> ## Documentation Index
> Fetch the complete documentation index at: https://badixth-dc85e378.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Potassium Deficiency in Rubber

> How potassium deficiency limits latex synthesis in mature tapped rubber, Whorl 2 tissue thresholds, and the K fertilizer program for tapped stands.

Potassium is the most critical nutrient for latex synthesis. Mature tapped rubber is a heavy K user: latex export removes 40 to 60 kg K/ha/year. K deficiency causes tip die-back on older leaves, reduced latex flow, and elevated TPD incidence. It is the second most common nutrient issue in Malaysian rubber after N.

## Cause

* **Heavy tapping without K replacement** (K export in latex is significant)
* **Sandy soils** with low K reserves and high leaching
* **Coastal lowland** with K leaching after heavy rain
* **Peat soils** with low K
* **Erosion** on hilly blocks

## Effect

| Stand age         | Symptom                                                                |
| ----------------- | ---------------------------------------------------------------------- |
| Immature          | Marginal chlorosis on older leaves, reduced growth                     |
| Tapped (5+ years) | Yield reduction (10 to 25%), higher TPD incidence, delayed refoliation |

Field signs:

* Older leaves yellow-orange with **tip die-back** and marginal necrosis (classic K deficiency signature)
* Younger leaves normal, deficiency concentrated on lower whorl
* Reduced latex flow, watery latex
* Elevated TPD incidence
* Bark cracking on tapping panel

## Leaf-tissue thresholds

Sample **Whorl 2** leaves.

| K level (% dry weight) | Interpretation |
| ---------------------- | -------------- |
| \< 1.1                 | Deficient      |
| 1.1 to 1.3             | Marginal       |
| 1.3 to 1.7             | Optimal        |
| > 1.7                  | High           |

<Warning>
  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](/snippets/tissue-diagnosis).
</Warning>

## Satellite signals

| Index                    | What to watch                              | Threshold                    |
| ------------------------ | ------------------------------------------ | ---------------------------- |
| NDVI                     | Slow whole-block decline over 1 to 2 years | -0.05 vs multi-year baseline |
| NDRE                     | Sensitive to canopy quality                | -0.03 sustained              |
| Autumn/wintering pattern | Delayed refoliation                        | Compare to previous years    |

K deficiency is easily confused with over-tapping or [TPD](/guides/Crop/Rubber/biotic/tpd); tissue analysis is essential.

## Action

<Steps>
  <Step title="Confirm with tissue">
    Whorl 2 K \< 1.1% confirms deficiency. If borderline (1.1 to 1.3%) combined with heavy tapping, treat as deficient.
  </Step>

  <Step title="Apply muriate of potash (KCl, 60% K2O)">
    Split into 2 to 3 applications per year:

    * Immature: 100 to 200 g KCl/tree/year
    * Mature tapped: 300 to 500 g KCl/tree/year, split

    Apply after main rains, worked into the top 5 cm around the drip zone.
  </Step>

  <Step title="Reduce tapping intensity on deficient blocks">
    Switch to d/3 or d/4 until K status is restored. Continued heavy tapping on K-deficient trees is the top nutrient cause of [TPD](/guides/Crop/Rubber/biotic/tpd).
  </Step>

  <Step title="Follow up">
    Re-sample Whorl 2 leaves 3 months after application. Latex flow response takes 3 to 6 months.
  </Step>
</Steps>

## Recommended alert settings

| Trigger           | Condition                            | Severity                                     |
| ----------------- | ------------------------------------ | -------------------------------------------- |
| Latex yield drop  | -15% vs prior 6-month baseline       | Medium                                       |
| Leaf tissue K     | \< 1.1% on scheduled sample          | High                                         |
| NDVI slow decline | -0.05 over 12 months on tapped block | Medium                                       |
| TPD cluster       | > 5% TPD incidence in a block        | High (triggers K + tapping-frequency review) |

## Related

* [Tapping Panel Dryness](/guides/Crop/Rubber/biotic/tpd)
* [Rubber Diagnosis](/guides/Crop/Rubber/rubber-diagnosis)
* [Magnesium deficiency](/guides/Crop/Rubber/nutrient/magnesium)