- Economic importance
- Crop history
- Chemical composition
- Cultivation areas and yield
- Botanical description
- Technological properties of cotton fiber
- Biological features
- Crop rotation
- Fertilizer system
- Tillage system
- Crop care
Cotton fiber is the main type of plant raw material for the textile industry. Various fabrics are made from cotton fiber of long-staple varieties: chintz, satin, knitwear, flannel, batiste and others, in addition, it is used for the production of threads and cord. Mixed with wool or chemical fibers, cotton fiber is used to produce a wide variety of fabrics.
The down of seeds (lint or linter) is used for the manufacture of hygroscopic cotton wool, especially durable grades of paper, film, plastic, nitro-varnishes, and artificial leather.
Cotton cake can serve as a good concentrated feed for farm animals. The protein content in it reaches 40%. It is fed in small quantities (2-3 kg per day for
per head of cattle), as it contains the poisonous substance gossypol. Pigs should not be fed cake.
The peel (husk) of seeds serves as raw material for the production of ethyl and methyl alcohols, glucose, furfural, lignin, resins, feed proteins. Acetic acid, paper, biofuels are obtained from the stems and flaps of the boxes. From the leaves and bark of the stems – citric acid (the content in the leaves is up to 10%) and malic acid, resins. Plant residues can be used as organic fertilizer.
Cotton raw materials are used to make safety glass, artificial felt, fire hoses and other products.
From 1 ton of raw cotton can be obtained: (320) 340-350 kg of fiber, 570-580 kg of linted seeds, 30-40 kg of lint, 20-30 kg of other waste. When processing this amount of cotton seeds, the following can be obtained: 98-110 kg of refined oil, 20 kg of laundry soap, 225-230 kg of cake, 210-230 kg of husks.
The output from 1 kg of cotton fiber fabrics is: 12 m of chintz or 20 m of cambric, or 140 spools of thread.
Cotton is a valuable honey plant.
In addition to the spinning crop, cotton is also considered as one of the main oilseeds. Cotton seeds, whose share of the total mass of the raw yield reaches 65%, contain (18) 20-27% oil, including 35-40% in the kernel. The oil is suitable for eating and for producing margarine, drying oil, phytin, stearin, glycerin, soap.
Cotton has been cultivated since ancient times. It has been grown since 3000 BC. in India and China and was used to produce spinning fiber. Approximately 500 BC cotton penetrated from China to Egypt, and in the IV-V centuries. cotton growing began to develop in Central Asia and Iran, in the 9th-10th centuries. high-quality fabrics were made from cotton fiber.
In the XIII century. cotton appeared in Transcaucasia.
In America, cotton appeared independently in Mexican and Peruvian cultures and has been known for several millennia.
The industrial processing of cotton fiber increased dramatically in the second half of the 18th century, after the invention of machine spinning and the cotton gin. In the 19th century cotton growing provided 73% of all spinning raw materials, and in the 20th century. – over 85%.
Cotton growing in Russia developed very quickly. In 1922 V.I. Lenin approved the “Regulations on the state organization of cotton growing, the cotton ginning industry and cotton procurement.” In 1929, measures were taken to free the USSR from dependence on foreign supplies of raw cotton. Special attention was paid to the development of cotton growing in the republics of Central Asia and Transcaucasia. As a result, within 3 years, the import of cotton to the USSR was greatly reduced and amounted to only 7% of the country’s need for cotton fiber, and in the prewar years it was completely stopped.
The USSR was the northernmost country in the world where cotton was grown. After the Great Patriotic War, the USSR ranked first in world agriculture in terms of yield and quality of cotton fiber.
The chemical composition of the green mass, mowed in the phase of mass flowering:
- water – 65-70%;
- carbohydrates – 17%;
- protein – 2.5%;
- fats – 0.8%.
Also in the green mass contains a large amount of calcium and phosphorus.
Cultivation areas and yield
The world area occupied by cotton crops in 1984 was 33-34 million hectares, and the gross harvest of raw cotton was 42-45 million tons. The main cotton-growing countries of the world were the USSR, the USA, China, India, Pakistan, Brazil, Mexico , Egypt and Turkey. They accounted for approximately 80% of all raw cotton produced in the world.
In the early 2000s, cotton was grown in about 60 countries around the world. The total sown area was 35 million hectares, including:
- India – 7.5 million hectares;
- USA – 4.5 million hectares;
- China – 4.8 million hectares;
- Brazil – 1.9 million hectares;
- Pakistan – 1.8 million hectares;
- Egypt – 0.6 million hectares.
In the USSR, the main cotton-growing regions were the republics of Central Asia: Uzbekistan, Turkmenistan, Tajikistan, Kyrgyzstan, Kazakhstan and Transcaucasia (Azerbaijan). The sown area in the USSR reached 3.2-3.3 million hectares, and the yield of raw cotton in 1984 was 2.3-2.6 tons/ha, the gross harvest was 8.6 million tons.
Record yields reached 4-5 t/ha.
For the period up to 2000, the USSR planned to achieve a harvest of 2.8-3 million tons of cotton fiber and 9.1-9.4 million tons of raw cotton. In addition, it was planned to improve the quality of the fiber, its output and reduce losses.
Cotton (Gossypium) belongs to the Malvaceae family (Malvaceae). A perennial plant, but more often, especially in temperate regions, it is cultivated as an annual crop.
An adult plant is a bush with a height of 90 to 130-180 cm.
The root is taproot, well developed, penetrates the soil to a depth of 1.5-2 (3) m. In the upper part, many lateral roots depart from it. Horizontally extends to 1.5-2 m.
In the first month of plant development, the root system grows very quickly. Before the budding phase, the main root develops especially intensively, while after this phase, the lateral roots develop. In the first two weeks, the growth of the main root averages 2.5-3.2 cm per day, and the total growth of lateral roots reaches 30-45 cm.
The stem is straight, branching, strong enough, woody (rough) in the lower part, covered with hairs.
There are 2-3 buds in the axils of the leaves. Those of them that are in the axils of the first leaves usually remain dormant, and branches begin to form from the buds of the axils of subsequent leaves, more often 3-5 leaves.
The branches are divided into growth (monopodial), or monopodia, and fruit (sympodial), or sympodia.
Monopodia are formed in the lower part of the stem and depart from it at an acute angle. Monopodia grow in a straight line and are usually stronger than sympodial ones.
Fruit branches on the stem are located above the growth branches. They form a more obtuse angle with the stem and grow articulated, along a broken line. Sympodia are peduncles, on which fruits (boxes) then appear.
The number of monopodial branches on the main stem before the formation of the first sympodium is different and depends on the forms and varieties of cotton species, as well as on growing conditions.
In the tropics, there are forms of cotton, in which the number of monopodial branches is from 15 to 40 pieces. This type of cotton branching is called monopodial.
A typical cotton plant is treelike. Its sympodial branches form high and bloom very late.
In the conditions of the countries of Central Asia, there are usually only 2-3 monopodia on a cotton bush before the formation of the first sympodium. This type of branching is called sympodial. The height of the laying of the first sympodial (fruit) branch on the main stem is one of the signs of the precocity of cotton.
There are forms of cotton that do not form branches, and the fruits sit on shortened stalks, 1-2 in axils of the leaves of the main stem. This type of branching is called zero. Bushes of this type are very compact. Such forms of cotton were bred in the Soviet period and were used to produce fine-staple cotton.
