फसल उत्पादन में महत्वपूर्ण भूमिका और नगण्‍य अावश्यकता वाले शुक्ष्‍म तत्‍व (ट्रेस एलीमेंट्स) 

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:-

 (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:-

Normal, deficient and toxic levels of supply of trace elements

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

Trace elements deficiency syndrome in various crops:-

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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