Guava occupies an area of 262 thousand hectare and annually produces 3648 thousand MT. There is a lack of information on the response of guava to micro-nutrients. However, experience has shown that zinc is one of the most important micronutrient responsible for maintenance of yield and quality of fruits. The deficiency of Zn is also one of the main reason for the bronzing disease in guava. In the absence of complete information we have attempted to prepare an update on the zinc deficient area, deficiency symptoms and its management in guava. This appraisal is essential for preparing strategic guide in realizing potential yields of guava in different regions of the country for efficient management of Zn deficiencies to enhance the yield and quality of guava fruits.
Guava Crop boundary:
Ten states covering 131 districts were identified as prime guava producing states of India. The boundary map of guava was prepared using district maps of respective leading producing states (Figure 1).
Figure 1. Major guava growing areas in India
Deficiency symptoms:
High soil pH, water logged and low lying soils and soils with a high calcium carbonate content can cause zinc deficiency in trees. Expression of leaf symptoms are not strong in guava trees(Plate A, B, C,D). Symptoms occur in the spring and include chlorosis of the youngest shoot leaves(A) Later they become stunted and narrower than normal giving a “little leaf” appearance(B & C). Zinc deficiency may also cause brown patches, spots or streaks of dead tissue on the leaves and chlorosis between the leaf veins(D). The leaves may be deformed near the tips, may show a wavy margin and bunch together to form rosettes with overcrowded fruits with reduced size. Blind bud and rosetting can also occur. There may be some dieback of new shoots. Fruit may be smaller than normal and with lower yields than normal. Extreme deficiency results in shoot defoliation and the production of misshapen and poorly coloured fruits.
Plate A, Zn deficiency in guava showing chlorosis of the youngest shoot leaves, B & C, Zinc deficiency in advanced stage showing stunted growth and narrower than normal leaves bunch together and deformed near the tips, giving a “little leaf” with wavy margin, D: Zinc deficiency showing brown patches, spots or streaks of dead tissue on the leaves and chlorosis between the leaf veins.
The Zinc status map of leading guava producing states is present in Figure 2. It was found that soils in 47 districts showed deficiency in available zinc and an 66 districts showed medium status of available zinc. Since a sizable number of districts have low zinc availability in their soils, response of guava to applied zinc is expected. Foliar feeding is better than soil application as the use efficiency of zinc applied through soil is very low compared to foliar feeding.
Figure 2. Zinc fertility status of guava growing regions of India
Management of Zinc in Guava:
Guava plants do not generally show field level deficiency symptoms. But certainly the trees do experience varied levels of hidden zinc hunger. Under such situations farmers generally neglect zinc application to guava trees. This leads to reduction in fruit quality and yield. First farmers required to check the field conditions whether the soil pH is high and then check whether the soil is calcareous and further check whether there is any water stagnation near the tree basins. Under these circumstances generally zinc deficiencies are noticed. The use of zinc nutritional sprays (Zinc sulphate 0.5%) for fertilizing a guava tree is suggested. Apply these foliar sprays three times a year, from spring to summer, for the first two years of growth and then once a year there after. To increase the yield, spray Urea 1 % + Zinc sulphate 0.5% twice a year during monsoon period.
Zinc deficiency is also a culprit in bronzing in guava. However, spraying with only zinc micronutrient will not solve the problem of bronzing. A combined spray should be given containing ZnSO4, MgSO4 and MnSo4 @ 0.5%, CuSO4 and FeSO4 @ 0.25 % plus adjuvant @ 1ml per 5 lit of solution on various stages viz., new flush, one month after, flowering and fruit set stages. Avoid applying foliar sprays after buds have opened, as zinc sulfate is harmful to delicate leaves, flowers and fruits. If zinc is needed after this stage, repeat the sprays. Soil application of zinc sulfate is suggested after the monsoon and retreat when leaves are still green, though one can use higher concentrations of spray during dormant early spring months. In north and north western Indogangetic belt apply zinc sulfate to soils of guava trees in their late dormant stage at the tail end of winter or beginning of spring. But it is always advised to get the soil tested for Zn before applying zinc sulfate to soil.
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