1992–94. Gradual withdrawal of cassava's special treatment in Europe's feed market in the past decade is now forcing diversification of the export industry. Whereas in 1982 chips and pellets represented 88% of the total utilization of Thailand's production, this share declined to 70% by 1992. In the same period, starch increased from 12% to 28%.

Indonesia has maintained a relatively stable production for over 30 years, with most used internally as human food. In India, cassava is concentrated in the southern states of Kerala and Tamil Nadu, which accomplish the world's highest national average yield levels through intensive cultivation. China and Viet Nam are expanding production to meet rapidly growing internal demands for industrial starch and animal feed.

Technology and markets are allowing higher-value crops to displace cassava in some of the traditional growing areas. Cassava is then pushed to continually more marginal lands. The downward pressure on yields from this push to lower-productivity lands has been offset by adoption of new technology such as high-yielding varieties.

There are also some examples where cassava is cultivated under more favorable conditions - on larger plantations in southern Sumatra and the Philippines, and in Kerala, India, where early-maturing varieties are planted after a first paddy crop.

Assuming application of improved production and post-harvest technology, substantial levels of institutional investment in research, and supportive agricultural and trade policies, there are good prospects for sustained growth in cassava demand and production for the next two decades (Rosegrant and Gerpacio, 1997). Most of this growth will come from yield increases averaging about 0.4% per year. Total area in Asia will climb from 4.0 million (1993) to 4.2 million hectares.


Successful interventions to exploit cassava's potential rely on alleviating constraints in the system, as well as pursuing new opportunities. These are impacted by both the larger socio-economic and political milieu, and the characteristics of the cassava sector itself.

An evolution toward more open trade policy brings cassava and its products into direct competition with alternative energy sources for food and industry. A competitive position depends on improving efficiencies of production and processing, and on developing new markets.

External influences strongly impact cassava demand and supply

Urbanization and income growth are changing food consumption habits, with greater diet diversity, less demand for starchy staples, and more demand for convenience foods. Cassava's versatility is a decided advantage for adapting to these changes.

Comparative advantages for production in marginal and fragile agricultural areas mean that management of the resource base is an acute concern. Thailand has invested in crop diversification programs in the Northeast, mainly in response to pressure from Europe to reduce exports, but also in part out of concern about inappropriate practices leading to soil degradation. Concentrated research attention to this issue in the past decade is bringing new options to protect the environment in cassava-based systems, especially with soil erosion control and fertility maintenance technologies.

General trends in commodities are closely linked with cassava's competitive edge in different markets. These linkages are related to two principal factors. First, much of Asia's cassava enters markets where raw product substitution can readily occur. These are primarily rice and wheat for food and maize for feed and starch industries. Secondly, protein supplementation, e.g. soybeans, is necessary to compensate for cassava's low protein content in animal feeds. In inflation-corrected terms, prices of agricultural commodities have been on a downward trend for the past fifty years, driven by improved efficiencies in production and transportation, and, recently, lowered trade barriers. Cassava will have to meet and surpass the rates of improvement in efficiency achieved by the major grain crops in order to sustain a competitive edge.

Inadequate infrastructure, especially in rural areas, limits the ability of growers to obtain inputs at reasonable prices, and to market their products. Cassava's bulkiness, especially as fresh roots, makes it especially vulnerable to infrastructure constraints. The need for local value-added processes becomes especially critical-as a way of sustaining income growth.

Improving cassava's capacity as a catalyst for development requires both a long-term and a multi-faceted agenda. This will only be possible with a network of institutional resources that provide the capacity and motivation to see a viable cassava-based development in Asia. The region has some of the world's strongest cassava research programs. But without greater investment it will be increasingly difficult to compete with the well-funded, advanced research systems in competing commodities from more developed countries. Networking to achieve complementarities has already been highly effective in agronomy, genetic improvement, and post-harvest research. The continuation and strengthening of this work needs to be assured.

An extensive survey to quantify constraints to production and post-harvest factors (Henry and Gottret, 1996) showed that cassava yields in Asia could be almost doubled by applying technology within reach of typical cassava farmers.

Cassava's productivity in Asia could be doubled with practical genetic and management inputs.
ConstraintsPotential increase (%)
Soil erosion10
Soil fertility22
Planting material8
Intrinsic yield potential24
Pests and diseases5
Sources: Henry and Gottret, 1996.

Soil erosion control and fertility maintenance are now widely recognized as critical to sustainable income generation from cassava. Soil fertility is most commonly maintained by fertilizer inputs, although still at quite low levels in comparison to many crops. The technology for reducing erosion includes land preparation practices, fertilization, plant density and varietal canopy characteristics, vegetative erosion barriers, and intercropping or understory crops. Alleviating the constraints from these two components of soil management would increase yields by 33%.

As a whole, Asian countries employ relatively intensive cassava crop management practices, probably the major contributing factor to the higher yields as compared to Africa or Latin America. Still, there are significant improvements to be made. Vegetative reproduction introduces several potential constraints. Appropriate management of planting material can alleviate the effects of biological and physical stresses, for yield gains of about 8%. Weed control is mainly manual, and applying additional labour inputs is impractical for most growers. Farmers are increasingly looking to mechanical or chemical weed control. Improvements should contribute 7% to current yields.

Asia appears to have a narrower range of genetic diversity, relative to Africa or the Americas, a constraint that impacts mainly cassava's intrinsic yield potential. The constraint of a narrow genetic base among the local landrace varieties is being met by massive introductions from Latin America since the mid-1970s. New varieties already occupy nearly a third of Thailand's cassava area. Growers in Indonesia, Viet Nam, the Philippines, China and India are increasingly experimenting with and adopting new hybrids from national and international centers.

Pests and diseases are a minor constraint in most of Asia. Highest potential gains can come from controlling mosaic virus in India and bacterial blight in the subtropics.

The crop's remarkable adaptation to drought is one of the main factors that define its distribution: two-thirds of Asia's cassava is grown in the sub-humid or semi-arid tropics. Northeast Thailand, eastern Java, and southern India (mainly Tamil Nadu) are all dry areas where cassava is widely cultivated. Low winter temperature is a second climatic constraint in the sub-tropics, mainly affecting southern China and North Viet Nam. Cassava's relatively poor adaptation to cool temperatures is compensated by its tolerance to poor soils in these areas.

Even with diverse and highly developed cassava markets in Asia, post-harvest factors pose significant constraints on economic output of the system.
ConstraintPotential increase (%)Attributed to:
Quality13Price premiums
Processing4Cost reductions
Product marketing4Reduced consumer prices

While Asia has a highly diversified cassava market sector, the CIAT survey results estimate that a 21% increase in economic yield is possible through improvements in quality, processing, and product marketing. The largest share of this (13%) is attributed to potential market premiums for quality improvement, mainly improved root starch content to increase the efficiency of extraction for industrial uses. Longer term, there are possibilities to substantially reduce losses from rapid post-harvest deterioration. Although cassava competes with alternative carbohydrate sources in several major markets, there is potential for developing more markets where unique starch characteristics are required, to bring a market premium to growers and processors. Technology for improving efficiency of starch extraction, and for value-added by-products of processing, will contribute both to the financial position of processors, and to a cleaner environment.


Cassava needs to compete with steadily lower grain prices in its main markets. Its long-term viability hinges on a combination of increased on-farm efficiency and productivity, and expanded market opportunities. Most cassava farmers have limited options for other crops, because of soil and water constraints. For them; cassava must be a link to-new economic opportunities.

Cassava can fulfil its potential as a catalyst for development only in an appropriate socio-economic and policy context.

The broader economic and policy context is crucial to cassava's potential contributions to development: policies that support infrastructure development in rural areas, promote trade policy that brings long-term growth with broad benefits, seek equitable investment between urban and rural sectors, build capacity in research and development. While recognizing the importance of this broader environment, this review focuses on cassava itself, and the specific goals and activities of cassava research and development. These interventions are broadly divided into demand side and supply side.

On the demand side, the challenge is to target growth sectors with product and market development. In the animal feed and native starch markets, cassava products will compete largely on price, consistency of supply, and quality. Product and process development is already well-advanced in parts of Asia, and there are considerable opportunities for technology transfer within the region. As industry attempts to achieve greater economies of scale, processing is moving away from household and village-level to larger centralized plants, especially for starch. Large plants can better control the variables of production, but at the same time diminish opportunity for growers themselves to add value to the cassava they produce. This, combined with a long-term trend of downward pressure on prices for raw agricultural commodities, challenges the ability of the small Asian farmer to derive reasonable income from cassava. Growers'/processors' cooperatives are an effective way to distribute benefits among a broader base of society. Another opportunity for raising incomes is the development of specialty markets. Cassava starch has several unique properties that create demand for particular industrial processes: resistance to shear stress and freezing, high viscosity, and production of transparent gels. Starch content and quality will increasingly become criteria for adding value for producers. Specialty starches, by definition, need to be of the highest quality, a challenge for growers unable to control the variables of production, or for smaller processors. The private sector is well-positioned to engage in this type of research, but needs support and collaboration from development-oriented public institutions.

