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Rice-prawn culture in the Mekong Delta of Viet Nam

Le Thanh Duong

Rice-prawn farming, a traditional practice in freshwater areas of the Mekong Delta, has become more popular for the past few years. This paper is based on two rice-prawn farming systems tried in one of the key sites (Phung Hiep district, Han Giang) of the Mekong Delta Farming Systems Research and Development Centre as part of an OXFAM-funded project. In 1990, the following farming systems were tried in the site:

Culture practices

The following are the eight main steps in rice-prawn culture:

1. Field selection

2. Land preparation

3. Selection of prawn juveniles and rice seed varieties

4. Rice crop establishment and prawn stocking

After broadcasting/transplanting wet season rice crop in March-April, allow prawn into the ricefield at 10 days after broadcasting or 5 days after transplanting.

5. Feeding, weeding and fertilizing

- Cassava, sweet potato, broken rice, milled rice (soaked or cooked), rice bran
- Crabs, snails, trash fish
- Copra
- Combined feeds: 50 percent rice bran, 10-20 percent cooked broken rice, 20-30 percent trash fish, 10 percent oil cake

- Feeding ratio: 3-5 percent of prawn weight
- Feeding times: at least twice a day (1/3 at 5-6 a.m. and the remaining 2/3 at 5-6 p.m.)

Put the feeds in feeding trays and place them anywhere along the bottom of the trench.

Fertilizer formula for modern rice per hectare:

- 200 kg monosuperphosphate + 200 kg urea + 50 kg potash
- or 100 kg 18-46-0 days after planting + 100 kg urea + 50 kg potash

And for transplanted local rice per hectare:

- 200 kg monosuperphosphate + 100 kg urea + 50 kg potash
- or 100 kg days after planting + 50 kg urea + 50 kg potash

Material flow in rice-prawn integrated farming systems of Mekong Delta, Viet Nam

6. Management of water, sluice gates and dikes

7. Other management practices

8. Harvesting of rice and prawn

Average prawn and rice yields in the 1990 crop season

DSMVR: dry season modern variety rice
WSMVR: wet season modern variety rice
WSTPR: wet season transplanted rice
2MV: dry season modern rice followed by wet season modern rice
MVTPR: wet season modern rice followed by wet season transplanted rice

Partial budget (in thousand VND/ha) for two dominant rice-prawn systems

1992: US$1 = 7 000 VND
This table shows partial budget of rice monoculture and of prawn integrated in the two
dominant rice cropping systems. Net return from prawn in the two systems seems to be the
same while net return from WSMV/TPR is higher than that of 2MV system. Prawn contributed
significantly to net income of rice farmers in the site.

Issues for further consideration

The system described is characteristic for the Mekong Delta and other areas where wild or hatchery-reared Macrobrachium juveniles are available and rice production is of moderate intensity. The existing rice varieties and culture systems (e.g. wet season, modern varieties, transplanting, etc.) and options for modifying these will influence the design of an adoption.

With a harvest of 13-24 kg/ha, questions arise as to the continued viability of these systems. Different options exist to improve these systems. Associated risks to the farmers will need to be considered.

In assessing economic viability in given local situations, additional rice fertilization due to more frequent water exchanges, feed costs for prawns, costs of other off-farm materials such as trash fish, have to be included.

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