Tissue Culture Banana: 16. Micronutrients and their application schedule

Micronutrients:

Essential Elements:

Sixteen elements are considered as essential to plant growth. Carbon (C), Hydrogen (H) and Oxygen (O) are the most abundant elements in plants and are not considered as mineral nutrients.

The other 13 elements are Nitrogen (N), Phosphorus (P), Potassium (K), Sulphur (S), Calcium (Ca) and Magnesium (Mg), Iron (Fe), Zinc (Zn), Manganese (Mn), Copper (Cu), Boron (B), Chlorine (Cl) and Molybdenum (Mo).

These 13 elements are classified as macronutrients and micronutrients and the classification is based on their relative abundance in plants.

Primary nutrients:

Nitrogen (N), Phosphorus (P) and Potassium (K).

Secondary Nutrients:

Sulphur (S), Calcium (Ca) and Magnesium (Mg).

Macronutrients:

Both Primary and secondary nutrients are collectively called as ‘Macronutrients’. They are Nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca) and magnesium (Mg).

Micronutrients:

Iron (Fe), Zinc (Zn), Manganese (Mn), Copper (Cu), Boron (B), Chlorine (Cl) and Molybdenum (Mo). Compared to the macronutrients, the concentrations of the above seven micronutrients in the plants are very small.

Five additional elements – sodium (Na), cobalt (Co), vanadium (Va), nickel (Ni) and silicon (Si) have been established as essential micronutrients in some plants.

Micronutrients are often referred to as minor elements and their deficiency or toxicity can reduce plant yield similar to macronutrient deficiency or toxicity.

In fact, plants absorb many nonessential elements, and over 60 elements have been identified in plant materials. When plant material is burned, the remaining plant ash contains all the essential and nonessential mineral elements except, C, H, O, N and S which are burnt off as gases.

Essential Elements (All the 16 essential elements are listed here except Carbon (C), hydrogen (H) and oxygen (O) which are not considered as mineral nutrients).
Macronutrients				Micronutrients
Primary Nutrients		Secondary Nutrients		Micronutrients
1	Nitrogen (N)	1	Sulphur (S)	1	Iron (Fe)
2	Phosphorus (P)	2	Calcium (Ca)	2	Manganese (Mn)
3	Potassium (K)	3	Magnesium (Mg)	3	Zinc (Zn)
				4	Copper (Cu)
				5	Boron (B)
				6	Chlorine (Cl)
				7	Molybdenum (Mo)

Causes of Micronutrient deficiency:

Micronutrient deficiency generally occurs in sandy soils, which lacks micronutrient elements.

High pH clay soils rich in micronutrients have less micronutrient supplying power. In such types of soils, micronutrient deficiency is very common.

Micronutrient deficiency occurs in soils where mono crop culture is practiced without crop rotation. In fields where banana is the routine crop with many ratoons, deficiency of all nutrients is definitely expected.

Micronutrients requirement in banana:

One of the major impediments to achieve higher yield in Banana is due to the application of only N:P:K fertilizers by the farmers. To attain high yield in Banana, it is essential to apply both Secondary nutrients and Micronutrients also along with N:P:K fertilizers.

Farmers are blindly following ‘Blanket recommendations’ of Agriculture Universities, Fertilizer / Biotech / Drip Irrigation companies without considering the native fertility of their farm soil. Farmers have to understand that the Secondary Nutrients and Micronutrient recommendations for Banana cultivation provided by the above Institutions as mere guidelines and the correct method is to arrive at a Micronutrient application schedule based on their field’s detailed soil test reports.

Nutrient removal by banana in 1 hectare of land

One of the General Micronutrient recommendations for 1000 numbers of Tissue Culture banana Grande Naine raised in soils where nutrient status is moderate to deficit is given here below:

Soil application:

Soil application of 15 kgs of micronutrients for 1000 plants (15 gms / plant) at 4th month after planting (MAP) is a general blanket recommendation for banana and this quantity may vary depending upon the soil quality.

Banana plants commonly exhibit micro nutrient deficiency symptoms for zinc and boran. To correct these deficiencies soil application of additional dose of 25 g zinc sulphate/plant and 5 g of borax is recommended.

Foliar application:

Application of micronutrients fortnightly is mandatory after 1 month of planting as a foliar application up to 3-4 months to avoid their deficiency.