An increase in demand is, in turn, an opportunity to deploy technologies, policies or methodologies that increase supply. The urgent needs on the production side are to substantially increase returns to land and labour, while conserving and improving the resource base.

Cassava can exploit specialty markets that require its specific starch characteristics.

Some elements of better production technology now exist for many regions, including high-yielding varieties and an effective package of cultural practices. Fertilizer is often the input with best economic returns, but access is a problem. New varieties are spreading rapidly in Thailand, and beginning to make inroads elsewhere.

Genetic improvement is a continuing long-term process, and optimizing progress in Asia will depend on targeted germplasm introductions from the Americas, continued investment in both classical breeding and biotechnology, and expanded networking. Involvement of the private sector in genetic improvement should be encouraged. Risks of introducing new pests or diseases must be minimized with continued vigilance through standard quarantine procedures and training in plant protection.

Meeting development goals for the cassava sector.
Goal Strategy
Stimulating higher demandMarket development
Adding post-harvest ValueProcess and product development
Increasing long-term profitability for producers• Production efficiency; resources conservation;
adding pre-harvest value
Support to production, processing and marketingInstitutional strengthening and policy support

With modest levels of inputs and management, and new varieties, on-farm trials can easily achieve over twice the national average yields, except in India where farm management is already high. Achieving these increases requires little additional labour input. Greater efficiencies in labour productivity will come with further mechanization in land preparation, harvest, and weed control with herbicides or mechanization. However, given the sloping and irregular topography of many production areas, combined with small farm size, full mechanization will be difficult.

For both demand-side and supply-side interventions to succeed, broad institutional strengthening is needed. Most countries have some research activity, linked by regional and global networks. Research investment for cassava, on a production value basis, is well below that for the major grain or specialty export crops.

There are effective approaches to achieving a balance in supply and demand that will optimize long-term benefits to the cassava sector. For cassava systems, synchrony between the interventions that target demand and those that target supply is often a special challenge. Production technology may be slow to reach farmers because development time is longer than for most crops (long growing cycle; limited research capacity), extension services are understaffed and under-funded, and the private sector is only beginning to get involved in cassava technology development or diffusion.

A system in balance:

Market demand may develop more quickly, especially where private industry has a strong vested interest. Integrated projects are a development model that specifically keeps supply and demand in balance during the early phases of technology introduction. Expansion of both market demand and production can then usually continue with less institutional intervention. Finally, a full commercial phase is reached when demand and production spontaneously find the appropriate level where producers, processors and marketers make a fair profit, and consumers obtain a product at a competitive price.

 Technologies and methodologies to alleviate poverty, address equity issues, improve food security, and protect the environment 
 Marginal and fragile
production environments;
production efficiencies
Adapted germplasm 
Erosion control practices
Cropping systems management
Fertilizer and lime
 Intrinsic varietal traitsHigh yielding hybrids 
Rapid propagation techniques
Adaptation to mechanization
 Biological constraintsIntegrated pest management 
Mechanized and chemical weed control 
Quarantine protocols
 Processing constraintsMechanization 
High-starch varieties
Genetic, chemical or physical starch modification for specialty markets
Improved shelf life
Pollution control
Economic use of by-products
 Marketing constraintsValue-added products 
Market channel development

A complex array of forces acts on the cassava sector, some of which favor its competitiveness, and others that are a detriment. The outcome will be crucial to the segment of rural Asia that depends on cassava. Because of environmental constraints in most of the areas where it is cultivated, growers have few options for alternative crops. Cassava is a key, sometimes the only key, to economic and social opportunity for these farmers. Cassava markets are highly diversified in Asia, stimulating a demand-led growth of the cassava sector in the past. A significant part of this demand grew out of special international trade agreements with Europe, which are now being withdrawn. In global markets, cassava competes mainly with coarse grains, whose prices have tended gradually downward for the past fifty years in response to increasing production efficiencies. The degree to which its production and utilization bring adequate benefits to the poor is very much dependent on future research and development investment. The key elements of that investment will focus on- production efficiency and profitability, conservation of the resource base, processing efficiency, and market development of specialized products. Private and public sectors have a mutual interest in supporting a vital cassava industry. A significant institutional and technological base is already in place, on which to build new initiatives. The investments required to achieve these goals are substantial, but assuring a dynamic cassava sector in Asia will bring urgently needed benefits of poverty alleviation, equity, enhanced food security, and protection of the environment.



Targeting development in the rural sector is highly appropriate for most of tropical Asia. Despite rising urbanization, the majority of households still derive a significant part of their income from agriculture. Further, urban dwellers, especially the poor, rely on the success of agriculture to consistently fulfill their nutritional needs at an affordable cost. Historically, few countries have realized sustained economic growth without the precursor of success in agriculture.

Agricultural systems are universally complex - the interaction of multiple physical, biological, social and economic elements. Overall improvement is rarely accomplished by changing a single factor. On the other hand, individual components within these complex systems may sometimes serve as a catalyst to stimulate and drive the changes needed to benefit specifically targeted populations. Cassava in Asia is a good example. Because the crop and its products have specific linkages to common development goals, the cassava system is an appropriate focus for a concerted investment in research and development.

In Asia's largely rice-based food systems, cassava has fundamental roles in supporting farmers where soils are marginal and rainfall uncertain. The urban poor benefit from availability of a low-cost calorie source. Industry and consumers alike gain from the multiple products for which cassava is a raw material. National economies balance trade with cassava products through exports, or through import substitution. Cassava in Asia is almost wholly a commercial crop, and its success is strongly affected by the broader economic environment. Diversified markets are the driving forces of Asia's cassava sector, providing a demand-led incentive for growth.

Continuing to realize, and expand, cassava's opportunities is neither automatic nor simple. The global economic environment continues to evolve rapidly, and agricultural research is changing farmers' options. Liberalized trade, regionally and globally, is breaking down the artificial cost barriers between internally and externally-produced goods. Strong research investment in grains, especially in export-oriented developed countries, is driving prices downward and making them more attractive in food, animal feed and starch markets. Continued acute underfunding for cassava could leave it in a less competitive position for new markets, and even in its traditional markets.

Does this matter? There are compelling reasons to assure cassava's competitive position in the mature, diversified Asian markets. This review explores cassava's role in Asian agriculture, commerce, and industry, with emphasis on future potential for contributing to sustainable and equitable rural development. The objective is to set a framework for planning and prioritizing continued investment in research and development of cassava-based production, processing and utilization systems, toward meeting broad development goals. Recommendations follow from evidence that strategic investments in cassava have critical benefits for the rural poor, who could be left behind if development policies exclude consideration of this crop's special roles.


In discussions leading to development of a global cassava strategy, a broad representation of stakeholders in the cassava sector endorsed the goals of food security, poverty alleviation, equity, and protection of the environment. Appropriately-focused research and development strategies can contribute substantially to meeting these goals.

Food security
Use of cassava for food in Asia is defined by its complementary position relative to rice, the highly preferred staple. From its introduction to Asia, through the middle part of this century, cassava was widely planted as a famine reserve crop. The Green Revolution in rice in the 1960s and 1970s considerably improved the food situation throughout Asia, and cassava's importance as a food security crop declined in response. Nonetheless, malnutrition remains a deep concern. In the Asia-Pacific region as whole, about 762 million people were chronically malnourished in 1970. This declined to about 540 million in 1990 - from 40 to 20% of the population. Most of the improvement took place in Southeast Asia, while South Asia was about constant (Cohen and Reeves, 1995). During the past two decades, much of the media and aid attention turned to Africa, where the numbers of chronically malnourished people doubled in this same period. However, in absolute terms, in spite of remarkable improvements, malnutrition is far more prevalent in Asia, affecting about three times more people than in Africa.

Like in Africa, cassava gains importance as a food security crop, relative to other staples, in times of political unrest, wars and famines. In modern times, this has been especially relevant for China and Viet Nam. Across developing Asia, average annual per capita cassava consumption is just under 7 kg fresh root equivalent. A generally positive income elasticity for cassava at the lower income levels creates a situation where increased production and lower prices will bring benefit almost exclusively to poor consumers.

Indonesia has the highest per capita consumption levels, with an intake of about 135 kcal/day in 1997 (FAOSTAT). Cassava nearly parallels maize in its consumption patterns across different income levels. Rice consumption falls off rapidly at the lower end of the income scale, and cassava and maize rise. The region's largest producer, Thailand, has almost no consumption. Cassava is consumed at low levels throughout the Philippines and Viet Nam. In India and China consumption is localized in the southern regions. For much of tropical Asia, cassava still has a modest role as a backup crop to rice - should the rice crop be in short supply, cassava will likely still have some yield.

Poverty alleviation and equity
Poverty is a root cause both of food insecurity and environmental degradation in developing countries. Asia as a whole has realized astonishing economic growth in the past two decades, but poverty is still widespread, and especially among those who are dependent on agriculture. The rural poor account for up to 75% of the poor in many Asian countries. Rural development stems the tide of migration to the cities, which brings even greater burdens to public institutions.

Throughout the region, cassava's main role is income generation potential in more marginal environments. Its versatility in products and markets enhances its role in poverty alleviation through income security and stability for the poorest farmers. These farmers usually occupy land where other crops simply cannot be grown, or their production is risky and results in wide year-to-year yield variations. A focus on these poorest farmers is a move toward some measure of equity of income distribution.

Protecting the environment
Before scientific research showed otherwise, cassava was often criticized as a crop with a propensity for depleting soil nutrients and causing erosion. The reputation stems from the crop's ability to thrive on soils already depleted by other crops, or which are inherently marginal. Cassava is thus relegated to the erosion-prone hillsides, to soils of low nutrient status, and to regions of uncertain rainfall. The ensuing environmental concerns are associated with, but not necessarily caused by, cassava cultivation practices. Farmers may be unaware of the extent of soil loss or nutrient depletion, but more often simply do not have the resources to apply remedial inputs. The desperation of poverty generally does not engender environmental sensitivity. Without some management interventions, these cassava-based systems on erodable hillsides are not sustainable.

Environmental concerns are starting to attract government attention throughout Asia, as more scientific evidence becomes available. Average soil losses are considerably higher than in Africa or Latin America. Because of population pressure, even steep slopes are cultivated. Even on lesser slopes, many cassava soils are light-textured and prone to erosion, particularly in Thailand, parts of Viet Nam and Bohol Island in the Philippines. Highest losses have been measured on Hainan Island, China, of 154 t/ha/year dry soil loss (Howeler, 1995). There is still some opportunity for expanding agricultural area in Thailand, Indonesia (outer islands), Malaysia and the Philippines. These are almost exclusively areas of poor soils and/or erratic rainfall. Cassava will continue to have a fundamental role on the frontier, and technology for protecting the environment will be ever more important.

Asian farmers, especially in high population density regions, have some experience in intensive crop and soil management to protect fragile soils. Technologies for erosion control are tested and available, and farmers have already begun to adopt some of these. The challenge is to present effective methods that provide short-term profit as well as long-term benefit. Farmer participation in the search for better methods is a key to success.

A lesser, but increasingly important, environmental concern is waste and waste-water management from processing plants. Starch processing factories use large volumes of water, first to wash roots, and then for the starch extraction itself. The total process consumes 15–40 tonnes of water for every ton of starch extracted. The two main concerns are the potential cyanide poisoning of water life, and the oxygen depletion from organic matter in the effluent. Generally, small factories cannot afford the investment for proper water treatment. Throughout the region there is a tendency toward consolidation into larger processing facilities. With the greater capitalization and economies of scale of these larger plants, there is better possibility to invest in pollution control systems, and in systems that commercialize the by-products of processing.


8 This section draws heavily on Lynam, 1987, for the period up to the mid-1980s.

Cassava in Asia has been a highly versatile crop, able to succeed in diverse physical, socio-economic, and political environments. The species is a relatively recent introduction to the agriculture of Asia, in comparison to the several-thousand-year-old rice culture. Best evidence indicates it was first introduced to the Philippines during the Spanish occupation. By the beginning of the 19th century, explorers and traders had effectively distributed the crop throughout tropical Asia. Colonial administrators promoted cassava culture by developing a starch processing and export industry in Malaya in the 1850's, and later in Java. The Dutch in Java and the British in southern India also promoted cassava as a famine reserve crop. In this heavily rice-dependent region, cassava found a niche in environments where rice was risky or difficult to grow. Production was concentrated on Java and Malaysia for much of the period up to World War II. The disruptions of the war and the rising prominence of maize as a source of starch brought a decline to the cassava starch export industry. Markets for internal consumption remained strong in Indonesia, and this country led production in Asia up to the late 1970s.

Figure 1.

Figure 1

Two powerful influences dominated the cassava sector in the post-World War II era, through the 1970s. First, the green revolution in rice brought a measure of food security in the region, diminishing the importance of cassava as a famine reserve crop. Secondly, rapid growth in the animal feed industry in developed countries, and a twist on Europe's import policies, brought opportunities for dried cassava exports. From the beginning, Thailand dominated the export market for animal feeds.

From the 1980s to the present, the main influences on cassava production and commerce were:

  1. rapid growth in many Asian economies, with accompanying changes in food consumption patterns;
  2. increased demand from industry for starch; and
  3. increasing implementation of trade policies that reduced cassava's preferential treatment in European markets. Except for a few products such as krupuk in Indonesia, cassava generally enters markets where other calorie or industrial starch sources may readily be substituted. Future growth, therefore, is largely linked to cost competitiveness. Alternatively there is growth potential in markets that require specific characteristics that only cassava provides.

This review concentrates on seven countries which together account for 99% of current production: Thailand, Indonesia, India, China, the Philippines, Viet Nam, and Malaysia (Figure 1). Thailand and Indonesia alone produced 70% of the region's cassava in 1999. Sri Lanka was a significant producer in the 1970s, with over 150 000 ha, but this has declined to about 30 000 ha. Cambodia, Laos and Myanmar each produce cassava on about five to seven thousand hectares.

Country briefs

Thailand has, in a sense, put cassava on the map, in Asia and in the industrial world. The pellet export industry to Europe that developed out of a series of fortuitous circumstances (see details in later section on Products and Markets) has virtually defined the cassava sector in Thailand. How these circumstances were exploited by agriculture and industry, and supported by national policy is a major lesson from Asia.

Evolving from an early concentration of production in the Southeast, almost two-thirds of the cassava is now planted in the seasonally dry Northeast. Nearly all is grown on small farms of one to five hectares. Chipping and drying is done on simple drying patios nearby, while processing for starch is generally done in large factories. The pellet export industry depends heavily on the middle-men who either own trucks or drying patios, and who consolidate production from these small farms into processing and marketing channels.

For many years, a single variety, Rayong 1, occupied almost 100% of the country's area. This began changing in the mid-1980s as new hybrids gained popularity for the market premium assigned to higher starch content. By 1999, new hybrids from the national program and Kasetsart University extended over more almost half of the total area. The research program established by the Department of Agriculture, based at Rayong Station, is among the most productive in the world. Breeding and agronomy are the main focus. Private industry (mainly starch factories) plays an important role in promotion and distribution of new technology. Mechanized land preparation, fertilizer application, and mechanical or chemical weed control are becoming more common,

Thailand has been keenly aware of the need to develop domestic markets and diversify export markets. In 1982 chips and pellets represented 88% of the total utilization of production; this share declined to 70% by 1992, as starch increased from 12 to 18% in the same period. By 1996, root utilization was about equally divided between starch and pellet production, and use of roots for starch now surpasses pellets.

Indonesia is historically by far Asia's largest producer, outpaced by Thailand in terms of area planted only in the mid-1980s. The relatively stable area of planting across years is a function of market diversity and comparative advantage in upland environments not suited to rice. The multi-use characteristics are fully exploited and provide a range of market options to stabilize prices. The traditional products in the internal markets are gaplek (dried cassava chunks used in a variety of local dishes), and krupuk, a crispy snack wafer made from cassava starch.

Production systems in Indonesia are in general more complex than elsewhere in Asia. Intercropping is common on Java, especially where there are not severe soil and water constraints. Common intercrops are upland rice, maize and various legumes. Farms are small and intensively managed, with few purchased inputs except fertilizer. On the outer islands rainfall is usually less limiting, but poor soils are a constraint on ability to intercrop cereals and legumes. The starch industry in Sumatra is partially based on large, vertically integrated plantations where moderate input levels are applied, and new high-yielding varieties planted. However, many of these starch factories supplement their own production with that of nearby. Some of these industries have joined with the national program in supporting production research, which has benefited surrounding small independent farmers as well as the plantations. Small scale processors have found it increasingly difficult to compete with large processors, and some are switching to other raw materials.

Cultivation in India is concentrated in the southern states of Kerala and Tamil Nadu. The country is distinguished by the world's highest average yields - about 24 t/ha. These high yields are accomplished by intensive cultivation, and, in Tamil Nadu, by irrigation. In Kerala, much of the production is consumed as boiled roots, one of the few regions in Asia where this is common. Cooking quality is one of the principal criteria farmers use in selecting varieties for cultivation. In Tamil Nadu nearly all of the production is for starch.

A geminivirus similar to the African mosaic virus affects much of the cassava area in India. While it does not appear to cause widespread yield losses, its presence poses severe restrictions on germplasm exchange with other countries. The Central Tuber Crops Research Institute in Trivandrum, Kerala, has a well-staffed interdisciplinary research team which has contributed significantly to the global knowledge base on cassava, especially in cytogenetics, genetics, physiology, and post-harvest issues.

