| Viet Nam
by Dr. Nguyen Thi Mui |
| 1. INTRODUCTION Viet Nam stretches 1,600 kilometres from China to the Gulf of Thailand, encompassing virgin forests, rugged mountains and fertile valleys. Shaped like an elongated S, or to the more imaginative a "descending dragon", Viet Nam covers the length of the Indochinese peninsula, bordering the China Sea in the East, Laos and China in the north, and Cambodia in the west (see Figure 1). Viet Nams territory includes a vast sea area including a large continental shelf and various islands. Viet Nam is endowed with considerable diversity and is located between 80 33' and 230 20' North and 1020 and 1090 27' East. At either end of the country are two alluvial plains, the Red River Delta in the north and the Mekong Delta in the south.
Figure 1. Map of Viet Nam. Viet Nam has a history of 9,000 years. The capital is Hanoi and there are big cities such as Haiphong and Halong in the North and Ho Chi Minh, Danang, Hue, Nhatrang, and Cantho in the South. Although Viet Nam has 60 different ethnic groups and languages, Viet Namese is used throughout the country. According to the World Factbook the July 2006 population was 84,402,966 with a growth rate of 1.02%. There are a number of administrative units at province, district, city, town and commune level. Table 1 shows the extent of various land-cover types. Specific classes like marsh and mangrove are mainly in the Mekong Delta; forest is categorized as evergreen or deciduous; other groups like scrubland, agricultural area and water bodies are also noted.
At constant 1994 prices, Gross Domestic Production (GDP) increased by 8.71 percent in 1995. In comparison with the index of 1995 (1995=100), GDP increased 40 percent in 2000. From 1995 all sectors of the economy continued to grow. Agriculture, forestry and fishing were 24.3 percent of GDP in 2000 (General Statistics, 2000). Gross output of agriculture in 2000 was 125,384.3 billion dong (1 US$ =15,000 Dong); crops had the highest share with 77 percent, livestock was 20 percent and services 3 percent. The two major classifications of land are alienable (tenured land and farm land) and forest lands, both of which are lands of the public domain. Forest land covers 9,280,230 hectares of which 1,471,400 hectares are planted. There are types of forest classified as public forest, permanent forest or forest reserves, timber land, grazing lands and others and which are not alienated. Total area of crops was 12,470,700 hectares in 2000 including cereals, annual industrial crops, perennial industrial crops and fruit. About 83 percent of farm land is used for annual crops and only 17 percent for permanent crops. Planted area and gross output of cereals (paddy and maize) in 2000 were 8,368,900 hectares and 34,483,500 tons, respectively. Data show a total area of 7,540,900 hectares of paddy and an output of 32,554,000 tons. All paddy is based on smallholders and is irrigated. Gross output of cereals per capita was:
Average farm area was 0.82 hectares, with close to 50 percent of farms below 0.50 hectares. Land areas and yield of crops and crop categories are shown in Tables 2 and 3. Farm work is done by the farmers themselves with some help from their families or between families. In larger enterprises in the Mekong River Delta, farmers may hire other persons for field preparation, planting and harvest. Management of farms is in the hands of the family members. Payments to labourers are in cash or in kind depending on the prevailing rate in the locality. The labour required for different agricultural activities or for certain crops varies with location and cropping systems; the use of animals, tractors or machines facilitate work.
For the livestock sector, from 1994 to 2000, the average increase in cattle numbers was 2.1 percent, 6 percent for goats and sheep, 4.4 percent for pigs and 6.6 percent for poultry. The ruminant population has been increasing for the last six years, except for buffaloes which recorded a 0.43 percent reduction and although there was no change in the horse population between 1994 and 2000 there was a decline thereafter. Viet Namese statistics on animal numbers are given in Table 4.
Of the countrys land area, forest has the highest share with 28.6 percent. Agricultural land has about 18.7 percent while land for special use (hospitals, schools and universities, industry, mining and quarrying) and homesteads (fisheries, settlements and open land) account for 4.7 and 1.3 percent, respectively. At present, grazing areas are on community forest lands. In terms of value of production at current prices cattle, buffaloes and small ruminants contributed 11,919.7 billion dong or around 65 percent of the total animal production in 2000. Poultry contributed 3,295.7 billion (18 percent), while non-meat production contributed just over 15 percent (2,802 billion dong). Livestock is a major source of income for smallholders. Production data are given in Table 4. Due to shortage of local milk, 90 percent of the countrys milk requirement is imported, largely in dry form (see Table 4). |
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| 2.
SOILS AND TOPOGRAPHY Viet Nam can be divided into four physiographic regions: the Annamese extending from north to south through west-central Viet Nam, the Red River delta in the north, the Mekong River delta in the south, and the coastal plain in the east. The extremely rugged and densely forested Cordillera, a southward extension of the Yunnan Plateau, covers about two-thirds of the country. Parallel northwest-southeast ranges with several peaks rising to more than 1,800 metres dominate the northern half, and a series of heavily eroded longitudinal plateaus average elevation 750 to 1,500 metres extend into the southern half. Figure 2. Soil map of Viet Nam Viet Nam has fourteen soil groups and 31 soil units (a simplified soil map is shown in Figure 2), however, for easier evaluation these soils can be grouped into 2 big combinations: Mountainous and hilly soils: most are Acrisoils, Ferralsols, or Alisols. Under annual cropping, without reasonable improving measures, the soil is rapidly degraded. The mountainous and hilly soils should be reserved for afforestation, cultivation of perennial crops, and fruit crops with appropriate protection measures. Delta Soils. The centres of food production are mainly the deltas of the Red River, the Mekong River and other rivers. These are regions with high levels of intensive cultivation and crop intensity. With irrigation, moisture is sufficient, the rate of soil degradation is low; alluvial deposits bring fertility annually; this is often augmented by organic and mineral fertilizers. The soil and vegetation characteristics of the main agro-ecological regions are described below: North-eastern Region The topography slopes from Northwest to Southeast with an average altitude from 400-500 metres. In coastal regions bordering upon the deltas, there are sloping hills and land with an altitude above 200 metres. Soil developed on calcareous low hilly and mountainous regions belongs to the yellow and red group. Alluvial soils are found in the valleys, along rivers and deltas. Two thirds of the forest has been removed and bare hills remain, or a thin secondary forest cover which can regrow in areas of high rainfall. Highland soils are easily lost through erosion. Northeast Hoang Lien Son Region This region and the Northeast are bordered by a range running from Nag Son and Coc Xo to Tam Dao. The border with the Northwest is the Hoang Lien Son range. Bare hills, and mountains cover 3,300,000 hectares. The main geomorphological units are
The soil developed on low calcareous hills belongs to the yellow and red group. Alluvial soils are found in the valleys along rivers and deltas. Two thirds of the forest has been removed and bare hills remain; a thin secondary forest cover can regrow in areas of high rainfall. On highland areas soils are easily lost through erosion. The North-west (Tay Bac Region) The land slopes from northwest-east south, bounded by the Hoang Lien Son range and Pulasan-Pudendinh and Panamas ranges along the Viet-Lao border. Mountain ranges and highlands are divided by valleys, large rivers and streams running North West-Southeast. This region can be divided into geomorphic forms as follows:
