Potassium & magnesium deficiency in coffee – Signs and treatment
Which nutrients is coffee often short of?
Coffee is a long-lived industrial crop with high nutrient needs – especially potassium (K) and magnesium (Mg). When short of these two elements, trees often:
- Support fruit less well
- Drop leaves early, have small fruit that ripens unevenly
- Become more susceptible to disease
Symptoms of potassium (K) deficiency
| Symptom | How to recognise |
|---|---|
| Leaves yellow from the edge inwards | Yellowing around the leaf margin, scorching from the edge inwards |
| Leaf veins still green | Centre of the leaf still green, only the margin turns brown |
| Lower leaves drop | Many old leaves drop, bare branches |
| Small, uneven fruit | Uneven ripening, low yield |
Potassium helps the tree transport sugars, improves stress tolerance and fruit quality
Symptoms of magnesium (Mg) deficiency
| Symptom | How to recognise |
|---|---|
| Yellowing from the veins towards the edge | Midrib still green; the area between veins and margin yellows first |
| Usually on older leaves | Older lower leaves yellow clearly first |
| Weak trees, small fruit | Poor photosynthesis, slow growth, little fruit |
Magnesium is a component of chlorophyll – Mg deficiency = less photosynthesis → less growth
Comparison of potassium and magnesium deficiency in coffee
| Factor | Potassium deficiency | Magnesium deficiency |
|---|---|---|
| Where it appears | Older leaves, leaf margins | Older leaves, middle of the leaf (between veins & margin) |
| Colour | Yellow, scorched leaf margins | Yellow from the middle of the leaf, veins still green |
| Effect on fruit | Small fruit, early drop | Little fruit, weakened tree |
| Treatment | Apply KCl, KNO₃ | Apply MgSO₄ (magnesium sulfate) or dolomite lime |
Supplying & preventing K and Mg deficiency
✅ Apply at the right time:
- Flowering – fruit fill: prioritise potassium
- Strong growth, prolonged rain: add magnesium
✅ Suggested products:
- Potassium (K): soluble KCl, KNO₃
- Magnesium (Mg): magnesium sulfate (MgSO₄), dolomite lime
- Combined micronutrients: add Zn, B, Mn to improve uptake
Need advice on a coffee nutrition programme?
Contact Vietcropchem technical staff:
Read more:
Products for mealybugs and aphids on coffee – a two-way systemic approach
Coffee nutrition & fertilising by growth stage
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[NEWS 25/8/2025]