China produces cassava in the southern provinces of Guangxi, Guangdong, Hainan, and more recently Yunnan. Most is planted on hillsides surrounding rice paddies, with few production inputs. Historically cassava was a famine reserve crop, grown in marginal areas with high risk of crop failure. Production data from China are not very reliable, but according to FAO, area peaked at 420 000 ha in 1980. This came when China had begun to enter the European market with dried chips, along with Thailand and Indonesia. Although a minor crop in China as a whole, it is increasingly looked upon in the South as an efficient producer of raw material for starch and on-farm pig feeding. China imported 300 000 tonnes of dried cassava, and 320 000 tonnes of cassava starch in 1998 (FAO). The possibility of replacing these imports with local production is an incentive for supporting research. There are modest research programs at the provincial level, concentrating efforts on varietal testing, soil erosion control and fertility maintenance, and utilization.

Like Indonesia, the Philippines is a multi-island economy, but differs in that population is spread more uniformly across different islands. Cassava fits well within an agricultural policy that emphasizes self-sufficiency in basic foods (except wheat), import substitution, and development of the small farm sector. Cassava is produced throughout the Philippines, but is more concentrated on the southern islands, especially the Visayas region and Mindanao. Most production is on small farms, although there are some large plantations supplying starch factories. Rainfall is generally not a limitation, but, as in other countries, cassava usually occupies the poor upland soils unsuited to grain crops. Input use is low in comparison to other countries and is reflected in some of the lowest yields in Asia (about 8.5 t/ha in 1999). Nonetheless, increasing adoption of improved varieties and cultural practices should begin to improve yield performance.

Cassava is distributed more uniformly across Viet Nam than perhaps any other Asian country. Area planted peaked in the late 1970s at nearly half a million hectares, but then declined to nearly half that level because of lack of markets and competition from other crops. It occupies the poor soils of mountainous and hilly areas, mainly in monoculture systems. Since many of these soils are highly erodable, their recuperation and conservation is currently a major research thrust. In early years, most of the plantings served as a food security crop, but human consumption now occupies only 10-20% of production. About 30% is used as animal feed, much of it on-farm for chickens and pigs, after chipping, drying and milling the roots. Industrial uses are on the increase as Viet Nam undergoes rapid economic development. Industry absorbs about 30-40%. Since the mid-1980s, a small but dedicated cadre of scientists has given the first significant research attention to cassava since its introduction. New varieties, mainly introduced from Thailand's breeding programs, are gaining popularity, especially in the South, for their high yield potential and high starch content.

Early production in Malaysia was based on the starch and tapioca export market. Area peaked near the turn of the century at about 45 000 ha, but declined rapidly due to competition from Java, and internally from the expanding rubber and oil palm industries. Malaysia is unlike most of Asia in having relatively ample per capita land resources. As a result, policy has focused on plantation agriculture. Labour costs are comparatively high, a strong incentive for use of labour-saving inputs such as mechanized land preparation and herbicides. The Malaysian Agricultural Research and Development Institute (MARDI) had a modest but effective research program on cassava for many years. The program concentrated on genetic improvement and agronomy, and most recently on adapting production to the acid peat soils. However, MARDI no longer carries out cassava research.

Production trends

FAO monitors cassava area and production in thirteen countries of South and Southeast Asia (Table 1). Together, these represent 32% of global production. To a large degree, Thailand has defined the variations in total annual output for Asia over the past 30 years. Other countries have made relatively modest contributions to the fluctuations in aggregate production (Figures 2 and 3).

Table 1. Area, yield and production of cassava in Asia, 1999.
CountryArea (ha)Yield (t/ha)Production (tonnes)
ASIA3 366 39813.645 767 700
Brunei13011.51 500
Cambodia7 0001.067 500
China230 06515.93 650 903
India250 00024.06 000 000
Indonesia1 205 33012.214 728 292
Laos5 10013.770 000
Malaysiaa39 00010.3400 000
Myanmar8 00011.592 000
Philippines210 0008.51 786 710
Sri Lanka30 0648.5257 153
Thailand1 150 00014.716 930 200
Viet Nam231 7007.71 783 400
Source: FAOSTAT, 2000.

Production trends for Asia divide roughly into three periods:

  1. pre-1960s. Internal consumption and early international trade in starch absorbed most of the production. There were overall modest increases in area planted over time.

  2. 1960s and 1970s. This era was defined by growth in the export market for dried cassava for animal feed, mainly to Europe. Other countries, especially India and Indonesia, were also responding to deficits in rice production and increasing planting of cassava as a food security crop. In post-war Viet Nam, production surged in the latter part of this period as the country began to rebuild its economy.

  3. 1980s and 1990s. Area planted and production leveled off overall. Indonesia steadily decreased area planted, but realized steady slow growth in production due to greater use of fertilizer, to satisfy growing internal demand in the starch markets. Production in Thailand fluctuated strongly from year to year in response to pressures to reduce exports to Europe and the search for new external and internal markets. Area planted peaked in 1989 at 1.6 million hectares, with a steady decline thereafter and reaching levels of a decade earlier (1.2 million hectares) by 1996.

In the period 1986–1995, aggregate annual decline in area planted in Asia (0.9%) was slightly less than the annual average yield increase (1.2%), giving a nearly stable production over the period (Table 2). Supply growth in the previous decade (1976–1985) was almost equally divided between area expansion and yield increase. In some countries, especially Thailand, reduction in area is not being offset fully by yield increases, as the crop continues to be pushed toward more marginal land.

Table 4. Cassava production costs, farmgate prices, and product prices in three major producing countries (average for 1990–1994, US$/tonnes).
 Cassava production costsFarmgate price of cassava  
 For industrial useFor fresh consumptionDomestic chip priceCassava starch price
Source: Henry arid Gottret, 1996.
Figure 2
Figure 3

Production systems

Most crops occupy the micro-environments where they are best adapted within a region. Cassava, though, rarely does. Paddy rice occupies most lowland farming systems in tropical Asia. It is the highly preferred calorie source, and cassava does not normally compete on land suited to its cultivation. In rainfall-limited areas such as eastern Java, Northeast Thailand, or non-irrigated southern India, few crops can match the stability of production of cassava. As a broad generalization, cassava occupies the hillsides and drought-prone areas, and acid soil regions where other crops can be successfully grown only with high input levels.

Table 3 and Figure 1 compare area planted in the broadly-defined agro-ecological zones. Compared to either Latin America or Africa, a higher proportion of cassava in Asia is planted in dry climates (sub-humid or semi-arid). By these estimates, two-thirds of cassava is seasonally drought-stressed in Asia, compared to about two-fifths in Latin America and half in Africa. Area planted in the subtropics is midway between that of Latin America and Africa, at about 15%. Almost none is grown in highlands (over 1500 masl), which may be due in part to scarcity of adapted germplasm. Early introductions from the Americas probably did not include highland-adapted materials, and this never developed as a priority in Asia.

Table 2. Annual growth rates (%) In cassava production, area and yield, by continent, 1976–1995.
Latin America-1.20.0-1.1-0.3-0.10.2
Source: Henry and Gottret, 1996.

Production practices vary widely across the region. The vast majority of farms in Asia are small, usually in the range of 1-5 ha. In the more land-rich areas, cassava competes principally with tree crops: coconuts in the Philippines coconuts; and rubber in Kerala, India; oil palm and rubber in Malaysia and the off islands of Indonesia; and rubber in southern Thailand.

Table 3. Global cassava area (%) by continent and climatic zone.
 Latin AmericaAsiaAfricaWorld
Lowland humid tropics15183427
Lowland sub-humid tropics33413838
Lowland semi-arid tropics826813
Highland tropics150108
Total area (000 ha, 1993)2 7813 9218 92115 623
Source: CIAT

Cassava is mainly monocropped, but intercropping is common on parts of Java where there are not severe soil and water constraints. Main intercrops here are upland rice, maize and various legumes. In Kerala, intercropping with peanuts (groundnuts) has become relatively common. In China and Viet Nam, maize, peanuts, soybeans and various minor species may be intercropped, usually at a low density. Cassava is commonly used as an intercrop during the establishment of young tree crops like rubber, especially in China and Viet Nam.

In contrast to both Latin America and Africa, genetic diversity is extremely limited in commercial plantings in Asia, with the exception of Indonesia. In most countries only a few varieties account for most of the production. The narrow genetic base has apparently not led to any major production disasters. It did, however, limit the possibilities to extend the range of adaptation, or to make adequate improvement in some characters. By good fortune, few of the pests and diseases of the New World found their way to Asia, so a broad genetic base was less critical for supplying resistance genes, as compared with Africa or Latin America.

