In this essay we will discuss about:- 1. Origin and Distribution of Cotton 2. Area and Production of Cotton 3. Climate, Soils and Tillage 4. Seeds and Seeding 5. Nutrient Management 6. Cotton Based Cropping System 7. Water Management 8. Weed Management 9. Harvesting, Processing and Quality.
Contents:
- Origin and Distribution of Cotton
- Area and Production of Cotton
- Climate, Soils and Tillage of Cotton
- Seeds and Seeding of Cotton
- Nutrient Management in Cotton
- Cotton Based Cropping Systems
- Water Management for Cotton
- Weed Management for Cotton
- Harvesting, Processing and Quality of Cotton
1. Origin and Distribution of Cotton:
India is considered the home of arboreums. G.herbaceum might have been introduced into western India from Arabia, Persia and Baluchistan and from race acerifolium. The barbadense seems to have evolved in South America as a wild species, which later evolved into cultivated species.
The native perennial barbodense has given rise to Tanguis cottons, which are ratooned and represent 90 per cent of the Peruvian crop. Cytological studies indicate that all the four species are monophyletic (evolved from a single interspecific hybrid combination). G. hirsutum must have moved from the center of diversity near the border of Mexico and Guatemala.
Cotton is the most important vegetable fibre cultivated in about 60 countries in the world. The countries such as Russia, USA, China, India, Brazil, Pakistan, Turkey, Egypt, Mexico and Sudan account for about 85 per cent of the total cotton production.
Cotton, the king of fibres, is an industrial commodity of worldwide importance. It is one of the most important commercial crops playing a key role in economic and social affairs of the world. The Arabic word qutun or kutun has given rise to English word cotton. Similarly, it is kateon in Dutch, colon in French, cottone in Italian and algodon in Spanish.
Despite the recent setbacks, cotton continues to remain the backbone of Indian rural economy, particularly in dryland areas. Besides being a monetary spinner, it is an employment generator as its cultivation provides 200 man- days ha-1 of employment. About 60 M people earn their livelihood through its cultivation or trade and processing.
The current crisis in cotton revolves around the main issues such as rising cost of production, hiked use of pesticides without adequate pest suppression, inability to enhance production during the bountiful monsoon due to ineffective water management, deterioration in genetic purity of the multitude of cotton cultivars, inadequate price support and paucity of infrastructure to ensure value addition products at farmers’ level.
Given the present market scenario, cotton growers need to reorient their approach to the package of practices that they follow to cultivate cotton. Wasteful input use with wishful thinking of more harvest needs to be dissuaded.
2. Area and Production of Cotton:
Globally, cotton is cultivated in an area of about 35 M ha with a production around 23 M t and productivity of about 650 kg ha-1. In India, the cotton area fluctuates between 7.5 and 9.0 M ha with a production of 10 to 14 M bales (one bale = 170 kg).
As per the latest statistics (FAOSTAT 2009), top ten cotton producing countries (M bales) are China (32.0), India (23.5), United States (12.4), Pakistan (10.8), Brazil (5.5), Uzbekistan (4.4), Australia (1.8), Turkey (1.7), Turkmenistan (1.1) and Syria (1.0).
India has the largest area (10.13 M ha) under cotton (30% of world cotton area) at global level with a productivity of 400 kg ha-1 (GOI 2010) and ranks second (15% of world cotton production) in production (22.28 bales) after China. The area under cotton in India is more or less constant around 9.0 M ha.
On the other hand, productivity during the same period increased four-fold from 104 kg ha-1 in 1956-67 to 400 kg ha-1 during 2009-10. Production increased from a meager 4.2 M bales in 1947-48 to 22.3 M bales daring 2009-10. Over the last five years, cotton yield in India increased nearly by 50 per cent Thus, both qualitative and quantities transformations have taken place in cotton production in India.
Development of cotton hybrids in 1970s, which now occupies around 50 per cent of the total cotton area is a significant milestone in Indian cotton scenario. The requirement of cotton in the country has been estimated at 40 M bales by 2015. With the adoption of new technology, it is possible to increase the productivity beyond 600 kg ha-1 to augment additional production around 12 M bales.
As per latest statistics, largest area under cotton in India is in Maharashtra (3.50 M ha) followed by Gujarat (2.45 M ha). These two states account for about 52 per cent of the total area in the country. Cotton production is highest in Gujarat (7.01 M t) followed by Maharashtra (4.75 M t). These two slates account for about 40 per cent of the total cotton production in the country. Highest productivity (667 kg ha-1) is in Punjab followed by Haryana (646 kg ha-1) and Gujarat (510 kg ha-1).