Cotton varieties differ in the number and length of internodes of fruit branches. Some varieties have fruit branches with one internode, at the end of which all the buds give buds and boxes, so the branch stops further growth. This type of branch is called limiting. The cotton bush with the limiting type of branching has a compressed columnar shape.
Fruit branches with several internodes are of the unlimited type.
Depending on the length of the internodes, the unlimited sympodial branches are divided into subtypes:
- I – with shortened internodes 3-5 cm;
- II – with average internodes 6-10 cm;
- III – with long internodes 11-15 cm;
- IV – with very long internodes 16-25 cm.
A subtype with very long internodes is characteristic of Soviet varieties of fine-staple cotton.
The length of the internodes of fruit branches is an important varietal trait that determines the total length of the branches, the degree of spreading or compactness of the bush. The longer the internodes, the longer the branches and spreading of the bush and, conversely, the shorter the internodes, the shorter the branches and the more compact the bush. The large spreading of the bush creates some difficulties in inter-row tillage and harvesting.
In the USSR, forms of cotton with an unsaturated type of fruit branches were usually grown. Cotton with a marginal type of branches is considered to be less productive and produces fiber of a slightly worse quality.
In the axils of the leaves of monopodial branches, branches of the second order can form, and, just like on the main stem: in the axils of the first 2-3 leaves, the branches usually do not form, and the buds remain dormant here. Monopodia can form from the axils of the next 2-3 leaves, and only sympodia can form from the axils of the next leaves. Thus, in its development, the monopodial branch, as it were, repeats the development of the main stem.
The later the cotton plant is, the more often it forms monopodial branches of the second order. In early ripening varieties, only sympodia are usually formed as branches of the second order on monopodial branches. The total number of fruit branches on the stem is 16-18.
Leaves vary in size and shape on the same plant. The first 2-3 leaves developing on the main stem are whole, extreme, heart-shaped. The rest of the leaves on this stem and branches are lobed. The number of leaf lobes varies in different varieties and varies from 3 to 7.
On the main stem and on the growth branches, the leaves are located at each node, while on the fruiting branches – opposite each bud.
The flower is large, consists of five petals fused at the base, yellow, cream or white, depending on the variety. At the base of the petals of some types of cotton, for example, Peruvian or goose, there is a raspberry-red spot.
Stigma 3-5-lobed, large. There are many stamens. Anthers yellow, cream or orange. Calyx green, underdeveloped.
The flower has three large bracts.
Mainly self-pollinator. Cross-pollination is rare.
The fruit is a round-ovoid capsule. The size of the box depends on the number of flaps (nests), which can be 3-5. In one nest there can be from 5 to 10 seeds, in one box – 25-40 seeds.
When ripe, the box cracks at the seams, and the valves in most species open, while raw cotton is exposed, which consists of seeds covered with long (fiber) and short (down) hairs.
The mass of dry raw material in one mature box is from (2) 5 to 8 (10) g and depends on the variety and growing conditions. The mass of raw cotton accounts for 30-40%, for downs (linter) – 0.2-1.5%. Strong, well-developed bushes can produce over 100 open boxes. Opening stops at frosts of -3…-4 °C, which usually occur in the main cotton-growing regions at the end of October.
Seeds are ovoid, with a very large number of fibers – up to 7-15 thousand, 9-12 mm long, 6-8 mm wide. After removing the fibers from the seeds, they are left with a downy layer of short fibers. It accounts for 3-4% of the mass of seeds.
The seeds are covered with two shells: outer (peel) – lignified dark brown and inner – membranous. The kernel (without shell) consists of two cotyledons, rudiments of root and stalk.
Weight of 1000 seeds (80) 90-150 (160) g.
Types of cotton
The genus Cotton (Gossypium) includes 35 species, of which 5 are cultivated and 30 are wild, in addition, the genus has many forms and varieties. Two types were cultivated in the USSR:
- ordinary cotton, or Mexican (medium fiber), – Gossypium hirsutum L .;
- cotton Peruvian, or Egyptian (fine-fibered), – Gossypium peruvianum Gav. (Gossypium barbadense L.).
Herbaceous cotton (guza) – Gossypium herbaceum L. – is considered unproductive and was not grown in the USSR.
Tree-like cotton, or Indochinese – Gossypium arboreum L. and three-pointed cotton – Gossypium tricuspidatum Lam. – cultivated in tropical regions.
Cotton ordinary (medium fiber)
Cotton ordinary (medium fiber) comes from Mexico.
In culture, this semi-shrub reaches a height of 1-1.5 m. The stem is strong with developed branches, which are pubescent with one tier of hairs.
Leaves 3-5-lobed. The blades are medium, shortened triangular.
The flowers are yellow, medium in size, there is no spot on the petals of the corolla, they open well.
The boll is round, large, with a beak at the top, 4-5-leaf (3-5 nested), the surface is smooth, when ripe it opens wide, 5-11 seeds in each nest.
Seeds are covered with down, consisting of dense short hairs. The fiber is white, 30-35 mm long, 17-20 microns thick. Fiber yield 35-38 (40)%. The fiber quality is high. Metric number 4200-5500.
Cotton is the most widespread species in all cotton-growing countries. Most of the cultivated varieties belong to this species and are characterized by precocity and cold resistance.
Peruvian cotton (fine fiber)
Peruvian cotton (fine fiber) comes from Peru.
It is a semi-shrub with a height of 1 to 3 m with a large number of long, hairless branches.
The leaves are 3-5-lobed, the lobes are elongated-triangular in shape.
The flowers are large, creamy, have a crimson-red spot on the petals of the corolla.
The boll is cone-shaped, large (but smaller than that of medium fiber cotton), with an elongated top, the surface is finely pitted, when ripe it opens wide, 3-4-leaf, 5-8 seeds per nest.
Seeds are almost bare, there are almost no downs. Fiber yield 31-34%. The fiber is strong, long 39-41 mm, of the highest quality, 12-18 microns thick, metric number 6000-7500, silky, has high spinning qualities.
Fine-staple cotton is characterized by a longer growing season and high heat requirements, so its varieties are grown in the warmest countries and regions.
Technological properties of cotton fiber
Cotton fiber is an elongated cell of the epidermis of the peel, slightly twisted, curving and covered with a thin layer of wax, which gives the fiber a shine. The ratio of cell thickness to its length is 1: 1500-2000. There is a cavity inside the fiber. Usually the fiber is white, in some varieties it can be cream, greenish or brown.
The fibers of the seed down are also formed from the cells of the outer epidermis of the peel, but their length is much less.
After cracking the boxes, the fibers dry quickly, as if flattened, while acquiring the shape of a ribbon. At the same time, they twist, become spirally twisted. Sometimes there are overripe fibers with thick walls. When dried, such fibers do not twist and remain rounded in cross section. In immature or immature fibers, when dried, the walls are easily flattened, but their crimp is weak, under a microscope they look like flat ribbons. Such abnormally developed fibers are called “dead fibers” in the textile industry.
In a well-developed box, not only abnormally developed fibers can be present, but also whole voles, that is, seeds with fibers sitting on it, which are formed due to the infertility of some ovary ovules. The fiber of the fly begins to form on the day of flowering, before fertilization. But the development of unfertilized ovules and the fibers that have begun to develop on them quickly stops, and they die off. Dead ovules, when dried, are nodules with short fibers, they are called small auks.
In addition to the small uluk, when the fertilized ovules die in the phase of a more or less developed embryo, a large uluk, that is, an underdeveloped volulet, can form.