The soils of the region are: yellow-red, yellow-red humus group on the mountains and humus soil on high mountains. The soils on the level land are alluvial, black, deposited soil, brown soil on neutral and volcanic rocks, and red-brown soil on calcareous rocks. In general, soils are acid and poor, and very shallow. On the calcareous highlands and Dien Bien and Pudendinh regions, the soils are relatively deep. Northern Central Region Average mountain height is 1,000 -2,000 metres : these mountains form a narrow range along the Viet-Lao border, including some with altitudes above 1,000 metres and some are above 2,000 metres. However, hills under 1,000 metres account for much of the region. The main soil groups in the mountains are yellow-red, with humus soil. The main soil group of low hills is yellow-red soil on sedimentary rocks. In the delta the soils are alluvial coastal soil and coastal sand soil. Central Southern Coastal Region The Central southern coastal region consists of Bach Ma and the South-eastern Nam Truong Son ranges, which account for a large area. Deltas cover small areas. The arc-shaped mountains make up adjoining ranges with their branches stretching to the sea. Above 1,000 metres the main groups of soil are: yellow-red humus and humus soil while below 1,000 metres the main soil belongs to the yellow-red group. Nam Ngai delta has the highest amount of alluvium in Quang Nam and Quang Ngai provinces. Northwest Delta Region Except on mountains, most soil is alluvial from the Red and Peace rivers. Alluvial land on river banks is extended by about 13,000 hectares by annual silt deposits, of which 74 percent is from the Red river and of light mechanical composition, fertile, suitable for industrial trees, food crops and food trees. Alluvial soil covers the highest areas within dykes. On lower minor areas, swampy soil covers about 46,000 hectares. In coastal regions there is alkaline soil. Around the margin of the delta, there is infertile, eroded grey soil which has been cultivated for a long time. Tay Nguyen Region Tay Nguyen, at average altitudes of 500 to 600 metres, is mainly on Bazan red soil, calcareous rocks and granite hills. Dac Lac highland is lower than Gia Lai highland, and average altitudes are 400 metres to 500 metres. In the South, on the Di Linh and Bao Loc highlands, the main soils are brown ferralitic red soil generated from Bazan rock, with 10-12 metres thick, black, colour faded grey soil, yellow-red ferallitic soil on the sediment rocks and alluvial soil deposited by rivers and streams. The South-eastern Region There are two main soil groups. Grey soil covers 34.26 percent of the region. Yellow red soil covers 44 percent. The yellow-red soil group of red-basalt soil generated on basalt rocks, is heavy with a, high silt and humus content. Mekong delta Region The Mekong delta, a major area of food production, is alluvial and of low relief. |
| 3. CLIMATE AND AGRO-ECOLOGICAL ZONES Its latitude range means that Viet Nam has a tropical monsoonal climate with hot winters in the south and cool winters in the north. The main climatic zones and number of wet and dry months are shown in the agro-climatic map in Figure 3. Nine agro-ecological zones are recognized which are described briefly below (and see Figure 4): Figure 3. Viet Nam: The
main agro-climatic zones North-eastern Region The Northeast suffers most from the effects of the Northeast monsoon. The cold season comes earlier than in other provinces. Winter temperatures are from 1 to 10 oC lower than other regions. Average January temperature in Cao Bang is 11.5 oC and in July 26-27.7 oC; in Quang Ninh in January is 15 to 16 oC and in July 47- 28.8 oC. The rainy season starts between May and September and its duration can vary from 4 to 10 months with the yearly rainfall more than 1,276 mm, except for coastal regions. The number of rainy days reaches 120-160. This supplies enough moisture for 7 to 9 months. At altitudes of 500-600 metres, trees remain of walnut, Pines such as Pinus caribaea, Pinus khasya, Pinus dalatensis, green ironwood Cephalotaxus mannii, Cephalotaxus oliveri, Amentotaxus argotaenia, Manglietia chevalierii, Manglietia conifera, Manglietia insigni, Vatica cinerea, Vatica mangachapoi, Parashorea chinensis which can grow in the cold and dry climate. These trees also remain in minor forests. Figure 4. Viet Nam: the nine