3. Climate, Soils and Tillage of Cotton:
Climate:
Cotton is a warm weather crop and the cultivated species are not limited to the tropics. Adopted cultivars are successful in regions where the frost-free period is less than 180 days. Cotton is a short day plant but day neutral cultivars exist. It is grown around the world in tropical latitudes and as far north as 43°N in the USSR and 45°N in China. In India, cotton is grown from 9° to 31 °N.
There is a linear relationship between heat units and cotton yield. Temperature seems to be a more critical climatic parameter, which dictates cotton production. The required growing degree days are 2,000 to 2,640 over the base temperature of 10°C. For Asiatic cotton, temperature requirement during vegetative phase is 21° to 27°C and below 15°C it makes hardly any growth.
Optimum temperature for germination is 32° to 34°C. Studies in India reveal that at optimum soil moisture conditions, cotton can be grown in a temperature range of 43° to 46°C but for hirsutams the upper limit is 42°C and for barbadense it is 37.5°C. Optimum night temperature is 15° to 20°C.
Cotton can be grown from sea level to an elevation of 1200 to 1500 m but low temperature at higher elevations limit its productivity. As a rainfed crop, it can be grown in regions receiving 500 to 2,000 mm rainfall. Well distributed rainfall of 900 to 1,000 mm during vegetative phase helps in better growth and yield. Cloudy weather results in boll shedding. A minimum of 4 hrs bright sunshine is a prerequisite. A light intensity of 400 to 500 Cal cm-2 day-1 appears to be ideal for cotton crop.
Soils:
Major soils on which cotton is grown are alluvial soils, black cotton soils, red sandy loams to loams and larerites. Cotton is grown as rainfed crop in deep black cotton and medium black soils and as an irrigated crop in alluvial and other light soils. It does not stand waterlogging. Cotton crop is considered moderately acid tolerant and the critical pH range is 5.5 to 6.0 and the upper limit is 8.5.
The crop is considered saline tolerant and salinity threshold (initial yield decline) is about 7.7 dS m-1. The main criterion for suitability of soils within ideal pH range is a depth of atleast 0.6 m and freedom from prolonged waterlogging.
Deterioration of the quality of soils as a natural resource base is evident in traditional cotton belt. High external input based cropping has degraded the soil-water system, depleted soil organic carbon, productivity of the soil and resulted in secondary salinisation and waterlogging in some canal irrigated tracts.
Tillage:
The black soils of central and south India are prepared for sowing rainfed cotton by harrowing the field 3 or 4 times with blade harrow. The land is given deep ploughing only once in 4-5 years for controlling perinnal weeds. Red and lateritic soils of south India are usually ploughed 2-3 times for a rainfed kharif crop or harrowed 2-3 times for a rabi crop. For an irrigated crop, the field is ploughed once after giving an irrigation and land prepared well for sowing the irrigated winter crop.
For the irrigated cotton crop following wheat in north India, land preparation is usually hurried since the time interval between harvest of grain crop in March-April and sowing of irrigated cotton in April-May is very short. The soil is first given a heavy irrigation and ploughed once or twice. Thereafter, a light irrigation is given followed by one or two ploughings. Then the soil is planked with wooden plank before seeding.
4. Seeds and Seeding of Cotton:
Delinting of seed is accomplished through overnight treatment with cowdung slurry followed by shade drying. Concentrated sulphuric acid is also used to delint the seed. Seeds are also treated with zinc chloride for 10 to 15 minutes to remove fuzz and then washed.
Seed Rate and Spacing:
Depending on the cultivars, soil and cultural practices, recommended seed rate and spacings are given in Table 19.3.
Cotton is highly flexible in respect of spacing and plant densities. In general, closer spacing is ideal under conditions of heavy weed infestation and delayed sowings. Wider spacings are ideal under conditions of timely seeding, perfect weed control and recommended fertiliser schedule. There may not be much significant differences in yield with plant populations from 50,000 to 1,00,000 plants ha-1. However, the yield declines at plant populations below 30,000 and above 3,00,000 plants ha-1.
Method of Seeding:
Generally, rainfed cotton is sown on flat beds. Seeds are drill sown, dibbled or sown behind a country plough. In the case of ridge sown irrigated crop, hand dibbling of seed at recommended spacing is commonly followed. This method is also followed in some dryland areas of Madhya Pradesh, Maharashtra and Andhra Pradesh, adopting the square-pocket system of cultivation. Thinning and gap filling should be completed within three weeks after emergence.