The formation of small and large uluk occurs primarily due to improper nutrition of the plant and its individual parts. Most often this is due to the low level of agricultural technology and cotton diseases, especially wilt.
Increased volatility of raw cotton is usually noted in the first cone and peripheral cones, starting from the 4th-5th. Within one box, lucidity is observed at its base and in the lower parts of the lobules.
The formation of uluk leads to a decrease in the yield of raw cotton and loss of fiber quality. In different varieties of cotton, the mass of uluk varies from 0.7 to 1.2%.
The quality of cotton fiber is characterized by various technological characteristics, the main of which are the following:
- fiber yield;
- fiber length;
- average breaking load (fiber strength);
- linear density (metric number);
- breaking length;
- fiber maturity.
Technological characteristics (properties) of the fiber determine the quality of fabrics made from it. The thinner, stronger and longer the fiber, the more valuable it is, and the higher the quality of the fabrics produced from it.
The yield of fiber is the ratio of the mass of the fiber to the mass of the raw cotton from which it is obtained and expressed as a percentage. The yield of fiber depends on the growing conditions and the location of the bolls in different tiers of the cotton bush. The output of fiber from the boxes of the lower tiers is 2-4% more than from the upper tiers.
Fiber length – the distance between the ends of the fiber in the straightened state. Expressed in millimeters.
The average breaking load (strength) of the fiber is the maximum force that the sample can withstand before breaking. It is expressed in newtons (N) or gram-forces (gs). Characterizes the amount of load that one fiber can withstand before breaking. The average breaking load of the fiber depends on the grade and is usually 0.004-0.006 N or, respectively, 4-6 gf.
The linear density (metric number) of the fiber indirectly characterizes the fineness of the cotton fiber. It corresponds to the total length of all fibers in 1 g of fiber. Expressed in meters. So, for grade 108-f, the metric number is 5550, which means: the length of all fibers of 1 g of fiber is 5550 m. The greater the linear density of the fiber, the thinner it is. The metric number of fiber of different grades varies from 5000 to 8000.
The breaking length of the fiber is a complex indicator equal to the product of the strength of the fiber and its metric number. For example, with a fiber strength of 0.0049 N (4.9 gf) with a metric number of 5200 m, its breaking length will be 25,480 m (5200 m x 4.9 gf), or 25.48 km. The breaking length is expressed in kilometers. Physically, the characteristic is the length of such an imaginary fiber, which is torn under the action of its mass. The greater this characteristic, the stronger the fibers, and, accordingly, the yarn.
The maturity of the fiber reflects the filling of the fibers with cellulose. The characteristic is determined by the thickening of the walls and the reduction of the channel. An increase in maturity leads to a change in the basic properties of the fiber: its strength, linear strength (thickness) and the degree of dyeing increase.
Technological properties of cotton fiber differ on the same bush. Thus, the fiber yield decreases from the first bolls to the next. In the box itself, in each lobule, medium bats have a longer and stronger fiber. The fibers also vary within the bat. The longest fibers are located on the chalase of the seed, while the short ones are located at the micropyle end. The degree of fiber maturity decreases from micropyle to chalase.
For industrial use, a fiber that is more uniform in terms of technological characteristics is important.
The technological properties of the fiber depend on the hereditary characteristics of the varieties, soil and climatic conditions and cultivation methods. The most variable is the length of the fiber, which changes, for example, from irrigation and fertilization.
Types of cotton fiber
The Central Research Institute of the Cotton Industry was proposed to conditionally divide the entire range of cotton fiber into seven types, for each of which the approximate demand of the cotton industry (USSR) was established.
Fiber types I, II and III are obtained from varieties of fine-staple cotton. These varieties are late ripening and are cultivated only in the southern regions of the countries of Central Asia on relatively small areas (10% of all cotton crops). From the fiber of these varieties, especially thin and strong fabrics are obtained – satin, batiste and high-quality knitwear.
Fiber IV, V, VI and VII types are produced from varieties of medium staple cotton. These varieties are characterized by greater precocity and yield. They account for about 90% of all cotton sown areas. Type IV fiber is similar in quality to type III. It is used for the production of thread, voile and other fabrics. Type V fiber (basic) is used to produce the most common fabrics – linen, dress, lining and others. Suit and fleece fabrics are made from type VI fiber, they are also mixed with wool. Type VII fiber is not planned, as its quality does not meet the requirements.
Cotton seeds begin to germinate at a temperature of 10-12 °C, but the optimum temperature is considered to be 20-25 °C. Even small frosts down to -0.5 … -1 °C lead to the death of seedlings. The minimum temperature required for the emergence of cotton seedlings is 14-15 °C, for the formation of generative organs and flowering – 20 °C.
The optimum temperature for plant development is 25 °C. A higher need for plants in heat up to 26-30 °C falls on the period of flowering and budding.
Lowering the temperature below 10-12 °C results in a short or unripened cotton fiber.
The sum of active temperatures for early-ripening varieties of cotton is 3000 °C, mid-ripening – 3400 °C, late-ripening – 4000 °C.
Cotton is considered a relatively drought-resistant plant.
Due to the deep penetrating root system, plants make good use of the water of the subsoil layers.
Cotton can be grown in areas with an annual rainfall of 350-400 mm, but under these conditions the yield is very low.
Transpiration coefficient (400) 500-600 (800).
The greatest need for moisture falls on the period of flowering – fruit formation.
Higher air humidity contributes to the production of a long and thin fiber.
It responds very well to irrigation, while the yield increases sharply. In the conditions of the USSR, cotton was cultivated only with irrigation. To obtain good yields, cotton crops must be provided with 5-8 thousand m3/ha of water.
In the countries of Central Asia and Transcaucasia, cotton is cultivated on soils characteristic of these regions: sierozems, sierozem-meadow and meadow-marsh. Light fertile soils with a pH of 7-8 are considered optimal.
Fields with a close occurrence of groundwater and with high acidity of the soil are of little use.
Cotton is able to tolerate slight salinity, especially towards the end of the growing season.
Cotton is a light-loving plant with a short day, so the orientation of the leaf blades changes during the day: during the day the blades are facing the sun, at night they fall in the shade.
Scattered light leads to a delay in the development of plants and an increase in the vegetative mass.
Direct and too bright light, together with exposure to high temperature and dry air, often reduces assimilation.
In cotton, the following vegetation phases are distinguished:
Seed germination begins with the absorption of 70-80% of their mass. First, the root starts to grow, then the curved hypocotyl knee of the stem, which brings the cotyledons to the surface of the soil.
Cotyledons appear on the soil surface under favorable conditions 5-6 days after sowing, and 8-10 days after that the first true leaf is formed. Each subsequent leaf appears after 3-5 days.
When 7-8 true leaves are formed in the axil of the 4-5 (6)-th leaf or slightly higher, the first fruit branch with a bud is formed. This moment is considered to be the beginning of the budding phase. From the moment the first leaf appears to the beginning of budding, (20) 25-30 days pass.
The formation of buds on a bush occurs in two directions: along the fruit branch (horizontally) and upward in a spiral.
In accordance with the timing of the formation of buds, flowering also takes place. The period from the development of the first bud to the opening of the first flower is 25-35 days, by this time 9-10 fruit branches are formed.
It has been established that higher yields of raw cotton can be obtained with early flowering and fruit formation.
