> ## 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.

# Diagnose and Respond to Magnesium Deficiency in Pineapple

> Identify magnesium deficiency in pineapple from interveinal chlorosis and red-purple margins on older leaves, and correct it with kieserite, dolomite, and balanced K:Mg fertilization.

Magnesium is the central atom of chlorophyll, so Mg deficiency shows as chlorosis on older leaves while young leaves stay green. On pineapple, the classic pattern is **interveinal yellowing plus red-purple margins** on the lower rosette. Mg deficiency often follows heavy K applications (K induces Mg deficiency by cation competition).

**Regional priority:** High on sandy, BRIS, and leached soils, and on any block with heavy MOP use without matching Mg.

## When pineapple is most vulnerable

From **late vegetative (month 8) onward**, worsening if not corrected before fruit development.

## How magnesium deficiency shows in satellite data

* **NDVI slightly below phase baseline** on affected blocks, but NDRE is more sensitive because chlorophyll is directly depleted.
* Pattern is block-wide or matches sandy zones within a block.
* Not detectable at individual-plant scale.

## Field symptoms

* **Interveinal yellow chlorosis** on older leaves, veins staying green
* **Red-purple margins** on the yellowed leaves
* **Older leaves affected first** (Mg is mobile and moves to young growth)
* **Reduced fruit sugar** and off-color fruit shells
* **Overlap with K deficiency** but Mg shows the vein-band pattern; K shows uniform tip and margin burn

## Reduce the damage by

* **Kieserite (MgSO4)** as the standard fast-acting Mg source - 200 to 400 kg/ha per cycle, banded on the mulch.
* **Dolomite (CaMg carbonate)** on acid soils - corrects Mg and raises pH at the same time.
* **Foliar MgSO4 (2%)** for rapid correction during the season.
* **Balance K:Mg** - target K:Mg of 3:1 on mineral, 2:1 on sandy or BRIS soils. High K without Mg induces deficiency.
* **Split kieserite and MOP** into separate applications to reduce cation competition at uptake.
* **D-leaf analysis** - target 0.3 to 0.4% Mg in the D-leaf. This is a generic target with no site, soil, cultivar or season qualifier, so it supports *inside* or *outside* and no finer grade — see [Reading a tissue analysis](/snippets/tissue-diagnosis).

## Set an alert for early warning

<Tip>
  Turn the diagnosis into a trigger. Mg deficiency is chronic and slow, so schedule sampling and trend alerts rather than event alerts.
</Tip>

Recommended settings for magnesium on pineapple:

* **NDRE trend alert** - trigger when 4-week moving NDRE drops 5% or more below phase baseline.
* **D-leaf sampling reminder** - month 8 to 10, sample both K and Mg simultaneously.
* **Soil test reminder** - every 2 cycles, focused on exchangeable Mg and K:Mg ratio.

## Related

* [Pineapple Diagnosis](/guides/Crop/Pineapple/pineapple-diagnosis)
* [Potassium](/guides/Crop/Pineapple/nutrient/potassium) - overlapping and induced by excess K.
* [Set up automated crop alerts](/guides/alerts-notifications)