agro-ecological zones Northeast Hoang Lien Son Region In the mountains, the monthly average temperature is over 20 oC from March to November. The highest monthly temperature is hardly above 28 oC, but night temperature in some places falls to below 1 oC. In high mountains, the winter is cold and it can freeze with snow and hoar-frost; average temperature exceeds 20 oC from July onwards. Winter lasts from 70-100 days. The average day temperature is 15 oC. The average number of days below 10 oC is 50. This region is moist throughout the year, with much heavy rain, and the highest rainfall in the country. Rainfall in the less rainy season is 30-40 mm to 60-70 mm/month. By the end of winter, drizzling rains increase strongly. The number of drizzle days exceeds 50-70. The highest rainfall reaches 3,000 mm. In heavy rain centres the amount of rainfall reaches 1,500 mm/month but in drier years, does not exceed 1,500 mm/year. In the mountains rainfall is over 200 mm/month, lasting for 5 months constantly. In low hills and mountains the growing season is under 8 months and rainfall is from 1000-1100 mm/year. Cattle and buffaloes have a long tradition. There are many precious forest trees such as Hopea recopei, Shorea henryana, and Vatica cinerea. The North-west (Tay Bac Region) Due to the geographical structure, the winter is cold, with hoarfrost on high belts. In the summer there is hot wind. During winter the diurnal temperature range is 12 oC to 14 oC. Summer comes sooner than to other regions, from March night temperatures are over 30 oC, and the weather in April is really hot. The month with the highest average temperature is June, but in Lai Chau it is August, in Moc Chau, it is July. The maximum temperature measured is from 41.1 to 42.5 oC. The minimum temperature is from - 0.8 oC to 3.9 oC. The valleys are sheltered from wind, so the dry seasons are longer, and the yearly amount of rainfall decreases. Dry seasons last from 4 to 5 months. The rainfall is usually under 1,500 mm. The varied climate and terrain has created a variety of forest forms. In the North and South East, there is evergreen, tropical-humid forest. The main families are Lauraceae, Fagaceae, Magnoliaceae, Araliaceae and Euphorbiaceae. These forests are characteristic of the ecology of the North-western region and cover a large area; they are also found in Hoang Lien Son on a much smaller area. The East and Southeast of the region have a sparse tropical forest. On high belts, under 700 metres, forests are evergreen-wet and tropical. Trees include Dipterocarpus costatus, Dipterocarpus intricatus, Dipterocarpus kerrii, Vatica fleuryana, Vatica astrotricha, Hopea chinensis, Neohouzeaua. On low lands there is a type of deciduous forest, able to withstand wet and dry climate; broad leaved trees grow among conifers such as Keteleeria davidiana, Pinus khasya, Pinus mercusia and Podocarpus fleurgi. Under 700 metres trees are mainly Dipterocarpaceae, Vatica fleuryana, Vatica astrotricha. Northern Central Region Winters are cold, the average temperature in December to February is below 20 oC (about 16 oC to 19 oC). Average temperatures in July are from 28 oC to 29 oC. In January average temperatures of the North are from 16.5 oC to 17.5 oC and of the South from 17 oC to 20 oC. There is much rain, distributed unevenly. This region suffers from violent storms, hot winds and a winter monsoon. The number of sunshine hours is from 1,500 to 1,700/ year. Calculated radiation is from 105 kcl to 130 kcl/cm2/ year. The yearly average rainfall of Tay Hieu is 1,268 mm, of the North it is 2,399 mm, and of the South is 1,300 mm. In the North and Northwest the flora is partially isolated, deciduous, wet forests with: Combretaceae, Lythraceae, Meliaceae, Sapindaceae, Sterculiaceae and Leguminoseae. In the West above 700 metres, the flora is evergreen and isolated rain forests with Dipterocarpus costatus, Dipterocarpus intricatus, Dipterocarpus kerrii, Symplocos olivacea. On low land along the coast, uncultivated land accounts for approximately 1,400,000 hectares in which there are 85,000 hectares of planted forests and 300,000 hectares of bamboo. Central Southern Coastal Region The yearly average temperature is above 25 oC. There is no cold winter. The rainy season lasts from September to December or January. Above Quy Nhon, the average temperature is above 23 0C; the yearly temperature range of the North is about 5 oC, of the South from Nha Trang it is about 3 oC. In the North (Quang Nam, Quang Ngai), there is heavy rain with 1,600-4,000 mm/year. In the South (from Binh Dinh to Ninh Thuan) rainfall only reaches 1,300 to 1,400 mm/year. Phan Rang is a dry area, the yearly