Flowers open in the morning. The petals of the corolla at this time have a light yellow color. In the afternoon, the corolla turns red, and in the evening, withering, it closes. The next day, the corolla turns purple and falls off.
The opening of flowers in the bush occurs from the bottom up, in groups or cones. The first cone includes the first three flowers, which are located on the three lower branches closer to the stem. The second cone consists of the second flowers of the first three branches and the first flowers on the 4th, 5th and 6th branches. The third cone consists of flowers of the 1st, 2nd and 3rd branches, the second flowers of the 4th, 5th and 6th branches and the first flowers of the 7th, 8th and 9th branches, etc.
Flowering in an ascending line, that is, from branch to branch, occurs at intervals of approximately 2-3 days (short queue), while along the same branch – at intervals of 5-7 days (long queue). The duration of short and long flowering lines depends on the varietal characteristics of cotton, growing temperature, agricultural technology, etc.
The period from the flowering phase to the opening of the boxes is (45) 50-65 days. The external formation of the box ends 25-35 days after fertilization, but for the maturation of seeds and the formation of fiber, another 25-30 days are needed, during which nutrients are reutilized from the vegetative organs of the plant.
The opening of boxes on one bush often stretches up to 2 months. Clear and warm weather accelerates this phase and, conversely, cool weather slows it down.
The entire period from sowing to the opening of the first box, that is, the beginning of the ripening phase, is:
- for Soviet varieties of medium staple cotton – 130-140 days;
- for Soviet varieties of fine-staple cotton – 145-160 days.
The duration of interphase periods for the most common group of mid-ripening varieties is (Vavilov):
- from sowing to germination 14-16 days;
- from germination to the beginning of the formation of the basket 37-43 days;
- from the beginning of the formation of the basket to flowering 27-30 days (according to other sources, 50-60 days after germination, Kolomeichenko);
- from flowering to ripening 44-50 days.
The total duration of vegetation for this group of sunflower varieties is 120-140 days. Depending on the variety or hybrid and growing conditions, seeds may ripen in (70) 80-120 (140) days after germination.
In the first period of its development (2-3 pairs of leaves), sunflower plants develop relatively slowly. At this time, they are easily drowned out by weeds . However, then the growth accelerates and reaches its maximum, which is 3-5 cm per day, in the period from the formation of the basket to the beginning of flowering. In the flowering phase, growth in height slows down and stops completely by the end of flowering.
The beginning of the formation of the basket in early maturing varieties of sunflower in the conditions of the South-East of Russia falls on 2 pairs of leaves, in mid-season – at 3-5 pairs. The laying of the basket in mid-season varieties begins in the conditions of the Krasnodar Territory with 5 pairs of leaves.
Flowering of one basket lasts 8-10 days, and growth – until it turns yellow. The basket grows most intensively within 8-10 days after the end of flowering. The filling of achenes lasts for 32-42 days from the time of their fertilization.
Simultaneously with the growth of the plant in height and the formation of a basket, dry matter begins to accumulate. During this period, this process is slow, and by the beginning of the formation of the basket, sunflower accumulates only 15% of dry matter. By the beginning of the flowering phase, the amount of dry matter in the plant reaches 50%, and it continues to increase until the beginning of the filling of seeds, but is also spent mainly on the formation of the basket.
Physiological ripening of achenes after harvesting can be 10-50 days.
Cotton-alfalfa crop rotations are widespread in cotton-growing regions. The main ones are 8-, 9- and 10-field, in which 2-3 fields are occupied by alfalfa and 5-7 fields by cotton. The share of cotton in cotton-alfalfa crop rotations accounts for 60-70%.
For cotton-alfalfa crop rotations, the designation is accepted by numbers, for example, 2:5, 2:6, 3:7, etc., the first digit in which means the number of alfalfa fields, the second – cotton.
Depending on soil conditions, the following crop rotation schemes are recommended:
- non-saline dark typical serozems and meadow soils – 3:9, 3:7, 2:8;
- uninhabited and slightly saline light gray soils and meadow soils – 3:7, 3:6, 2:7;
- moderately saline gray soils and meadow soils – 3:6;
- lands subject to severe salinization – 3:5:1, 3:6:1, where 1 denotes an reclamation field.
In the first field of cotton-alfalfa crop rotations, alfalfa is usually sown under the cover of cereal crops (barley) or together with corn, jugar or Sudanese grass for silage. In the second and third years, alfalfa grows as a single crop, and after plowing, cotton is sown, which occupies the field for 6-7 years in a row.
In diagrams 3:5:1 and 3:6:1, the last field, marked 1, is ameliorative. Before sowing alfalfa, leveling, washing, etc. are carried out on it.
Alfalfa is important as a precursor to cotton in soils subject to salinity. Due to the well-developed above-ground mass, it shades the soil surface, significantly reducing the evaporation of moisture and thereby preventing the movement of salts from the lower layers of the soil to the upper ones. When irrigated, large amounts of salt are washed into deeper horizons.
Alfalfa is also of great importance in wilt-infested fields. The causative agents of the disease do not develop on the roots of alfalfa and for the most part die without finding the substrate they need. According to the data of experimental institutions, when using cotton varieties with low resistance to wilt, their susceptibility in the first 3 years after plowing alfalfa is no more than 20-35%, while when sown on old arable land, the same varieties of cotton already in the first year are more than 90% afflicted with wilt.
Alfalfa helps to improve the physical properties of the soil, reduces subsequent water consumption for irrigation and activates the activity of soil microflora. Alfalfa of the third year of use leaves up to 15-18 t/ha of organic matter.
Other crop rotations can be used, which are developed taking into account the intensification of cotton growing and more efficient use of irrigated land. In addition to alfalfa, sorghum, corn, legumes (mung bean, peas, soybeans, sweet clover) can be good cotton precursors.
Sowing green manure crops, such as rape, mustard, vetch, peas, etc., is important for increasing soil fertility and productivity. Sowing green manure is carried out after harvesting corn or under cotton in the 4-6th year after plowing alfalfa.
The use of cotton monoculture, which is practiced in some countries, is not recommended, as this is associated with a large annual removal of nutrients from the soil and adverse mechanical effects associated with multiple irrigations and inter-row treatments. With permanent cotton crops, fertility decreases, the arable layer is sprayed, the concentration of harmful salts increases and the level of groundwater rises, the structure and phytosanitary condition of soils deteriorate.
Cotton can be grown in one place of crop rotation for 4-7 years in a row only in case of systematic fertilization, systematic control of weeds, pests and diseases.
Cotton crop rotations
Cotton occupies large areas in areas where irrigated agriculture is used, in the Central Asian and Transcaucasian countries. To increase the share of cotton in special crop rotations, repeated crops are introduced for 3-4 or more years in a row.
In the Central Asian countries, nine- and ten-field cotton-alfalfa crop rotations are used. On cultivated highly fertile soils, the following alternation schemes have been introduced:
- 1-2 – alfalfa, 4-10 – cotton;
- 1-2 – alfalfa, 3-6 – cotton, 7 – corn for grain, 8-10 – cotton;
- 1 – alfalfa, 2-4 – cotton, 5 – corn for grain, 6-10 – cotton.
In these crop rotations, cotton accounts for 70, 75 and 80% of the area.
On poorly cultivated, but relatively fertile, for example, slightly and moderately saline soils, cotton crop rotations are recommended:
- 1-2 – alfalfa, 3-6 – cotton, 7 – corn for grain, 8-10 – cotton;
- 1-2 – alfalfa, 3-6 – cotton, corn for grain with stubble sowing of rapeseed or green manure, 8-10 – cotton;
- 1-3 – alfalfa, 4-7 – cotton, 8 – corn for grain, 9-10 – cotton. In these crop rotations, cotton occupies 75%, 70% and 66.7%, respectively.
To improve the efficiency of cotton-alfalfa crop rotations, alfalfa crops are combined with Sudanese grass or corn, autumn and winter intermediate crops are introduced, harvested in spring for green fodder or plowed under cotton. The best intermediate crops are winter vetch, winter barley or rye, wintering peas, shabdar, mustard, rapeseed, etc.
Intermediate crops, as a rule, are used for 3-5 years of cotton cultivation, after alfalfa plowing.
It should be noted that in the countries of Central Asia, when growing cotton in a crop rotation to produce 100 kg of raw cotton, 24% less labor is spent than with permanent cultivation, fertilizers – 34% less, irrigation water – 20% less.
Cotton is one of the crops that consume a large amount of nutrients. For the formation of 100 kg of raw cotton with good development of plants, cotton consumes 5 kg of nitrogen, 1.7 kg of phosphorus and 5 kg of potassium.
Providing cotton plants with an optimal nutritional regimen can reduce the growing season by 5-10 days, increase yields and plant resistance to diseases. The lack of nutrients in the initial phases leads to a slowdown in the development of the root system, the fall of buds and ovaries. Lack of nutrition in the later phases of the growing season reduces the rate of formation of fruit branches, buds and delays flowering.
Absorption of nutrients during the growing season is uneven:
- before budding, 3-5% of nitrogen and phosphorus are consumed from the total amount of these substances needed throughout the growing season, and 2-3% of potassium;
- from the beginning of budding to flowering – 25-30% nitrogen and phosphorus, up to 15-20% potassium;
- during flowering and fruit formation, which coincide with the most intensive plant growth, – 65-70% nitrogen and phosphorus, 75-80% potassium.
In the first phases of development, plants are most sensitive to phosphorus deficiency.
Intensive growing technologies involve providing cotton with an optimal nutritional regime during the growing season and increasing the efficiency of applying mineral fertilizers.
The fertilizer system includes the application of organic and mineral fertilizers. However, it should be taken into account that cotton, which is placed in the crop rotation after plowing alfalfa, makes good use of the nutrients accumulated by it and experiences less need for organic fertilizers than cotton, which is grown in fields more distant in time from alfalfa. As a rule, within 2-3 years after alfalfa, organic fertilizers are not used for cotton, but mineral fertilizers are applied.
The norms and methods of applying mineral fertilizers depend on the type of soil, the form of fertilizer and the placement of cotton in the crop rotation. In cotton-alfalfa crop rotations on gray soils in the first two years after plowing alfalfa, nitrogen fertilizers, as a rule, are applied in smaller quantities than phosphorus ones. The ratio of nitrogen and phosphorus in the annual norm of mineral fertilizers is 1:1.3 or 1:1.5. In subsequent years, for cotton in the same fields, the application rates of nitrogen fertilizers are increased, the ratio between nitrogen and phosphorus is set to 1 : 0.8. This ratio reduces the incidence of cotton wilt. In addition, it is favorable for cotton with an increase in nitrogen doses up to 240-300 kg/ha.
On meadow and meadow-marsh soils with a high nitrogen content, it is advisable to set the ratio N:P 1:1.5.
The norms recommended by SoyuzNIHI for applying mineral fertilizers for cotton on gray soils with a planned yield of raw cotton of 3.5-4.0 t/ha are N 270-300, P 190-210, K 120 kg/ha. In the third year after plowing alfalfa into cotton fields for autumn plowing, it is recommended to apply at least 10-15 t/ha of manure.
With industrial cultivation technology, fractional fertilization is recommended:
- under deep plowing;
- before sowing;
- when sowing;
- during the growing season.
When distributing fertilizers according to the timing of application, it is necessary to take into account the supply of nutrients to plants during the growing season. 25% of the total rate of nitrogen fertilizers should be applied before sowing and 75% – at sowing and in top dressing. With two top dressings, nitrogen is introduced in the phases of the beginning of budding and the beginning of flowering, with three, it is additionally applied in the phase of 3-4 true leaves.
At the first (early) top dressing, fertilizers are applied at a distance of 15-16 cm from the row to a depth of 12-14 cm. When top dressing in the budding phase – at a distance of 20-22 cm from the row to a depth of 3-4 cm below the bottom of the furrow. The third dressing is applied in the middle of the row spacing.
For fertilization, cultivators-plant feeders КРХ-4 are used with row spacing of 60 cm or cultivators-plant feeders КРХ-3.6 with row spacing of 90 cm.
When using increased nitrogen rates, approximately 1/3 of them are applied before sowing, the rest is used as top dressing during the budding and flowering period.
Lack of nitrogen leads to poor plant development and greater wilt damage.
Phosphorus is recommended to be applied for plowing at the rate of 60-70% of the annual norm, the rest of the amount – simultaneously with sowing and in top dressing.
A good effect is given by row application when sowing granulated superphosphate in the amount of 15-20 kg/ha P2O5. Phosphate fertilizers are added to top dressing together with nitrogen fertilizers in the cotton budding phase.
Potash fertilizers are more effective on light and non-saline soils with a high standing water table. The recommended rate is 80-100 kg/ha of K2O. Potash fertilizers are usually applied in equal proportions for plowing and top dressing, which are also carried out at the beginning of budding.
It should be borne in mind that the intensive use of nitrogen and phosphorus fertilizers increases the need for cotton in potassium nutrition. A lack of potassium leads to a violation of carbohydrate metabolism in plants, the conditions for the formation of bolls worsen, especially the outer cones of flowering, the main one becomes thinner and prone to lodging. In addition, the technological properties of the fiber are significantly reduced: metric number, strength and maturity.
According to the experimental data of SoyuzNIKhI, the most optimal ratio of nitrogen and potassium is 1:0.5. With the introduction of increased norms of nitrogen and in areas infected with wilt, the ratio shifts to 1:0.7 and even up to 1:1.
Potash fertilizers are a necessary component of fertilizer mixtures for all types of soils, except for saline ones, in which the potassium content is quite high, and with a planned raw cotton yield of more than 2.5 t/ha.
Sulfur, calcium and magnesium are important in the development of cotton.
The lack of sulfur, especially on alkaline soils, leads to stunting of plants, the leaves become yellow in color. A good result is the introduction of ammonium sulfate in the initial period of plant development.
The soils of the main cotton-growing regions of the countries of Central Asia, as a rule, contain a sufficient amount of calcium and magnesium. For these areas, the introduction of microfertilizers is effective: boron, manganese, copper, zinc, molybdenum or, accordingly, macrofertilizers enriched with these microelements. Microfertilizers are applied directly to the soil or used to soak seeds. In the latter case, the concentration of microelement salts in the soaking solution should be 0.02-0.04%, and the ratio of seeds and solution should be 2:1, soaking time should be 12 hours. basic fertilizers.
For gray soils, it is recommended to apply 0.5-1 kg/ha of a.i. boron, for meadow-marsh soils – 1.5-2 kg/ha.
Recommended norms of manganese – no more than 18 kg/ha, copper – 2-3 kg/ha, zinc – 3-4 kg/ha. Molybdenum is added as part of molybdenized superphosphate.
Autumn tillage for cotton depends on the predecessor.
When placing cotton after alfalfa, plowing is carried out in the second half of October with plows with skimmers to a depth of at least 28-30 cm. Before plowing, peeling is performed to a depth of 5-6 cm to cut the roots of alfalfa and prevent its growth in spring.
In fields littered with pigs (Cynodon), huma (Sorghum halepense), sytsia (Cyperus) and other rhizomatous weeds, after harvesting, guza-pai loosen the soil to a depth of 16-18 cm with plows with removed mouldboards, combing the rhizomes of weeds with mounted harrows, or chisels. Combed rhizomes are removed from the field. Before loosening, heavily dried soils are watered with a water flow rate of 600-800 m3/ha.
When placing cotton after cotton, the field is first freed from stems (guza-pai) and the irrigation furrows are leveled. Uprooting should be completed no later than the first decade of November. The uprooted stems are removed from the field. Especially thorough harvesting of goose-pai should be carried out in fields infected with wilt. In fields not charged with wilt, cotton stalks can be chopped and plowed.
When placing cotton after grain crops, after harvesting, fine stubble peeling is carried out to a depth of 5-8 cm, for better weed germination, it is recommended to carry out pre-arable watering. After the appearance of weeds, surface tillage is carried out. The optimal time for autumn plowing is August-September.
When stubble crops of annual crops are harvested, watering is done, after which deep plowing is carried out with plows with skimmers.
Two-tier plowing to a depth of 30-40 cm on fertile soils and combined plowing with soil deepening, in which a 20-25-cm soil layer is cultivated with a layer turnover, and the lower one is loosened (on saline lands with a compacted subarable horizon), have proven themselves well. In this case, when placing cotton after alfalfa, peeling is also carried out before plowing. For two-tier and combined processing, a ПД-4-35 plow is used.
Early spring and pre-sowing tillage differ depending on the state of arable land in each area. As a rule, tillage in the spring begins with two-track harrowing of the fallow in one pass of the tractor. However, in fields where leaching irrigation was carried out, harrowing in early spring may be ineffective due to the strong compaction of the topsoil. Instead of harrowing on such soils, chiselling or disking is carried out with simultaneous harrowing.
For 5-10 days or immediately before sowing on non-saline soils, harrowing is carried out with thinning. On fields clear of weeds, it can be limited to leveling the surface with the help of a planner or small, on medium and heavily weedy lands – cultivators or chisels with flat-cutting working bodies coupled with harrows and small.
To meet the demand of cotton for water, the soil moisture in the root layer should be more than 65-70% of lowest soil moisture capacity, which is achieved by the use of irrigation. When soil moisture is less than 65% of lowest soil moisture capacity, the yield decreases, while at moisture content above 80% of lowest soil moisture capacity, branches grow.
Irrigations are spare (moisture charging, in some cases they are also flushing) and vegetative. Spare irrigation improves the physical condition of the soil, helps remove harmful salts from the upper layers of the soil, creates a moisture reserve for the normal development of cotton, and helps reduce the number of pests.
Spare, or water-charging, irrigation in the autumn-winter period serves to accumulate moisture in the soil, ensure seed germination and the emergence of cotton seedlings. They are carried out after harvesting cotton along furrows, strips and large checks. Also, watering is carried out in the winter, before the onset of severe frosts. For these purposes, furrows are cut along which water moistens the soil. On light soils and with deep groundwater, spare irrigation is done in early spring.
The reserve irrigation rate in winter is 1000-1500 m3/ha, spring – 800-900 m3/ha. On saline soils, reserve irrigations are also leaching, the irrigation rate in this case reaches 3000 m3/ha.
In spring, to preserve moisture, harrowing is carried out in 1-2 tracks or continuous chiselling is used to a depth of 6-8 cm.
Vegetative irrigation is done during the growing season of cotton: before the flowering phase, during flowering and during the ripening period. For example, two waterings are carried out – before flowering, three or four – during flowering, and one – during the ripening period. Such distribution of irrigations is conditionally designated 2-3-1 or 2-4-1 and is called the irrigation scheme. Also, irrigation can be carried out with a decrease in soil moisture to 65-75% of lowest soil moisture capacity for a stable supply of plants with water.
The total number of vegetative irrigations, depending on the type of soil and the occurrence of groundwater, ranges from 2 to 12. Based on numerous studies, SoyuzNIHI developed approximate irrigation norms for medium-fiber cotton varieties on old arable lands.
|Thin soils with close occurrence of pebbles and sand and deep groundwater|
|Gray soils with groundwater at a depth of 3–4 m or more|
|Gray-meadow soils with groundwater at a depth of 2–3 m|
|Meadow soils with groundwater at a depth of 1–2 m|
|Meadow-marsh soils with groundwater at a depth of up to 1 m|
For old-arable fields with deep groundwater during furrow irrigation, the following norms are recommended.
On heavy soils, watering rates are increased, but watering is carried out less frequently.
The irrigation rate for plowed alfalfa is increased by 100-300 m3/ha.
Starting cotton irrigation too early is not recommended. With early and frequent watering, its root system develops in the upper horizons of the soil and therefore does not adequately supply water to the above-ground part of the plants during flowering and maturation. In addition, excess moisture in the early growing season contributes to the abundant development of the vegetative mass at the expense of generative organs.
However, it is important to carry out the first watering in a timely manner, as a delay can greatly delay the development of cotton plants. Depending on the condition of the soil and seedlings, the first watering is carried out 2-3 weeks after emergence. To ensure good growth of cotton, about 2-3 waterings should be carried out before flowering (by early June). Intensive watering in August and September promotes intensive growth of vegetative organs, which leads to a delay in the maturation of bolls.
The timing of irrigation is determined by the state of the plants: before flowering – by the darkening of the leaves and their slight wilting at noon, while during the flowering period – by the position of the upper flower. Properly watered cotton at the beginning of flowering has 8-9 fruit non-flowering branches above the last flower, at the end of July – 6-7 branches, at the end of August – no more than 4. However, the most objective indicator of establishing the timing of irrigation is soil moisture, which should not fall below 70% of lowest soil moisture capacity. In addition, a method has been developed for determining the timing of irrigation according to physiological indicators: the sucking power of cells and the concentration of cell sap.
Usually cotton is irrigated along the furrows. Furrows for the first irrigation are cut to a depth of 16-18 cm, for subsequent irrigation – up to 20 cm. The length of the furrows is determined depending on the permeability of the soil and the slope of the bottom of the furrow. With medium slopes (from 0.001 to 0.005) and low water permeability of the soil, furrows are made 120-150 m long, with an average – 100-120, with strong water permeability – 90-100 m. The strength of the water jet with small slopes should be up to 1-1, 2 l/s, for large – 0.1-0.3 l/s. For furrow irrigation, flexible polyethylene siphon tubes are usually used.
When using industrial technology for cultivating cotton for irrigation, instead of cutting furrows, rigid and semi-rigid polyethylene irrigation pipelines, flexible hoses, siphon tubes, machines of the ППА-165У type or sprinklers (ДДА-100М, Volzhanka, Fregat, etc.) .
When using pipelines, water is supplied to the fields through concrete trays, fixed at a certain height above the soil surface to provide water pressure. Water is taken into pipelines with the help of hydrants. The use of pipelines and sprinkler systems allows you to ration the water supply, use it economically and automate the irrigation process.
The sprinkling method allows to reduce water consumption by 2-4 times, while there is no need to cut furrows and level the field. In addition, sprinklers allow spraying of plants to control pests and diseases.
