A complete guide to establishing and managing 2–3-leaf-whorl polybag rubber nurseries in Vietnam — covering nursery design, soil preparation, fertilization, and care practices for strong, uniform seedlings.
1. Planting Season, Site Selection, and Nursery Design
Table of Contents
To produce 2–3-leaf-whorl polybag seedlings (tum bầu) for new planting or replanting seasons, the budding stumps must be planted in polybags 5–6 months in advance.
-
Planting periods:
-
October–November for early planting in the following year.
-
February–March for planting between June–August.
-
-
Select areas with suitable climate, stable water sources, and easy transportation access for management and care.
-
The nursery design must ensure good drainage, erosion prevention, and convenient operations.
Divide the nursery into 20 m × 10 m plots, separated by 3 m pathways. For large-scale nurseries, design a main road 5 m wide for vehicle access.
Plant density:
-
120,000–130,000 polybags/ha for 18 cm × 35 cm bags.
-
150,000–160,000 polybags/ha for 16 cm × 33 cm bags.
Planting layouts:
-
Double rows: Two rows of polybags per furrow, placed close together with a small air gap in between. The gap should remain unfilled with soil. The distance between the centers of double rows is 1.2 m.
-
Single rows: One row per furrow, with spacing between centers 0.7–0.8 m.
-
Place polybags so that two-thirds of their height is below ground level or the top of the bag rises about 10 cm above the soil surface.
2. Polybag and Budded Stump Specifications
-
Polybags: Use virgin PE bags, 0.08 mm thick, with 5 mm holes spaced 6 cm apart covering the lower half of the bag for drainage.
-
Sizes: 18 cm × 35 cm or 16 cm × 33 cm for stumps aged 6–8 months.
-
Budded stumps (tum):
-
Graft unions must be healthy and stable.
-
Stem diameter (10 cm above root collar): ≥ 12 mm for 6–8-month-old stumps, and < 22 mm for stumps over 10 months.
-
-
Root preparation: Select stumps with a single, straight taproot measuring:
-
27–30 cm below the graft for 18 cm × 35 cm bags.
-
25–28 cm for 16 cm × 33 cm bags.
Coat the cut end with vaseline and apply rooting compound before inserting into polybags.
-
3. Soil Preparation for Polybags
Use loamy soil with good structure and moisture retention from local or external sources. Avoid sandy soil to prevent bag breakage. Soil must be dry to slightly moist before use.
Basal fertilizers per bag:
-
Fused phosphate: 10 g/bag.
-
Bio-organic fertilizer: 10 g/bag, or 50–100 g well-decomposed manure/bag.
Filling process:
Mix the soil evenly with basal fertilizer. Fill two-thirds of the bag, compact slightly, then fill to 1 cm below the rim. Bags should be firm, cylindrical, and unbroken at the middle.
4. Planting Budded Stumps into Polybags
Water polybags thoroughly one day before planting. Use a pointed stick to make a hole at the center of the bag, deep enough for the full taproot length. Insert the stump vertically so that the graft union sits 1 cm above the soil, with the graft facing outward.
After planting, water daily until the first leaf whorl develops, then every two days or as needed to maintain adequate moisture during the dry season.
5. Nursery Maintenance and Care
-
Keep the nursery weed-free, removing all weeds inside and between polybags. Avoid plastic mulching (PE film).
-
In hot climates, install shade nets during early growth. In cold regions, use transparent PE covers to protect seedlings. Remove shading once leaf whorls are stable and weather improves.
-
Regularly remove rootstock shoots and lateral sprouts to maintain bud growth.
6. Fertilization Schedule for 2–3-Leaf-Whorl Polybag Nurseries
Apply fertilizers following the schedule below.
a) For 16 cm × 33 cm Polybags
| Stage | N (g/tree) | P₂O₅ (g/tree) | K₂O (g/tree) | NPK 16-16-8 (g/tree) | Notes |
|---|---|---|---|---|---|
| 1st application | 0.4 | 0.4 | 0.2 | 2.5 | 1 leaf whorl |
| Subsequent | 1.0 | 1.0 | 0.5 | 6.2 | every 30–45 days |
| After topping | 1.4 | 1.4 | 0.7 | 8.7 | before planting |
Alternate formula (DAP + urea + K₂SO₄) may be used following equivalent nutrient rates.
b) For 18 cm × 35 cm Polybags
| Stage | N (g/tree) | P₂O₅ (g/tree) | K₂O (g/tree) | NPK 16-16-8 (g/tree) | Notes |
|---|---|---|---|---|---|
| 1st application | 0.6 | 0.6 | 0.3 | 3.7 | 1 leaf whorl |
| Subsequent | 1.4 | 1.4 | 0.7 | 8.7 | every 30–45 days |
| After topping | 2.0 | 2.0 | 1.0 | 10.0 | before planting |
Application technique: Mix all fertilizers before use. Drill a 3 cm-deep hole near the bag wall (not close to the stem) and apply fertilizer. Water immediately after each application.
Foliar feeding: Supplement with foliar fertilizers and pest-control sprays when necessary, ensuring compatibility between products.
Post-Fertilization Operations
Once seedlings develop two stable leaf whorls, perform the first rearrangement (bag rotation) to promote uniform growth.
Repeat the process one month before field planting and group seedlings by growth uniformity.
Standard for ready-to-plant polybag stumps:
-
Graft shoot with at least two stable leaf whorls, vigorous and healthy.
-
Soil bags intact, moist, and unbroken.
-
Root system firmly anchored without shaking or looseness.
Conclusion
Producing 2–3-leaf-whorl polybag rubber seedlings requires careful scheduling, precise grafting, and well-balanced fertilization.
Through meticulous nursery management — from soil preparation and irrigation to shading and nutrition — growers can ensure high survival rates, healthy root systems, and uniform growth ready for field planting.
Vietnam’s technical standards for polybag rubber nurseries serve as a foundation for sustainable replanting and productivity improvement in the rubber industry.