Dosage: The recommended dosage for foliar application (total drenching) of Foliar Grade Micronutrient mixture is 2.5 gm/lit minimum (for young tender plants up to 3 months age) to a maximum of 5 gm / lit (for the plants above 4 months of age) depending upon the soil quality. Spray micronutrients viz., Zinc sulphate (ZnSO4) (0.5% i.e.,5gm in 1 litre ), Ferrous sulphate (FeSO4) (0.2% i.e.,2 gm in 1 litre), Copper sulphate (CuSO4) (0.2% i.e.,2 gm in 1 litre) and Borax (H3BO3) (0.1% i.e.,1 gm in 1 litre) at 3, 5 and 7 MAP (Months After Planting) to increase yield and quality of banana.

Application of macro elements such as Calcium (Ca), Magnesium (Mg) and Sulphur (S) separately around 120th and 150th day of planting is useful. Normally, banana requires additional dosage of Magnesium and Calcium. So, apply 3-4 split doses of Magnesium sulphate (Epsom salt) 125 grams/plant and Calcium Nitrate 75 grams/plant.

Most of the Sulphur requirement of the plant is met from the sulphates applied in the form of Ammonium sulphate (S-23%), Gypsum (Calcium sulphate – ‘S’ - 18%), Sulphate of Potash (S- 18%) Etc. In case of non-application / limited application of the above sulphates, ‘S’ nutrient can be supplemented by applying 20 gm /plant of Bentonite Sulphur (‘Gromor’ from Coromandel), which contains about 90% of Sulphur in elemental form and only 10% as Bentonite clay.

Though soil application of micronutrients is the best way to treat severe deficiency symptoms, it is advisable to adopt foliar application because of the following benefits:

Particulars	Soil application of Micronutrients	Foliar application of Micronutrients
Recommended grades	Use only ‘Basal grade’	Use ‘Foliar grade’
Specific usage	Recommended for soil with pH less than 8.5	Recommended for plants cultivated on soil with pH more than 8.5 to avoid fixation of micronutrients in the soil.
Choice of application	Best option. With the exception of certain micronutrients, it is difficult for most plants to absorb sufficient nutrients through their leaves to meet their yield potential.	-
Nutrient entry to plant cell	Nutrients pass first through the root system and then travel through the xylem before reaching plant cells.	Nutrients pass through cracks and/or stomata openings in the cuticle of the leaf and directly enter plant cells.
Compatibility with other fertilizers	Never mix with phosphatic fertilizers. Can be mixed with Calcium Nitrate (CN), Magnesium Sulphate (MgSo4) and Sulphur (S).	Never mix with phosphatic fertilizers. Can be mixed with CN, MgSo4 and S.
Mode of application	Conventional Method: Apply 30 cm away from the plant in a circular fashion and flood irrigate the field. Fertigation: Through drip fertigation since all the elements of micronutrients are soluble in water.	Use chelated foliar grade Micronutrients only. Add wetting agents / adjuvants in the spray solution for best results.
Mode of action	For steady and slow correction of deficiency where the soil is already known to be under nutrient deficit.	For faster correction of deficiency once the symptoms are clearly observed in the plant.
Risk factor	No risks	Chances of foliage burn.
Specific benefit	-	Enhanced size and quality when used on banana bunches.
Fertilizer consumption	More	Less
Nutrient use efficiency	5 to 10%	30 to 40%
Recovery period	Delayed recovery (15 to 30 days)	Fast recovery (48 hours to 5 days)
Cost (Fertilizer cost + Labour cost)	High	Cheap. Benefit cost ratio 9 : 1.
For severe deficiency symptoms	Combination of both Soil and Foliar applications is the best way to treat severe deficiency symptoms.	Only optimum result. More number of sprays is needed.

Secondary nutrients in drip fertigation:

In Secondary Nutrients, Calcium as Calcium Nitrate, Magnesium as Magnesium sulphate (Epsom salt) and Sulphur as Bentonite Sulphur (‘Gromor’ from Coromandel) can be effectively used for fertigation.

