Sustaining Agriculture in the Sloping Lands of Northern Vietnam through Integrated Watershed Approach

The rainfed sloping lands compose approximately one-third land area of the northern Vietnam and are threatened with degradation due to improper land use practices. The key constraints for crop production are remoteness and inaccessibility, low biological productivity, degraded soil, pest and diseases. The sloping land ecosystems have much lower carrying capacity and respond to crop intensification by rapid declines in productivity, even total collapse. Growth in population densities, combined with deforestation leading to environmental degradation, has created a crisis in the sloping land ecosystems. There are currently no economically viable and environmentally sustainable alternatives available for sloping ecoregions of northern Vietnam.


Why Watershed Approach?

These sloping lands are made up of a combination of upland and lowland ecologies or a toposequential complex of ecologies representing upland, lowland and a costal ecosystem. Watershed framework provides necessary inter-ecological linkages. Watershed combines biophysical, social and economic inputs for optimal management, lead to diversified and high production, control environment degradation and provide a mechanism for the recharge of ground water aquifers. The research partnership between the Vietnam Agricultural Science Institute (VASI) and the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT) was aimed to address these concerns through the Asian Development Bank's (ADB) Regional Technical Assistance # 5812 which began in April 1999. The project "Improving Management of Natural Resources for Sustainable Rainfed Agriculture" is addressing primarily two issues:

• Enhance and sustain crop production and
• Combat degradation of natural resource base
  

With specific objectives:

• Introduce improved soil, water, nutrient and pest management technologies for efficient use of natural resources;
• Reduce soil degradation and increase rain water use efficiency through better infiltration, water harvesting and ground water recharging; and
• Identify and evaluate suitable cropping systems based on the agroecological potential of the region for sustained increases in agricultural productivity and farm income.
  

The approach followed is to encourage maximum participation of farmers' in planning and execution of all activities. All watershed interventions are thoroughly discussed and decided by the farmers. Researchers and extension workers aid in decision-making process and facilitate agreed activities by providing technical support.


Thanh Ha Watershed: Facts and Figures

The watershed is located in Kim Boi district of Hoa Binh Province. Baseline surveys were conducted covering the watershed as a whole for general description of macro-economic, population, infrastructure, institutions and other aspects. But most of the work concentrated at village and household level. Information on physical (rainfall, temperature, solar radiation, topography and soil) and biological (natural vegetation, plant pests and diseases) elements were obtained to determine what crops can be grown in an area, given a suitable environment (economic, institutional and social elements).

Major crops in terms of cropped area are maize (83%), sugarcane (8%), legumes (13%) and watermelon (6%). Groundnut was grown in the past but went out of cultivation due to severe problem of pod rot disease. Cereal monocropping (maize- maize) is predominant and occupies 77% of the cultivated area followed by watermelon- maize cropping system (11%). Cereal - legume cropping is practiced in only 2-3% cultivated area.

Crops and cropping systems

The average yields are low to moderate with a wide range [maize 0.9-7 t ha-1; watermelon 10-36 t ha-1; and mung 0.3-1.2 t ha-1] and low cost: benefit ratio [0.4 (maize), 0.7 (watermelon) and 0.9 (mung)]. Discussions with the farmers revealed that production potential is high if appropriate crops and production technologies are used. Improved seed and cultural practices are being adopted only in maize.

The climate in the landscape watershed is monsoonal with hot, wet summers (April to August) and cool, cloudy, moist winters (December-February). The total rainfall is 1300-1800 mm per annum. The average annual temperature is 25° C, with an average maximum of 35° C (in August) and an average minimum of 12° C (in January). The southwest monsoon occurs from May to October, with high temperatures and heavy rainfall. November to May is the dry season with a period of prolonged cloudiness, high humidity, and light rain.


