Oats are more susceptible to zinc (Zn) deficiency than wheat or barley.
What to look for
Paddock
Patchy growth, with plants in poor areas.
Heavily limed soils, sands and gravels or alkaline grey clays tend to be most affected, often in cold wet weather. Plants frequently recover in spring and produce (fewer) normal panicles.
Zinc deficient crops are often patchy in appearance.
Plant
Middle and older leaves turn pale green; pale yellow areas develop between the mid-vein and leaf edge towards the tip. Discolouration spreads downwards and darkens.
Brown edged spots appear in the affected areas, increasing in size until the leaf tip dies, often turning red-brown to black (main characteristic).
Base of the leaf remains green, mid section yellow and tips red-brown to black.
Youngest leaves usually remain green.
Severely deficient plants have very short stems and young leaves have difficulty emerging fully.
Where does it occur?
Soil type
Soil ph
Most sandy surfaced soils required copper and zinc treatments when initially cleared for agriculture.
Where soil levels are marginal, zinc deficiency can be induced by applications of lime, high nitrogen fertiliser, and copper fertiliser.
Zinc deficiency is more common in high pH and clay soils, and on young plants in cold wet weather.
The use of root-pruning herbicides, particularly groups A and B can induce zinc deficiency.
Zinc is relatively immobile in soil and can become unavailable to crops in dry soil.
Management strategies
Spraying foliar
Soil application
Seed treatment
Foliar spray (effective only in current season) or drilled fertiliser.
A foliar spray of 1kg/ha zinc sulphate (23% Zn) in 50-100L of water should be applied as soon as Zn deficiency is detected to prevent grain and hay yield losses.
As zinc is immobile in the soil top dressing 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 zinc when the topsoil is dry.
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 where Zn soil supply is marginal.
How can it be monitored?
Soil test
Tissue test
A 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.
