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* Professor and Senior Scientist, Cuulong Delta Rice Research Institute, Omon, Cantho, Vietnam.

Crop diversification as understood in Viet Nam is defined as the strategy of shifting from less profitable to more profitable crops, changing of variety and cropping system, increasing exports and competitiveness in both domestic and international markets, protecting the environment, and making conditions favourable for combining Agriculture-Fishery-Forestry-Livestock.

Before 1989, when Viet Nam was a net food importer, crop diversification was studied under the National Cropping Systems Project based on rice and under the International Farming Systems Network, coordinated by the International Rice Research Institute (IRRI). The Project aimed mainly to increase food production.


2.1 Crop Production

There are 18 major food crops, in addition to the main fruit species, cultivated in Viet Nam. The cultivated area, yield and production of these crops are presented in Table 1. Rice occupies around 85 percent of the total area under rice, corn, sweet potato and cassava.

Data from Statistical Publishing House (Hanoi, 1999) show that the total area under crops was increased by 2,665,000 ha from 1990 to 1998. The increase of food crop area was the lowest (20.1 percent). The perennial industrial crop area was the highest (83.4 percent). Vegetables, annual industrial crops and fruit crops, increased by 50 percent as compared to the extents of 1990. Diversification on rice land has decreased, especially in the Mekong Delta, because of the fluctuation of prices of upland crop products grown in rotation with rice or through diversification of rice land. Farmers have frequently met with risks and uncertainty in prices. In the Mekong Delta non-rice food crops only contributed 10 percent to food production.

2.2 Economic Scenario of the Agricultural Sector

Crops, fishery and forestry contributed to the national GDP in 1990 to the tune of 40.7 percent, which decreased to 23.5 percent in 1998, although the net value increased by a big margin.

In terms of value structure, agriculture shared above 80 percent of the total value from agriculture, fisheries and forestry (1995-1998). In the rural economy, agricultural production accounted for around 80 percent with animal husbandry (17 percent) and services (3 percent) making up the remainder. The country is trying to increase the proportion of the value structure from animal husbandry and services through industrialization and modernization.

With regard to trade of agricultural products, rice, rubber, coffee, tea, cashew nut, peanut, black pepper and other horticultural commodities are exported. Agricultural products imported are cotton, edible oil, milk and tobacco. Major crops for export are shown in Table 2. In 1999, 4.5 million tonnes of milled rice were exported from Viet Nam, which became the second largest rice exporter, after Thailand.

Table 1. Cultivated Area, Yield and Production of the Major Crops


Area (1000 ha)

Production (1000 tonnes)

Yield (quintal/ha)

Paddy rice








Sweet potato




















Jute, kanef








Sugar cane
































Cash crops




Fruit crops




Source: Statistical Publishing House, Hanoi, 1999.
Table 2. Main Crops for Export (thousand tonnes)







Milled Rice






























Cashew nut






Black pepper






Source: Statistical Publishing House, Hanoi, 1999.

3.1 Crop Diversification in Rice Land

Rice is cultivated mainly in the Red River and Mekong River deltas. It is difficult to practice crop diversification in the rainy season in both river basins. From November to May or June, upland crop(s) can be grown in rotation with rice if farmers have the capacity to invest on inputs and can get net returns from such cropping patterns. Upland crops in rotation with 2 rice crops are considered as “sub-crop(s)”, for which farmers need not pay taxes.

