Deficiency symptoms first appear on middle leaves as loss of green colour, followed by development of brown spots which grow between the veins. Zinc deficient plants are stunted & produce small, thin grains.

The zinc deficiency symptoms appear on third & fourth leaves. These leaves are light yellow to yellow and then develop brown colour spots with increase in severity of deficiency. The plants have stunted growth. The size of kernels is reduced (Plate 1 &2).

Symptoms of Zn deficiency appear on older leaves as loss of gree.n colour between the veins (chlorosis) which starts from margins & proceeds towards midrib. As the severity of deficiency increases the chlorotic spots turn brown (necrotic). Sometimes reddish brown spots are also seen on chlorotic parts. The leaf size is reduced. Leaves dry at advanced stage of deficiency (Plate 3).

Zinc deficiency symptoms appear within 3 weeks of sowing oil first true leaf. Leaves are small and pinkish on margins. Interveinal tissues turn yellowish white with veins remaining green. There is upward or downward cupping of leaves. Flowering and fruiting is delayed.

Soil application is the most widely used method of correcting Zinc deficiency in oil seeds crops. If soil application is not done at the time of sowing and the deficiency symptoms are seen in the standing crop foliar spray of zinc sulphate solution is a quick method of correcting zinc deficiency.

To correct zinc deficiency as is appears in the standing crop, 0.5%. Zinc Sulphate solution should be sprayed (neutralise with 0.25% slaked lime). To prepare 0.5% zinc sulphate solution 2.5 kgs zinc sulphate & 1.25 kgs slaked lime is dissolved in 50 litres of water. To make this solution effectively sticking to the leaves, one litre Teepol is added before spraying on the crop.

Zinc Sulphate is applied broadcast & incorporated in the top soil with the last ploughing at the rate of 25 kg per hectare.

In the field experiments conducted in different parts of India, the additional yields at optimum rate of zinc sulphate application to different oil seed crops has been found as follows: