{"id":1578,"date":"2026-09-26T01:59:49","date_gmt":"2026-09-25T16:59:49","guid":{"rendered":"https:\/\/vietnam-agri.com\/industry_news\/shrimp-rice-rotation\/"},"modified":"2026-09-26T01:59:49","modified_gmt":"2026-09-25T16:59:49","slug":"shrimp-rice-rotation","status":"publish","type":"industry_news","link":"https:\/\/vietnam-agri.com\/en\/industry_news\/shrimp-rice-rotation\/","title":{"rendered":"Vietnam's 190,000 hectares of shrimp-rice: splitting the year between saltwater and freshwater, and the timing of planting and sourcing"},"content":{"rendered":"

On September 21, 2026, the Vietnamese seafood trade site tepbac.com published a technical article on reorganizing from 'doing things at the same time' to 'doing them at the right time.' It sets out 't\u00f4m \u2013 l\u00faa,' which rotates shrimp and rice in the same field, as an example of dividing the year into saltwater and freshwater, then broadens into a proposal to stagger stocking times in improved-extensive ponds. The author is Phan Giang, published in the aquaculture section. The area it places at the foundation is 191,073 ha nationwide. For Japanese staff sourcing shrimp from Vietnam, what kind of land these 191,000 ha are ties directly to the monthly outlook for volume and species.<\/p>\n

Shrimp-rice totals 191,073 ha nationwide, about 26% of the brackish-water shrimp farming area<\/h2>\n

What it places in the first section is area. As a figure from Department of Fisheries (C\u1ee5c Th\u1ee7y s\u1ea3n) data cited by a Can Tho University study, it puts the national shrimp-rice area at about 191,073 ha, equivalent to about 26% of the brackish-water shrimp farming area. Working back from 26%, the author gets a total brackish-water shrimp farming area of about 735,000 ha.<\/p>\n

These 191,000 ha are a secondary citation of Department of Fisheries data<\/h3>\n

The original merely says 'a Can Tho University study cited the Department of Fisheries' data,' giving neither the study's name nor its year of publication, nor the year the area refers to. By province it clearly marks 2023, yet only the national figure carries no year. If using it as a premise for volume, you will want to confirm the year yourself.<\/p>\n

180,000 ha in two provinces; 'An Giang' refers to the present provincial area<\/h3>\n

By province, An Giang Province had over 106,000 ha and nearly 70,000 tonnes of shrimp in 2023, and Ca Mau Province about 74,491 ha in 2023. Adding them, the author gets 180,491 ha, with about 94% of the national figure concentrated in two provinces. The province name is a trap. The province's official portal lists its seat as 'R\u1ea1ch Gi\u00e1 ward' and includes the Phu Quoc Economic Zone Management Board among its bodies. Present-day An Giang Province is a provincial area that includes the coast, and drawing a map by the old provincial borders will mislocate the producing area on the inland side.<\/p>\n\n\n\n\n\n\n\n\n
Item<\/th>\nFigure<\/th>\nSource<\/th>\n<\/tr>\n<\/thead>\n
National shrimp-rice area and share<\/td>\nabout 191,073 ha \/ about 26% of the brackish-water shrimp farming area<\/td>\nDepartment of Fisheries data, no year stated<\/td>\n<\/tr>\n
An Giang Province's area and output<\/td>\nover 106,000 ha \/ nearly 70,000 tonnes (2023)<\/td>\nOriginal text<\/td>\n<\/tr>\n
Ca Mau Province's area<\/td>\nabout 74,491 ha (2023)<\/td>\nOriginal text<\/td>\n<\/tr>\n
Shrimp per hectare in An Giang Province<\/td>\naround 0.66 tonnes<\/td>\nAuthor's own calculation (actually somewhat lower, since the original gives a range)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Swapping saltwater and freshwater by the year in the same field<\/h2>\n

The rotation the article describes is neither about dividing plots nor about reducing items; it switches the function of the same area by season. In the rainy season salinity falls and suits rice; in the dry season saltwater returns and the field is turned over to shrimp as a pond. Rice tolerates only low salinity, while black tiger shrimp (t\u00f4m s\u00fa) needs a suitable brackish environment. Having them coexist means that high salinity cuts the rice yield and low salinity strains the shrimp.<\/p>\n

