Diagnosing potassium deficiency in oats

Potassium is required for photosynthesis, transport of sugars, enzyme activation and controlling water balance within plant cells. Deficiency causes reduced root growth, restricted leaf development, less grains per head and smaller grain size. Potassium deficiency can reduce the tolerance of plants to environmental stresses such as drought, frost and waterlogging, as well as pests and diseases.

CSBP oat nutrition trial showing oat crop with symptoms of potassium deficiency
Drooping older leaves
Oat crop with both N and K deficiency showing more arrow shaped necrosis
Worse septoria on K deficient plant
Three tone appearance with green younger leaves, green with yellow to bronze colours on the middle leaves and brown dead older leaves

What to look for

    Paddock

  • Smaller lighter green plants with bronze and necrotic leaf ends, generally on sandier parts of the paddock or between header or swathe rows.
  • Affected areas are more susceptible to leaf disease.

    Plant

  • Plants appear smaller and paler but tillering may not be affected.
  • Plants may look unusually water-stressed despite adequate water and cool conditions.
  • Older leaves are affected first with dark yellow chlorosis then necrosis that moves down from the leaf tip and edges.
  • Another early symptom is development of bronze yellow areas in the mid-section of the leaf that quickly spreads to the leaf tip. Grey-brown spots develop and cause the leaf to bend at that point.
  • Typically, the deficient plant develops a three tone appearance with green younger leaves, green with yellow to bronze colours on the middle leaves and brown dead older leaves.

Where does it occur?

  • 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.
  • Potassium deficiency can be induced by root pruning factors such as pests and root disease.

Where did it come from?

  • Top-dressing potassium will generally correct the deficiency.
  • Foliar sprays generally can not supply enough potassium to overcome a severe deficiency and can scorch crop leaves.

Management strategies

Top dressing
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 scorch crop leaves.
  • Potassium can be banded at seeding, or top-dressed before or after seeding. Banded potassium can be more effective where root development is inhibited by factors such as water repellence or nematodes.

How can it be monitored?

Tissue test
Tissue test
Soil test
Soil test
  • Use whole-top plant test to diagnose suspected potassium (K) deficiency, and compare paired good/poor plant samples where possible. The critical concentration for the whole shoot varies from 4.5% for young plants to about 1.5% at the boot stage.
  • The critical level for the 0-10cm Colwell K soil test is about 45-50mg/kg for deeper sands. However for duplex soils potassium reserves may be present in the clay. Therefore, the reliability of soil test potassium is frequently improved with potassium soil test values from deeper in the soil profile.
  • Hay crops remove greater amounts of potassium (about 10kg K/tonne) compared to potassium losses in grain.
Source URL: https://www.agric.wa.gov.au/mycrop/diagnosing-potassium-deficiency-oats
This print version was generated at 7:53am on the 26th of April, 2024.
The original document was last revised at Fri, 19/02/2016 - 12:09pm

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Important disclaimer

The Chief Executive Officer of the Department of Primary Industries and Regional Development and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.