Diagnosing potassium deficiency in barley
Potassium is a major nutrient that is increasingly required as soil reserves become depleted. Potassium deficiency results in poor water use and other nutrients, making crops more susceptible to drought, waterlogging, frost and leaf diseases.
What to look for
- Areas of plants that have leaf tip death and bright yellowing extending down from tip of older leaves.
- Symptoms are worse in sandier areas or between header/swathe rows.
- Plants look unusually water-stressed despite adequate environmental conditions.
- Affected areas may have more leaf disease.
Paddock
- Stunted plants with short stout stems and pale foliage, but tillering may not be affected.
- Older leaves affected first with leaf tip death and yellowing that progress down from the leaf tip and edges.
- There is often a marked contrast in colour between yellow leaf margins and green centre.
- Yellowing leaf tip and leaf margins often generates a characteristic green 'arrow' shape towards leaf tip.
- Leaf symptoms can be accompanied by increased leaf disease and physiological leaf spot.
- Affected plants can appear water stressed, hay off prematurely, and produce shrivelled grain.
Plant
What else could it be
| Condition | Similarities | Differences |
|---|---|---|
| Diagnosing root lesion nematode in cereals | Small, water stressed plants | Root lesion nematode plants have 'spaghetti' roots. |
|
Nitrogen, molybdenum or phosphorus deficiency
|
Smaller and pale green plants. This similarity only occurs in mildly deficient plants. | Potassium deficient plants differ in that tillering is often not affected, and older leaves have a more marked contrast between yellow and green sections, often in an arrow-shape pattern towards the tip. |
Where does it occur?
Soil type
- Sandy soils and deep grey sandy duplex soils tend to be more susceptible to potassium deficiency.
- High rates of hay or grain removal can result in potassium deficiency.
Management strategies
Top dressing
- Top-dressing potassium will generally correct the deficiency.
- Foliar sprays generally can not supply enough potassium to overcome a severe deficiency and can also scorch crops.
How can it be monitored?
Tissue test
Soil test
- Use whole-top plant test to diagnose suspected potassium deficiency.
- 0-10 centimetres soil test for potassium is reliable in deep sands but may not be for duplex soils that have potassium reserves in the clay.
Further information
Where to go for expert help
Page last updated: Friday, 17 April 2015 - 2:06pm