Among fruit crops in India the area under mango is the largest (2263 thousand ha) with a production of 19.87 million tonsin 2016-17. It is one of the least cared fruit crops in India. As a consequence the productivity of mango is abysmally low(8.7t ha-1). The main reasons for this low productivity are the poor nutritional status of the mango trees and the poor status of the health of the soils in mango orchards. Multiple nutrient deficiencies are common leading to low yields. Among micronutrients zinc is the most deficient in mango growing regions of India.
Mango crop boundary:
Mango is grown throughout the country on all types of soils and in all the agro ecological sub regions except in very cold or extremely dry desert areas. Based on area and production, one hundred eleven districts spread in ten states were identified as prime mango growing districts of India (Figure 1). The boundary map of mango was prepared using district maps of respective leading mango producing states.
Figure 1.Major mango growing areas in India:
Deficiency symptoms:
The main zinc deficiency symptom is exhibited in the leaves which become small, narrow, curved, thick and inflexible. Between veins a speckled brown chlorosis is sometimes seen(Plate 1A,1B,1C). The branches produce few secondary branches and the internodes are of short length and these results in rosette appearance. Floral malformation and/or vegetative malformation or “witch broom” may, in part, be associated with zinc deficiency since the plants emit small, irregular, multiple and distorted panicles. Zinc deficiency may be more severe in fertile soils, in calcareous and limed soils or in orchards receiving high amounts of phosphorous fertilizers.
Plate 1(A,B,C) zinc deficiency in mango(A&B) showing interveinal chlorosis with veins remaining green and (C) field view of a zinc deficiency Showing emerging little leaves
Soil status of zinc and appearance of deficiency in mango do not match closely. Several studies have reported widespread zinc deficiencies in Indian soils. Out of 111 mango districts, soils in 60% of area (67 districts) are well supplied with zinc. Only 33% area(33 districts) shows deficient levels of soil zinc(Figure 2). Zinc deficiency occurs during peak growth period or fruit development stage when the demand for zinc exceeds supply rate from the soil. Being immobile re-translocation from older leaves or woody part is slow. As a result the deficiency is exhibited both as hidden hunger and expressed as leaf symptoms. Foliar application of zinc corrects such deficiencies.
Figure 2. Zinc fertility status of mango growing regions of India
Management of Zinc in Mango:
Continuous soil application of zinc leads to its accumulation in the soil leading to nutrient imbalance in the soil. Further the uptake of foliar‐applied zinc in mango is more rapid than that of soil applied zinc. Hence foliar application is preferred over soil application. Zinc deficiency in mango, can be ameliorated by foliar application of zinc sulphate. Spray the plants with 0.25-0.5% zinc sulphate solution (250-500g zinc sulphate per 100 liters of water depending upon severity of deficiency) soon after cessation of monsoon and before October flush and repeat the spray before panicle emergence. However, in some places where new flush emerges late, the spray should be done in June and if further delayed flush appears then zinc sulphate should be sprayed during August-September. Apart from this zinc deficiency becomes acute in mango, immediately after first fruit set on plants; therefore one maintenance spray of 0.3% zinc sulphate solution may be given in pre-monsoon from the third year of planting(12, 34). Arka Mango special developed by ICAR-IIHR may be used @ 5g per liter to correct zinc deficiency in addition to other micronutrient deficiencies. Those growers who wish to apply Zn to soil may apply one kg zinc sulphate per tree once in two to three years.
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