5. Nutrient Management in Cotton:
Cotton crop yielding 500 kg ha-1 removes approximately 40 N, 15 P2O5 and 17 K2O, 7 Mg and 4 Ca kg ha-1. In tropical India, crop yielding 3.2 t ha-1 seed cotton removes 190 N, 60 P2O5 and 200 K2O kg ha-1.
Manuring:
Cotton crop responds to bulky organic manures and green manuring. Incorporation of green manure before seeding or inclusion of legumes in crop rotation considerably improves seed cotton yield.
Farm yard manure is rarely applied to rainfed cotton in north India. Irrigated crop, occasionally receive around 10 t ha-1 of FYM, depending upon the availability. In the Peninsular and south India, FYM at 10-12 t ha-1 is applied to rainfed cotton once in 3-5 years. In Tamil Nadu and parts of Andhra Pradesh, irrigated hybrid cotton usually receive around 15 t ha-1 of FYM supplemented by fertilisers.
Nutrient Concentration:
Adequate concentrations of nutrients in cotton plant parts at different growth stages are presented in Table 19.4.
Since cotton culture involves growth of many cultivars in different soil, climatic and management environments, it is reasonable to expect sufficiency levels to vary among different regions.
Fertiliser Schedule:
Nitrogen application improves all growth and yield attributes leading to high yield. The average response to nitrogen varies from 4 to 6 kg seed cotton kg-1 N applied in the case of rainfed desi cottons to 6 to 8 kg in the rainfed American cottons, 10 to 12 kg in the case of irrigated hybrids. Peak demand for nitrogen is at flowering and boll formation.
Cotton has relatively low phosphorus requirements. Inconsistent field response of cotton to phosphorus application is due to phosphorus fixing capacity of different soils. The average response to added phosphorus ranges from 3 to 4 kg seed cotton kg-1 P2O5 applied under rainfed conditions to 5-6 kg under irrigated conditions. Response of cotton to applied potassium is uncertain under different cotton growing environments. Optimum NPK ratio for cotton is 2:1:1.
Associative nitrogen fixers like Azotobacter and Azospirillum can save up to 20 kg N ha-1. Based on the results of several experiments under different ecosystems, fertiliser schedule recommended to cotton is given in Table 19.5.
Location specific fertiliser schedules have been formulated in all the cotton growing areas Recommended schedules (N, P2O5 and K2O kg ha-1) in Andhra Pradesh are:
Coastal AP:
American cotton: 90-45-45
Hybrid cotton: 120-60-60
Rayalaseema:
Desi cottons: 20-20-0
American cotton (rainfed): 40-20-20
(irrigated) 90-45-45
Hybrid cotton: 120-60-60
Telangana:
Desi cotton: 40-20-20
American cotton: 90-45-45
Rice fallows cotton:
Straight varieties: 135-45-45
Hybrid cotton: 150-60-60
Time and Method of Application:
To improve fertiliser use efficiency, it is desirable to apply recommended nitrogen in three sprit doses: half at sowing, one-fourth at squaring and the remaining one- fourth at flowering for rainfed cottons. For irrigated hybrids, nitrogen is recommended in four equal splits at sowing, 30, 60 and 90 DAS.
In general, entire recommended dose of phosphorus and potassium are recommended at sowing. In Andhra Pradesh and parts of Tamil Nadu, recommended potassium dose is applied in splits as in the case of nitrogen application, especially on black cotton soils.
Recommended basal dose of fertilisers should be applied by drilling just before sowing. Fertiliser can also be applied in plough furrows behind traditional plough. In the case of top dressing, spot application or point placement in moist zone or banding is always superior to broadcasting.
Black cotton soils with inadequate internal drainage will be under waterlogged conditions or at saturated condition for one to two weeks during active monsoon. These situations adversely affect the growth and development of cotton crop. To give a boost to such a crop, it is desirable to apply additional 25 per cent of the recommended fertiliser dose by placement around each plant, immediately when the soil conditions permit fertiliser application.
Fertliser consumption pattern in some cotton growing areas near Adilabad (AP) indicated that the nitrogen applied was 5-290 per cent above the recommended rate while potassium applied was lower by 75-100 per cent. Nandyal area (AP) is not much different from Adilabad. Such high rates of nitrogen application and imbalanced fertiliser use resulted in pest build up beyond controllable limits.
Among the secondary and micronutrients, in sulphur deficient soils, 20 kg S ha-1 is beneficial. Soil application of zinc at 25 kg Zn SO4 ha-1 or foliar application of zinc (2%) is recommended if the soils are deficient in zinc. Boron deficiency is associated with bool rot. In boron deficiency sandy soils, application of 5 kg borax ha-1 is recommended.
