The first effect of zinc deficiency appears at the tillering initiation stage in the form of fading of tissue between midrib and edges of the leaf (third leaf from the top) in middle or lower half of lamina. This is followed by loss of green colour between the veins and light to dark brown spots (necrotic lesions) in middle of the leaf blade. The necrotic areas intensify and coalesce resulting in collapse of affected leaves from the middle (Plate 1). Plant growth is restricted. Earing and maturity are delayed (Plate 2).

Soil application of zinc sulphate is the most common and suc¬cessful method. Foliar application should be considered as a temporary measure and not a substitute to soil application.

The rate of zinc sulphate application varies with type of soil and its available zinc status as well as with crop cultivars. By and large, zinc deficiency in wheat is best corrected by application of zinc sulphate at 50 kg per hectare to top soil by broadcast and incorporation method immediately before sowing.

If zinc deficiency symptoms appear on the crop, zinc sulphate solution of 0.5% concentration is sprayed at intervals of 10 to 14 days. For one hectare crop 2.5 kg zinc sulphate with 1.25 slake lime in 500 litre water is required.

In various field experiments conducted in different parts of the country, average response (yield increase) to zinc sulphate application was found to be 360 kg per hectare. A typical response of wheat to zinc application is depicted in Plate 3.