Production practices may be fully manual, or with mechanized/animal-powered land preparation. The broadly rising incomes and labour costs in Asia are motivating increased mechanization, especially in Thailand and Malaysia, and in the plantation systems of other countries. Most other operations are manual. The largest production cost for cassava in Asia is consistently labour, especially for land preparation, weed control, and harvest. For example, Ratanawaraha et al. (1997) indicate that labour requirements are 95.7 person-days per hectare in Thailand, comprising 42.6% of production costs. But many of the labour inputs for cassava are technically difficult to substitute with mechanization on small holdings with irregular terrain.

Production costs vary significantly across the region. In general, Asian countries are comparatively efficient producers, by use of some inputs, good management, and low pest and disease pressures. Table 4 illustrates production costs for Thailand, Brazil and Colombia, and the competitive advantage that Thailand has had in world markets in part because of lower costs, both in production and processing.

Products and markets

Diversity is the defining characteristic of cassava products and markets in Asia, both within and across countries. About 40% of cassava in the region is destined for human consumption (FAOSTAT, 1997). In Indonesia, the level is about two-thirds. Most of the remainder is processed for industrial purposes, principally pellets for animal feed, and starch. Raw roots are not traded on any significant scale. The initial processing defines to some degree the market sector to which roots can be destined. This is unlike the grains such as maize which are traded as whole, unprocessed grain, to be converted into any number of products in the importing country.

Figure 4

Fresh for human consumption
Outside of Kerala, India and some poorer districts of China and Viet Nam, nearly all cassava for food is first processed; direct consumption of baked or boiled fresh roots is minor. This form of consumption is largely a rural practice, and often by households having their own backyard garden. Fresh consumption has limited growth potential, and in fact will probably decline with increasing urbanization and changes in dietary preferences.

Chips and pellets for animal feed
The cassava pellet industry has its origin in Thailand, which has a long history of an agricultural economy driven by exports. With a surplus land base, rice exports became the foundation of Thai trade up to World War II. Development of the upland sector in the North and Northeast brought diversification to agriculture, adding maize, kenaf, cassava and sugarcane. The country was always able to produce surplus rice, however, and maize or cassava did not become significant parts of human diets, as in Indonesia or the Philippines.

Following the World War II, modern starch processing machinery was introduced to the Chonburi region of eastern Thailand, and exports soon supplanted those of Indonesia and Malaysia. However, it was starch wastes that became the basis for cassava's future expansion. In 1956 an enterprising West German importer introduced waste from starch processing as a substitute for high cost local grain. The economics were highly favorable, and soon the starch byproduct supplies were inadequate.

A new industry grew around cassava meal, beginning in 1960. Because of high government-supported grain prices in Europe in the post-war period, the expanding animal feed sector sought cheaper carbohydrate sources. Cassava from Indonesia and Thailand filled their needs, going from 131 000 tonnes in 1955 to 323 000 tonnes in 1960. By the end of this period, Thailand had substantially outpaced Indonesia as the principal supplier. With implementation of the Common Agricultural Policy (CAP) in the early 1960s, internal prices of feed grains throughout the European Union were insulated from world market prices, operating between artificially set floors and ceilings. Cassava meal and cassava chips were treated differently in the tariff structure, which completely dictated the trends in import of these two products.

Within a few years, the Thais had developed an efficient production, processing and marketing infrastructure with which almost no other country could compete. The system was based on integrating small-scale production, chipping and drying, with village-level coordination of supply to middlemen who delivered chips to the cargo ships. It soon became clear that shipping expenses were very high relative to product value. This fact, along with complaints about dust pollution in Europe, motivated a shift from chips to pellets already in the late 1960s, and to hard pellets in the early 1980s. Cassava imports to Western Europe climbed dramatically from 400 000 tonnes in 1960 to a high of 7.8 million tonnes in 1982 (Figure 4).

Table 5. World trade of cassava products (chips, pellets and starch: million metric tonnes).
World exports9.
China & Taiwan0.
World imports9.
European Union6.
China & Taiwan0.
Korea, Rep.
Source: FAO Commodity Market Review 1996–97.

The budgetary strains of this grain policy became acute by the early 1980s. The European Union (EU) sought to resolve this by reducing importation of cassava. Because it was politically and legally difficult to mandate these reductions, they sought voluntary restrictions, especially with Thailand. Thailand agreed, first, because of links to other trade agreements, especially textiles; secondly, because of the possibility of more severe restrictions if left to EU members reaching agreement; and thirdly, because of promised development aid for Thailand's Northeast for agricultural diversification. The EU also reached voluntary agreements to export restraints with Indonesia and Brazil. In 1986, Thailand and the EU ratified a new agreement for the period 1986 to 1989, specifying a maximum volume of 21 million tonnes. In 1993 the EU set a quota of 5.25 million tonnes for 1995-1996, with possible reduction in the future. Within the quota, cassava enters the EU at a preferential 6% tariff, and beyond the quota a 30% tariff applies. However, even at these preferential terms, Thailand has not met its quota since 1994 because of competition from grains (Ratawawaraha et al., 1997).

The negative effects of reduced exports to Europe were eased somewhat by growing demand in other countries, and Thailand aggressively pursued these markets. Other countries initially quickly absorbed the excess production, importing over three million tonnes of pellets by the early 1990s. About two-thirds went to Japan, Taiwan and Korea to supply a rapidly growing animal feed industry. Thereafter, grains have also taken an increasing share of that market (Table 5). By 1995, of 3.3 million tonnes of chips and pellets exported from Thailand, 93% went to Europe. This shows that Thailand is still in a somewhat tenuous situation with regard to diversification of its export possibilities for pellets.

Starch for industry is classified as native or modified. The technology for modifying starches with physical, chemical and biological processes is highly advanced and evolving rapidly, These modified starches are absorbing an increasing market share. At the same time, there is pressure in some industries, especially foods, to move away from modification, especially that based on chemicals. Starch-derived products include sweeteners (high fructose syrup, glucose syrup), dextrins, monosodium glutamate, pharmaceuticals and various chemicals. Starch is used in large quantities in the manufacture of paper, plywood, textiles, and as a filler/stabilizer in processed foods. New products from starch are continually entering the marketplace. Throughout the region, the industry is moving toward larger, more technologically advanced plants, and small, less efficient factories are closing.

Figure 5

Thailand is leading the Asian starch boom, surpassing Indonesia in recent years (Figure 5). Both export sales and domestic use have increased significantly. Although the starch export industry of Thailand has been active since the 1940s, it was rejuvenated in the 1980s when Europe began to set limits on imports of dried cassava (Figure 4). This was also a time of rapid economic growth in Thailand, and the starch industry attracted the attention of entrepreneurs. The focus for exports has been on modified starches, to get around some of the import barriers imposed against native starch. Nonetheless, the increase in starch exports has not nearly kept pace with the decline in pellet exports. Private and public sectors are cooperating to identify and exploit internal growth markets for starch as a complementary strategy to export-orientation.

Internal markets absorb most of Indonesia's starch. Nearly two-thirds goes into krupuk. Because of the specific starch characteristic required for this product, maize starch is not a competitor. This gives some insulation from the fluctuations of world starch prices. Both China and Viet Nam have significantly expanded and modernized their starch industries. Monosodium glutamate and glucose (starch derivatives) are rapidly growing markets in both countries. In Thailand, Indonesia, and Viet Nam, cassava is virtually the only raw material for starch production. Any growth in the starch market will benefit the cassava sector. In China, India and the Philippines, there are other starch sources (specially sweet potato and maize in China), but these are often used in industries such as noodle-making where cassava starch does not compete. Hence, even in these countries the market potential for cassava starch is strong.

Cassava flours come in many forms. The most common is gaplek in Indonesia. Roots are peeled, chipped or sliced, and dried. The dried chunks are ground or milled to a meal, which is then used in a wide array of food preparations. It is consumed especially in times of rice scarcity, and partially substitutes for rice in rural daily diets. Cassava flour may partially substitute for wheat flour in bakery and other products. This is still minor in Asia, but is reported unofficially from several countries (Henry and Gottret, 1996).


Thailand's continuing campaign to reduce its dependency on the European animal feed market will dominate directions of the Asian cassava sector for the next decade. This will take several forms: introducing production technology to keep prices competitive with alternative energy sources; aggressively seeking new markets outside Europe; development of internal feed markets; and further diversification into starch and flour, with strong support for research on new processes and products. Other countries of the region, once with aspirations to penetrate export markets for pellets, are now recognizing that opportunities will depend very much on increasing production and processing efficiencies.

Table 6. Projected production and utilization of cassava in 2020.
 Growth rate for utilization
1993-2020 (% per year)
Utilization in
Production in 2020
 FoodFeedTotal(million tonnes)(million tonnes)
Other East Asia-0.951.090.633.50.0
Other South Asia1.000.000.830.60.6
Southeast Asia1.40.131.2527.051.1
Latin America0.261.260.7839.340.5
Sub-Saharan Africa2.510.292.47166.0166.0
Source: Adapted from Rosegrant and Gerpacio, 1997.

