Zinc
Zinc is a component of many plant enzymes and essential for healthy plant growth and leaf formation. Oats are highly susceptible to deficient levels of Zn in the soil. After the initial recommended application, most micronutrients have a long residual value in the soil. Therefore, both tissue testing and soil testing,in conjunction, can be used to determine the need for re-application.
Plant symptoms may help to diagnose Zn deficiency, however a tissue test may be required. Zinc concentrations in the young leaves of less than 14mg/kg indicate that the plant is Zn deficient.
An initial application of 1-2kg/ha zinc oxide (75% Zn) will correct a deficiency for many years. 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.
Zn deficiency symptoms
Zinc deficiency causes patchy growth, with plants in poor areas stunted with pale green leaves and yellow or orange-red tips. Youngest leaves usually remain green, middle and older leaves turn pale green and pale yellow areas develop between the leaf edge and mid-vein at the tip. Brown spots occur in the affected areas, increasing in size until the leaf tip dies, often turning red-brown to black.
With severe deficiency the stem remains very short and youngest leaves have difficulty emerging fully. The symptoms can be mistaken with that of barley yellow dwarf virus and severe P deficiency.