Subsoil irrigation is carried out using porous pipes or perforated hoses, which are placed at a depth of 40-50 cm in rows of 1-1.5 m. During the growing season, water pressure is maintained in them, thereby ensuring sufficient soil moisture.
The combination of furrow irrigation and sprinkler irrigation is economically more profitable than conventional furrow irrigation.
For sowing, cotton seeds with a purity of at least 97% and a germination rate of at least 85% are used.
The seeds obtained from the raw material of the first opened bolls are considered the best in terms of sowing qualities. According to the experiments carried out in Uzbekistan, the field germination of seeds of the first harvest was 94%, while the last pre-frost harvest was less than 50%. So, when sowing seeds from bolls ripened on September 4-10, 3.9 t/ha of raw cotton was obtained, and from bolls ripened on September 29 – October 9 – 2.3 t/ha.
Raw cotton for seeds at ginneries is subjected to primary processing, including ginning, linting and deletion. In addition, the preparation of seed material includes calibration, dressing and pelleting in the presence of pubescence.
Ginning is the process of completely separating the fiber from the seeds. Lintering is the process of partially separating the down from the seeds. During ginning and linting, cotton seeds can be mechanically damaged.
Delintering is the process of completely removing the down from the seed. Delintering can be mechanical, chemical (impact on the seeds of acids) and aerochemical (exposure to gaseous reagents). The aerochemical method is the most interesting, since it does not damage the seeds and does not reduce their sowing qualities. In addition, under the action of gaseous reagents, the seeds are disinfected from gommosis and other diseases, thus eliminating the need for the use of chemical means of protection.
The Research Institute of Plant Protection (Tashkent) recommends coating bare and pubescent seeds, which consists in enveloping the seeds with a mixture of nutrients, protective and stimulating substances. Dragee seeds are more free-flowing and protected from diseases and rotting in the soil.
Hairy seeds can also be used for sowing. From gommosis and root rot, they are treated with 65% feptiuram at the rate of 10-12 kg/t of seeds. Before sowing, such seeds are moistened with water in three doses (600 l/t of seeds), for which they are scattered on a cemented site with a layer of 20-30 cm, moistened and shoveled 2-3 times with an interval of 4-5 hours. Moistened seeds are collected in heaps and covered with a tarpaulin or film for languishing. At early terms of sowing in moist soil, languor is completed in 8-12 hours, at later dates in 20-24 hours.
Bare seeds are sown dry.
It is not allowed to moisten pubescent pelleted seeds.
Cotton sowing is started when the soil warms up at a depth of 10 cm to 12 (13) °C and the average air temperature (12) is 13-15 °C. As a rule, in the southern regions of cotton growing, such conditions are created in the third decade of March, in the middle regions – at the end of March – early April, in the northern regions – in the second decade of April.
Too early sowing of cotton leads to a lengthening of the growing season, while too late sowing – to a delay in the opening of the boxes and a decrease in the pre-frost harvest of raw cotton.
Sowing dates are recommended to be specified taking into account soil, hydrological and weather conditions. Sowing usually begins on light, well-warmed lands of the southern slopes. The duration of sowing is not recommended to stretch.
When sowing pubescent seeds, ordinary (tape) or often nested sowing methods are used. Often preference is given to the wide-row sowing method, which allows for better warming of plants, a decrease in the incidence of wilt, facilitates inter-row cultivation, irrigation, mechanized harvesting, speeds up the ripening of boxes by 4-7 days, reduces labor costs and obtains an increase in yield up to 0.3-0.5 t/ha.
With the industrial technology of growing cotton, sowing is carried out with bare seeds with the exact sowing of a given number of seeds in each nest, thus obtaining a given plant density without thinning.
In cotton growing, the row spacing is usually 60 and 90 cm with distances between nests of 10-30 (60) cm. When using the dotted sowing method, seeds are sown every 10 cm, 1-2 per nest. Such a scheme provides the most uniform distribution of plants and a given density of standing – 100-150 thousand plants per 1 ha without thinning seedlings.
A relatively new method of sowing is sowing on removed ridges (ridge method). It is carried out with the help of a bed maker or hiller, with which furrows are cut and ridges 20-30 cm high are formed. With a special device – a comber – when sowing, the top dry layer of soil is removed and the seeds are planted in loose, moist, well-heated soil. This method allows you to get early and uniform shoots.
With industrial technology, sowing is carried out by 4-row seeders СТХ-4Г, equipped with a device for applying herbicides and sowing along the ridges. Seeders СХУ-4 and СХУ-8 are also used.
The sowing rate of cotton seeds depends on the row spacing, nest placement patterns, the quality of the seed material, and the conditions during the sowing period. The norm varies from 35-40 kg/ha to 70-80 kg/ha (Vavilov). According to other recommendations, the seeding rate for bare seeds is 20-25 kg/ha, for pubescent seeds – 90-100 kg/ha.
To obtain a high yield of raw cotton, the plant density should be 100-110 thousand/ha, on thin and sandy soils – up to 130-150 thousand/ha.
The seeding rate is increased by 10-15% when sowing on fields infected with wilt, as well as on saline soils.
On gray soils, the sowing depth is 4-5 cm, on meadow-marsh soils – 3-4 cm.
With early sowing in moist soil, the embedment depth should be 3-4 cm, and as the soil warms up and dries, the depth is increased to 4-5 cm.
Bare seeds are recommended to be sown 1 cm smaller than pubescent ones, but always in moist soil.
Care for cotton sowing before germination consists in destroying the soil crust with the help of light harrows or rotary hoes.
When the topsoil dries up, it is recommended to carry out recharge irrigation with a consumption rate of 600 m3/ha. For its implementation, irrigation furrows are cut during sowing.
To ensure optimal plant density, thinning is carried out no later than the phase of formation of the first (second) true leaf. Depending on the agricultural technologies used, soil fertility, varietal characteristics and sowing method, the sowing density should be in the range from 70 to 160 thousand plants per 1 ha. When using precision seeding and under optimal conditions, a given planting density can be obtained without the use of thinning.
When shoots appear, inter-row tillage is started. Depending on the purpose of each treatment, various working bodies can be used on cultivators: shaving or flat-cutting paws, hillers, rotary sprockets, etc.
The first longitudinal cultivation is carried out to a depth of 6-8 cm with simultaneous loosening of protective zones, the width of which during this period of plant development is 10-12 cm on each side of the row. The second cultivation is recommended to be done before the first vegetation watering. Subsequent cultivation – 2-3 days after each watering with some drying of the soil.
To loosen the row spacing, the extreme working bodies of the cultivators are set to a depth of 8-10 cm, the middle ones – by 12-15 cm. Starting from 2-3 cultivation, the width of the protective zones is increased to 16 cm.
The number of treatments between rows after irrigation is determined by the number of irrigations during the growing season and the onset of complete closure of cotton rows, which usually occurs in the second half of the flowering phase.
Weed control with the use of herbicides is of great importance in the care of cotton crops. Against annual weeds, a continuous pre-sowing application of treflan is used, followed by its incorporation by harrowing or disking. To apply the herbicide, sprayers of the type ОВХ-14 are used. The application rate of treflan is 4 kg/ha on light soils, 6 kg/ha on medium and heavy soils. The flow rate of the working fluid is 400 l/ha.
