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Nitrogen drives canopy build in immature rubber and sustained latex synthesis in mature stands. Deficiency shows first as uniform pale-green canopy across the whole tree, and satellite signals appear before ground symptoms are obvious.

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Cause

  • Immature blocks without cover crop or fertilizer program
  • Leaching on sandy soils after heavy rain
  • Peat blocks with N locked in organic matter
  • Poor cover crop establishment (Mucuna, Pueraria, Calopogonium)
  • Over-tapping depleting stored N

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Effect

Field signs:
  • Whole canopy uniformly pale green to yellow-green
  • Older leaves yellowing first, then progressing to whole canopy
  • Reduced leaf size on new flush
  • Slower girth increment (immature) or reduced tapping yield (mature)

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Leaf-tissue thresholds

Sample Whorl 2 leaves (second whorl from top, fully-expanded, 3 to 4 months old), 20 trees per block.
This is a generic band for the crop, with no site, soil, clone, age or season qualifier. Deficient and Optimal resolve. Marginal does not — that tier exists because the transition is not sharp. High does not either, because no page states what High means or what to do about it. And where more than one nutrient reads deficient, only the most deficient rating is valid. See Reading a tissue analysis.

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Satellite signals

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Action

1

Confirm with leaf tissue

Sample Whorl 2 leaves before fertilizing. Blanket application without confirmation wastes money on well-supplied blocks.
2

Apply corrective fertilizer

Use urea (46% N) or ammonium sulphate (21% N) split into 2 or 3 applications per year.
  • Immature (year 1-5): 100 to 200 g urea/tree/year, split
  • Mature (year 6+): 200 to 400 g urea/tree/year, split
Adjust for MRB clonal recommendations.
3

Maintain cover crop on immature blocks

Mucuna and Pueraria fix 100 to 200 kg N/ha/year and reduce fertilizer need in years 1 to 3.
4

Follow up

Re-sample Whorl 2 leaves 3 months after fertilizer application. Expect NDRE recovery within 6 to 8 weeks.