The Miracle nutrient called Zinc

The same zinc that protects galvanized steel from rusting and the same zinc that is inside our pennies is the same zinc that is needed in infinitesimal amounts for all living things. An acre of healthy oats contains only one ounce. Yet, without this essential ounce of zinc no crop would grow at all! A grown man needs only seven one-thousandths of an ounce (25gm) of zinc per day. Yet this small amount helps build body protein, generate energy, promotes growth, and enhances taste and smell.

Only two ounces of zinc per ton of feed will prevent parakeratosis, or elephant hide, in hogs, promote hair growth on cattle, and generate healthy egg and chick development. Zinc is really a miracle micronutrient for plant life …an acre of corn needs only two ounces! But, this two ounces can increase yields by over 60 bu. per acre. Zinc is involved in most plant growth functions. Zinc helps produce auxins. Zinc is a growth promoting substance that controls the development of the shoot. Zinc also forms enzyme systems, which regulate plant life. Yet zinc is the most common micronutrient deficiency in agriculture today! Zinc deficiency can limit yields of corn, beans, wheat, cotton, sorghum, fruits, and vegetables.

The use of high yielding cereal varieties along with the increasing use of fertilizers containing major nutrients (N, P, and K) but without micronutrients through inorganic or organic fertilizers dramatically increased food production under intensified systems in early seventies. However, as a result of depleted Micronutrient reserves in the soil, this practice resulted in a number of nutrient disorders and associated nutrient imbalances. A sharp decline in the available micronutrient status of soil is reported in irrigated agricultural production systems in India under continuos cropping with recommended rates of only major nutrients.

Micronutrient deficiency in irrigated production and dry land systems:

For Example field scale deficiencies of Zinc in rice and wheat on alluvial soils, Fe deficiency in sugarcane, upland rice, chickpea and groundnut on sandy calcareous soils. Mn deficiency in rice-wheat systems on sandy soils and B deficiency in chickpea and rice on high pH, calcareous soil have been reported, mostly in intensified production systems. The deficiencies of micronutrients have assumed critical importance of sustaining high productivity in some areas of country. Among these Zinc deficiency is most prevalent in intensely cropped light textured alkaline soils. Boron deficiency has become more critical on highly calcareous soils, limed acid soils and reclaimed soils.

As an example, the Micronutrient requirement and removal of a few major cropping systems in intensified production systems are given below in Table 2. It is clear that micronutrient removal by various cropping systems varies from crop to crop {Source: Takkar (1996)}

Amounts of micronutrients (gm) removed by major intensified system in India

Cropping systems Total Yield (T/Ha) Zn Fe Mn Cu B Mo
Rice - Rice 8.0 320 1224 2200 144 120 16
Rice - Wheat 8.0 384 3108 2980 168 252 16
Maize - Wheat 8.0 744 7296 1560 616 - -
Soybean - Wheat 6.5 416 3362 488 710 - -
Pigeonpea -Wheat 6.0 287 4356 493 148 - -

Under dry land agriculture, especially in the semi arid tropics with subsistence agriculture, the situation differs from the under irrigated intensified systems. In the first place soil erosion in some case, yields levels are low. Secondly soil erosion is severe resulting in the removal of top surface layers. Compounded with low use of organic manure, which were the dominant source of nutrients, micronutrients especially have dwindled in recent past.

Hence, there is a wide spread deficiency of Zn and B in watersheds of most parts of country. The deficiency is especially severe in Andhra Pradesh, MP and as indicated in table no. 1 intensive cropping area of Punjab, Haryana, West Bengal, UP and other states differing in severity. Hence, there is need for developing site specific nutrient management strategies for increasing the productivity of rainfed systems sustainability.

Effects on Plants

  • Affects several biochemical processes in the plant, such as
  • Cytochrome and nucleotide synthesis, auxin metabolism, chlorophyll production, enzyme activation and membrane integrity
  • Growth is severely affected

Effect of application of Micronutrients particularly Zn on the crop yields:

Fundacao Mt/PMA (1999) took up the study on effect of micronutrients on soybean yields. He took different treatments of fertilizers that included one which had all fertilizers including NPK and fortified with micronutrients B, Cu, Mn and Zn. One treatment was without NPK and rest without one particular micronutrient. The results were as under:

Treatments Yield (Kg/Ha) % Yield
Complete ( C )
Complete - B
Complete – Cu
Complete - Mn
Complete - Zn
Complete -Micro