In the Red River Delta, farmers have experience in growing an upland crop between two rice crops. Spring rice is harvested in June and early 'Mua' rice crop is harvested at the beginning of November. The possible upland crops to follow in this cropping pattern are potato, vegetables, beans etc., or at the end of October it could be corn, sweet potato or soybean. They are sown immediately after harvesting rice to avoid low temperature in winter. Short duration and non-photosensitive rice varieties are chosen for the early Mua rice crop. When necessary, crop seedlings for each hill are prepared by sowing seed in separate boxed seedbeds made of leaves or plastic. Sometimes farmers put seedlings of the upland crop in rice fields about 10 days before harvesting the rice crop. Such cropping systems (rice-rice-upland crop) are practiced on hundreds of thousands of hectares in the North, including the Red River Delta. Farmers can get more cash from the upland crops, especially by growing temperate vegetables such as cabbage, cauliflower and potato which can yield 15-20 tonnes/hectare. There is a residual effect from the upland crop for the subsequent spring rice crop which includes minimizing land preparation and weed control costs, and spending less on fertilizer.

In the Mekong delta, there is no problem of low temperatures. Farmers have grown many upland crops in rotation with rice, except crops of temperate origin such as cauliflower. Farmers grow winter-spring rice from November to February, then follow up with an upland crop before summer-autumn rice. It is interesting to note that in Longxuyen quadrangle, peanut has been grown on heavy soils (60 percent clay) on thousands of hectares, which can yield 3-4 tonnes/hectare. The soils in this region are perhaps high in organic matter (5-6 percent) and the difference of diurnal day/night temperature is high (6-10°C). In terms of residues for the next rice crop, groundnut and vegetable soybean (65 days) are considered the best. Generally, no tillage is applied for upland crops. After burning rice straw, farmers make planting holes and place the seed. One of the problems of crop intensification for crop diversification on rice land is damage from floods in the rainy season. Floods occur from the middle of August and recede in November. Farmers are attempting to experiment with new technologies to overcome such constraints, for example, by using rice varieties with a duration below 90 days, or to apply a method of water seeding for the winter-spring rice crop in order to shorten the duration of the crop in the field.

In the 1960's and 1970's, Azolla was cultivated on a large scale in about 0.5 million hectares in the north, especially in the Red River Delta. Azolla could replace 30-50 percent of N fertilizer for winter-spring or spring rice crop, but this practice has since been abandoned. The reason is that Azolla cultivation requires a lot of labour with very precise conditions in the winter season and farmers had to spray insecticides and apply phosphorous fertilizer every 5 days. They also had to manage water and remove dew to dry Azolla every day when temperature was low (below 15° C), if not, Azolla would die. Leguminous crops such as groundnut, soybean, mungbean for either cash crop or green manure are feasible cultivation alternatives under these conditions. These leguminous crops can be grown in rotation with rice or intercropped with corn as well. Data from production experiments show that vegetable soybean (65 days for green soybean, 90 days for soybean seed) and peanut are the best for the above purpose, grown either as a cash crop or for green manure. Yield of the following rice crop can be increased by 20-30 percent, or it can decrease N requirement by 30-40 kg/ha. When grown as an intercrop with corn, spacing of 80 cm × 25 cm should be replaced by spacing of 120 cm × (25 × 40 double lines), as by these configurations the corn population will have the same plant density of 50,000 plants/hectare, which gives the same yield. Three lines with 40 × 20 cm of leguminous crop can be grown between two lines of corn with a spacing of 120 cm.

3.2 Crop Diversification on Sloping Land

The movement of soil, water and nutrients is the major problem on sloping land. For example, the Red River Basin is located on a split topography with steep slopes measuring 19-37 percent on the average and the Red River, therefore, annually loads 137 billion cusecs of water with a substantial amount of soil and nutrients, leading dramatically to erosion and rapid degradation of soils. Serious deforestation in the past for agriculture development reduced forest cover to 28 percent, but in recent years (1999) it has increased to 33 percent by using different measures.

According to the results of surveys of the National Institute for Soils and Fertilizer (1998), in the North the crop yields have decreased from year to year after clearing forest for crop cultivation. Some of the results are given below:

Crop Yields after the Third Year of Shifting Cultivation (kg/ha)


First Year

Second Year

Third Year

Upland Rice












Depletion of the Organic Matter (0-30 cm depth) after Forest Cleaning

Cultivation Cycle

Organic Matter (%)

First year after forest cleaning


After 5 years of tea cultivation


After 5 years of cassava cultivation


Human activities under severe population pressure and poverty conditions often neglect erosion control measures on cultivated sloping land, although the best control measures are to keep a forest cover or re-forest, or to plant perennial industrial or fruit crops. In this situation, methods of farming activities are recommended such as planting crops on the contour, in combination with agro-forestry and intercropping.