Soil and Water Conservation

For increased water and soil conservation various measures such as landform treatments (ridge and furrow, contour planting), waterways and drainage channels, field bunds, vegetative barriers, storage of excess water through construction of dugout ponds, cropping intensity increase etc. were undertaken. Three water storage structures with a capacity of 40 cu m were constructed. Fifteen thousand Glyricidia saplings were planted on the field property bunds and contours for stabilizing the bunds and to conserve the rainwater and soil. Staggered trenches, silt traps were dug to capture rainwater, reduce the velocity of runoff and to increase the opportunity time for infiltration. Runoff and soil loss are monitored with automatic data loggers. Preliminary results indicated about 9t soil loss during 2000 rainy season.

Ground water level in 10 open wells (8 inside and 2 outside the watershed) is being monitored at fortnightly intervals. About 1 m rise in the water level was recorded in the wells near the percolation tanks.

Dugout Water Storage Structure

Integrated Nutrient Management

Improved nutrient management practice (180 N: 90P2O5: 90K2O; 10 t FYM; 400 kg lime and biofertilizer) was compared with farmers' practice (200-250 N: 80-85P2O5: 45-50K2O) in maize with an objective to wean the farmers away from high dependence on inorganic fertilizers and encourage balance fertilization. Higher grain yields were obtained with improved practice (5.2 t ha-1) in the second consecutive year and indicated considerable scope for savings on N fertilizer. Application of bio-fertilizer in groundnut resulted in 19.8% higher pod yields (2.1t ha-1) over no bio-fertilizer (1.7 t ha-1) application.


Improved Cropping Systems for Productivity gains and Sustainability

Cereal monocropping (spring maize-autumn maize) is predominant resulting in decline in soil fertility and increase in input costs. Trials to evaluate/identify improved cropping systems with soybean; groundnut and mungbean were taken up. All the new cropping systems were profitable over the traditional maize-maize cropping system indicating considerable scope for productivity gains and efficient use of NRs. Watermelon mung-groundnut, watermelon-mung-soybean, and watermelon-mung-maize cropping systems gave highest income (201 to 268%) over the traditional cropping system.

More than 3/4 cropped area was under maize monocropping before the intervention of watershed based technologies. Technical backstopping and provision of improved seeds of the remunerative crops like groundnut, mungbean, and soybean resulted in reduction in maize area by about half during the last one year in the micro-watershed.

Farmers in the watershed were following traditional cultural practices due to technological inaccessibility. Improved production practices (integrated nutrient, pest and disease management and agronomy) were compared with the farmers' practice in maize during autumn-winter 1999 and spring 2000. A yield increase of 8% was possible with 28% reduction in N fertilizer use. Improved cultivars of soybean, groundnut and mungbean were introduced for large-scale cultivation with improved agronomy.

Grain yields of soybean, groundnut, mungbean, and maize were delineated based on the toposequence in the landscape watershed to find out the influence of land degradation/soil fertility on crop productivity In general, higher grain yields were obtained in mid and lower part of the toposequence compared to top of the toposequence due to less degradation and better soil fertility. Among the crops grown, soybean suffered most due to fertility differences on the toposequence. Groundnut can be grown successfully on top, mid and lower part of the toposequence while mungbean and soybean need high level of management on top of the toposequence and for obtaining good yields. This information would assist in land use planning and development of appropriate nutrient management options.

Influence of toposequence on crop productivity

Conclusions

The conservation of soil and water resources in the sloping land ecoregions has not been followed for too long. Thorough understanding of constraints and development of appropriate technology with focus on land and water management will help to optimizing food production and arrest further land degradation. Watershed based technologies offer excellent opportunities for sustainable land and water development in sloping land ecoregions. In the coming years, the strategic goal is sustainable agricultural development in the sloping land ecoregions through new crops and cropping systems to make cultivation more profitable. Agroforestry in the higher elevations of the toposequence to arrest erosion; horticulture and animal raising to raise the household economy also will be evaluated.

For more information please contact:

Dr A Ramakrishna
Scientist (Agronomy),
ICRISAT-Patancheru 502 324.