'One rice crop + one to two shrimp crops' is not a fixed formula<\/h3>\n

The article does not fix the number of crops, writing that it changes with rainfall, the timing of saltwater intrusion, the capacity for water supply and drainage, and local conditions. What must be decided is not the number of crops but which period to assign to rice and which to shrimp. From the sourcing side, it becomes a matter of 'the calendar differs by producing area.' Local reporting from Thoi Binh District, Ca Mau Province in 2018 put late August as the first day of planting, and the farmer interviewed had sown seedlings in mid-July.<\/p>\n

The rice period becomes a rest for the pond, but it does not become sterile<\/h3>\n

After a shrimp crop, organic matter, leftover feed, and waste accumulate at the pond bottom. Adding freshwater to remove the salt and switch the environmental conditions creates a break in the ecosystem of the previous shrimp crop. The original goes on, however, to write that during this period the pond does not become 'sterile,' nor do pathogens vanish completely. What can be done is to curb the year-round buildup of bacterial populations, intermediate hosts, and organic matter. Because rice straw decomposing excessively under low-oxygen conditions worsens the pond bottom, it stresses that rotation is not neglect.<\/p>\n

A proposal to stop stocking all at once and introduce in sequence<\/h2>\n

Here the article moves to the vu\u00f4ng of improved-extensive (qu\u1ea3ng canh c\u1ea3i ti\u1ebfn) farming. A single vu\u00f4ng may hold black tiger, whiteleg shrimp (t\u00f4m th\u1ebb), crab (cua), giant freshwater prawn, and some fish at the same time. The article does not deny polyculture itself; it takes issue with stocking many species at the same point in time.<\/p>\n

The vulnerability just after molting, and a simultaneous peak in demand<\/h3>\n

Right after molting, a crustacean's shell is soft and its defenses drop. When density is high, size differences are large, and hiding places are scarce, competition intensifies. Because all of them share the same oxygen, natural food, and carrying capacity, stocking all at once and growing all at once brings the demand of the whole system to a peak at the same point in time.<\/p>\n

Not monoculture, but 'multi-species with an order'<\/h3>\n

The proposal is to stagger the stocking times relative to one another. Introduce first the species that suits the conditions at the start of the season, and once that group has passed its small stage and gained resistance, add the next. The original calls this 'multi-species with an order (\u0111a canh c\u00f3 th\u1ee9 t\u1ef1)'<\/strong> and clearly states that it does not turn the vu\u00f4ng into a monoculture. Because biomass is introduced in stages, seed can be added after observing growth rate and survival.<\/p>\n

The effect is an explanation of mechanism, not figures from a comparative trial<\/h3>\n

The original presents no measured values for how much this arrangement improved survival or yield. What is written is the mechanism and the operational aim, not the results of a comparative trial. It is not a notice from a province or a research institute but a trade outlet's technical argument. Shrimp-rice rotation is already running across 191,000 ha; what is new is the part proposing the stocking order.<\/p>\n

'Watch the water, not the calendar' unsettles the sourcing outlook<\/h2>\n

The latter half of the article turns to the criteria for stocking. Its framing is that the calendar matters but the date is a reference value, and what decides is the actual environmental conditions. Salinity, water temperature, oxygen, pH, and water movement show which species is suited now, and if the rainy season comes early or drags on, the stocking window moves.<\/p>\n

100 mm of rain puts about 1,000 m\u00b3 of freshwater into a 1 ha pond<\/h3>\n

A separate piece the same site ran three days later, on September 24, puts this 'watch the water' into numbers. In the meteorological classification, 51\u2013100 mm in 24 hours is heavy rain and over 100 mm is very heavy rain. According to the separate piece, 100 mm of rain puts about 1,000 m\u00b3 of freshwater into a 1 ha pond \u2014 over 8% of the volume at a depth of 1.2 m. If it mixes completely into a pond at 20 ppt salinity, it theoretically drops to about 18.5 ppt; at a depth of 0.8 m, 200 mm of rain takes 20 ppt to about 16 ppt. Recalculating, the author gets 1 ha \u00d7 1.2 m = 12,000 m\u00b3, with 1,000 m\u00b3 being 8.3% and the post-mix value 18.46 ppt, which matches the separate piece.<\/p>\n

