Diagnosing zinc deficiency in canola

Although canola is moderately susceptible to zinc deficiency, it is rarely seen in the paddock because many fertilisers have trace zinc levels, canola appears to be more effective in using soil zinc, and mild deficiency is difficult to identify.

Stunted plants with pale younger leaves
Zinc deficient plants on the right have slower maturity, reduced and more variable plant growth

What to look for

    Paddock

  • Stunted pale plants with areas of poorer growth alongside healthy, apparently normal plants giving the crop a patchy appearance.
  • Worse symptoms are expected on sandy or alkaline grey clay soils, particularly if newly limed, and better on old windrows . Plants often improve on windrows.

      Paddock

    • Stunted pale plants with areas of poorer growth alongside healthy, apparently normal plants giving the crop a patchy appearance.
    • Worse symptoms are expected on sandy or alkaline grey clay soils, particularly if newly limed, and better on old windrows . Plants often improve on windrows.
  • Stunted plants with pale green young leaves, particularly between leaf veins.
  • Leaf blades bend down.
  • Shortened internodes as stems elongate.

Where does it occur?

Dry conditions
Dry conditions
Spraying herbicide
Spraying herbicide
Soil ph
Soil ph
  • Most sandy surfaced soils required copper and zinc when initially cleared for agriculture
  • Zinc is relatively immobile in soil and becomes unavailable to crops in dry soil.
  • Where soil levels are marginal, zinc deficiency can be induced by applications of lime, increased nitrogen fertiliser, and copper fertiliser
  • The use of root-pruning herbicides can induce zinc deficiency
  • Zinc deficiency is more common in high pH and clay soils

Management strategies

Soil application
Soil application
Spraying foliar
Spraying foliar
  • Foliar spray (effective only in current season) or drilled soil fertiliser
  • Zinc foliar sprays need to be applied as soon as deficiency is detected to avoid irreversible damage
  • As zinc is immobile in the soil topdressing is ineffective, only being available to the plant when the topsoil is wet
  • Mixing zinc throughout the topsoil improves availability due to more uniform nutrient distribution.
  • Zinc drilled deep increases the chances of roots being able to obtain enough molybdenum in dry seasons
  • Zinc seed treatment is used to promote early growth where root disease is a problem, but the level is lower than a plant needs in the current season.
  • Zinc present in compound fertilisers often meets the current requirements of the crop

How can it be monitored?

Soil test
Soil test
Tissue test
Tissue test
  • A DTPA zinc soil test provides at best a rough guide to soil zinc status
  • Whole-top plant test provides a rough guide if paired good/ poor samples are taken, but this should be confirmed with a youngest emerged blade (YEB) test.
  • Whole shoots of young plants [40 days] below about 23 mg/kg, and YEB levels below about 15 mg/kg indicate zinc deficiency

Further information

Plant nutrition [1]

Links
[1] https://www.agric.wa.gov.au/crops/production-postharvest/plant-nutrition

Source URL: https://www.agric.wa.gov.au/mycrop/diagnosing-zinc-deficiency-canola
This print version was generated at 2:47pm on the 17th of May, 2024.
The original document was last revised at Wed, 06/05/2015 - 11:25am

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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.