Thus, it is clear that treatment with all fertilizer minus micronutrients had least yields (66%). Similarly treatment with all nutrients minus Zn yielded only 83% of control with all fertilizers including micronutrients, indicating that deficiency of Zn is very crucial and it deficiency results in very large reduction in yield

Signs of Zn deficiency on plants

  • Dusty brown spots on upper leaves of stunted plants
  • Uneven plant growth
  • Decreased tillering in cearals
  • Increased spikelet sterility in rice
  • Chlorotic midribs particularly near the leaf base of younger leaves
  • Leaves lose turgidity and turn brown as brown blotches and streaks appear on lower leaves, enlarge, and coalesce
  • White line sometimes appears along the leaf midrib
  • leaf blade size is reduced


  • important throughout the growth cycle of the rice crop
  • Occurs in neutral and calcareous soils, intensively cropped soils, paddy soils and very poorly drained soils, sodic and saline soils, peat soils, soils with high available P and Si status, sandy soils, highly weathered, acid, and coarse-textured soils, soils derived from serpentine and laterite, and leached, old acid sulfate soils with a small concentration of K, Mg, and Ca
  • Associated with S deficiency

Symptoms of Zn Deficiency:

  • Burning appearance of plants
  • Reduction in growth
  • Reduction in yields
  • Symptoms appear between two to four weeks after transplanting in case of paddy
  • Dusty brown spots on upper leaves of stunted plants
  • Uneven plant growth and patches of poorly established hills in the field, but the crop may recover without intervention
  • Tillering in paddy decreases and can stop completely and time to crop maturity increases under severe Zn deficiency
  • Increase spikelet sterility in rice
  • Chlorotic midribs, particularly near the leaf base of younger leaves
  • Leaves lose turgidity and turn brown as brown blotches and streaks appear on lower leaves, enlarge, and coalesce
  • White line sometimes appears along the leaf midrib
  • Leaf blade size is reduced

Confirmation of Zn Deficiency:

There are plant or soil tests to show Zinc deficiency .

The optimal ranges and critical levels of Zn in plant tissue are mm/kg:

Growth stage Plant part Optimum Critical level for deficiency
Tillering Y leaf 25-50 <20
Tillering Shoot 25-50 <10

On plant, the ranges of Zn deficiency in the whole shoot during vegetative growth (tillering) are as follows:

  • <10 mg kg -1 definite Zn deficiency
  • 10-15 mg kg -1 very likely
  • 15-20 mg kg -1 likely
  • >20 mg kg -1 unlikely (sufficient)

Problems with similar symptoms

The symptoms of Zinc deficiency may resemble those of Fe deficiency, which also occurs on alkaline soils. On alkaline soils, Zn deficiency is often associated with S deficiency. They may also resemble Mn deficiency and Mg deficiency.

Leaf spots may resemble Fe toxicity in appearance but the latter occurs on high organic status soils with low pH.

Why and where it occurs

One or more of the following factors can cause Zn deficiency particularly in paddy:

  • Small amount of available Zn in the soil.
  • Planted varieties are susceptible to Zn deficiency (i.e., Zn-inefficient cultivars).
  • High pH (close to 7 or alkaline under anaerobic conditions). Solubility of Zn decreases by two orders of magnitude for each unit increase in pH. Zn is precipitated as sparingly soluble Zn(OH) 2 when pH increases in acid soil following flooding.
  • High HCO 3- concentration because of reducing conditions in calcareous soils with high organic matter content or because of large concentrations of HCO 3- in irrigation water.
  • Depressed Zn uptake because of an increase in Fe, Ca, Mg, Cu, Mn, and P after flooding.
  • Formation of Zn-phosphates following large applications of P fertilizer. High P content in irrigation water (only in areas with polluted water).
  • Formation of complexes between Zn and organic matter in soils with high pH and high organic matter content or because of large applications of organic manures and crop residues.
  • Precipitation of Zn as ZnS when pH decreases in alkaline soil following flooding.

Mechanism of damage

Zinc is essential for several biochemical processes in the rice plant, such as:

  • Cytochrome and nucleotide synthesis
  • Auxin metabolism
  • Chlorophyll production
  • Enzyme activation
  • Membrane integrity

Zn accumulates in roots and can be translocated from roots to developing plant parts. Because little retranslocation of Zn occurs within the leaf canopy, particularly in N-deficient plants, Zn deficiency symptoms are more common on young or middle-aged leaves.

