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I shot this photo at Tân An in the Mekong River Delta, of the woman soaked in deep and cold water several hours a day, collecting tiny duckweeds for sale.

Duckweeds: friend or foe?



According to scientists, duckweeds are among the fastest growing multi-cellular plant in the world, frequently doubling their biomass under optimum conditions in two days or less. Based on growth rates recorded in the literature, duckweeds can grow at least twice as fast as other higher plants. As an invasive species of concern, duckweeds can completely cover the surface of quite large water bodies in only a few weeks and, if conditions are favorable, can grow in layers forming mats up to 10 cm thick, which exclude light and oxygen. As a result other plants, and animals, can be severely stressed or even killed. Some people consider duckweed with its speed of growing the enemy of rice. Some others say it is the ideal water plant to introduce into an integrated farming system.

Duckweed is good for the environment because it doesn’t require artificial fertilizers, on the contrary it cleans up waste by removing organic and inorganic nitrogen. It doesn’t need fungicides and has no significant natural pests. Duckweed is a competitive source of plant protein.

The value of duckweed as a source of feed for fish and poultry has been promoted by the World Bank in Vietnam based on the fact that duckweed has been fed to pigs, cattle, sheep, chickens, ducks, and fish. Also, dried duckweed can provide vitamins, minerals, and pigments such as beta carotene in livestock diets, reducing the need to add these compounds to rations and thus saving the feed producer money. Duckweed has been ensiled with other feed crops such as corn or cassava leaves to produce an alternative diet for pigs raised on small farms in Vietnam. In developing countries like Vietnam where fertilizer is scarce and expensive for the small farmer, duckweed can provide a cheap and effective fertilizer for rice and other crops.

With the production rate of 30 million ducks raised yearly in Vietnam, in term of their food, duckweed has its confirmed role. In the countryside, the ducks are raised by scavenging in the rice fields especially in the harvesting season. In other systems the ducks are raised in the backyard or in the gardens of households or kept in the canals.

Since duckweed appears to be more resistant to pests and diseases than other aquatic plants in the area with a high content of nutrients, it has been used traditionally in Vietnam to feed fish and poultry. As part of the overall development strategy of the integrated farming system, duckweed can be a useful candidate to be developed as a feed resource for ducks so as to improve production all the year round.


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Additional Photos by Ngy Thanh (ngythanh) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 471 W: 125 N: 2332] (8458)
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