Introduction

Sunflower is considered an inefficient converter of plant nutrients as measured by its low harvest index, i.e. weight of seed produced is low in proportion to total plant weight, often less than one-third. Thus the price received for sunflower seed or oil must be substantially higher than for other more efficient crops which could be grown, and the accurate determination of optimum fertilizer application rates is important. Adequate nutrients are essential for high seed yield; for instance , in the USSR 100 kg seed contained 6 kg nitrogen, 2 kg phosphorus, and 18 kg potassium and the three-quarters of the total phosphate uptake by the plant was contained in the seeds. A major factor affecting the level of fertilizer application to sunflower was the relatively low profitability of the crop, but with higher-yielding cultivars, expanding oilseed demand and price increases, fertilizer use has become more general. On acid soils, liming will increase sunflower seed yield, but in general this has not be profitable. Adequate nutrients are essential for high seed yield; for instance , in the USSR 100 kg seed contained 6 kg nitrogen, 2 kg phosphorus, and 18 kg potassium and the three-quarters of the total phosphate uptake by the plant was contained in the seeds.

• A major factor affecting the level of fertilizer application to sunflower was the relatively low profitability of the crop, but with higher-yielding cultivars, expanding oilseed demand and price increases, fertilizer use has become more general.
• On acid soils, liming will increase sunflower seed yield, but in general this has not be profitable.
• Coarse-textured soils are better suited for sunflower as the crop requires good drainage and responds to fertilisers in soils of pH 6.5-8.5. With balanced fertilisation, seed yields of upto 3000 kg/ha can be obtained.
• Higher rates of P and K are recommended for hybrid seed production than for a regular crop .

Fertilizer requirement

Condition of cultivation	Amount of nutrients (Kg/ha)
	N	P	K
Inter crop	80	60	40
Rainfed crop	30	20	20

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Area Specific Recommendations Of Fertilizers (kg/ha)

State and region	Nitrogen	Phosphorus	Potassium
Andhra Pradesh and Telangana
Rainfed
a)Scanty rainfall areas	50-60	30	0
b)Assured rainfall areas	60	60	30
Irrigated
a)Hybrids	60	90	30
b)Populations	30	60	30
Karnataka
Rainfed
Region-II	50	25	25
All other regions	40	50	40
Irrigated (All regions)	60	75	60
Maharashtra
Medium to long duration varieties and hybrids	40	60	0
Early maturing varieties	40	40	0
Tamil Nadu(Rainfed and irrigated)	40	20	20
Uttar Pradesh,Punjab, Haryana, Bihar and other non-conventional areas.	80	60	40

Note

• Half of Nitrogen, entire phosphorus and potash will be applied at sowing. Remaining half of N at 20 days age of crop (Rainfed conditions)
• Half of nitrogen, entire phosphorus and potassium will be applied at sowing remaining half of N in two splits at 35 and 55 days age of crop (irrigated conditions)
• Top dressings should be given by placement method for effective use of nutrients.

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Nitrogen

• Sunflower responds to 30-80 kg N/ha depending upon soil moisture status.
• Hybrid sunflower, though a high yielder, does not have a high demand for N.
• On sandy loam and slightly alkaline soils, significant yield increases have been obtained upto 80 kg N/ha ,but in fine textured soils, the optimum rates are much lower.
• Sunflower respond upto 80-90 kg/ha but only 40-60 kg N/ha was profitable .
• Very high rates of N can depress the oil content and impair seed quality.
• For rainfed crop the nitrogen schedules are adjusted as per soil moisture status.
• Excess nitrogen application reduces the yield and oil content of seed

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Phosphorus

• Sunflower responds markedly to P, even somewhat more than to N.
• Under rainfed conditions, optimum rates vary from 0 to 50 kgP2O5/ha ,and responses may even be absent .
• Spring-planted crop with irrigation can respond upto 70 kg P2O5/ha.
• Optimum yields can be had through balanced fertiliser use in which the basal dose should be drilled 10-15 cm deep at sowing.
• Full dose of N and P applied pre-plant as side placement or broadcast was superior but drilling N+P below the seed adversely affected crop emergence and produced the lowest yield .
• In light textured soils phosphatic fertilizer application preferably in the form of single super phosphate.
• Sulphur in single super phosphate will improve the quality of oil.

