👕Cotton -- White Gold and King of Fibre Crops (Complete Guide)

Travel to the black-soil heartland of Gujarat — where cotton fields stretch to the horizon — and you witness a crop that has shaped global trade for centuries. Cotton is the backbone of the textile industry, meeting 45% of the world’s fibre needs. India, the original home of cotton domestication (with evidence from the Indus Valley Civilisation over 5,000 years ago), now leads the world in production. The introduction of Bt cotton in 2002 transformed Indian cotton farming, taking coverage to 90% of the cotton area. For exams, questions about Gossypium species, ginning percentage, H-4 hybrid, Bollgard, and delinting are perennial favourites.

This lesson covers:

1. Basics and species — four Gossypium species and their fibre characteristics
2. Climate, soil, and planting — black soil advantage, sowing windows, and UNR spacing
3. Fibre science — ginning, delinting, lint index, and the 170 kg bale
4. Bt cotton — India’s only GM crop, Bollgard genes, and GEAC approval
5. Varieties, diseases, and yield — landmark hybrids H-4 and Varalaxmi

All sections are high-yield for IBPS AFO, NABARD, and FCI exams.

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Basics

Cotton is classified under the family Malvaceae and is a day-neutral plant, meaning it flowers irrespective of day length. India is both the birthplace of cotton cultivation and the current global leader in production.

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Global and National Standing

India overtook China to become the world’s largest cotton producer, largely driven by the adoption of Bt cotton hybrids. Within India, the western and southern Deccan states dominate production due to their extensive black soil belts.

• Gujarat alone contributes approximately one-third of India’s total cotton production due to widespread adoption of Bt cotton hybrids and favourable black soil conditions.

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Cotton Species

Four species of Gossypium are commercially cultivated worldwide. The two Indian (Desi) species produce shorter fibres but have higher ginning percentage, while the two New World species produce longer, finer fibres preferred by the textile industry.

• G. barbadense (Sea Island Cotton) produces the finest fibres, prized for luxury textiles.

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Indian vs American Cotton

The key distinction between Indian (Desi) and American (Upland) cotton lies in fibre length and ginning percentage. Indian species (G. arboreum, G. herbaceum) produce short-staple fibre (<22 mm) with higher ginning percentage (36-42%), while American upland cotton (G. hirsutum) produces medium-long staple fibre (25-30 mm) with lower ginning percentage (28-32%). Indian textile mills increasingly demand longer staple for finer fabrics, which is why G. hirsutum now covers over 90% of India’s cotton area.

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Varieties of Cotton

India has a rich history of cotton breeding, producing both the world’s first commercial cotton hybrid and the first interspecific hybrid. Varieties are chosen based on fibre length, ginning percentage, and disease resistance.

Landmark Hybrids

• Two years after the release of H4 (the world’s first commercial cotton hybrid), the first interspecific hybrid between G. hirsutum and G. barbadense was released as Varalaxmi from the Cotton Research Station, Bangalore.

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Climate

Cotton is a warm-season crop that thrives in hot, sunny conditions with moderate rainfall. Each growth phase has distinct temperature requirements, and water stress or excess rain at the wrong stage can devastate yields.

• Critical stages for irrigation: Flowering and Boll formation — water stress during these stages causes flower and boll shedding, directly reducing lint yield.

• Abundant sunshine during boll maturation and harvesting is essential because UV light promotes fibre drying and prevents fungal contamination of open bolls.
• Heavy rain during fruiting causes shedding of flowers and young bolls because excess moisture disrupts pollination and triggers abscission.

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Soil

Cotton grows best in deep, moisture-retentive soils. The association between cotton and black soil is so strong that Vertisols are commonly called “black cotton soil” in India.

• Black cotton soil (Regur/Vertisol) is best — excellent moisture-retention capacity due to high clay content and the swelling mineral montmorillonite, which holds water in its crystal lattice and releases it slowly during dry spells.

• Not suitable: sandy, saline, and waterlogged soils — sandy soils cannot retain enough moisture for the long crop duration, while waterlogging causes root rot.
• Tap root system (depth > 1.6 m) makes it relatively drought-tolerant by accessing deeper soil moisture reserves.

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Plant Architecture

Understanding cotton branching is essential because the two branch types serve entirely different functions — one produces bolls (yield) and the other supports canopy structure.

• Squaring (flower bud appearance) occurs 35-70 DAS. Peak flowering: 70-100 DAS.

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Seed Rate and Sowing

Seed rate and spacing vary significantly between conventional and ultra-narrow row (UNR) systems. The sowing window depends on the onset of monsoon in each region.

Sowing Time

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Nutrient Management and Topping

Cotton requires balanced nutrition for both vegetative growth and boll development. Topping is a key cultural practice that redirects plant energy toward boll filling.

• Topping: Removal of terminal growing point at a height of 1.2 m (80-90 DAS) to encourage sympodial branching and redirect photosynthates from vertical growth to boll filling.

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Fibre and Seed — Key Concepts

This section covers the critical terminology around cotton fibre that appears in virtually every AFO and NABARD exam. Cotton fibres develop from the outermost cells of the seed-coat. Each fibre is a single elongated cell from the epidermis of the seed — making cotton a unique seed fibre (unlike jute or flax which are bast fibres).

Ginning Percentage

• Ginning % = (Wt. of lint / Wt. of Seed Cotton) x 100
• Lint Index = (Weight of 100 cotton seeds / 100) x Ginning %
• Indian species have higher ginning percentage but produce shorter, coarser fibres.

Delinting and Measurement

• Arealometer measures length of cotton fibre and judges maturity by measuring air permeability.
• 170 kg cotton = 1 bale (standard Indian trade unit, as defined by the Cotton Corporation of India).

Cotton Seed Products

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Bt Cotton — India’s Only GM Crop

Bt cotton is the single most transformative technology in Indian cotton farming. It introduced a gene from the soil bacterium Bacillus thuringiensis that produces a crystal protein toxic to bollworm larvae, dramatically reducing pesticide use.

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Disease and Pest

Cotton is susceptible to several diseases and insect pests that can cause significant yield losses. Bt cotton has dramatically reduced bollworm damage, but sucking pests have emerged as a growing concern.

Major Diseases

Insect Pests

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Yield

The yield difference is due to heterosis (hybrid vigour) — hybrid plants exhibit superior boll number, boll weight, and fibre quality.

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Explore More

• Cotton cultivation practices and management
• Cotton fibre processing and ginning

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Important Cotton Varieties ^{Asked in AFO/NABARD}

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Cotton: Species Selection and Practical Decision Guide

Which cotton species for which region?

Bt vs Non-Bt decision:

Key principle: Bt cotton controls only bollworms (Lepidoptera). All sucking pests, leaf spots, and wilt diseases need separate management. Farmers who believe “Bt means no spray needed” suffer heavy losses from sucking pests.

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Summary Cheat Sheet