The flowers are milky white, and soon after the flowering, they turn into deep red and then wither, leaving a small green capsule called a cotton boll. There is cottonseed in the cotton boll, and the hair on the cottonseed grows from the epidermis of the cottonseed, stuffed inside the cotton boll, and the boll is cracked when mature, revealing soft fiber. The fiber is white or yellow with yellow, about 2 to 4 cm (0.75 to 1.5 inches) long, containing about 87 to 90% of cellulose, 5 to 8% of water, and 4 to 6% of other substances. The countries with the highest cotton production are China, the United States, and India.
Cotton can be divided into three categories: the first type of fiber is slender (with a length of 2.5 to 6.5 cm (1 to 2.5 inches)), and the gloss is high, including island cotton, Egyptian cotton, and Pima cotton. Long-staple cotton has low yield, high labor cost and high price, mainly used for high-grade gauze and knitwear; the second category includes general medium-length cotton, such as American upland cotton, which is about 1.3~3.3 cm (0.5~1.3 inch) in length. The third category is cotton with a short length of the fiber, about 1 to 2.5 cm (0.375 to 1 inch) long, used to make cotton blankets and inexpensive fabrics or blended with other fibers.
- [Gold cotton] – also known as Asian cotton, native to India. Due to low output and short fiber length, it is not suitable for machine weaving and has been eliminated.
- [Long-staple cotton] – also known as island cotton, native to South America. The fiber length and high strength are its characteristics, which are suitable for spinning high count yarns. The fiber is thin and long, generally having a length of 33 mm or more, a linear density of about 1.54 to 1.18 dtex (6,500 to 8,500 metric), and a strength of 4.5 cm or more. Its high quality is mainly used to produce superior cotton yarns that are finer than 10tex. There are fewer plants in China. In addition to Xinjiang long-staple cotton, mainly imported Egyptian cotton and Sudan cotton.
- [fine cotton] – also known as upland cotton, native to Central America, so also known as US cotton. Wide adaptability, high output, long fiber, and good quality are the characteristics of the yarn. The general length is 25~35mm, the linear density is about 2.12~1.56dtex (4700~6400g), and the strength is about 4.5cN. Most of the cotton grown in China fall into this category.
- Color Classification
White cotton: a normal mature, normal smear of cotton, regardless of the color of the original cotton is white, milky white or light yellow, are called white cotton. Most of the raw cotton used in cotton mills is white cotton.
Yellow cotton: In the late stage of cotton growth, the cotton bolls die after frostbite, and the pigment on the bell shell is dyed onto the fibers, which makes the original cotton color yellow. Yellow cotton is generally low-grade cotton, and cotton spinning mills have only a small amount of application.
Gray cotton: cotton fiber grown in rainy areas. In the process of growth and development or after bolling, if there is too much rainfall, less sunshine, and low temperature, fiber maturity will be affected. The original cotton will be grayish white. This raw cotton is called gray cotton. Gray cotton has low strength and poor quality and is rarely used in cotton mills.
Colored cotton: colored cotton refers to cotton with natural color. It is based on the original colored cotton and is cultivated by biotechnology such as distant hybridization and transgenic. Natural colored cotton still maintains the original softness, comfort, and breathability of cotton fiber. The cotton fabric can reduce the printing and dyeing process and processing cost, and can avoid environmental pollution. However, the hue is missing and the color fastness is not enough. In the observation of stable inheritance.
- Growing environment
Xinjiang cotton is mostly early-maturing, early-maturing and early-maturing varieties, and is not sensitive to light length response. It is a hi-light crop suitable for growing under sufficient light conditions. Both cotton light compensation points and light saturation points are high. According to the measurement, the light compensation point of a cotton single leaf is 750~1000lx, and the light saturation point is 7~80,000xx. Under normal circumstances, the suitable range of cotton leaves for light intensity is 8000~7000 lx. Under this range, the photosynthetic intensity increases with the increase of light intensity.
Moisture is an important component of cotton, and cotton needs to absorb water from the soil. The physiological water requirement requirements of cotton at each growth stage are sowing to emergence, the water content of 0~20 cm soil layer accounts for 70~80% of the field water holding capacity; in the seedling stage, the water content of 0~40 cm soil layer accounts for the water holding capacity of the field. 60 ~ 70% is suitable; in the early bud period, the water content of 0~60 cm soil layer accounts for 65~75% of the field water holding capacity; after the bud stage, the water content of 0~80 cm soil layer accounts for 70% of the field water holding capacity. ~80% is appropriate, not less than 60~65%; in the boll opening period, the relative water content of the soil is maintained at 55~70%. According to relevant research, about 2/3 of the cotton is consumed in transpiration throughout the growing period, and 1/3 is consumed in the evaporation of land.
The growth and development of cotton require water and nutrients, which are mainly obtained from the soil through the root system. The required temperature and air are taken from the soil and the mechanical support of the soil is required to grow. The physical and chemical properties of cotton soil and the biological properties of cotton fields largely restrict the yield and quality of cotton. Soil moisture, nutrients, temperature, air, saline content, texture and so on have a great impact on cotton growth.