What is cotton like? ()

Cotton is the seed fiber of Malvaceae, which belongs to angiosperms and is native to subtropics. The plant is shrubby and can grow to 6 meters high in tropical areas, usually 1 to 2 meters. The flowers are milky white, turn dark red shortly after flowering, and then wither, leaving a small green capsule called cotton boll. There are cottonseed in cotton bolls, and the fluff on cottonseed grows from cottonseed hulls and fills cotton bolls. The cotton peach splits when it matures, revealing soft fibers. The fiber is white to white with yellow, about 2 to 4 cm long and contains about 87-90% cellulose. According to the length and appearance of fibers, cotton can be divided into three categories: the first category is slender (2.5 to 6.5 cm in length) and shiny, including high-quality sea island cotton, Egyptian cotton and Pima cotton; Long-staple cotton is low in output, laborious and expensive, and is mainly used for high-grade fabrics, cotton yarns and knitwear. The second category includes cotton of average medium length (about 1.3 to 3.3 cm in length); The third category is cotton with short fibers (about 1 to 2.5cm in length), which is used to make carpets, cotton blankets and low-priced fabrics, or blended with other fibers. Cotton was picked after the bell cracked. If cotton is picked by machine, leaves are usually removed by chemical method first, and cotton bolls are cracked at the same time. The cotton gin strips fibers from cottonseed, and after cleaning and carding, the fibers are assembled into a soft rope shape, which is gradually elongated, straightened and reduced in diameter under the action of drafting. The fibers for spinning high-quality spun yarn need to be combed, short fibers removed and further arranged neatly. In the worsted process, the fiber is twisted into spun yarn, which is wound on the bobbin and then sent to the textile mill. Cotton is one of the most important crops in the world, with high yield and low production cost. Cotton can be made into fabrics of various specifications. Cotton fabric is durable and can be washed and ironed at high temperature. Cotton cloth absorbs and dehumidifies quickly and is comfortable to wear. The countries with the highest cotton production are China, the United States and India.

Cotton planting:

The amount of nutrients absorbed by cotton increases with its yield, and the absorption rate of nitrogen, phosphorus and potassium is about 1.0:0.3: 1.0. The proportion of NPK fertilizer is about 1:0.65: 1.0. Generally, 40% of nitrogen fertilizer is used as base fertilizer, 40% as flower and boll fertilizer, and 20% is applied at the early stage of peach setting. It is better to use the whole layer as base fertilizer for phosphate fertilizer and half of base fertilizer and topdressing for potash fertilizer. Cotton has a good reaction to zinc and boron, so attention should be paid to the application of zinc fertilizer and boron fertilizer.

I. Nutritional characteristics and fertilizer demand of cotton. (1) From emergence to germination. The nitrogen content of cotton is the highest in this period. (2) From germination to flowering. At this time, if too much nitrogen is supplied, it will often cause cotton plants to grow white and increase the loss of buds and bolls, so it is necessary to avoid applying too much nitrogen. Applying more potassium fertilizer can increase the potassium content in stems and leaves, especially in stems and leaves. (3) from full flowering stage to initial flocculation stage. The contents of phosphorus and potassium in reproductive organs increased rapidly. Insufficient supply of phosphorus and potassium will affect nitrogen intake.

Second, cotton fertilization technology.

Manure, compost and nitrogen fertilizer. They are common farmyard manure in cotton fields. General cotton fields use 30-45 tons of base fertilizer per hectare (1 hectare is about 15 mu), and high-yield cotton fields use 45-75 tons per hectare. In general cotton field, under the condition of applying total nitrogen 1 12.5- 150 kg per hectare, 37.5 kg of pure nitrogen is used as base fertilizer, which is applied to the soil together with farm manure before ploughing (the rest is used as topdressing at flowering and bolling stage), and good results can be obtained. The loam with medium and high fertility has a strong ability to maintain and supply fertilizer, and it is better to apply nitrogen fertilizer in two stages, one as base fertilizer is about 45%, and the other at flowering and bolling stage is about 55%. In cotton fields with high soil fertility and strong fertilizer conservation ability, a proper amount of nitrogen fertilizer can also be used as base fertilizer at one time; For cotton fields with poor soil fertility, sandy texture and poor fertilizer retention ability, nitrogen fertilizer can be applied in three stages, namely, 30% base fertilizer, 20% topdressing in bud stage and 50% topdressing in flower and boll stage.

It is better to apply half of base fertilizer and topdressing to potash fertilizer, and it is also good to apply only base fertilizer. The application of potassium fertilizer depends on soil fertility. On the basis of nitrogen and phosphorus application, potassium chloride or potassium sulfate is generally applied to cotton fields with medium soil fertility135-150kg/ha, and potassium chloride or potassium sulfate is applied to cotton fields with medium and low soil fertility of about 225kg/ha.

Boron fertilizer can be used as base fertilizer, seed fertilizer and topdressing. It is very effective to use 3.75-7.5 kg per hectare as seed fertilizer in cotton fields with serious boron deficiency (soil available boron is less than 0.2 mg/kg). Seedling stage and bud stage: the demand for nutrients in cotton seedling stage and bud stage is not great. Generally, in the case of applying sole fertilizer, cotton fields do not need topdressing. However, in the case of cotton-wheat intercropping, cotton seedlings are affected by fertilizer absorbed by wheat in the process of cotton-wheat symbiosis, and their growth is weak, so appropriate topdressing is needed to promote their growth. After wheat harvest, clear stubble as soon as possible and topdressing shallow water. Generally, the dosage of seedling fertilizer is about 52.5-75 kg of urea per hectare or 2250-3750 kg of decomposed human excrement and urine.

Phosphate fertilizer is mainly used as base fertilizer, which can meet the needs of cotton in the whole growth period, so cotton is generally not topdressing phosphate fertilizer.

Three. The situation in China

The largest planting area in China is upland cotton.

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