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Calcium deficiency in rubber is rare as a primary nutrient issue but common as a symptom of soil acidity. Most Malaysian rubber soils are acid (pH 4 to 5), and Ca correction usually happens as a byproduct of liming for pH and Mg management. Ca is essential for cell wall formation and healthy bark, so deficiency affects tapping-panel quality and bark renewal.

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Cause

  • Acid soils (pH < 5) with low base saturation
  • Sandy and peat soils with low Ca reserves
  • Heavy K and Mg fertilization displacing Ca on the soil exchange
  • No liming for many years

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Effect

Field signs:
  • Young leaves in the top whorl show interveinal chlorosis, green veins on yellow leaf (Ca is immobile, deficiency shows on new growth)
  • Distorted new flush, marginal leaf necrosis
  • Poor bark renewal on the tapping panel (thin, cracked, slow-regenerating bark)
  • Weak root system, elevated root-disease risk

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Leaf-tissue thresholds

Sample Whorl 2 leaves.
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

No direct satellite signal for Ca. Manage via routine soil pH and Whorl 2 tissue tests.

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Action

1

Test soil pH and base saturation

Confirm with soil analysis (target pH 5.0 to 5.5, base saturation > 30%).
2

Apply ground magnesium limestone (dolomite)

Dolomite (~30% CaO, ~20% MgO) supplies both Ca and Mg and raises pH:
  • Every 3 to 5 years: 500 kg to 1 t/ha broadcast across the block
  • New planting: 250 to 500 g dolomite per planting hole
3

Alternative: ground limestone (calcite)

If Mg is already adequate, use pure ground limestone (~40% CaO). Common on peat blocks where Mg is separately corrected.
4

Watch bark renewal on tapped panels

Ca-deficient trees have poor bark renewal; the new bark is thin and prone to cracking. This opens the tree to black stripe and pink disease.