Sources Of Zinc:

Some the sources of zinc are given as below:

Sl. No. Name of Compounds % age of Zn & other associated nutrients
1 Zinc Sulphate Heptahydrate ( ZnSO 4.7H 2O) Zn - 21%, S - 15 %
2 Zinc Sulphate Monohydrate (ZnSO 4.H 2O) Zn - 33%, S - 15%
3 Chelated Zinc as Zn-EDTA Zn -12%
4 Chelated Zinc as Zn-EDTA Zn - 9%
5 Zincated Urea Zn - 2% N - 43%
6 Zincated Phosphate (suspension) Zn - 19.4% P 2O 5-12.9%
7 Zinc Oxide Zn - 60-80%
8 Zinc Carbonate (ZnCO3) Zn – 52-56%
9 Zinc Chloride (ZnCl 2) Zn – 48-50%

Feature of these sources:

  • Among various inorganic sources, zinc sulphate hepta hydrate (ZnSO 4.7H 2O) containing 21-22% Zn is found the most effective, commonly available, economically cheapest source of correcting Zn deficiency in most of crops and diverse soils as compared to sparingly soluble Zn sources, chelates, and mixtures. Mono hydrated and hepta Zinc sulphate containing (33% & 22%) were found equally efficient for correcting zinc deficiency either through soil or foliar application.
  • Synthetic Zn-EDTA chelates were found better than zinc sulphate in combating Zn deficiency in crops in non-calcareous loamy sandy soils but at par in calcareous and aridisols soils. However, their high cost than zinc sulphate made chelated fertilizers most uneconomic and less effective for common use.
  • Zinc chelated Zn-EDTA is at least three times more effective than Zinc Sulphate so far as uptake is concerned.
  • Zinc chelate is easily is translocated within the plants, because unlike Zinc sulphate it is partly systemic.
  • Zinc sulfate reduced phosphorus uptake and the phosphorus content of the shoots in plants, while Zn-EDTA increased it (Nammuang and Ingkapradit 1986).
  • Micronutrient blended fertilizers sources such as zincated urea, zincated super and boronated super were found initially inferior to zinc sulphate or chelates in highly Zn or B deficient soils as they mismatched with nutritional requirement of crops. But long term effects of zincated urea, boronated super became as efficient as that of soluble sources in controlling hidden/emerging micronutrient deficiency in several crops.
  • Zinc oxide is effective for roots dipping and seed coating before transplanted crops than zinc sulphate. Zinc phosphate has been found efficient source of for seed coating to control hidden hunger and cheaper than ZnO.

Frequency of zinc application:

Based on extensive experiments by the scientist world over following inferences have been drawn on frequency of Zn application:

  • Zinc leaves marked residual effect of 11 kg of Zn in soil, so it is not necessary to apply Zn to every crop. The residual effect of 11 kg per hac added to soil persists in four following crops in calcareous and on six crops in noncalcareous soils.
  • In sandy loam alkaline alluvial soils 5.5 kg of Zn per hac for first four crops and 2.75 kg per hac for next 8 to 12 crops respectively gives the largest grain response and are found optimum.
  • Under brackish water irrigation in a highly sodic soil (pH 10.4) amended with gypsum, @50% of the gypsum requirement (GR) the residual effect of 22 kg Zn per hac could last for four crops of rice -wheat sequence and fifth crop required repeat application of Zn.
  • Alkali soil (pH10.4) when irrigated with normal quality water, the yield with fresh application of 2.25 kg Zn per ha continuously to each crop was not different from a single initial application of 18 kg Zinc per hac after seventh crop, suggesting that residual effectiveness of Zn applied once had not diminished.
  • The beneficial effect of FYM alone or in combination with Zn is higher compared to Zn application. Integrated nutrient management proves better than Zinc alone.
  • Organic manure 12 t per hac FYM, 5 t poultry manure and 2.5 tones of piggery manure were as efficient as 11.2 kg Zn per hac in meeting the Zn requirement of wheat – maize rotation. Also half or even less rates of these manures proved equally more efficient or better when amended with 5.6 kg Zn per hac for maize –wheat rotation.
  • Application of 12 kg Zn per hac, 8-16 ton FYM and 4 T FYM + 3 kg Zn per hac were found equally efficient for enhancing soybean-wheat productivity in vertisols. Application of 12 kg of Zn per hac left residual effect for 2-3 cropping cycles in medium to deep vertisols.