Micronutrient suppliers:

‘Banana Shakti’ from National Research Centre for Banana (NRCB), Trichy, ‘Banana special’ from Indian Institute of Horticulture Research (IIHR), Bangalore, SPIC, Nagarjuna, Aries, Prathista, Ranadey (Rohanna, IMT), Coramandal, Kothari Etc.,

Micronutrients in drip fertigation:

Fe, Mn, Zn, Cu, Mo could be used as micro nutrients in its sulphate form for drip fertigation. For the nutrient Boron, Sodium Tetraborate can be used.

Caution:

1. Micronutrients should never be mixed with phosphatic fertilizers at any time. For soil applications there should be a minimum gap of 1 week between the applications of phosphates and Micronutrients.

2. All micronutrients in ‘chelate form (EDTA)’ are very soluble and in readily available form to the plants. They prevent the formation of insoluble chemical compounds resulting in faster correction of nutrient deficiencies in plants. Since micronutrients in ‘chelate form (EDTA)’ are very expensive, it is recommended to use them for ‘Foliar applications’ alone.

Macro & Micronutrient application schedule for banana :

Macro and Micronutrients application schedule (Both Soil and fertigation) for 1000 (One thousand) plants of Tissue Culture banana Grande Naine raised in soils where nutrient status is moderate/deficit:

Age of plant	Name of Nutrient	Mode of application	Dosage / Plant	Total Nutrient for 1000 plants
Before planting	For alkaline soil Gypsum (or) any Calcium + Magnesium rich soil conditioner to lower pH. For acidic soil: Fine Dolomite powder to increase pH.	Incorporate Soil conditioners in the planting pit along with FYM, VAM, Vermi-compost, DAP, Etc,	Gypsum – 1 kg (or) 100 gm of Ca & Mg rich pH decreasing soil conditioner per pit. Dolomite - 1 kg (or) 100 gm of pH increasing soil conditioner per pit.	Gypsum – 1 Ton (or) 100 Kg of Ca & Mg rich soil conditioner. Dolomite - 1 Ton (or) 100 Kg of soil conditioner.
30^th day	Foliar grade Micronutrient mixture specially blended for banana	Foliar spray	2.5 gm/ litre + Wetting agent. Total 125 gm in 50 litres for a spray.	375 gm for 3 sprays.
45^th day
60^th day
75^th day		Foliar spray	2.5 gm/ litre + Wetting agent. Total 200 gm in 75 litres for a spray.	400 gm for 2 sprays.
90^th day		Foliar spray		400 gm for 2 sprays.
100^th day	Basal grade Micronutrient mixture specially blended for banana (Should not be mixed with phosphatic fertilizers)	Soil application	15 gm per plant (1 feet away from the plant in a circular fashion)	15 Kg
From 120^th day to 150^th day	Magnesium sulphate (MgSo4) and Calcium Nitrate (CaNo3)	Fertigation	Apply in 5 split doses of: Magnesium sulphate 10 gm/plant and Calcium Nitrate 6 gm/plant	MgSo4 - 50 Kg. and CaNo3 – 30 kg
From 151^st day to 164^th day	Zinc sulphate (ZnSo4), Sodium Tetraborate and Bentonite Sulphur (S)	Fertigation	Apply in 2 split doses of: Zinc sulphate 10 gm /plant, Borate 5 gm / plant and Bentonite Sulphur (S) 10 gm/plant	ZnSo4 - 20 Kg Borate – 10 kg and Bentonite Sulphur – 20 kg
165^th day	Foliar grade Micronutrient mixture specially blended for banana	Foliar spray	5 gm/ litre + Wetting agent. Total 500 gm in 100 litres for a spray.	Foliar grade Micro-nutrient mixture 500 gm.
From 165^th day to 210^th day	Magnesium sulphate (MgSo4) and Calcium Nitrate (CaNo3)	Fertigation	Apply in 5 split doses of: Magnesium sulphate 15gm/plant and Calcium Nitrate 6 gm/plant	MgSo4 - 75Kg. and CaNo3 – 30 kg
From 211^st day to 225^th day	Calcium Nitrate (CaNo3)	Fertigation	Apply in 2 split doses : Calcium Nitrate 7.5 gm/plant	CaNo3 – 15 kg
1 month after bunch emerge- -nce	Foliar grade Micronutrient mixture specially blended for banana	Foliar spray on entire tree and the developing bunch	5 gm/ litre + Wetting agent . Total 500 gm in 100 litres for a spray.	Foliar grade Micro-nutrient mixture 500 gm.