Prospects for starch vary widely depending on the specific market. There are two extremes: purely commodity starches with generic application, and highly specialized starches reliant on functionality. The latter are often derived from modified starches. However, in the middle, there are starches that are comparatively specialized, though sharing functionality with other starches. In this group, functionality is the initial criteria of suitability, followed by price and supply. For generic starch, the different sources (maize, cassava, sweet potato and white potato) compete with one another on the basis of price. The markets for specialized starch are rather uncertain. On the one hand there is increasing demand, but on the other, there is a continually evolving technology for modifying starches to meet specific product properties. While technology for modification is moving rapidly, at the same time there is a strong trend away from modified starches in some products and in some key markets like the US and EU. For example, baby foods use virtually no modified starches, and the amounts used in soups is much reduced compared to just five years ago. Ostertag (1996) suggests that most developing countries will use their resources most effectively to first concentrate on developing internal starch markets, to reduce the risks inherent in the export sector.

In a recent study of the major tropical root crops, Rosegrant and Gerpacio (1997) of the International Food Policy Research Institute (IFPRI) project cassava production and utilization in the year 2020, based on a model that takes into account virtually all the world's food production and consumption (International Model for Policy Analysis of Commodities and Trade (IMPACT). Moderate demand growth for cassava products in Asia through 2020 will sustain viable cassava-based development. The growth sectors vary within the region. In China, growth in feed demand will be among the strongest anywhere, at 2.1% per year, accompanied by a continuing trend for lower direct use as food. Southeast Asia should see healthy growth in all sectors: 1.4% in food, 0.13% for feed, and a total of 1.25% (including industrial use) (Table 6). The import demand in the non-cassava producing countries of East Asia will rise at 1.0% per year, providing some additional market possibilities.


Several key forces will define cassava's potential as a catalyst for development in Asia. A cassava strategy needs to delineate crop-specific objectives based on unique characteristics of the crop, but which also complement and exploit the broader socio-economic environment.

Impact of the external environment

The policy arena more than any other will set the stage for cassava's role in Asia. Both agricultural policy as well as broader economic policies impact the cassava sector. Distortions in input and output markets, asset ownership, and other institutional and market distortions adverse to the poor must be minimized. In order for agriculture to drive rural development, human resources must be improved through investment in education, health care, nutrition and sanitary environments (Pinstrup-Anderson and Pandya-Lorch, 1996).

Figure 6

Liberalized trade became the economic mantra of the 1990s. The watershed Uruguay round of multilateral trade negotiations, under the auspices of the General Agreement on Tariffs and Trade, was a fundamental influence on the direction of the global economy. While more recent attempts at broad trade agreements under the auspices of the World Trade Organization have been less successful, there is little likelihood of reversing the broad trend toward freer trade. Trade liberalization will bring complex and unpredictable adjustments in the agricultural sector. The implementation of regional trade agreements is well-advanced in Asia. The Asia Pacific Economic Co-operation forum (APEC) has 18 members, which in total comprise half the world economy. Most of the major cassava-producing countries of the region (excepting India) are members. APEC aims to achieve free and open trade and investment by 2010 for its industrialized members and by 2020 for the others. The Economist® magazine called APEC “potentially the most far-reaching economic agreement in history” (27 Sept. 1997).

Previously-protected sectors of the economy are in flux as they are subjected to the open market. Countries who expect to export their products are under strong pressure to open their markets to imports as well. Agriculture has been one of the most broadly affected sectors by this trend, since it is of nearly universal relevance to countries' economies, and touches fundamentally on the lives of nearly all people. On the whole, liberalized trade agreements should drive broad-based growth through specialization, efficiency gains, and increased trade in agricultural products. In a free trade environment, commodity prices typically fluctuate more (based on supply and demand) than in a regulated environment. Producers are more likely to switch in and out of crops to take best advantage of these fluctuations. The dilemma that cassava-producers often face, however, is the fact that they have little flexibility in choice of crops. First, on the more marginal soils, cassava may be the only choice without resorting to costly inputs. Secondly, the nature of cassava's propagation does not allow quickly gearing up for production if a supply of planting material has not been assured by the previous year's crop. Stabilizing demand in an environment of freer trade will depend on the ability of the industry to respond quickly to shifts in product demand.

 Table 7. Growth in gross domestic product and rural population In principal cassava-producing Asian countries. 
  Gross domestic product growth
Share of agriculture in GDP
Rural population
 1980-91 avg.199519931993 
  Viet Nam5.79.529.379.6 
 Source: World Bank. 

Demographics, income and food demand
The United Nations projects that global population will continue to rise to about the year 2040, when it will have doubled from today's level, to 8-11 billion. By far the greatest burden of this continued population growth will be felt in urban areas. Like much of the rest of the world, Asia has been moving toward greater urbanization for at least several decades (Figure 6). This is largely the dynamic that drives commercial agriculture - urban dwellers need to purchase nearly all their food. Still, populations continue to rise in rural areas, and pressure on land is increasing.

Population dynamics affect cassava production and marketing in various ways. In the simplest of cases, population increase imposes a proportional increase on food demand. With most of the productive land already cultivated, this places pressure on marginal environments where cassava has strong adaptive advantages. On the other side, urbanization typically reduces demand for cassava and its products for direct food use. Huang and Bouis (1996) note several reasons for shifts in food demand that follow urbanization:

An affluent diet requires about three times more primary production biomass per capita (about 1 570 kg/year) than a healthy, largely vegetarian diet. Penning de Vries et al. (1995) suggest that all regions of the world can produce the food required for an affluent diet, by 2020 except for East, South, and Southeast Asia, where almost half the global population will be concentrated. For these regions, only much less expensive diets, or massive food imports may be the only options.

Except in Indonesia and southern India, cassava has never been broadly popular as a dietary staple in Asia. In several countries there remains a considerable stigma against cassava as a food - a reflection of past difficult economic times. Rising incomes will further erode cassava's direct role in Asian diets. The overwhelming preference for rice as the starchy staple, and the increasing demand for meat (Figure 7), will keep per capita consumption levels low throughout Asia. This growth in meat consumption, however, is the basis for projecting strong potential to use cassava for on-farm feeding, or in balanced rations, especially for pigs and chickens. A caveat to this scenario is the tendency in developed markets to offer new products from traditional foods, as a way of repositioning a food's public image. For example, in China products derived from sweet potato are undergoing resurgence in urban areas, based on promotion as a healthy food, to counter the image as a poor person's staple (C. Oates, personal communication). In Thailand, cassava-based snack foods are entering the urban, middle-income consumer markets.

Figure 7

While not all countries have benefited equally, Asian economies on the whole have seen healthy growth in the past two decades (Table 7). Industrial development, the service sector and labour demand have all had impact that reverberates throughout all sectors of society. Rising household incomes open the way for purchase of consumer goods, education and health care. Improved tax bases contribute to public infrastructure in the form of roads, schools and public services. In this scenario, cassava tends to move toward industrial uses, such as animal feed and starch-based products.

Trends in associated commodities
Cassava's competitive position in national and international markets is closely linked to internal and world supplies and market prices of alternative commodities or products. Because of cassava's versatility, it may compete with a range of products in different markets.

Figure 8

In the market for balanced feed rations, cassava in dried chip or pellet form competes mainly with sorghum or maize, and sometimes barley. On a global level, maize is the principal source of starch.

In the principal cassava-producing countries of Asia, rice, maize and cassava production all increased three to five-fold in the past twenty-five years (Figure 8). Even this dramatic success, however, was not adequate for supplying growing and somewhat more affluent populations. Grain imports, especially of wheat and maize, rose from near zero in 1960 to 17 million tonnes in 1995 (Figure 9).

However, on a global basis, grain supplies have increased steadily and prices have been declining in inflation-corrected terms (Figure 10). Projections by IFPRI and FAO indicate that if governments pursue appropriate economic policy and invest in agricultural research, cereal prices will continue their downward trend (Pinstrup-Anderson and Garrett, 1996).

Figure 9

The cassava market will, for the most part, parallel these declining commodity prices. Rosegrant and Gerpacio (1997) project a price decline for cassava on world markets of 3.4% by the year 2020. While this is a lesser decline than projected for other roots and tubers, it represents a substantial challenge to growers. The ability of producers to remain economically viable depends largely on improving production efficiencies and/or incorporating value-added processes or products into their system.

Subsistence farming requires virtually no infrastructure - no need for purchased inputs, and no need for highways for reaching markets. Commercial agriculture, on the other hand, depends heavily on infrastructure. The World Bank notes that rapid economic expansion and urbanization have outstripped the capacity of existing infrastructure, and created serious impediments to further investments and growth. Insufficient electricity generation capacity, outdated and inadequate telecommunications facilities, poor roads and inefficient ports are the most crucial infrastructure problems.