rainfall is from 700-800 mm. The flora of this region belongs to the hot and dry climate of the low mountain belt. Because the dry season lasts for 3-6 months it has a special flora with large isolated bushes and hard leaves. In the East, along central coastal regions, there are also plantations; the main trees are Pinus patula, Pinus caribaea and Eucalyptus. Coastal deltas are used for crop production. Main limitations: violent storms, hot wind, droughts and floods damage the region. Northwest Delta Region Every year there are about 60 to 80 days below 15 oC and there is hot wind during 38 days. Rainfalls of over 50 mm occur 7-12 times. The amount of moisture is enough for over 10 months every year. Radiation is abundant, 105l-120 kcal/cm2/year. Photosynthetic radiation is also high, 56-62 kcal/cm2/year. Rainfall is 1,600-22,00 mm/year. Sunlight is from 1,600 to 1,800 hours/year. Tay Nguyen Region Annual average temperatures are from 21 oC to 23 oC. The hottest months are March and April, the coldest is January. Minimum night temperature are from 5 oC to 8 oC in Da Lat and some time it can be below 0 oC. The diurnal temperature ranges are from 8 oC to 10 oC. Moisture is insufficient from December to March. In many places it rains continuously for five months with more than 200 mm/month (from May to September). Cheo Reo has rainfall of more than 200 mm for two months but yearly amounts are from 1,200 to 1,800 mm and in Buon Ma Thuat it is no more than 1,400 mm. The flora belongs to the isolated and sub-tropical forests of the highland and mountainous region and consists, according to the altitude, of the following floristic types. Above 1,000 metres there is a highland climate, so there are isolated sub-tropical forests with Pinus patula and Pinus dalatensis. Main planted trees are pines, Pinus massoniana, Pinus khasya, Pinus dalatensis, Amentotaxus argotaenia, Amentotaxus poilanei, and tea. Below 1,000 metres, there is tropical, dry broadleaf forest with bushes and tall tropical grass. Main plants are: Cephalotaxus mannii, Amentotaxus yunnanensis, Manglietia chevalierii, Shorea guiso, Parashorea chinensis, Madhuca alpina, Madhuca firma Keteleeria davidiana, Pinus khasya, Pinus mercusia, Podocarpus fleurgi, and other families such as Lauraceae, Fagaceae, Magnoliaceae, Araliaceae and Euphorbiaceae. The South-eastern Region The yearly average temperature in the mountains is 21 oC. The winter diurnal temperature range (from November to April) is 10-14 oC and of the other months from 7 oC to 9 oC. In high and average mountains there is not enough moisture for the whole year; in low mountains and deltas, moisture is just enough for nine months - usually 7-8 months have above 100 mm/month and there is more than 200 mm for six consecutive months. The months, with the highest rainfall are July and August. Rainfall in the mountain is 1,100 to 1,200 mm/year and in the delta from 1,400 to 1,600 mm. The driest months are November and December. Yearly sunlight hours exceed 2000. January, February and March all have more than 200 hours/ month. September has the lowest sunlight time, 100-120 hours. Mekong delta Region Annual average temperatures are from 26-27 oC. In Can Tho, the maximum night temperature is 40 oC and the minimum night temperature is 14.8 oC. The amount of rainfall in the west is very variable with eight months receiving more than 100 mm among which there are six, consecutive months with 200 mm/ month. In Ca Mau it rains continuously for five months with 300 mm/month. In the East and the Northeast of the deltas rainfall gradually decreases from more than 2,000 mm to 1,400-1,600 mm. In some places, during seven months, it rains continuously and for two months receives over 200 mm/month, such as in Chau Doc, Cao Lanh, My Tho, Ba Tri and Moc Hoa; the yearly rainfall is more than 1,500 mm. Sunlight hours are more than 2,700 in the Northeast and 2,300 hours in the west. April has more than 200 hours of sunlight. The Mekong delta has violent floods in September and November. River levels rise at the end of September and the beginning of October and fall in November - then comes a dry season. In the floods, water covers a third of the delta; some places are flooded to 3-4 metres. In some places, salt water encroaches into the delta for 50 km. Salty lands (744,000 hectares) cover 18.9 percent of the region with high alluvium levels. |
| 5.