Methods of application:

Options on Zn application include

  • Soil application (broadcasting or band placement).
  • Foliar Application as sprays,
  • Dusting seeds with Zn powder or soaking them in Zn solutions.
  • Swabbing foliage or pressing wounds with Zn paste or solution.
  • Dipping roots of transplanted crops in solution or suspension of Zn salts and
  • Pushing galvanized nails or pieces of metallic Zn into tree trunks (Katyal and Randhwa 1983)
    • Of these, soil application and foliar spray are among the most extensively used. Soil application of Zn is preferred method over less efficient foliar sprays . Biweekly foliar sprays with 0.5 % ZnSO 4 +0.25 li m e suspension are recommended using 500 liters of water per hectare on crops exhibiting Zn deficiency symptoms, spraying continues until the disappearance of deficiency symptoms. Zn sprays are almost exclusively used to alleviate Zn deficiency in trees and Zn-sources are more effective if sprays are made before the spring flush of the growth.

    We can summarize the method and mode of application as below:

    • Basal application of Zn to soil through broadcast and mixed or its band placement below the seed proved superior to top dressing, side dressing or band placement, foliar sprays or soaking or coating of seeds/ seedlings in Zn solution/ slurry as well as transplanting Zn enriched nursery because of later application led delayed cure of Zn deficiency than basal use
    • Foliar feeding of crops with application of 0.5 to 2.0 % ZnSO 4.7H 2O solution is the supplement of soil application but it is not a substitute . In field crops it is proved inferior in case of Zn and boron, however, in horticultural and plantation crops foliar feeding of crops with repeated foliar sprays or boron generally excelled to soil application.
    • Seed coating of Zn materials like concentrated zinc, zinc phosphate was found good in correcting Zn deficiency in bold seed crops in marginally deficient soils. But in these areas ZnO proved superior but inferior to soil application of Zinc in highly Zn deficient soils. However seed treatment to potato with ZnSO 4.7H 2O solution proved equally effective as that of its foliar sprays or soil application.
    • Dipping of rice seedlings in 2-4 % ZnO slurry before transplanting proved less effective with other sources in combating Zn deficiency or could not catch with farmers because of certain limitations of as that of zinc. Dipping of vegetable seedlings in ZnO suspension and sugarcane sets could not meet full Zn requirement of these crops.

    Rate of Zinc Application:

    • Rates of soil application of Zn vary with soil type. Amount of zinc required for alleviating zinc deficiencies that vary from severity of deficiency, soil type, nature of crop and cultivars.
    • Alkali soils are generally deficiency in Zn and Ca. So higher yields of rice, wheat, berseem and other crops can not be achieved unless toxicity of Na /deficiency of Ca and Zn are corrected simultaneously. Use of 9-10 kg of Zn/ha to alkaline soils and 4.5 kg of Zn in reclaimed alkali soils for rice-rice, rice-wheat/mustard/barley was found optimum.
    • Zinc requirement of crops in alkali soils is reduced substantially by 20-25%depending upon the levels of amendments added (25-100% GR) or reducing the levels of sodicities.
    • Fertilizer Zn requirement of crops was found to be double in coarse textured sandy soils than in fine textured loam or clayey soil for wheat and rice.

    Quantities of Zn in some of crops are given as below crops:

    Name of crop Quantity of Zn kg Zn/ ha
    Wheat, Rice, Sorghum, Chickpea
    Soybean, Sugarcane
    G nut, Raya & Ragi, gram, linseed, green gram
    Range in all crops
    5 – 20
    Upland crops on coarse soils
    Upland crops on Heavy soils

    Source: (Takkar et. al. 1997)

    Time of application:

    • Time of zinc application mainly depends upon its contents in seed or severity of its deficiency. Best time of Zinc application is prior to sowing or transplanting of crops because maximum zinc absorption by plants takes place upon tillering or pre-flowering stages.
    • Split application of zinc suphate in rice is recommended as 50% at the time of sowing or transplantation and remaining 50% before or upto tillering stage.
    • Basal application of zinc in soil is found to be best. However, if missed zinc deficiency can be corrected by top dressing of zinc upto 45 days. Seed coating with ZnO, Teprosyn zinc, and Zn phosphate slurry successfully corrected deficiency in marginally deficient soils.
    • Foliar sprays of 0.5 % zinc sulphate two to three times at 7-10 days interval just after the appearance of its deficiency can control zinc deficiency more efficient and effectively.

