Fertilization for Immature Rubber Plantations (KTCB)

Inorganic Fertilization

Applying fertilizers during the immature stage of rubber trees (KTCB) plays a critical role in ensuring proper growth, canopy formation, and early yield potential.

• Priority: Fertilize based on regional nutrient diagnostics for optimal economic and technical efficiency. Where no diagnostics are available, apply fertilizer according to the recommended rates.

• Fertilizer Type: Use the recommended fertilizer formulations. Any substitution must be approved by the Group.

• Soil Type:

  • On flat land, prioritize compound NPK 16-16-8.

  • On sloped areas or contour planting, use NPK 16-16-8 instead of single nutrients to ensure even distribution and reduced runoff.

• Application Rate: Based on soil class (I–III) and tree age.

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Table 11. Inorganic Fertilizer Rates for Immature Rubber (KTCB)

*When soil pH (H₂O) ≥ 6, replace fused phosphate with superphosphate.

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Fertilization Methods

• Flat Land:

  • Year 1–2: Dig circular trenches or holes 30–80 cm from the base (under the canopy projection).

  • Year 3 onward: Encourage mechanical fertilizer application using trenching and covering methods.

• Sloped Land (>10°) or Contour Planting:

  • Year 1–3: Dig circular trenches 30–70 cm from the base depending on age.

  • Year 4 onward: Apply fertilizer in multi-purpose pits between trees, 50 cm from the contour’s inner edge, with each pit about 80 × 20 × 20 cm.

  • Apply 1–2 times per year depending on rainfall. Split evenly if applying twice. Only fertilize when soil moisture is adequate; avoid heavy rain.

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Multi-Purpose Fertilizer Pits

To reduce nutrient loss on sloped or highly leached soils:

• Position: At the zone where feeder roots are active.

• Layout:

  • On flat land (Year 2–pre-canopy closure): alternate staggered layout, 1.5 m from the tree row.

  • After canopy closure: position between tree rows in a staggered diamond pattern.

  • On slopes: dig along contour lines, 1 pit every two trees, near the upper side (talus).

• Pit Dimensions: 60–80 cm (length) × 40–60 cm (width) × 30–40 cm (depth).

• Timing: Early or late rainy season when soil is moist for at least one month.

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Foliar Fertilization for New Rubber Plantings

• Apply only during the first year after planting.

• Exclude cold regions (Northern Highlands, North Central Coast) and sloped contour plantings.

• Frequency:

  • Up to 3 times in Southeast and Cambodia.

  • Up to 2 times in Central Highlands and spring-planting areas.

• Timing:

  • Start when the tree has stable leaves.

  • Interval between sprays: 30 days.

  • Only spray in dry weather, with air temperature above 15 °C, between 7–10 a.m.

• Can be combined with pest and disease control.

• Use only legally approved and quality-certified foliar fertilizers.

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Adjusting Fertilization Regimes

Adjust inorganic fertilizer levels (reduce, pause, or increase) under these conditions:

• When nutrient diagnosis results and approval are available.

• If legume cover crops (Kudzu, Mucuna) are established—reduce or omit organic fertilizer, and cut nitrogen by 50%.

• If trees are damaged by storms or wind—reduce nitrogen to help rebalance growth.

• For strong, healthy trees—reduce or pause fertilization; increase for underdeveloped plots.

• Adjustments must be evaluated annually and reported to the Group.

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Organic Fertilization for KTCB Rubber

• Apply organic fertilizer when topsoil (0–30 cm) organic matter < 2.5% or carbon < 1.45%.

• Helps improve soil fertility and boost inorganic fertilizer efficiency.

• Important Notes:

  • Organic fertilizers cannot replace inorganic ones.

  • Do not apply organic fertilizer if:

    • Soil already has sufficient organic matter.

    • Green manure pits or legume cover crops exist.

    • Soil is waterlogged or compacted.

    • Fertilizer is unprocessed (not decomposed) or from industrial/agro-waste without treatment.