Growing Cotton

Known simply as ‘cotton’, this plant belongs to the Genus Gossypium and to the family Malvaceae. Though the Genus contains 49 species, only 4 are commercially cultivated for lint. These are two Old World diploids, G.herbaceum and G.Arboreum and two New World tetraploids, G.Hirsutum and G. Barbadense.

The origins of cotton and the way it has been processed are lost in antiquity, yet many of the older civilisations that grew cotton such as India and South America still retain some of the agricultural and processing practices such as ploughing with oxen, and twisting and spinning the fiber by hand to produce yarn. Perhaps this speaks for the amazing range of technologies cotton strides from highly mechanised and sophisticated to a simple cottage style production and processing.

It has only been in the last 40 years that cotton has been grown as a 'monocrop' on a large-scale; using significant amounts of fertilizers and pesticides. In some places cotton is grown organically 'by default' meaning agrichemicals have never been introduced to the area. But increasingly cotton is being grown organically 'by design'; because it's proving the best way to to it. 

Cotton grows near the equator in tropical and semitropical climates, in a band that stretches around the world between latitudes 45 North to 30 South. It requires a long growing season (from 180 to 200 days), sunny and warm weather, plenty of water during the growth season, and dry weather for harvest. In many regions extra water must be supplied by irrigation.

Known as simply ‘cotton’, this plant belongs to the Genus Gossypium and to the family Malvaceae. Though the Genus contains 49 species, 4 are commercially cultivated primarily for lint. These are two Old World Diploids, G.herbaceum and G.Arboreum and the New World tetraploids are G.Hirsutum and G. Barbadense.

Mostly an annual in the tropics, but also a short lived perennial short bush, averaging between 2 to 6 feet (0.8–1.8 m) depending on the species. It has a deep tap root and secondary roots for anchoring and nutrient intake, a central vertical stem with many branches and is usually covered with minute hairs. The plant usually has a pyramidial form.

Leaves can be palmate, digitate or semi digitate, and are usually alternate, spirally arranged and mostly hairy. Flowers are complete and border on perfect with a calyx, corolla, stamen and petals that range from white to purple, with distinctions such as a dot at the base of the petal. The fruit is a boll with a shape that can range from oval to spherical, and colours ranging from light green to pink. The weight of a boll can vary from 3 to 13 grams, and one plant can contain more than a hundred bolls. The boll contains the lint or fibre, which can be classified as short, medium long, or extra long and is mostly white, though there is some coloured cotton with brown and green lint.

Cotton grown organically may not produce folliage to the same extent that synthetically fertilized cotton may do. This is no refelction on the quantity of cotton the plan is capable of producing. Studies in Egypt indicate that folliage growth can actually be detrimental to the yield of the cotton plant.

The soil is prepared and given nutrition, kept soft and levelled. Seeds are planted within a uniform depth, should not be sown too deeply and should be sown at a depth of 2 to 4 cms. It should be ensured that seeds are of sound quality, i.e. disease free and viable. In fertile soils usually one seedling per hole is allowed and in poor soils farmers allow two seedlings per hole. The rest are thinned out usually on the 15th day of sowing.

Usually the seeds are planted in rows, with spacing depending on the variety. Many countries have established intercropping patterns with cotton over centuries, that provide the required nutrients for the soil as well as allow cotton farmers some degree of food self sufficiency, and usually oil seeds and lentils are grown with cotton. In such cases the fields are prepared for this planting pattern, with ridges and furrows. In more developed countries where cotton is grown on large tracts, the planting is done in one contiguous pattern.

These days, access to non genetically modified (GM) seed is of growing concern. Organic agriculture does not permit the use of GM seed. In fact, the existance of organic agriculture - and rules of production - is contributing to seed diversity around the world although more needs to be done to safeguard regionally-appropriate, culturally significant seeds on one hand and invest in non-GM seed R&D on the other. 

The period of growth and vegetation ranges from 90 to 110 (up to even 200 days). The growing period from sowing to boll ripening sees five distinguishing phases.

The next few slides show the phases for the 120-130 days maturing types of cotton. There may be variations in the lengths of each phase depending on variety, climatic conditions, soil quality etc.

Phase 1: Days 1 to 10 - Germination and Shoot emergence

 

Phase 2: Days 11 to 13 - True Leaf Phase

Phase 3: Up to 45 days - Formation of buds or Flower budding

Phase 4: 60 to 65 days - Blossoming

Phase 5. 120 to 130 days - Boll Ripening

Cotton prefers alluvial soils, which should be loose, well drained and have good humus content with a pH of 6.5 to 7.5. Some countries grow cotton in a varied agro climatic conditions ranging from sandy to loamy to red laterite and shallow black soils. Cotton is considerd a thirsty crop that requires irrigation, but it does well in completely rainfed conditions as well. Yields are higher when irrigation is possible.

Water requirement of cotton can vary between 60 to 120 cm depending on various factors such as variety or hybrid, soil type, quality of water and the general agro-climatic conditions. The highest needs are around the flowering and boll formation stage.

Studies in Africa show that under climatically stressed growing conditions organic production tends to fend better than non-organic i.e. organic crops are more tolerant of extreme conditions, such as droughts and floods.

In organic cultivation, no herbicides are permitted, and weed control is done mechanically or manually. In rainfed conditions, the weeds grow along with the cotton plants and must be removed within 20 to 30 days.

It is said that more than 170 pests attack cotton though the significant ones are much less. The major pests are thrips, jassids, aphids, whitefly, leafworm, leaf roller, pink bollworm, spotted bollworm , american bollworm, stem weevil, boll weevil, army worms, loopers.

 

Picking is done when the bolls are fully mature. Picking should be done skillfully with proper care taken against contamination, segregation of good and poor bolls.

Developing countries adopt manual picking by hand, and developed countries use machines for mechanized picking. Post harvest handling is equally important with respect to drying of bolls and contamination, storage and transportation to the market yards or gins.

The history of cotton ginning is fascinating, from the simple charkas of yore to the the highly modern gins with highly sophisticated cleaners and driers. Large gins are becoming the order of the day, due to the high costs involved.

There are different systems in different countries. However primarily cotton is classified on the basis of staple length of the fibre, the uniformity of this length, strength and colour, with creamy white to white being the desired colour. The type of cultivar used, agri-practices, contamination controls to reduce trash and the ginning methods determine the quality and the price the cotton can command. 

For cotton textiles, whilst it is fundamentally important that quality of the original fibre is good, quality issues can also arise during the spinning, knitting and dying phases of textile production.

Find out what happens to the cotton once it leaves the farm in our Fiber to Fashion learning journey.