To control weeds in cotton rows during sowing, the herbicide Kotoran is applied in strips 20-30 cm wide at a rate of 0.8-1.75 kg/ha and a working solution flow rate of 200 l/ha. For these purposes, devices ПГС-2.45 or УГС-4 can be used, which are aggregated with cotton seeders.
The use of chemical control agents causes the death of 93-96% of weeds, accelerates the ripening of cotton and increases the collection of pre-frost raw cotton.
In the care of cotton crops, the chasing technique is important, which consists in removing the growth points of the main stem and monopodial branches. Chasing helps prevent the fall of buds and ovaries, as it creates more favorable conditions for nutrition and lighting for them. According to the experiments of SoyuzNIKhI, chasing cotton increases the yield of raw cotton up to 1.1 t/ha.
The efficiency of minting cotton depends on the duration. With too early terms of its implementation, the yield decreases. First of all, minting should be carried out from July 15 to July 25 in areas with a strong development of plants with the formation of 17-18 fruit branches on them. On medium-developed plants, chasing is carried out in the presence of 15-16 fruit branches no later than August 5. On underdeveloped plants – with the formation of 12-14 fruit branches no later than August 10 (Vavilov). According to other recommendations, minting should be carried out when 12-16 sympodial branches are formed on plants for medium-fiber varieties and 14-20 branches for fine-fiber varieties.
Chasing can be carried out using the 4ВХ-4 device, which is designed to cut the tops of cotton plants. It is hung on a tractor with a КРХ-4 cultivator.
Mechanized coinage is carried out in the second half of July – early August in two terms. The first minting begins when 40-50% of the plants have 15 or more fruit branches, the second – 7-10 days after the first. In the second pass, the tops of the plants lagging behind in growth and development are cut off. In this case, the knives of the device for chasing are set 3-5 cm higher than during the first chasing. Usually, chasing is recommended to be combined with cutting furrows for irrigation or loosening row spacings.
According to the calculations of research institutions, the costs of double mechanized chasing are 3.7 times less than those of manual chasing.
Wilt and Fusarium wilt are considered the most harmful diseases for cotton. To combat them, approved chemical plant protection products are used.
The maturation of cotton bolls does not occur simultaneously and lasts about two (three) months (until frost). Therefore, the harvesting of raw cotton is carried out as the bolls open: with mechanized harvesting – in three steps, two of which are using cotton pickers and one – chicken harvesters; with manual cleaning – in four steps.
The vertical-spindle cotton pickers developed in the Soviet era did not allow the harvesting of raw cotton from plants with a large number of green leaves. Therefore, the technology of mechanized harvesting of such crops involves defoliation before harvesting – the treatment of cotton with chemicals to quickly fall off the leaves.
As a defoliant, spraying with magnesium chlorate is used, in the calculation for medium-staple cotton – 8-12 kg/ha, fine-staple – 13-15 kg/ha. Instead of magnesium chlorate, calcium chlorate-chloride can be used, at a rate of 20-30 kg/ha.
Relatively new preparations include Hydrel, with a recommended application rate of 6-8 kg/ha for medium staple cotton or mixed with butyl-caitax in formulations from 3+3 kg/ha to 5+5 kg/ha. UDM-type defoliants are based on magnesium chlorate mixed with nitrogen fertilizers. Spraying of crops is carried out from airplanes or helicopters, when most plants open 2 bolls in the northern regions of cotton growing, 2-3 bolls in the central regions and 4-5 bolls in the southern regions (Vavilov). According to other recommendations, defoliation is recommended when opening 3-4 bolls on medium-staple cotton plants or 4-5 on fine-staple cotton (Kolomeichenko). Falling leaves after treatment occurs on the 8-10th day.
The use of the OVKh-28 ground sprayer makes it possible to reduce the negative impact of chemicals on the environment and increase the efficiency of defoliants.
With insufficient effect from defoliation, they resort to desiccation, that is, drying plants on the vine. As desiccants, magnesium chlorate is used at the rate of 25-30 kg/ha or calcium chlorate-chloride – 45-50 kg/ha. Desiccation makes it possible to speed up the maturation of the bolls remaining after the first collections in years with adverse weather conditions, as well as to clear headlands when using a mechanized harvesting method.
For harvesting raw cotton, two-row vertical-spindle cotton pickers ХВН-1.2А can be used on crops with a row spacing of 60 cm, ХНП-1.8 – on crops with a row spacing of 90 cm, four-row cotton pickers 14ХВ-2.4А on row spacings of 60 cm. harvesting of seed raw cotton, machines for tiered collection of seed raw cotton ХВА-1.2 (60 cm) or ХВБ-1.8 (90 cm) can be used.
To collect kurak, that is, boxes that have not opened after frost, they are carried out with chicken harvesters СКО-2.4 with row spacings of 60 cm or СКО-3.6 and СКО-5.4 with row spacings of 90 cm.
Mechanized harvesting of raw cotton is carried out in fields cleared of weeds and when 75-80% of the leaves of cotton plants fall off after defoliation. The collection is carried out in three stages:
- the first harvest – by cotton-picking spindle machines when opening no more than 50-60% of the boxes;
- the second collection – by the same machines when opening another 20-30 (35)% of the boxes, which usually occurs 12-15 days after the first collection;
- the third collection – chicken harvesters, which remove the remaining boxes on the bushes.
Fallen raw cotton after the first and second harvests is picked up from the ground by mechanical pick-ups ПХ-2.4 (at 60 cm row spacing) or ПХС-3.6 (at 90 cm row spacing).
Raw cotton is unloaded from the bins of cotton pickers into bulk vehicles and delivered to the procurement point. Before being sent to the procurement point, raw cotton must be dried to a moisture content of 8-12% and cleaned.
Manual harvesting of raw cotton is carried out in four (in some cases up to eight) receptions on fields clean from weeds. The first collection is started when the plant has an average of 3-4 well-opened bolls. At the second harvest, the selection of raw cotton from well-opened bolls is completed until the end of the growing season of cotton plants. When carrying out the first and second collections, the selection of unripe raw cotton from incompletely opened bolls or the collection of raw cotton in case of heavy dew in the fields is not allowed.
At the third and fourth collections, the raw cotton remaining on the bushes is sampled.
Hand-picked raw cotton, depending on the strength of the fiber, is divided into four grades.
The mechanized method of picking raw cotton compared to manual picking makes it possible to reduce labor costs by 3-4 times and to reduce the cost of raw cotton by 2 times.
Harvesting of stalks (guza-pan) of cotton after harvesting all the cotton is carried out by rooters КВ-4А and КВ-3.6А.
The use of industrial technologies, for example, at the state farm. The five-year plan of Uzbekistan made it possible to reduce labor costs to 459 man-hours per hectare, which is 2 times less than the average for other farms. The yield of raw cotton at the same time reached 4 t/ha, production costs – 11.5 man-hours/100 kg, which is 3 times less than in other farms.
Crop production / P.P. Vavilov, V.V. Gritsenko, V.S. Kuznetsov and others; Ed. P.P. Vavilov. – 5th ed., revised. and additional – M.: Agropromizdat, 1986. – 512 p.: ill. – (Textbook and textbooks for higher educational institutions).
V.V. Kolomeichenko. Crop production / Textbook. — M.: Agrobusinesscenter, 2007. — 600 p. ISBN 978-5-902792-11-6.
Fundamentals of agricultural production technology. Agriculture and crop production. Ed. V.S. Niklyaev. – M .: “Epic”, 2000. – 555 p.