Not the value it dropped to, but the speed of the drop<\/h3>\n

What the separate piece emphasizes is the speed of change over the absolute value. As a study on the fleshy prawn (t\u00f4m he Trung Qu\u1ed1c), it cites a result that a sudden drop from 22 ppt to 14 ppt within an hour lowered some immune indicators and increased the WSSV load in latently infected individuals. In practice, about 3\u20134 ppt\/hour is the rule of thumb for caution, though it adds that this cannot be applied rigidly to every species and every condition.<\/p>\n

What do the 191,000 ha bring to bear on Japanese shrimp sourcing<\/h2>\n

From here on is the sourcing side's interpretation, not in the original. The original deals with the production technique of shrimp-rice and does not venture into residual pesticides, certification, or exports.<\/p>\n

During the rice period the shrimp pond is resting<\/h3>\n

The 191,000 ha are land used by splitting the year into freshwater and saltwater, and during the rice period the shrimp pond on that plot is resting. An estimate that places monthly volumes evenly falls apart at its premise. Because the original writes that both the number of crops and the stocking window move with rainfall and saltwater intrusion, read a producing area's monthly outlook not as a fixed value but as a figure conditioned on the rain calendar. Do not line it up with the same sense of volume as a supply running whiteleg-shrimp intensive ponds year-round.<\/p>\n

0.66 tonnes per hectare \u2014 a thinness an order of magnitude apart from intensive ponds<\/h3>\n

Dividing An Giang Province's 2023 figures gives around 0.66 tonnes per hectare, a thin, broad supply base an order of magnitude apart from intensive farming. Because traceability and certification become a collective matter rather than one company's, cooperative-level ASC certification<\/strong> comes to work as a passport for sourcing. In Ca Mau a farming cooperative has obtained ASC (A Vietnamese shrimp-farming cooperative earns ASC certification: a rare passport for sourcing to Japan and the EU<\/a>), and in Dam Doi 721 ha of black tiger shrimp runs under ASC (Dam Doi's 721 hectares of ASC black tiger shrimp: will it benefit Japanese seafood sourcing?<\/a>). Confirm the scope of certification by hectares, not by the number of cases.<\/p>\n

Ask into how many grades a single harvest splits<\/h3>\n

If the sequential-stocking arrangement is adopted, groups of different ages are present in the same vu\u00f4ng at once. On the buyer's side the premise changes. Rather than asking 'what size is this lot,' asking 'into how many grades does a single harvest split' meshes better. Because crab and giant freshwater prawn also come out of the same vu\u00f4ng, reaching for products other than shrimp runs into the same calendar constraint (Vietnamese seafood hits US$8 billion in eight months: crab (+34%) and shellfish (about +31%) break the reliance on shrimp<\/a>\uff09\u3002<\/p>\n

Before an estimate, get a one-page cropping calendar from the producing area<\/h2>\n

There is one action to take next. Have your supplier or a candidate producing area provide the one-year cropping calendar for that plot. Holding this before entering negotiations lets you talk about why the monthly outlook moves on the same premise.<\/p>\n

Five items to ask your supplier<\/h3>\n\n\n\n\n\n\n\n\n\n
What to ask<\/th>\nWhat it tells you<\/th>\n<\/tr>\n<\/thead>\n
The rice period and the shrimp period, by month<\/td>\nWhich months produce no shrimp<\/td>\n<\/tr>\n
The number of shrimp crops a year, and how that year is decided<\/td>\nWhether the number of crops is fixed or moves with the rain<\/td>\n<\/tr>\n
Whether stocking is all at once or staggered in timing<\/td>\nHow many generations are in the same pond<\/td>\n<\/tr>\n
Whether salinity and dissolved oxygen are recorded, and how often<\/td>\nWhether the stocking window is managed by numbers<\/td>\n<\/tr>\n
The scope of certification (hectares, plots, cooperative level)<\/td>\nHow far the passport works<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

For producing areas without records, have them give two outlooks, for the rainy and dry seasons<\/h3>\n

There is no need to drop a producing area that cannot produce records. The original writes that the value of environmental measurement and an electronic logbook lies less in an alarm at the time of an abnormality than in 'the judgment of when to do what.' Rather than making them commit to a single monthly volume, having them give two outlooks \u2014 for the rainy and dry seasons \u2014 is closer to the actual harvest.<\/p>\n

Sources<\/p>\n