RUBBER NEWS

Establishing and Managing Rubber Polybag Nurseries with Leaf Tiers in Vietnam

Posted on by content02.vinahugo
13
Oct

Rubber polybag nurseries with leaf tiers are essential for producing high-quality grafted seedlings that ensure strong growth, uniformity, and high latex yields. Under the Vietnam Rubber Group (VRG) guidelines, every stage—from seed preparation to grafting and transplanting—is scientifically managed to maintain seedling vigor and genetic purity.

1. Season, Site Selection, and Nursery Design

  • Planting season: From July to September.

  • Site conditions: Choose areas with suitable climate, irrigation access, and convenient transportation for seedling care and distribution.

  • Design principles: Ensure good drainage, erosion control, and ease of management and irrigation.

  • Layout:

    • Divide the nursery into plots 20 × 10 m, with 3 m-wide paths between plots.

    • Large nurseries: main roads 5 m wide, secondary roads 3 m wide.

  • Planting density:

    • 120,000–130,000 bags/ha for 18 × 35 cm bags

    • 150,000–160,000 bags/ha for 16 × 33 cm bags

  • Row arrangement:

    • Single rows: bags placed in furrows spaced 0.7–0.8 m apart (center to center).

    • Double rows: bags placed in pairs 5–10 cm apart, with 1.2 m between double rows for irrigation pipes.

  • Bag placement: bury 2/3 of the bag height, or keep the bag mouth 10 cm above the ground.

2. Soil Preparation and Bag Filling

  • Bag material: virgin PE plastic, thickness 0.08 mm, with perforated drainage holes (5 mm diameter, spaced 6 cm apart) on half of the lower bag.

  • Bag sizes: 14 × 33 cm, 16 × 33 cm, or 18 × 35 cm (depending on local conditions).

  • Soil selection:

    • Use loamy soil—light, friable, and well-drained.

    • Avoid coarse sandy soil (to prevent bag breakage).

    • Soil should be moist but not wet when filled.

  • Basal fertilizer mix per bag:

    • Fused phosphate: 8–10 g

    • Organic manure or biofertilizer: 30–50 g (or 50–100 g decomposed animal manure)

  • Bag filling process:

    • First fill 2/3 of bag height, lightly shake to settle soil.

    • Fill to the top, leaving 1 cm below the rim.

    • Bags must be firm, round, and evenly filled (no mid-bag cracks).

3. Rootstock Seed Preparation

  • Seed requirement: 1,200–1,600 kg/ha (depending on bag density and seed size).

  • Preferred clones: GT1 and PB 260, followed by other common VRG-approved clones.

  • Seed selection: Choose freshly fallen seeds with shiny shells and moist endosperm.

  • Storage: Keep under shade, spread ≤20 cm thick, and pre-germinate (soak and sprout) within 3 days.

  • Germination (pre-sprouting):

    • Crack shell slightly and soak seeds for 24 hours, changing water every 12 hours.

    • Place on germination beds 1 m wide × 15 cm high, with 5 cm of fine sand.

    • Arrange seeds embryo side down, touching each other, then cover with sand.

    • Density: 1,000–1,200 seeds/m².

    • Water twice daily (morning and evening) with 4 liters/m² per watering.

    • Protect against ants and termites using approved insecticides around the bed edges.

4. Transplanting Seedlings into Bags

  • Timing: 1–2 days before transplanting, water the soil in bags thoroughly.

  • Selection: Choose seedlings with strong shoots and a single healthy taproot (3–10 cm long)—straight, undamaged, and untwisted.

  • Planting method:

    • Work in cool weather.

    • Make a hole in the bag center, insert one seedling per bag with straight taproot, press soil firmly, and cover with fine soil.

    • Discard weak, albino, or damaged seedlings.

  • Replacement: Within 20 days, replace any dead or deformed plants.

  • Alternative (for red soil regions): Directly sow two pre-germinated seeds per bag, then thin to one plant after the first leaf whorl stabilizes.

5. Rootstock Care

  • Watering:

    • Irrigate thoroughly after planting to compact soil around roots.

    • During dry season, maintain soil moisture to the bag bottom (~10 liters/m² per watering).

  • Weed management: Keep nursery weed-free manually or with herbicides.

    • Note: Avoid using PE mulch to retain moisture or suppress weeds between rows.

6. Grafting Process

  • Grafting season: From February to May (main season), may extend to November for next year’s seedlings.

  • Rootstock size: minimum 8 mm diameter (measured 10 cm above soil).

  • Grafting time: Perform in cool weather, avoid watering or grafting when rootstocks are wet.

  • Scion wood: Use budwood similar in age to rootstocks and easily peelable.

    • Types: green buds, light green-brown buds, or brown-green buds.

  • Post-grafting: Keep the nursery well-irrigated and shaded as needed.

7. Top Cutting and Bag Handling

  • Band removal: 20 days after grafting.

  • Top cutting: Perform ≥15 days after removing the band, when the graft is well fused.

    • Cut 5–7 cm above the bud (or 10–12 cm for smaller stocks).

    • Apply vaseline immediately on the cut.

  • Bag handling:

    • Lift bags gently, trim roots protruding outside, and place near transport areas.

    • Maintain moisture during transport to prevent bag cracking or root disturbance.

8. Leaf-Tier Stage Care

  • Transfer: Move top-cut grafted bags to the leaf-tier nursery area.

    • Arrange in double rows, burying bags 10 cm deep with buds facing outward.

    • Space 60 cm between double rows.

  • Care:

    • Water regularly to maintain moisture.

    • Remove wild shoots, control weeds manually.

    • Apply foliar fertilizers and preventive fungicides periodically.

  • Before field planting: Select seedlings with stable top leaf whorls and uniform size.

    • “Rotate” (rearrange) the bags one week before transport to improve root aeration.

Conclusion

By following VRG’s standards for nursery design, soil preparation, grafting, and care, rubber polybag nurseries can produce vigorous, uniform, and disease-free seedlings. This process forms the backbone of Vietnam’s sustainable rubber replanting strategy, ensuring long-term productivity and environmental balance.