For proper growth and development of plants, require essential nutrients which are categorized in two groups on the basis of amount of requirement in plant body as macronutrients(more required) and micronutrients/trace elements(less required).Deficiency of trace elements in soil inhibits plants to complete its life cycle properly which ultimately affect on crop production. Therefore, farmers should give more emphasis on this aspect and extension agency should provide more information on trace elements to farmers for their awareness and better knowledge.

Plants require food for growth and development. At the beginning of the new phase of the life process from a seed or other propagule, plants are nourished by the food reserved in such structures or organs. This period is very short and in latter stages when the plants are growing then generally 16 nutrients are very essential for proper establishment and completion of life cycle. These are: carbon, hydrogen, oxygen, nitrogen phosphorus, potassium, calcium, magnesium, sulphur, boron, copper, chlorine, iron, manganese, molybdenum and zinc. In addition, more elements viz., sodium, cobalt, vanadium, silicon etc. are absorbed by some plants for special purposes. All these elements are not required for all plants, but all have been found essential for one plant or the other. Trace element deficiencies in Indian soil and crops have been on the increase since the adoption of modern agricultural technology with increased use of NPK fertilizers generally free from trace elements. Among the trace elements, zinc deficiency is widely encountered followed by boron, iron, copper and manganese. The term micronutrient or trace element is quite often used interchangeably, though most of the scientists prefer to use the term micronutrients to denote the elements which are essential for the plant but are required in small amounts.

Criteria of essentiality:

Arnon (1954) has laid down the criteria for the essentiality of elements in plant nutrients. These are: - a) the plant must be unable to grow normally or complete its life cycle in the absence of the element; b) the element is specific and can not be replaced by another; and c) the element plays a direct role in metabolism.

Macro and microelements:

Depending upon the quantitative requirement, the essential elements are grouped into macronutrient and micronutrient elements. Elements which are required by plants in considerable concentrations are called macronutrients and the elements which are required by plants in minute quantities are termed micronutrient or trace elements, eg. B, Cu, Cl, Fe, Mn, Mo and Zn mainly.

Forms of trace elements used by plants:-

Trace Element

Ionic Form

Non-ionic Form

B

Bo33-, B4o72-, H2Bo3-, HBo32-

-

Cu

Cu+, Cu2+

CuSo4 with EDTA

Cl

Cl-

-

Fe

Fe 2+ , Fe3+

FeSo4 with EDTA

Mn

Mn2+ , Mn 4+

MnSo4 with EDTA

Mo

MoO42-

-

Zn

Zn2+

ZnSo4 with EDTA

 (Plants can absorb organic and molecular N in addition to the above forms; EDTA means ethylene diamine tetra acetate)

Mobility of trace elements in plants:

Knowledge of the mobility of nutrients in the plant helps in finding what nutrient is deficient. Zn is moderately mobile. Fe, Mn, Cu, Mo and Cl are less mobile. B is immobile.

Causes of deficiency of trace elements in soil:

  1. Cultivation of crops for a long period in a particular land without application of trace elements.
  2. High yielding varieties demand more trace elements compare to desi varieties.
  3. Cropping intensity
  4. Rain as well as natural causes of soil erosion.
  5. Application of organic fertilizers is less in field now-a-days.
  6. Tendency to apply compound fertilizers which content less amount of trace elements.

Factors influence on absorption of nutrients: 

Though essential nutrients are present in the soil, the absorption of nutrient depends on several external and internal factors:-

External factors:- Oxidation reduction state of elements, Concentration of the elements, Moisture content of the soil, Aeration, Temperature and soil Ph.

Internal Factors:- Cell wall, Aeration, Type of cells and stage of development, Transpiration 

The nutrient content of trace element fertilizer is as follows:-

Fertilizers

Nutrient  content

Ferrous sulphate

Manganese sulphate

Zinc sulphate

Copper sulphate

Sodium borate (Borax)

Sodium molybdate

20% Fe +18.8% S

23% Mn +12.4% S

23-35% Zn +17.8% S

25-35% Cu + 12.8% S

10.6% B

37-39% Mo

Normal, deficient and toxic levels of supply of trace elements

Nutrient element

Threshold of deficiency (ppm)

Optimum growth (ppm)

Threshold of toxicity (ppm)

Boron

0.0001 to 0.02

0.1 to 0.5

 

1 to 10

Copper

0.0001 to 0.005

0.05 to 1.0

2 to 50

Iron

0.05 to 2

5 to 10

30

Manganese

0.005 to 0.02

0.55 to 5.5

10 to 55

Molybdenum

0.00001 to 0.0001

0.2 to 1.0

20 to 100

Zinc

0.0001 to 0.005

0.05 to 1.0

2 to 50

Trace elements (TE), their role in plant body, deficiency syndrome and preventive measures

