Potassium
Potassium is important for fruit colour, winter hardiness, tree growth and disease resistance.
Identification
- Usually first appears on older leaves.
- Interveinal purpling start at leaf margin and working into the centre of the leaf.
- Leaf margins become brown.
- Necrotic spots develop between leaf veins and may drop out.
- Fruit will ripen unevenly and have poor/variable colour development.
Often Confused With
Chemical:
- spray damage yellowing and browning of leaf margins and interveinal areas,
- herbicides such as triazines (simazine, atrazine); ureas (diuron, linuron), uracil (terbacil, bromacil); dichlobenil,
Diseases:
- canker diseases along trunks and branches
- anthracnose
Insects:
- aphids
- leafhoppers
Mechanical:
- damage to tree bark,
- leaf scorch
- root injury
Soil & planting conditions:
- leaching from sandy soils
- waterlogged soil conditions
- dry soil conditions
- soil compaction
- High levels of calcium, magnesium, sodium, nitrogen or phosphorus can affect uptake, especially if potassium deficient
Weather:
- Late spring or summer frosts
- High winds at high temperatures on succulent spring growth
- Drying and shriveling of leaf margins from wind
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