Leguminous plants such as Sesbania cannabina, Crotalaria strata, Cassia tora, Vigna indica, Tephrosia candida, Leucaena glauca and Medicago hispida, are used on sloping land either for soil loss reduction or green manure. Cropping patterns of cassava with intercropped peanut and Tephrosia candida as hedgerows, or hedgerow tea culture on the contour with mulching using rice straw can reduce soil loss by 60 percent or 80 percent, respectively, as compared to traditional cassava monoculture.


4.1 Food and Nutrition Security

Products from crop diversification can be used for food and nutrition security. According to surveyed data in recent years milled rice use per capita decreased by about 1-2 kg/month; whereas there is an increased consumption of other products from agriculture (vegetable, fruits, sesame, peanut, mungbean, chicken, egg, pork, etc.) and from fisheries (fish, shrimp, crab) as a result of diversification of agricultural systems.

Data from surveys in Ho Chi Minh City in 1993 and 1996 showed that per capita/month consumption of milled rice decreased from 10.3 kg to 7.8 kg; whereas meat, fish, and egg consumption increased from 1.44 kg to 1.7 kg, 1.8 kg to 2.2 kg and 7 to 8.7, respectively. There is evidence of an increased consumption of fruits and vegetables. It is also evident that the volume of milled rice exported from Viet Nam is increasing from year to year. This is not only because of rice production increases, but also the improved eating pattern has contributed to this, since rice per capita consumption has decreased.

4.2 Judicious Use of Land, Water and Other Resources for Income Growth, Poverty Alleviation and Employment

Farming systems (popularly known as 'VAC') have become a popular movement throughout the country, led by the National and Provincial Horticulturist Associations, and supported strongly by the government. VAC can be considered as an economical and ecologically stable system within the framework of small farming households amounting to 13 million. Farmers are able to diversify not only crops, but also fisheries and forestry as well. From the original idea of 'VAC', there are several variations to the concept according to different situations and conditions, such as biogas production, field crops husbandry, agriculture, cropping hilly areas, agro-forestry, etc. There are many farmers growing traditional pesticide-free vegetables such as Moringa oleifera lamk., Basella rubra L., Telosma cordata Merr. and traditional medicinal plants for the “green medicine box”, such as barleria lupulina for healing toothache, and Paederia lanuginose Wall for healing abdominal pains, as well as organically grown vegetables. Hence, these are clean vegetables and clean herbal medicines, devoid of any fertilizer or pesticides in their culture.

Farmers in the Mekong Delta exploit the favourable conditions for practicing crop diversification. Because of the experience of flooding in the rainy season every year and drought condition in the dry season, farmers dig small canals around their fields, and make dikes to prevent submergence of farms. Ditches and dikes also help to keep water when flood waters recede. There are drainage pipes through these dikes to take water with silt and aquatic fauna and to wash away acid from decomposing organic matter when necessary. Framers call such a system 'Vuong'. On the dike they plant many crops, feed fish and/or shrimp in canals, and grow rice crops in the fields. Before the arrival of floods, they harvest the rice and fish, and when floods recede, fish colonize the canals once again as the next rice crop is planted. Farmers can, and have to minimize chemical usage to protect the fish/shrimp in canals and the poultry and pigs living on the dikes.