TE

Main Role in Plant

Deficiency Syndrome

Preventive Measures

B

Development of tissues, carbohydrate metabolism, translocation of photosynthates

Death of stem and root tips, abscission of flowers, symptom of sugar deficiency, sterility and malformation of reproductive organs, growth abnormalities

Spraying of 0.01% Borax solution  for two times in 10 days interval, application of Borax or Sohaga @ 4kg/acre

Cu

Electron transport during photosynthesis, carbon assimilation

Chlorosis, bleaching and withering of the apices of the younger leaves, leaves fail to unroll,  chlorotic mottling

Spraying of 0.3% Bordeaux mixture  for 2-3 times, application of CuSo4 @ 2 kg /acre

Cl

Oxygen evolution in primary photosynthetic reactions and cyclic photophosphorylation

 

Wilted appearance of the foliage, stuffy roots, profusely branched laterals, leaves show chlorotic mottling, bronzing and tissue necrosis

 

 

 

Apply KCl in the field

Fe

Chlorophill synthesis, pigmentation, N fixation

Chlorosis in the younger leaves, parallel veined leaves show chlorotic stripping, under severe deficiency leaves become dry and papery

Spraying of 0.1% FeSo4 solution for two times, application of FeSo4 @ 20kg/acre

Mn

Role in respiration, N metabolism, photosynthesis, synthesis of chlorophyll

Appearance of chlorotic and necrotic spots in interveinal areas of the cereal leaves, fine chlorotic mottling in the leaves of dicot plants

Spraying of 0.02%MnCl2 solution for two times, application of MnSo4@ 12kg/acre

Mo

Part of the enzyme nitrate reductage, nitrate assimilation , protein synthesis

Chlorotic mottling,  severe stress mottled areas become necrotic,  scorching and withering, younger leaves fail to expand fully, flower formation  inhibited

Spraying of Sodium molybdate solution @ 0.5 gm per litre of water, appln. of 2kg Ammonium molybdate per ha.

Zn

Biosynthesis of Indole Acetic Acid resulting in flowering and fruiting, photosynthesis, N metabolism

Interveinal chlorosis, shortening of internodes, reduction in the size of young leaves, discolouration of foliage, cause a number of disorder

Spraying of ZnSo4 solution 0.1-0.2 %, apply 5-50 kg of ZnSo4/ha, application of soluble Zn salts or Zinc chelates

Trace elements deficiency syndrome in various crops:-

Trace Element

Crop

Deficiency Syndrome

B

Sugarbeet

Heart rot

 

Marigold

Heart rot

 

Cauliflower

Browning or hollow stem

 

Tobacco

Top sickness

 

Walnuts

Snakehead

 

Table beet

Brown heart disease, Canker

 

Brinjal

Fruit cracking

 

Pome granate

Internal and external cork development

 

Alfa alfa

Cracked stem, Rosetting

 

Citrus

Hard fruit

Cu

Cereals

Reclamation disease

 

Legumes

Reclamation disease

 

Citrus

Die back disease

Fe

Sugarcane

Leaf bleaching

Mn

Oats

Grey speck

 

Sugarbeet

Speckled yellows

 

Peas

Marsh spots

 

Sugarcane

Phala blight, Boda disease, Fizi disease

 

Rice

Phala disease

Mo

Cauliflower, Brassica sp.

Whiptail

 

Radish

Downward Cupping

 

Beans

Scald

 

Lucerne

Downward leaf curling

 

Grapevine

Bunch development disorder

Zn

Rice

Khaira disease

 

Maize

White bud

 

Citrus

Little leaf, mottled leaf

 

Apple

Little leaf/ rosette

 

Pineapple

Little leaf/ rosette

 

Peach

Little leaf/ rosette

Conclusion:- 

Plants’ proper growth and development as well as better yield depend on availability of its all essential nutrients. Trace elements’ requirement is less in plant body but play an important role in plants’ life cycle which ultimately reflects on production of crop. Previously farmers were not so aware about trace elements, but now-a days they know very well (especially who are cultivating crops commercially) the importance of trace elements on plant body and yield. It is the general observation of persons engaged in agricultural production that application of manures and fertilizers and proper plant protection measures could in some cases not result in targeted yields. The probable reasons have been ascribed trace element deficiency. The main reasons of traceelement deficiency (1) cultivation of crops for a long period in a particular land without application of trace elements (2) cultivation of high yielding varieties which demand more trace elements (3) cropping intensity and (4) application of organic fertilizer is less in field now-a days. Therefore, the farmers should give more emphasis on the following aspects to remove trace element deficiency (1) try to know the nutrient status of soil by soil testing and application of fertilizers accordingly (2) foliar spraying (3) soil application of trace elements every 4-5 years interval (4) follow the integrated nutrient management practices and aboveall (5) application of organic fertilizers in field.

 


Authors:

Hiralal Jana

Assistant Professor,

Department of Extension Education, N.M. College of Agriculture,

Navsari Agricultural University, Navsari-396450, Gujarat

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