Figure 10

Purchased inputs for agriculture are for the most part available, but may not be used on cassava because of other constraints. There is little likelihood of major investment in infrastructure aimed solely at supporting cassava development, but the general development of the region will bring collateral benefits to cassava production, processing and marketing.

Institutional resources

Cassava research is generally supported by departments of agriculture and/or universities, along with CIAT through its office in Bangkok. India and Thailand have major root crop centers with full interdisciplinary research teams. As in much of the world, government attempts to control spending growth have cut into agricultural research budgets in many Asian countries. The private sector has filled this gap in a few cases, but for the most part there remain serious deficiencies in support to the cassava sector.

Table 8 compares national research and development capacity across different disciplinary areas and sectors. Overall, the highest research capacity is in varietal development. Thailand has a clear predominance in broad-based R&D strength, with 22 researchers working on cassava (Ratawawaraha et al, 1997).

 Table 8. Relative strengths of national cassava R&D systems in Asia. 
  Varietal developmentPest/crop interactionsCrop/soil interactionsProcessing/ marketingBasic extension services 
 Sri Lanka*     

There are three cassava-specific networks active in Asia. These networks have a considerable potential to facilitate and coordinate research, in order to make efficient use of scarce resources. Funding is a continual challenge, and none of the existing networks has been able to reach the potential that its members represent.

Cassava breeders formed an informal network in 1984 during a regional meeting. The group later incorporated agronomy, and became the Cassava Breeding and Agronomy Network, and later, simply the Asian Cassava Network. It has held triennial scientific meetings and published widely-read proceedings. The network serves to inform members of research activities, provides guidelines and resources for germplasm exchange and testing, and coordinates specific regional projects with high regional priority. A coordinated series of soil fertility maintenance and erosion control trials were a landmark project of this network.

The Cassava Biotechnology Network (CBN) acted as a stimulus to interest a number of research institutes and private companies in cassava in the early years of the biotechnology revolution in agriculture. The network continues in an informal way, but without funding for coordination. Projects include work in propagation, transformation and regeneration, cyanogenesis, and starch modification. The network is evolving toward a regional structure, in order to bring a better focus to addressing specific regional problems and opportunities.

The Manihot Genetic Resources Network (MGRN) is the newest of the networks, formed in. 1992. As with CBN, it does not have specifically funded coordination or activities, and operates on an informal basis. Its principal activity in Asia has been to plan transfer of the CIAT core collection to Thailand to improve security of conservation, and to broaden the genetic base of Asian cassava.

The resource base and production technology

There are several fundamental issues surrounding development strategies that exploit marginal lands, both from the economic and environmental vantage points. Although less-favored areas make up only about 24% of the total land area in developing countries, they contain more than 36% of all the rural poor. The largest share of these people, 263 million, live in Asia. In the past, governments and donors adopted a strategy of investment in high-potential areas, since by definition, these generate more agricultural output and higher economic growth at lower cost. Even with these strategies, however, population growth and pressure on the environment have continued to worsen in less favored areas. A consensus is now evolving that critical investment in these areas is socially necessary, economically viable, and imperative for reversing serious land degradation. Hazell and Garrett (1996) suggest four key elements of a strategy for agricultural intensification for less-favored areas:

Cassava can be a key component within this strategy. The adaptive advantage that cassava has here is quite strong, but there are trends that could change this. First, other crops may begin to offer broader alternatives to cassava farmers. Breeders of several species, especially maize and sorghum, have paid more attention to stress tolerance in the past twenty years. There are certainly practical limits to which breeders can take a given species in adapting it to new environments, but there is also apparently considerable margin for improvement for most crops in stressed environments. This progress could displace cassava from some areas, and perhaps continue to push the crop toward the very poorest soils. The need for effective and economical soil fertility maintenance and erosion control will increase with this trend.

Secondly, farmers' increased purchasing power, and technology for soil stabilization, will allow improvement in some areas, from marginal to moderately productive conditions. This would also tend to displace cassava. In either scenario, cassava will probably be pushed further toward the very poorest soils, exacerbating the risk of environmental degradation.

Most national cassava programs have given research priority to resolving production constraints, especially through varietal improvement, and crop and soil management. This approach evolved from the era of explosive growth in cassava markets, and the need to meet market demand with increased production. As the challenges of marketing cassava products become more acute and environmental concerns more apparent, programs are shifting the balance of research investment to include both demand and supply factors.

Asia has been a leader in developing innovative systems for technology transfer. There are a number of successful experiences and examples involving joint private/public cooperative programs. Most have been initiated by starch industry entrepreneurs, with a vested interest in improvements in productivity and root quality. In Thailand, the Thai Tapioca Development Institute helps multiply new varieties, distribute these to farmers, and provide training in technology adoption (Ratanawaraha, 1997). In Sumatra, vertically integrated starch industries support technology development by funding national and international center research, transfer to surrounding farmers as a way of assuring their supply of raw product, and as a contribution to regional development. In China and Viet Nam, the private sector is beginning to experiment with involvement in technology transfer.

In an exercise to quantify constraints on global production, processing and marketing, CIAT surveyed a broad range of scientists and others knowledgeable about the cassava system, for their experience and perspectives (Henry and Gottret, 1996). A follow-up study (van Norel, 1997) obtained further information from national programs, intending especially to upgrade information on post-harvest constraints. Table 9 summarizes key information for Asia, with comparison to global estimates, for:

Table 9. Cassava constraints analysis for Asia, with comparison to global.
ConstraintsYield gain in affected area
Area affected
Total yield gain
Total yield gain (000 tonnes)Total yield gain as % of globala
Soil Management  3517 06736
 Low soil fertility32682210 69032
 Soil erosion1760105 03943
 Surface temperature112631 33862
Crop Management  2110 29122
 Sub-optimal land prep.8333126222
 Quality of planting material174883 95819
 Inadequate spacing84741 85330
 Weeds183773 21823
Intrinsic Varietal Traits  2411 38431
 Low yield potential26892411 38431
Climate  115 15325
 Drought165894 49626
 Low winter temperatures08165854
Diseases  29293
 Root rots6501515
 Bacterial blight61915536
 Other leaf/stem pathogens08221 04230
Pests  31 4787
 Green and red spider mites63821 1129
 Mammalian pests520463
 Scale insects59021152
 Tipicola plagiata11009100
Total Potential Production Increase 9646 30123
Post-harvest  219 92332
 Processing152441 80630
 Product marketing201841 72747
Total Cassava Sector11656 22424
Source: adapted from Henry and Gottret, 1996.
a Yield gain in Asia as percent of expected global yield gain from alleviating a given constraint.

Soil management
Significant constraints from low soil fertility and erosion affect much of Asia's cassava. Nitrogen is frequently the limiting nutrient, in contrast to Latin America, where potassium and phosphorus tend to be more limiting (Howeler, 1995). Fertilizer recommendations have been established on the basis of extensive soil analyses and fertilizer trials. Fertility constraints are as much a function of education and credit availability as the lack of scientific information. In India, China, Viet Nam and Thailand, about half the farmers use small amounts of fertilizer, usually not at economically optimum levels. In Indonesia, associated crops tend to be fertilized, with some residual benefit to cassava. Elsewhere, fertilizer use is very limited except for special situations, such as large commercial plantations. Economically optimum use of practices to improve soil fertility could add 22% to current yields across the region, or over ten million tonnes.

Limiting soil erosion is a challenge in virtually any system involving annual crops on sloping fields. Cassava has two features that increase this challenge somewhat: it is easy to plant on steep slopes, with minimal land preparation; and it has a relatively slow rate of canopy cover. On the positive side, the long growing season means that the soil is covered by vegetation and is undisturbed over a long period of time, once the canopy is established.

The CIAT survey estimated a potential yield increase of 0-10% by adoption of erosion control practices. More importantly, erosion control is indispensable for sustaining longer term productivity. Soil fertility maintenance and erosion control are closely inter-related. An obvious relationship is the loss of nutrients that accompanies erosion. A more subtle association follows from the effect of better fertility on more rapid canopy development. In trials throughout Asia, as well as Latin America, appropriate fertilization is consistently one of the most cost-effective ways to reduce erosion. It may not be enough on its own to reduce erosion to acceptable levels, but it is often a good starting point (Howeler, 1995).

Crop management
On a regional basis, Asia has higher average yields than either Latin America or Africa. Farmers tend to manage their crops intensively, because of high population density and the need to optimize productivity of land. Hence, only modest yield increases can be expected from improving-crop management (excluding -soil management) in the Asian situation. According to the CIAT survey, quality planting material {stakes) and better weed control could contribute 7-8% each to yield, while optimum land preparation and spacing would provide modest yield improvements of only 3-4% each.

