Banana is produced throughout India but commercially in the states of Andhra Pradesh, Gujarat, Karnataka, West Bengal, Madhya Pradesh and Maharashtra. This fruit is cultivated in 858000 ha. and producing 29163 thousand tons of fruits and this contributes 33.4 per cent of the total fruits production in India. It is one of the major zinc sources in human beings. Apart from other nutrients, deficiency of zinc is common throughout the banana growing regions and hence needs special attention.
Crop boundary:
We identified 76 districts spread in eleven states as prime banana producing states of India. But major states are Andhra Pradesh, Gujarat, Karnataka, West Bengal, Madhya Pradesh and Maharashtra. The boundary map of banana was prepared using these district maps of respective leading producing states (Figure 1).
Figure 1.Major Banana growing areas in India:
Deficiency symptoms:
Banana is susceptible to zinc deficiency. If the soil supply is not adequate the crop shows typical deficiency symptoms at all stages of the crop. Plant bears narrow pointed and chlorotic young leaves. Bunchy top crowns is a typical symptoms of zinc deficiency which is often falsely identified as banana bunchy top virus(BBTV) by the farmers. The emerging young leaves have high amount of anthocyanin pigment on the lower side of the leaves, which often disappears as the leaf unfolds. Leaves are narrow with yellow to white stripes between the secondary veins. Later on oblong, brown or necrotic patches develop on the yellow striped areas. The leaves of the young suckers may become distorted, comprising of mid-rib and serrated narrow lamina only (Plate A, B, C). Bunches developing on such plants have twisted fingers with prominent light green tip. The characteristics symptoms appear in young leaves which become significantly smaller in size and more lanceolate in shape.
Plate (A, B, C). Zinc deficient banana plant showing (A) Young leaf showing young plants showing distorted leaves comprising of mid-rib and serrated narrow lamina and(B) bunchy top crowns
Sufficient data base is available on soil zinc availability in India. Of the 76 banana growing districts, 22 districts have deficiency of zinc in the soils and 49 districts showed sufficient levels of soil available zinc(Figure 2). Keeping this in mind and the pattern of fertilizer use in banana and the crop ability to absorb nutrients it is advisable to go for foliar application of zinc rather than soil application as a precaution to avoid unnecessary accumulation in the soils leading to nutrient imbalances.
Figure 2.Zinc fertility status of banana growing regions of India
Management of Zinc in Banana:
Zinc deficiency has often been confused with virus infection. But a uniform spread of the symptoms in the field rather than in patches confirms zinc deficiency. This is the most widely reported micronutrient element deficiency in bananas. Deficiency is more common in calcareous and organic soils. Since Zn is leached under acid conditions and fixed under alkaline conditions it is easy to correct its deficiency with a spray of 0.5% ZnSO4. But the pH of the spray solution is very important. Maintain a solution pH in the range of 6.2 to 6.6 so that the scorching on leaves and fruits may be avoided. The Zn requirement of the banana is relatively small. On the basis of whole plant analysis application of 1.0 kg Zn/ha/yr is sufficient to meet the zinc requirement of a reasonably high yielding crop. Farmers are advised not to make it a habit of application of Zn to soil and are advised to undertake soil testing and based on the soil status undertake correction of deficiencies as it occurs.
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