THE PASTURE RESOURCE The pasture area in Viet Nam is presented in Table 10. Total grassland is 534,100 hectares, or 5.7 percent of all cultivated land, which can be suitable for crops, trees, aquaculture and forestry. The productivity of grasslands has been adversely affected due to their small extent and overgrazing; at present they are producing about 20 percent of their potential because of poor management. In hilly areas natural grazing is still important for feeding cattle and buffaloes.
Depending on cropping patterns from region to region, pastures in Viet Nam are classified as: In the high land, almost 70-80 percent of grasslands are covered with dominant species such as Digitaria adscendens, Panicum repens, Brachiaria dystachia, Brachiaria mutica, Chloris barbata, Cyperus rotundus, Cynodon dactylon, Axonopus compressus, Eragrostis nigra, Paspalum dilitatum and Panicum coloratum and shrubs or trees such as Artocapus heterophyllus, Hibiscus rosa-sinensis, Flemingia sp. Several plants from rice and maize fields serve as forage, the majority them are weeds, and include Cynodon dactylon, Digitaria sp. and Dactyloctenium aegyptium. Other grasses used as feed are Imperata cylindrica, Paspalum conjugatum and Cyrtococcum sp. which grow naturally in orchards and wastelands or idle lots where most of the broadleaf species, such as Synedrella nodiflora, Pseudo-elephantopus spicatus and Asystasia gangetica, are also found. In summer, most land is planted with rice, maize, groundnut, soybean and sweet potatoes. Forage from these crops provides the bulk of fodder for stall-feeding, especially for dairy cows. Urban cattle also feed on vegetable and fruit wastes. Community and government wastelands are used to some extent. Usually milking animals are stall-fed with green fodder and concentrates. Dry and draught animals are maintained on straw, maize stover, and community grazing lands. In winter all farmers sow green maize intercropped with vegetables. According to holding and herd size rice straw provides feed in winter. Other crop residues such as maize grain, maize stalk, cassava leaves, tubers, stalks and sugar cane tops, leaves or stalks are also components of livestock diets. Since the mid nineteen-seventies, a dramatic shift in the paddy growing system took place, from single cropping to two or three crops annually. As a consequence, there is a serious shortage of space and forage for livestock. With the increased demand for milk, meat, and other dairy products, some farmers cultivate large areas of Elephant grass (Pennisetum purpureum), Brachiaria sp., Guinea grass and maize. Some farmers around such big cities as Ho Chi Minh City plant grass to sell green fodder to farmers raising dairy cows and forage cut-and-carry feeding plays a vital role for dairy goats, cattle and buffalo production. Every farmer allocates a piece of land for fodder crops in irrigated areas if they keep ruminants. Several hundred improved tropical pasture accessions have been introduced and evaluated in different ecological environments over the last 20 years by the National Institute of Animal Husbandry (NIAH), and promising forages have been identified. Ruzi grass (Brachiaria ruziziensis), imported in 1991, grows well on grey-soil in the South East region and hilly land of the North of Viet Nam. The cutting cycle of Ruzi grass is quite good at regrowth 40 days with yields of 25 tons dry matter (DM) /ha/year (Duong Quoc Dung, 1995). In high land with low fertility soil Panicum maximum Hamil, Panicum maximum Likoni, Pennisetum purpureum King grass, and Brachiaria mutica, have good production records, from 10- 23 tons dry matter/ha/years (Nguyen Ngoc et al., 1995). Other promising grasses including Guinea (Panicum maximum ) and Signal Grass (Brachiaria decumbens) which are able to perform in any of the sedentary and alluvial soils in all agro-climatic zones (Table 11). Brachiaria humidicola and Tripsacum andersonii (Guatemala grass) are important on acid sulphate soil and in areas with a high water table (Dung et al., 1999); on all soil, Napier (Pennisetum purpureum) is outstanding, Brachiaria ruziziensis, Panicum maximum TD58, Panicum maximum K280, and Panicum maximum Likoni have shown vigorous growth in acid soil.
In Daklak in the Central Highlands, some 21 improved grasses and legumes which grow well have been extended to farms rearing ruminants. All are planted for cut and carry but receive neither fertilizer nor irrigation; the edible biomass yields are promising (Table 12).
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