ESSENTIAL PLANT NUTRITION & FERTILIZERS REQUIRED FOR TEA CULTIVATION চাহ খেতিৰ প্ৰয়োজনীয় শস্য-পুষ্টিকাৰক আৰু ৰাসায়নিক সাৰ

~ Ms. Gayatri D. Bhuyan

Like any other plants, tea plant also requires adequate amount of minerals nutrients for proper growth development and sustained production. However, many people confuse plant nutrients with plant fertilization. Plant nutrition refers to the chemical elements taken in by the plants that are essential to their growth and development. Fertilization is the term used when these elements are supplied to the environment (soil, leaf) around the plants.
Plants need 16 elements for normal growth. Carbon, Hydrogen and Oxygen are found in air and water. The remaining 13 elements are derived from soil. Nitrogen, phosphorous and potassium are required and taken up by plant in large quantities and are called primary or major nutrients. Calcium, magnesium and sulphur are termed secondary nutrients. The remaining 7 elements zinc, copper, iron/manganese, boron, molybdenum and chlorine are required in relatively less amount and are called micro-nutrients.
Deficiency of any one of the essential nutrients can be limiting factor for growth, development and yield of tea.
DEFICIENCY SYMPTOMS OF NUTRIENT ELEMENTS
Nitrogen – Nitrogen deficiency symptoms include reduced growth, yellowing of leaves (chlorosis) and reduced lateral breaks deformation begins with the lower leaves and extends to upper leaves, fewer shoots and small leaves.
Potassium – Potassium deficiency results in reduced growth, short inter-nodes, burned or scorched leaf margin,necrotic (dead) spots in leaf,reduced lateral breaks and a tendency to wilt readily,leaves turn yellow at the tip poor recovery from prune and drought.
Phosphorous – Phosphorous deficiency in plants generally is expressed in reduced growth,intense colouring, browning or purpling of foliage in some plants, thin shoots, reduced lateral breaks,loss of lower leaves and reduces flowering.
Calcium – When pH falls below 4.0. Downward curling of mature leaves, followed by marginal scorch from leaf tip, apical activities is much reduced and later leaves drop.
Magnesium – when soil pH is below 4.0. Distinctive interveinal chlorosis in mature leaves, inverted “v” symptoms may appear.
Sulphur – younger leaves appear pale- green to yellow, veins remain green and very distinctive chlorotic symptoms.
Zinc – Due to unequal development of lamina on either side to mid- rib leaves appear smaller, darker and sickle shaped with shorter inter-nodes.
Boron – Auxiliary buds abort and cluster of small shoots (rosetting) appear in the axiils, shoot apices die, leaves turn dark green and thick, cork formation on upper side of leaf stalk.
Manganese – Intervienal chlorosis of old and young leaves , irregular mottling, veins and surrounding areas remain green, necrotic spots develop within the chlorotic patches mainly close to leaf margin.
MANURING IN YOUNG TEA
For sustaining a high level of productivity adequate fertilizer application is required from the initial years. The root system in young tea plants is under a continuous process of development. Hence, manuring is required to be done at regular interval in small amounts. To prepare 100 kgs of YTD- 21.73 kg of Urea, 31.25 kg of SSP, 16.66 kg of MOP along with 30.36 kgs of filler(Dry sand) should be used. This mixture can subsequently be used as manure in young tea.
In case the amount of potassium in the cultivable land is less than 100 ppm then 25 kg of potassium and 22.02 kgs of filler (dry sand) should be used to prepare the YTD. YTD should be applied during the formative stage in rings around the collar region.After every 6-7 weeks till 3 years . In the 4th and 5th year, the YTD mixture may be applied in two equal splits in strips as show in Table no 1.

MANURING IN MATURE TEA.
Since the product obtained from tea bushes is green leaf and plucking is done multiple times in a year. It is important to ensure adequate replenishment of nutrients in the soil removed by crop. Manuring in mature tea above 5 years should be done as per Table no2.

TIME OF MANURING
In general, the best time for fertilizer application is after the first rain in spring that has moisture the soil to a depth of 45 cm and there is some new growth in unpruned tea. In pruned and skiffed tea the fertilizer should be applied after the bushed have produced two new leaves. Weeds should be removed and the garden should be weed free before application of manure.
Nitrogen is available to the plant only after a fortnight from fertilizer application, it reaches its peak in 5-16 weeks and absorption by plants continue for 4-5 months.
However, due to high rainfall received in North east India, it is usually recommended to apply urea and MOP in two splits, 60% of the dose of urea and MOP should be applicable in March- April (1st split) and remaining 40% should be applied in August- September ( 2 nd split). The entire quantity of SSP should be applied in the beginning of the season along with first split of urea and potash.
REQUIREMENT OF SECONDARY NUTRIENTS
Calcium and Magnesium : The requirement of Calcium and Magnesium to the tea plant can be fulfilled to a great extent by maintaining the soil ph at 4.5-5.5. However, foliar sprays of magnesium sulphate at 1 to 2 % can be sprayed between autumn and spring (October- March) which helps to prevent manifestation of deficiency symptom.
Sulphur : Different trials and experiments have showed that soil application of sulphur at 2.67-5.33kg/ bigha improves yield and quality of tea when the soil available sulphur is below the critical limit of 40 ppm. However, sulphur should not be applied in waterlogged soil as it will be reduced to hydrogen sulfide, which is toxic.
Micronutrients : Zinc has shown great response in unpruned and skiffed tea in North east India. Foliar application of Zinc sulphate at 1-2% concentration has been found beneficial and produced upto an average 10% increase in yield.

Foliar nutrient :

Foliar nutrition is beneficial under stress condition like water logging and droughty condition. Foliar spray of potash at 1% MOP during moisture stress period can enhance the water use efficiency of the bushes.MOP 1% and Magnesium sulphate 1% is suggested to be sprayed from January to March to ameliorate the ill effects of drought in unprune teas.

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Writer- Ms. Gayatri D. Bhuyan, Subject Matter Specialist (Tea Husbandry and Technology) from Krishi Vigyan Kendra, Tinsukia-786125

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