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Potassium

• A significant increase in seed yield due to application of 20 kg K2O/ha in combination with 20 kg N and 30 kg P2O5/ha has been reported.
• For the irrigated crop, the requirement is 80 kg N,80-100 kg K2O/ha.
• There is a positive relationship between the NPK accumulated at complete head formation and seed yield as well as oil production.
• Oil yield and nutrient uptake are increased with balanced NPK application.
• Seed yield of hybrid (MSFH-8) increased from 2100kg/ha in control to 3200 kg/ha with the application of NPKS.
• Potash can be applied only when the soil test reports showed K-deficiency need based micro nutrient application is taken up.
  

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Sulphur

Sulphur deficiency

Sulphur increases seed yield and also the oilontent. Yield increase is brought about largely by the production of larger heads and heavier seeds. Plants showing paling/yellowing of leaves. Yellowing spreads from the base to the apex. Growth of plants is reduced. The size of capitulum is severely restricted. Inflorescence may remain covered within the bracts. Maturity of flowers is delayed.

Control

• Sulphur added to S-deficient soils increases seed yield at 13 kg/ha.
• Application of 25 kg S/ha increases seed yield by 38%.
• An average increase of 3.8% in the oil content of seeds due to S application .
• In alkaline , clay soil having 12ppm available S, application of 10 kg S/ha more than doubled seed yield and increased oil yield.
• N+S application produces largest heads, heaviest grains and more seeds/head.
• 80 kgN+25 kg S will give more oil yield .

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Micro nutrients

• Among micro nutrients, iron, boron, manganese, copper and molybdenum are the important nutrients which show impact on the plant physiological aspects.
• Sunflower is also considered to be sensitive to boron deficiency.

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Copper

Nature and symptoms of deficiency

Copper deficiency

Copper deficiency symptoms appear as interveinal chlorosis of the upper half of the old leaves starting from the tip of the leaf. Chlorosis is generally restricted to the apical half of the lamina. Chlorotic areas later develop dark brown necrotic scorching, which spreads along the margins towards the base of the leaf. Due to the formation of necrotic lesions in the chlorotic areas, the affected portion of the laminae becomes shrivelled and withered. As deficiency persists, marginal scorching of the leaves becomes more pronounced and brown necrotic spots develop near the midrib.

• Size of the leaves is greatly reduced.

Control

• Two to three sprays of 0.2% copper sulphate solution at weekly intervals is recommended.

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Molybdenum

Molybdenum deficiency

Molybdenum deficiency in sunflower is characterised by pale green foliage, interveinal and marginal chlorosis of old leaves and inward curling of leaf margins of the young leaves giving them a "cupped" appearance.

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Manganese

Nature and Symptoms of deficiency

Manganese deficiency

Deficiency symptoms appear in the form of interveinal chlorotic mottling of apical part of the second set of leaves. When manganese supply is severely limited, the entire laminae become severely mottled and the interveinal chlorotic areas develop light brown irregular necrotic patches. These patches, which are initially more conspicuous near the leaf apices, later spread to the entire laminae which eventually turn severely necrotic. Symptoms gradually spread from the middle to the young and old leaves.

Control

• Manganese sulphate should be applied to the soil at 50 kg per hectare.
• Foliar spray of 0.2 - 0.3% manganese sulphate solution 2-3 times at weekly intervals is also recommended.

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Boron

Nature and symptoms of deficiency

Boron deficiency

When boron supply is severely limiting, at about 3 weeks growth, young and middle leaves of plants develop small chlorotic patches. Cotyledons of these plants become massive and the shoot apex becomes globose and deformed. Later, chlorotic patches become more pronounced and develop orange coloured necrotic areas in young leaves. Shoot apex of plants may turn necrotic and cease to grow.

• Young leaves show severe curling and distortion.
• This leads to appearance of side branches bearing small leaves.
• Eventually all the young leaves turn necrotic.

Borax application

• Give directed spray of Borax(0.2% i.e 2 gms/lit.of water) to capitulum at ray floret opening stage for increasing seed filling, yield and oil content.
• A spray mixture of 500 lits/ha is required.
• Dissolve required quantity of Borax (2gms/lit) in small quantity of hot water and make up the required volume.

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