Organic Cotton:
Input intensive commercial cotton crop receives relatively more quantities of pesticides, inorganic fertilisers and herbicides leading to environmental pollution. Further, cotton dying industry uses many hazardous chemicals to human health. As such organically grown cotton is receiving greater attention.
Organic cotton production involves the following production practices:
1. A minimum of 90 day cotton free period is essential.
2. All the cotton residues are incorporated in the soil to minimise pest and disease build up.
3. Naturally coloured cottons are encouraged to avoid chemicals in dying process.
4. Inorganic agrochemicals (fertilisers, pesticides, fungicides, herbicides etc.) are not used in cotton production.
5. Nutrient supply is through FYM, compost, oilcakes, green manuring, biofertilisers and other available organic residues. Biological pest management including biopesticide assumes significance.
There are several organic farms in Gujarat, Maharashtra and Haryana. Rainfed cotton productivity in organic farms of Maharashtra (Table 19.6) suggest profitability and sustainability of organic cottons as indicated in Table 19.6.
Enhanced soil organic carbon content as well as stable nutrient supply in organic farming improved the cotton yield. Augmented population of natural enemies under no insecticide umbrella offered a cheap and sustained option to the fanners. There are several villagers, where farmers have taken up organic farming for reaping wonderful crop harvests.
6. Cotton Based Cropping Systems:
Crop Rotation:
Cotton occupies the field for over five months. As such, it is rotated with other crops in two or more years rotations under dryland conditions.
Major rotations involving cotton are:
Cotton – sorghum
Cotton – pearlmillet
Cotton – sesame
Cotton – fingermillet
Cotton – chickpea
Cotton – mustard
Cotton – wheat
Under irrigated conditions of north India, the following are the major sequence cropping systems:
Cotton – wheat
Cotton – sorghum
Cotton – berseem
Cotton – chickpea
Cotton – mustard
In South India, important irrigated crop sequences are:
Cotton – rice
Cotton – groundnut
Cotton – sorghum
Rice – cotton
In cotton – wheat system under north Indian conditions, NPK at 120-60 60 kg ha-1 to wheat crop and 80 kg N ha-1 for cotton appears to be adequate due to residual effect of phosphorus and potassium applied to wheat crop.
Cotton after fallow or wheat resonds to 80 kg N ha-1 as against to 40 kg N ha-1 after berseem indicating beneficial effect of berseem on soil fertility. In rice-cotton or rice- rice-cotton system, phosphorus and potassium applied to rice is adequate for the succeeding cotton.
Intercropping:
Several crops are grown as intercrops with cotton throughout the country.
Major intercrops with dryland cotton are:
Cotton + sorghum
Cotton + maize
Cotton + setaria
Cotton + fingermillet
Cotton + groundnut
Cotton + pulse crops
Cotton + soybean
Cotton + castor
Cotton + onion
Cotton + chillies
In the recent past, intercropping in cotton is gaining importance, not with the object of yield advantage, but as a component in integrated pest management for cotton.
7. Water Management for Cotton:
Nearly 80 per cent of the area under cotton in India is depending entirely on rainfall during monsoon while supplementary irrigation facilities exist for about 20 per cent of the area. Supplemental irrigation is given to American and hybrid cottons, depending on the availability of irrigation water. A minimum of about 58 cm of moisture is needed to produce a crop of 0.75 bales ha-1.
Critical Stages for Irrigation:
Adequate available soil moisture should be present in the root zone at sowing for germination and seedling establishment. If soil profile is dry, a heavy irrigation to wet the root zone upto 1.8 m is essential.
Relatively dry soil moisture regime (75% depletion) during vegetative growth period will restrict vegetative growth but when followed by ample supply, vegetative growth will be relatively excessive, which may cause late flowering, boll shedding and reduced yield when the growing season is short. At flowering, soil moisture should be regulated to control vegetative growth in relation to productive growth.
Water deficit from onset of flowering to peak flowering may cause a more negative effect on the yield as compared to that occurring after peak flowering. With severe water deficits during late flowering and early boll formation, boll shedding can be excessive. Moderate deficit during flowering to restrict vegetative growth leads to good boll setting and higher yield despite a reduction in flower number. Squaring to peak flowering is considered critical for soil moisture.
Scheduling Irrigation:
For adequate stand establishment and root development, presowing irrigation is essential when stored soil water from rainfall is inadequate. Irrigation may be scheduled at 60 per cent DASM during vegetative period. During flowering, irrigation at 75 per cent DASM, in general, check vegetative growth without significant reduction in final yield. Delayed irrigation during this period, however, may cause considerable flower and bud shedding.
