Instructions for choosing winter-spring rice varieties
The Winter-Spring crop is the crop with the highest yield but also has the highest risk of pests and diseases. Instructions for selecting varieties according to four criteria — seasonality, disease resistance, productivity, market — for the Mekong Delta region.
Summary: The Winter-Spring crop in the Mekong Delta yields 6-9 tons per hectare — the highest of the three crops — but is also full of risks due to early cold weather, night dew, and blast outbreaks. Choosing the right variety determines 30-40 percent of success. This article shows how to choose varieties according to four actual criteria, not just according to dealer recommendations.
Applies to: Winter-Spring crop in the Mekong Delta, sown from November to January.
Duration: Decide 30-45 days before sowing.
Difficulty level: Basic. It's important not to choose based on habit or movement.
Estimated additional costs: 800 thousand to 1.5 million VND per hectare for rice varieties.
Why choosing varieties is important for the Winter-Spring crop
The Winter-Spring crop differs from the other two crops in a few ways:
- Huge difference in day-night temperature, morning dew. Creating conditions for rice blast outbreaks.
- Rice grows 10-15 days longer than the summer-autumn crop because of low temperatures.
- Other pests — brown planthoppers migrating from the Central region, leaf blast and cotton blast.
- Sudden cold weather can occur in December-January, affecting rice during the tillering period.
A suitable rice variety for this season must meet the above conditions. Varieties that yield well in the summer-autumn crop are not necessarily good for the Winter-Spring season.
Four criteria for selecting breeds
Criterion 1 — Growth time
The Winter-Spring crop in the Mekong Delta usually lasts 100-115 days. Divide into three groups:
- Short-day varieties 90-100 days: suitable for late sowing (after December) or when early harvest is needed for the Summer-Autumn crop.
- Mid-day variety 100-110 days: most popular, best yield.
- Long-term varieties over 115 days: suitable for early sowing (November) in flood-free areas downstream.
Choose according to the actual sowing schedule of the region. Don't try to plant long-term varieties when sowing late — the harvest will be late, affecting the next crop.
Criterion 2 — Pest and disease resistance
This is the most important criterion for the Winter-Spring crop. See three main types of diseases:
- Blast: average — fair resistance. Although rice blast-sensitive varieties (like IR50404) have high yields, they pose great risks in this season.
- Brown planthopper: moderate — fair resistance. Varieties with better resistance genes bph2 and bph3.
- Yellow dwarf disease: moderate resistance. Areas with a history of yellow dwarf disease need more resistant varieties.
Each Winter-Spring season, the Provincial Department of Agriculture has a list of recommended varieties. Consult this catalog first, don't just follow the dealer's recommendation.
Criterion 3 — Rice productivity and quality
High productivity is the criterion but not the only one:
- Average yield in Winter-Spring crop: 6-9 tons per hectare depending on variety.
- Rice quality: long grain, no whiteness, high percentage of whole rice.
- Aromatic smell: fragrant varieties (such as ST24, ST25, Dai Thom 8) have a selling price 30-50 percent higher.
High productivity but low quality — low selling price, poor economic efficiency.
Criterion 4 — Consumer market
This criterion is often overlooked by growers:
- Export varieties: OM5451, OM6976, OM7347, ST24, ST25, Dai Thom 8. Stable output, good price.
- Domestic varieties: IR50404, OM1490 — high yield but low price.
- Local specialty varieties: may have a niche market with high prices but need to link consumption first.
It is best to contact a cooperative or consumer business before choosing a variety — they will specify which varieties are needed and the purchasing price.
Comparison table of some popular winter-spring varieties
| Same | Time (day) | Productivity (tons/ha) | Resistant to rice blast | Resistant to brown planthopper | Rice quality |
|---|---|---|---|---|---|
| OM5451 | 95-100 | 7.5-8.5 | Fair | Average | Fair |
| OM6976 | 95-100 | 7-8 | Fair | Fair | Fair |
| OM7347 | 95-105 | 7-8 | Fair | Fair | Good |
| ST24 | 105-110 | 6.5-7.5 | Average | Average | Very good, fragrant |
| ST25 | 110-115 | 6-7 | Average | Average | Very good, fragrant |
| Radio Thom 8 | 100-105 | 7-8 | Fair | Fair | Good, lightly fragrant |
| IR50404 | 90-95 | 7.5-8.5 | Sensitive | Sensitive | Average |
Data for reference only, may vary between regions and years.
The preparation method is the same
Select seed source
- Buy certified seeds from a provincial seed center or licensed company.
- Avoid buying floating varieties or varieties without clear packaging.
- Requires original or certified seeds — do not use production-grade seeds from the previous crop.
Amount of seed
- Sparse sow: 80-100 kilograms per hectare. Suitable for varieties with good tillering and carefully managed orchards.
- Average sowing: 120-150 kilograms per hectare. Most popular.
- Avoid sowing more than 180 kilograms per hectare — thick sowing increases the risk of rice blast and brown planthopper outbreaks.
Treat seeds before sowing
- Soak the seeds in warm water at 54 degrees Celsius (3 boiling, 2 cold) for 10-15 minutes — kill pathogens on the seed coat.
- Soak in plain water for 24-36 hours.
- Incubate for 18-24 hours until the seeds germinate 60-80 percent.
- Rinse with clean water before sowing.
Combined with service design
Choosing a variety is not independent but needs to be compatible with:
- Soil type: heavy alum soil — choose alum-tolerant varieties. Heavy clay soil — choose low-till varieties.
- Water source: self-flowing area to ensure water — choose varieties that are sensitive to water. Rain-dependent areas — choose mild drought-resistant varieties.
- Pest and disease history of the field: the field has a history of severe blast — it is mandatory to choose varieties with high blast resistance.
- Investment ability: high quality varieties often require investment in fertilizer and careful management. Households with little capital should choose easy-going breeds.
Common mistakes
Choose varieties according to the agent: agents have the benefit of selling their varieties. Refer to the Department of Agriculture + experience from people in the same area.
News like "super yield 12 tons per hectare": usually an advertisement. Actual yield rarely exceeds 9 tons in the Winter-Spring crop even with the best varieties.
Using production-grade seeds from the previous crop: rice genes are degenerate, yield is reduced by 10-20 percent compared to certified varieties.
Choose blast-sensitive varieties for fields with a history: although the potential yield is high, the risk of losing the entire crop is very high.
Planting a single variety on a large area: orchards adjacent to many households of the same variety = the epidemic spreads quickly. Variety is better for the region.
Follow the production
- Actual yield of the selected variety.
- Pest level in the crop.
- Selling price and output.
- Compare with previous year or with households in the same region.
After 2-3 crops, you will know which varieties are truly suitable for your home field.
References
- *Handbook for selecting winter-spring rice varieties in the Mekong Delta* — Mekong Delta Rice Institute, 2024.
- *List of plant varieties allowed for production and business* — Department of Crop Production, updated annually.
- *Recommended rice varieties for the Winter-Spring crop* — Department of Agriculture and Rural Development of Mekong Delta provinces, annually.