An overview is given of the natural, socio-economic, agronomical and marketing conditions for vegetable production in the Red River Delta (RRD) of Vietnam. The seasonal variation in temperature in the RRD is the main determinant for the production season of vegetables. Heavy rainfall in the hot season increases production risks, as it may physically damage crops. Frequent rainfall in this period may enhance disease incidence. Landholdings are small and individual plots are the smallest of Indochina. Vegetables typically are produced in flooded rice based systems. Such systems are characterized by poor soil structure for vegetable production and high labour demand for the construction of raised beds. Highly perishable crops can only be grown close to the markets in the peri-urban areas. Less perishable crops can be produced further away from the city markets. Generally, large quantities of pesticides are used and there is increasing public concern about pesticide residues on products. The small landholdings, small plots and consequently the small amounts of product, limit effective marketing and make the producers dependent on collectors. Given the trends in population dynamics and human diets, urban vegetable demand in the RRD, however, has ample opportunities to grow.Effects have been analysed and categorised in opportunities and constraints for adopting improvements. A potential pathway to sustainable development is the development of permanent vegetable production systems, with producers co-operating in producers organizations, enabling them to work on a larger scale, produce larger volumes, introduce harvest date planning and quality control and aim for the integration of production with marketing in a vegetable value chain. By simultaneously adopting Good Agricultural Practices, consumers' food safety concerns can be addressed. The expected increase in vegetable demand is likely to open new opportunities for the RRD vegetable producers.
Vegetable production plays an important role in the rural economy of the Red River Delta (RRD), Vietnam. Data were collected on present vegetable production in the RRD, with the aim to characterise the vegetable production in terms of profitability, labour requirement and pesticide use and to evaluate vegetable production for its potential to increase rural household income.Three hundred and sixty data sets consisting of qualitative (planting and harvesting dates) and quantitative (yield, product price, material and labour input) data were collected from 42 different vegetable crops presently produced commercially in the RRD. Variables were converted into value (thousand Vietnamese Dong, kVND) or days per hectare per growing day in the field (Gday), enabling analysis of data independent of crop growth duration.The income derived from vegetable production ranged from 100 to 400 kVND/ha/Gday. Labour input varied from 3 to 9 days/ha/Gday. Profit increased with an increase in the labour input per growing day. Short growth duration crops required a higher labour input per growing day. The average cost of pesticide use was 25.7 kVND/ha/Gday. Planting in the summer season may result in a shorter growing period as compared to planting in the winter season. The range of variation in the data reflects the diversity in crops and cropping conditions in the RRD.The results indicate that permanent vegetable production has the potential to substantially contribute to an increase in rural household income in the RRD, while increased labour demand can likely be fulfilled by the family household. Thereby, developing permanent vegetable production systems may be a pathway for development of the vegetable production sector in the RRD.
S U M M A R YIn two field experiments in Suriname, competition between weeds and sorghum (Sorghum bicolor (L.) Moench) was studied in the rainy seasons of 1982 and 1983. The crop was kept either weed-free or without weed control for each of six different periods of time from planting. Observations made at the end of each period allowed an analysis to be made of the growth and development of a crop with and without weed control.Due to the crop canopy structure and fertilizer placement near the row, weed growth was concentrated in the rows. Starting at c. 20-30 days after planting, competition with weeds reduced ground-cover and leaf area index of the crop. Competition reduced growth rates, leading to lower yields. Plant population density was not affected, but competition reduced the number of leaves present. Stem length initially increased with competition in one season, but was retarded in another. Competition for nutrients was strong and was found as early as 15 days after planting. Nitrogen was the element most competed for initially. Competition for water occurred, but competition for light seemed unlikely. About 20 weed-free days after planting were necessary to avoid yield losses and around 30 weed-free days to attain negligible weed growth at harvest. Yield reduction was mainly due to a decrease in number of grains per panicle. Competition during floret establishment (c. 30-40 days after planting) should be avoided.
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