    Thus it has established clearly the vital part played by micronutrients in sustaining the economic and agronomic efficiency of micronutrients. How the unattended deficiency provokes fertilizer related environmental pollution highlighted the need for balanced nutrition. Of the eight micronutrients, role of Zn seems to be most imposing because of its wide scale deficiency in Indian soils and crops. The regions supporting intensive cropping systems and Zn deficiency prone soils exhibit tendency to become impoverished after a few cycles of rotations. These systems and soils need urgent attention on amelioration of Zn deficiency. Compared to extent of Zn deficiency area, use of Zn fertilizers fall short of demand by several thousand tons.

    Which is the best source of Zn application:

    • Zinc chelated is least three times more effective than Zinc Sulphate in so far as uptake is concerned.
    • Zinc chelate is easily is translocated within the plants, because unlike Zinc sulphate it is partly systemic.
    • Because of its organic structure Chelated Zinc is readily absorbed by roots and easily assimilated within the plant system. In case of Zinc Sulphate, Zinc may accumulate in the soil when reacting with phosphate in the soil or in the plant. Chelated Zinc therefore does not get locked in the soil.
    • Chelated Zinc can be easily combined with N-P-K foliar spraying or any other micronutrient without forming any insoluble precipate.
    • Organic part of Chelated Zinc has a strong growth promoting effect.
    • Chelated Zinc does not scorch the leaves but helps in better utilization of other nutrients.
    • Chelated Zinc is compatible with agrochemical and urea.
    • Chelated zinc is environment friendly, safe to human beings and plants
    • However, high cost of it than zinc sulphate made chelated fertilizers most uneconomic and less effective for common use.
    • Zinc sulfate reduced phosphorus uptake and the phosphorus content of the shoots in plants, while Zn-EDTA increased it (Nammuang and Ingkapradit 1986).
    • Zinc oxide can correct a Zn deficiency but is slowly soluble and not effective in a granular form. To effectively correct a Zn deficiency, zinc oxide must be finely ground. Spreading any finely ground material is a problem because of the wind. So use of finely ground zinc oxide is limited to situations where suspension fertilizers are used.


    The decreased yields in major crops like Paddy, Maize, Cotton, Oranges can be mainly attributed to the zinc deficiency in the soils. Due to Zinc deficiency the plant cannot take nitrogen available in the soil. There by the applied ” N ” is getting wasted and the plants become stunted in growth. Also Zinc is an essential element in enzymes which are useful in various metabolic activities. Hence in order to improve the yields we have to use good quality ZINC in addition to Nitrogen, Phosphorus and Potash.

    Attributes of MAHAZINC:

    • It consists ZnSO 4 H 2O (Zinc Sulphate MonoHydrate).
    • It is having highest zinc content. The Content of Zinc is 33 %.
    • It is having highest purity i.e., 95 %.


    For Paddy:

    To control the zinc deficiencies in paddy crop use 300 gm of Mahazinc for one acre. Use 2gm of Mahazinc per litre of water and spray 15 days after transplantation in Paddy crop.

    For Cotton, Mango & Oranges:

    To control the Zinc deficiency in cotton & Oranges use 1.5 gm of Mahazinc per litre of water and spray when the first deficiency symptoms occurs. The 2 nd spray should be done 10 days after first spraying.

    Mahazinc will supply zinc to the crops in two ways

    • The leaves as well as roots will absorb the zinc.
    • Mahazinc will supply more quantities of zinc to the crop. There will be very less wastage due to various activities. Hence value for your money.
    • Mahazinc will control the zinc deficiency completely and within very less time.
    • Mahazinc – Zinc Sulphate MonoHydrate, contains highest zinc –33 %.

    Note: It is advisable to spray Mahazinc alone for better results.


    Zinc Sulphate Tetra hydrate (21%) should be applied as basal @ 50 kg /ha to all the crops .

    Zinc Sulphate MonoHydrate (33%) should be preferably sprayed on the crops @ 300 grams per acre. The crop should be thoroughly drenched by using 200 litres of Water per acre.


    • Proceedings of IFA International Symposium on Micronutrients 23-25 February 2004
    • Fundacao MT PMA Report 1997-98
    • The Fertiliser (control) order 1985. The Fertiliser association of India.
    • Ram Rattan and PD Sharma, (2005). Paper presented International Symposium on Micronutrients 23-25 February 2005.