There are some advanced techniques used for increasing rice production, decreasing water use and other material inputs, and making appropriate conditions for diversifying crops in rotation with rice, or feeding fish or ducks with insects that inhabit the rice fields. Some of these techniques are described as follows:

An Improved Sowing Method for Rice in the Mekong Delta

Out of the 4 million hectares of rice grown, there are more than 3.5 million hectares where they apply the broadcasting method (the rest is transplanted) with a very high seed rate of 200-250 kg or even higher. These farmers are now using the row-seeding method with the improved IRRI Seeder to replace manual broadcasting. The results from tens of thousands of hectares in all 12 provinces of the region show that application of the row-seeding method can save at least 100-150 kg rice seed/hectare, making better conditions for feeding fish or ducks in rice fields, decreasing damage by rats and other pests, and with a concomitant paddy yield increase of up to 20 percent.

Use of Very Short Duration Rice Varieties to Reduce Rice Crop Duration in the Field

From 1985, the Cuulong Delta Rice Research Institute (CLRRI) has conducted a breeding programme for rice varieties named 'OMCS', which developed short duration types of less than 90 days. Many such OMCS varieties have been released on a million hectares, not only in the Mekong Delta, but also in the South Central region, while some of them used in the North are OMCS7 and OMCS96. The results from research and production on a large scale demonstrate that the very short duration rice varieties (80-90 days) can grow and yield normally. Many of them can yield nearly 7-8 t/ha with high grain quality and resistance to several pests and diseases. Although agro-techniques for these varieties are new to farmers, they prefer to use them to escape from floods in the wet season, from drought and saline intrusion in the dry season, and have the advantage of saving more cropping days for other crops, or for crop intensification. Attempts are also being made to adopt the seedling broadcasting method from China (preparing seedlings for each hill in plastic plates with small holes). Adopting this method and using OMCS varieties, it is possible to shorten the duration of the rice crop in the field by 20-25 days.


In each agro-climatic zone, there are certain physical constraints. Generally, the main constraints in mountainous, hilly, and middle elevation terraces are erosion, drought, temperature, and soil degradation. Typhoons, floods, low temperatures and pests; and floods, drought and pest infestation are the main physical constraints in the North and South delta, respectively. However, socio-economic constraints are considered as the challenges for the whole country. High inputs for crop production and low quality of crop products are the main problems because of low technology levels applied by many farmers. Credit, post-harvest technology and lack of proper infrastructure facilities are also constraints for crop diversification for the development of sustainable agriculture.

Viet Nam is trying to overcome the above mentioned constraints for agricultural development as well as for crop diversification, in order to meet the requirements of domestic consumption and trade. There are long-term as well as short-term programmes in applying new technologies to improve crop production. National programmes for the development of new crop varieties and animal races, as well as biotechnology in agriculture, are being funded by the national government.

Out of 22 agriculture research institutes, there are 15 institutes working directly on crops, 5 institutes serving crop production, irrigation and water management, planning and projecting, and policy formulation. They have responsibilities in studying and applying biotechnology, geographic information systems, informatics for planning crop production, breeding new crop varieties, post-harvest and processing, formulating policies for the government, and suggesting development strategies under varying conditions. The mandate of agricultural research institutes is to experiment and explore ways of improving technology for better effectiveness.

Agricultural extension systems are organized for villages, districts and provinces by the central government and are coordinated by the Department of Agricultural Extension. There are provincial extension centres for each province, and extension agencies or extension group at district or village level. Besides extension agencies, there are other extension organizations or activities of people's associations, companies, institutes and universities. All of them pay more attention to crop production.

Crop diversification will be given due attention, because of the requirement of improving consumption patterns, as well as for the benefit of all farmers who comprise approximately 80 percent of the population. Total calories from food of farmers and the poor are based on rice by 80 percent. This dependence should be gradually decreased to 60 percent, replaced by edible oil, vitamins, food rich in protein such as soybean, sesame, fruits, vegetables, peanuts, meat and fish. In terms of trade, total income from different kinds of crop products will be higher and more stable in local as well as in international markets. Finally, strategies for crop diversification have been developed and are available for implementation.


