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Ministry of Agriculture, Food and Rural Affairs

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
Potassium deficiency Potassium deficiency Potassium deficiency
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