All About Cotton: A Small Step for Mankind, a Giant Leap for Cotton

All About Cotton: A Small Step for Mankind, a Giant Leap for Cotton

On 2 January 2019, after orbiting for several days, the Chinese lunar lander Chang’e-4 finally landed on the moon. More impressively, Chang’e-4 landed on the moon’s far side, which had never been achieved before. Onboard, the lander carried a variety of things, including seeds. Carefully contained in a tank the cotton seeds began to germinate. This was the first time that seeds were successfully germinated and grown into tiny sprouts in space. 

Cotton was first grown around 3000 BC in what is today the Indus valley of India. Other ancient civilisations in China and Egypt too grew cotton. During the Middle Ages, the Arabs themselves had imported the cotton crops from Spain and India. As skilled farmers and traders, they soon became great producers of cotton. Specifically, the city Mosul which lies in today’s Iraq was a centre point for cotton production. By 1100 CE, the Arabic trade brought both the crop and its name to Europe. The word ‘cotton’ comes from the Arabic ‘qutun’, which is still used today. However, it was not only the people in Asia and Europe who liked the softness and versatility of cotton. When the first Europeans arrived in South America, the Aztecs and Incas had already mastered cotton cultivation and processing, producing intricate and colourful textiles. Fasting forward to 1600, the first cotton plantations in North America were established and in 1793 the cotton industry was revolutionised through the invention of the Cotton Gin. The Cotton Gin was a machine that automated the process of separating the soft cotton fibres from the seeds. With more cotton available its use cases increased and diversified. Between 1878-1880 Thomas Edison and his team worked on the invention of the so-called incandescent light bulb. Light bulbs as such work by using electricity to heat up a thin filament within the glass bulb until it begins to glow. A strong contender for this filament was cotton. Edison and his team took a thin strand of cotton, carbonised it and used it within the bulb. When turned on, the filament began to glow in an orange tone for 15 hours straight before it burned out. Though we may no longer try to use cotton in our lightbulbs, we continue to find it everywhere from our clothes, furniture, sails on boats and even currencies such as the American dollar. 

Today cotton remains one of the most important agricultural resources. The world’s biggest producers are India, China and the United States. The production forecast estimates that the United States will produce 17.5 million bales of cotton. China and India are both expected to produce much more, 29.0 million bales each. The yield of cotton for China is expected to be record high with ca 1,943 kg/hectare. India and the United States are expected to produce 475 kg/hectare and 925 kg/hectare respectively. 

How is Cotton Grown?

The soft white material, which we refer to as cotton, are fibres grown in the bud around the seeds after the flower has withered. They are between 87- 90% made out of cellulose, the same material that makes up the cell walls in plants. Different kinds of cotton flowers produce fibres with varying qualities. Varieties such as Egyptian and Sea Island cotton are known for producing thin and shiny fibres ranging between 2.5-6.5 cm. Cotton made from these plants is considered more exclusive due to their relatively low yields and are more cumbersome to grow. The American Upland produces cotton of medium quality. For this category of plants, the fibres tend to be shorter, between 1.3-3.3 cm. Lower quality cotton is known to be rather coarse in texture and has even shorter fibres that range between 1.0-2.5 cm. Depending on the quality and length of the threads, cotton is used for different purposes. The highest quality tends to be found in products such as hosiers, whilst the lowest is more suitable to make blankets or even mixed with other fabrics. 

Cotton grows best in hot, sunny and subtropical climates. Compared to many of the other major crops grown, cotton is especially susceptible to changes in its environmental conditions. For example, if the temperature falls below 15 degrees celsius, the crops may not grow or develop. When cotton seeds have been planted, it takes between 4-6 days for them to germinate. If the weather conditions remain good, the first root starts to develop within 2-3 days. The root grows fast during the early growth stage and can increase as much as 1.27-5 cm per day. After 50 days of growth, the roots can reach 91cm long. Between 80-100 days after the cotton has been planted, the first flowers start to emerge. At first, the flowers are white but later change to red. After fertilisation, the flowers wither, fall off and are replaced by co-called bolls. Bolls tend to be triangular in shape and contain the developing seeds and cotton fibres. It takes between 55-80 days for the bolls to mature and grow in size. 

Besides requiring hot heat to grow, humidity also plays an essential role in plant development and the quality of the fibres. Cotton plants that grow in regions where the air humidity is high produce better quality cotton. Unfortunately, not all areas in which cotton is cultivated is naturally subtropical. In areas where dry heat is the standard, farmers need to take extra care to irrigate the crops sufficiently. However, even if irrigation is on par with the plant’s needs, it is not the only factor impacting yield. 

There are thousands of insects that find cotton equally appealing as us humans. Among these are a variety of worms, spiders, mites and the notorious Boll Weevil. With evil in its name, this tiny beetle was one of the most significant losses of crops for American farmers for almost 90 years. Introduced from Mexico 1890s, it had the capability of destroying 30-50% of crops. This pest has largely been overcome through targeted pesticide programmes and is no longer considered a great threat. Fungi, bacteria and viruses are also a major concern for cotton growers. One virus that cotton growers still have to monitor is a cotton leafroll virus that causes Cotton Blue Disease (CBD) and is especially devastating during the early growth stages of cotton. Infected areas can lose up to 80% of their yields. The disease causes the growth of infected plants to halt the growth and development of plants. It is characteristically noticed on the topmost leaves of the plant, which look to have small, thick leaves. The leaves themselves can look to have yellow veins, while the rest of the leaves have a blue hue. After some time, the leaves will begin to curl down towards themselves. Ultimately due to stunted development and poor growth, the quality and size of the yield are greatly reduced. Threats to yield and crop quality of any kind need to be monitored and acted upon, especially early-onset viruses like CBD. Early detection and monitoring are utmost necessary to avoid losing up to 80% of the yield but are not always easily done. Precision farming and monitoring through satellite data can help farmers do this easily and efficiently before too much damage is done. Healthy plants maintained by correct nutrition and irrigation are also more resistant to threats, and precision farming can help with that too.

How is Cotton Harvested?

Once mature, the bolls will burst, revealing the soft fibre; they need to be harvested as soon as possible. Cotton is unfortunately not known to mature all at once, with large variations possible in one field. This causes the risk of losing valuable yield. To help overcome this problem, farmers can spread so-called defoliant over the plants. Defoliant is a mixture that makes the crops shed their leaves and helps the maturation of crops occur more evenly across the field. Once ready for harvesting, a cotton harvester is easily used to get the job done, and farmers have two varieties to choose from. Stripper Harvesters rip all foliage of the plant, including leaves, ripe bolls and unripe bolls. Even pieces of the stem may be included in the mix. The harvested mixture is then filtered through and separated according to desire in a Cotton Gin. Stripper harvesters are a helpful go-to for frostbitten plants that have died. The Picker Harvester is more precise in its cotton-picking approach. Instead of completely stripping the plant, it carefully plucks the soft fibres directly from the boll. This precise harvesting is achieved by carefully lowering rotating spindles into the centre of the boll. The fibres then attach themselves to the spindles and twist around them. The threads are then removed from the spindles through a doffer that collects and places the fibre balls in a collector attached to the harvester. 

 

To the moon and back, the use of cotton is seemingly endless. As one of the major field crops producing cotton sustainably and reliably is important for both the environment and farmers economic stability. From detecting threats optimising out precision farming can help increase production for an increasing population. 

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