Farmers are often unaware of the multitude of influences on stake quality. Many constraints do not conspicuously affect stake appearance, and are not recognized as yield-reducing constraints. Given the generally low incidence of pest and disease problems in Asia, it is likely that suboptimum quality of planting material derives primarily from a complex of physical rather than biological constraints. These may include: nutrient status, as an outcome of soil conditions or length of storage; poor stake selection (too young, too old, etc.); poor storage conditions; or poor post-storage management. Technology for optimum stake management is available from many trials at CIAT and elsewhere, and some could be tested further in Asia.

Weed control consumes the second highest level of labour input among crop management operations in Asia, from a low of 13 person-days/year in Malaysia and the Philippines, to a high of 97 in Tamil Nadu, India. In general weed control is good; CIAT survey results indicate inadequate control in about 37% of area planted, for an overall potential yield increase of about 7%. Currently, most weed control is manual, but herbicide use is increasing in all countries, and is most wide-spread in Thailand. As demand for herbicides grows, agro-industries will find it profitable to develop herbicides targeted more specifically to the cassava plant and cropping systems. Currently herbicides are adapted from other crop systems to cassava, and often have not been adequately researched to optimize their use.

Herbicide resistance is already being engineered in several crops and is widely used in the United States, especially in soybeans and maize. Within a few years, these technologies will also be commonplace in parts of the developing world. The technology will become so routine that developing resistance even for crops with low herbicide use, like cassava, will eventually become economically attractive. For cassava, herbicide resistance could have significant impact since the current options are so narrow. There are, nonetheless, many technical, economic and political barriers to remove before this technology could become reality.

Intrinsic varietal traits
Intrinsic yield potential may be the single most important factor limiting yields in Asia (Table 9). The definition of yield potential for cassava needs to be considered within the context of the crop's predominant role in Asia as an upland crop, in poor soils and with irregular rainfall. The classical definition generally considers yield where there are no limitations on sunlight, nutrients, water, or soil structure. Since cassava rarely comes close to these conditions, projecting the contributions to improving yield potential needs to be based on more practical goals. The CIAT survey exercise did not define precisely the conditions for which yield potential was being defined, but specified a moderate level of management inputs, within the reach of most farmers of the region. This would be a moving target, presumably increasing as agriculture develops.

For the medium-term future (10–15 years), this would rarely include irrigation, with the exception of existing irrigated areas. The definition specifies nutrient use at low to moderate levels, but with most other agronomic practices-at optimum levels - land preparation, planting systems (time of planting, stake position, spacing), and weed control. Within these specifications, the analysis suggested a possible 26% yield gain across 89% of the Asian cassava-growing area, or a 24% potential increase over all Asia.

A number of pathways are possible for increasing that potential. These can be broadly divided into approaches that increase harvest index (direct a greater proportion of photosynthate to the roots as compared to top growth); and that increase total biological yield. Much of the research in recent years has been directed at improving distribution of photosynthesis, but both approaches have been successful. Probably the greater difficulty and greater potential lie in improving total biological yield, since many individual mechanisms may each contribute - increased efficiencies in photosynthesis, nutrient uptake or utilization, and starch synthesis, for example. Breeders are already combining higher biological yield and higher harvest index as an effective multi-pronged strategy to improve yield potential.

Biologically, cassava is relatively straightforward as a target for genetic improvement. Two particular constraints confront the breeder: a low reproductive rate, either by vegetative or sexual means; and a long breeding cycle. On the other hand, vegetative propagation allows additional options in design of breeding schemes.

Until 15–20 years ago, the germplasm base in Asia was very narrow, with most countries relying on only a handful of varieties. The extreme case was Thailand, where all but a small percentage of area was planted to Rayong I. Indonesia has reasonably broad variability, but still narrow in comparison to Latin America. With establishment of the CIAT Regional Office in Bangkok, one of the main thrusts has been to increase genetic diversity in the region. Typically, breeders introduce ten to thirty thousand seeds, each genetically distinct, every year from nurseries in Colombia. Even though only a small fraction of this diversity ever reaches farmers' fields, there is little doubt that far more genetic diversity was introduced into Asia in the past twenty years than in the previous two hundred.

Climate constraints
Drought imposes severe constraints on cassava growth and yield in parts of Asia, particularly northeast Thailand, eastern Java, and southern India (especially Tamil Nadu). Survey results indicate a potential yield increase of 9%, through a combination of practical management, and breeding for varietal adaptation. Management can include improving the soil's water-retaining capacity through incorporating organic matter, surface mulching to reduce evaporation, or ridging to capture maximum rainfall. No increase is projected through expansion of area under irrigation.

Pests and diseases
Perhaps the single most striking contrast between production in Asia and elsewhere is the severity of pest and disease constraints. With a few important exceptions, these constraints are very limited in Asia. The Indian cassava mosaic disease, with etiology and symptoms similar to the African strain, occurs exclusively in India. Control is mainly through resistant varieties. The CIAT survey estimated a potential medium-term yield increase of 6% within the affected area. This low figure reflects the fact that moderately resistant varieties are already widely used by farmers. Root rots and bacterial blight are endemic in the more humid environments, especially in the Philippines, and the sub-tropics. Root rots can be controlled mainly through management (rotation, land preparation) and bacterial blight through resistance breeding.

Among the arthropod pests, only the red spider mite is of broad importance. Its control through host plant resistance or biological control could contribute about 2% to overall yields in Asia. The pest and disease situation will require constant monitoring. Introduction of new pests or pathogens, or changes in cultural practices could set the stage for new yield-reducing outbreaks.

Production potential
The sum of individual components defines a potential yield increase of 96% by moderate alleviation of constraints. Given the existence of technology components to address nearly all these constraints to some degree, it should be possible to test the reality of these figures. The detailed, long-term experiments to obtain good quantitative data have not been done, and are not currently planned. Nonetheless, empirical data from experiments having other objectives give some insight. The Cassava Breeding and Agronomy Network has carried out well-managed trials in Asia for almost two decades. While breeding trials are aimed mainly at identifying potential new varieties, the trials also include good soil preparation, optimum plant spacing and weed control, and moderate fertilizer use. Table 10 compares yields in several countries and regions, along with best local varieties and national average yields. Yields of the hybrids, under good management in representative cassava areas, were two to five times greater than the national average. Most of this increase appears to be from management, since hybrids yielded about 30% more than local varieties, similar to the potential increase projected by the constraints analysis. These figures suggest that the constraints analysis is quite conservative in its estimates of potential constraint alleviation. On the other hand, many actual production areas probably have greater levels of constraints than those where trials were conducted. In any case, the potential for doubling yields, as suggested by the analysis, does not seem to be out of reach, given strong research and development support.

Table 10. Potential of good management and Improved germplasm in increasing cassava yields.
 Region (No. of trials)
 Thailand (14)S.Viet Nam (15)N. Viet Nam (19)S. Sumatra (4) PhilippinesMean of all sites
Mean of hybridsa 33.6b44.730.238.944.138.3
Best local 28.422.521.933.141.929.7
National avg. 8.710.8
Hybrids over national avg.242%514%347%275% 507%355%
a Kasetsart 50 and Rayong 60
b Conversion from dry yield based on 32% DM
Source: Adapted from CIAT Ann. Rept., 1996, Improved Cassava Gene Pools Project.


In the context of the survey, post-harvest constraints do not quite fit into the same analytical scheme as production factors, for projecting yield gains from constraint alleviation. In order to be consistent with units for yield gain, the post-harvest elements are divided into three parts: quality improvements are based on expected price premiums; gains in processing on reduced costs per unit; and gains in marketing on reduction in marketing margins (mainly reducing consumer prices). These estimates have some highly subjective components, and are biased toward the very conservative side.

Improved root quality will have the highest overall positive impact on post-harvest constraints (Table 9). Two traits are especially relevant: starch and post-harvest deterioration. Starch content is key to nearly every use of cassava in Asia, and especially the industrial sectors of starch extraction and pellets for animal feed. Raising starch content by breeding is clearly feasible, and has been a major objective of genetic improvement in most programs. Much of the recent success of new varieties in Thailand derives from a higher starch content as compared to the landrace variety Rayong 1 (CIAT, 1996).

Cassava roots normally begin to deteriorate-within a few days after harvest. The processing industry has had to develop elaborate systems for coordinating supply of raw material with processing capacity. This has often worked best when roots are converted at the farm or village level to a more desirable product, such as dried chips. When fresh roots are delivered to a central factory, many small producers must coordinate their harvests. Even under the best circumstances factories processing fresh roots cannot operate at full capacity throughout the year. Extending_the post-harvest period could add valuable flexibility to cassava management systems.

Currently-known management techniques include refrigeration, paraffin-coating of roots, and treatment with microbial inhibitors, followed by storage in plastic bags. None of these are practical for managing large volumes of roots destined for processing. A genetic approach seems most appropriate, given the ease and low cost of implementation. Longer term, there is reason to believe biotechnology approaches could offer innovative solutions (Wenham, 1995).

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