In the past, when Viet Nam had to import food to meet the need for food security, food production had to be developed at any price, including clearing forest to plant cassava, upland rice, corn etc., on sloping land, resulting in severe erosion. Nowadays, the direction for agricultural development following the current strategy is to develop all aspects of agriculture based on national food security within the limits of resource availability. The strategy is also geared to increase within the short-term all sources of food and vegetables, in order to improve quality of consumption patterns and to decrease malnutrition. It is also planned to effectively change the structure of agriculture and the rural economy based on a stable food supply with emphasis on rice production (National Political Publishing House, Hanoi, 1996). Some of the salient policies of this proclamation are given below.

· The State has declared a policy on marketing economics from the end of the 1980's, which enables food and agro-products to be freely circulated between regions in the whole country, and even in the international markets. Farmers and companies are free to choose markets and consumers to derive the best benefits. Such an approach has promoted agricultural development, including a boost for crop diversification, which has helped to provide many commodities to consumers.

· The State promulgated the Law on agricultural tax with collection level ceiling at 7 percent of the output as against the previously levied 10 percent. Such tax benefits have encouraged agricultural land use efficiency and ensured equity between organizations, individuals and family householders who are offered land use rights when paying taxes to the government.

· Apart from the agricultural banking system, there are credit cooperatives and a credit fund for farmers. These institutions are promoting direct investment for various agricultural development enterprises. The State has formulated many programmes for financial support to the people in rural areas; special priorities were given to poor farmers and upland inhabitants at low interest. This policy has strongly promoted the development of the perennial industrial crop area and fruit tree culture, especially greening the barren land upstream of the Red River Basin and others.

· Crop diversification has been practiced in the country since 1989, when Viet Nam became a rice exporter. From 1990 to 1998, the growing area under rice increased by 20 percent; whereas the area under industrial crops increased by 83.4 percent; and annual industrial crops, fruit crops, vegetables and legumes recorded an increase of 50 percent.

· There have been a lot of State interventions and policies which support crop diversification and agricultural development in general, such as policy on marketing, on agricultural tax and credit; as well as programmes on poverty alleviation, creating job opportunities, greening the barren land, establishing facilities for transportation of inputs, irrigation and other infrastructure. The State also helped to re-organize and increase investment for agricultural research institutes as well as improving systems of agricultural extension organizations.

· There have been a number of technologies transferred to farmers in order to increase both quantity and quality of crops and improve cropping patterns in the delta regions or in the highlands. The results of production strategies show that almost all crops have yielded better, especially rice. Crop commodities exported from Viet Nam included not only rice, but also other crops. For instance, Viet Nam has become a cashew nut exporter and is ranked third in world commerce; it has also been ranked fifth in world coffee exports, and gained recognition for the export of many other commodities such as tea, rubber, peanut, black pepper, fruits and vegetables.

· The biggest constraints limiting crop diversification in the country are high cost of inputs and low quality of produce because of the use of archaic technologies, often resulting in low benefits. It is necessary to invest in research for developing not only improved varieties, but also better agro-techniques that can enhance the potential of varieties. Much attention should be paid on techniques that do not require inputs of expensive chemicals. Farmers should be encouraged to adopt measures to reduce crop duration, such as growing very short duration rice varieties (80-90 days), and application of the seedling broadcasting method in the Delta regions which can reduce crop duration in rice fields by about 20-25 days.

· Cultivated and growing area under rice amounts to 4.2 and 7.6 million hectares, which occupies 54 percent and 68 percent of the national crop area, respectively. It is necessary to reduce the area under rice for crop diversification in order to enable farmers to get higher incomes and practice sustainable agriculture. Two main directions should be applied to enhance crop diversification: a) to increase the trade value of crop products by growing more profitable crops and adding value through processing; and b) to educate farmers of the 13 million households in Viet Nam in improving their dietary habits by consuming non-rice food crops rich in protein, oil, vitamins and minerals.

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