Scheduling irrigation at 60 per cent DASM during boll filling and maturation is essential for high yield and quality fibre. As the season progresses, irrigation maybe terminated around 4 weeks before final picking. Scheduling irrigation at IW/CPE ratio of 0.6 during vegetative phase, at 0.75 during flowering and at 0.6 during boll filling and maturation is equally ideal for cotton.
Water Requirement:
Depending on climate, length of crop growing period, water requirement of cotton ranges from 700 to 1300 mm. In the early vegetative period the ET losses rages from 2 to 5 mm day-1, which gradually increase to around 8 mm at squaring but reaches 10 mm at peak flowering. Water utilisation efficiency is 0.4-0.6 kg m-3.
Furrow irrigation is most common. In region of scarce irrigation water, sprinkler and drip methods are more accepted to economise irrigation water application.
8. Weed Management for Cotton:
Weeds remove 5-6 times more nitrogen, 5-10 times more phosphorus and 2-5 times more potassium than cotton crop in the early stages of crop, leading to more than 50 per cent reduction in seed cotton yield.
Dominant weed in cotton fields are given below:
Critical Period of weed Completion:
Cotton seed is sown in wide rows. After planting, weeds germinate and begin to shade the slow growing cotton plants leading to sever competition for growth resources. Cotton crop, therefore, requires eight weeks weed free environment after emergence for economic productivity.
Cultural Management:
In most cotton growing areas, weeds are controlled by repeated intercultivations with blade harrows, since the cotton is sown in wide rows. Within the crop rows, weeds are removed by labour intensive hand hoeing. In hill planted cotton of equal row and plant spacing, however, cross cultivation can be adopted. In general, three intercultivations at 15 days interval, starting from 15 DAS, can maintain the cotton crop relatively weed free up to 60 DAS.
Once it rains, it will be difficult to control the weeds by intercultivation in heavy black cotton soils. As a result, the crop becomes susceptible to severe weed completion. After the monsoon rains, the field will be too hard to work blade harrows for removing the fully grown up weeds. Under such situations, it is desirable to plough the field with light country plough between the cotton fallows to break open the hard soil surface.
When once ploughing breaks the hard soil surface, one or two intercultivations with blade harrows can almost uproot the grown up weeds. The crop resume vigorous growth due to uprooting of weeds besides improving soil physical condition, especially soil aeration.
Use of Herbicides:
Herbicides can well supplement row cultivation in cotton to improve cotton yield.
The following herbicides offer effective management of weeds in cotton crop:
PPI herbicides:
Fluchloralin (1.0-1.5)
Pendimethalin (1.5-2.0)
EPTC (3.0-4.0)
PRE herbicides:
Bentazon (1.0-1.5)
Metolachlor (1.5-2.5)
Pendimethalin (1.5-2.0)
Pronamide (1.5-2.5)
Metribuzin (0.5-2.0)
Alachlor (1.5-2.0)
Cinmethylin (0.5-1.5)
Diuron (1.0-1.5)
POST herbicides:
Tralkoxydin (100-300 g)
Fluazifop (50 to 100 g)
Quizalofop (0.4-0.75)
Sethxydin (200-400 g)
Lactofen (20-30 g) may be ideal as POST directed spray against several broad leaf weeds. Glyposate (3.5-4.0) is a choice for dealing with perennial weeds standing in between the cotton rows. It should be applied as directed spray through hood sprayers. Paraquat (1.0-2.5) and Ansar 529 (2.0-2.5) can also be used as directed sprays at time of necessity.
9. Harvesting, Processing and Quality of Cotton:
Harvesting:
Duration of cotton ranges from 150 to 200 days. Hybrids are of relatively long duration cultivars. Ideal time for harvesting is when most of the leaves dry or in shedding stage. First picking can be when 10 per cent of the bolls have burst open. Manual harvesting is most common in developing countries. Depending on the skill, one person can harvest 10 to 60 kg seed cotton in a day. Machine harvesting is common in developed countries like USA, USSR, Australia etc.
Yield of rainfed varieties ranges from 800 to 1,000 kg ha-1 and that of hybrids from 1,000 to 1,500 kg ha-1. Under irrigation, the yield of hybrids and other improved varieties varies from 3-4 t ha-1 of seed cotton. Many progressive growers harvested around 7 t ha-1 with irrigation and good management practices.
Processing:
Ginning of seed cotton (kapas) is important in processing of material from field to factory. Separation of fibres from seed cotton is known as ginning. Roller gins or saw gins are used for ginning.
In India, mostly roller gins are used. When seed cotton is fed to the machine, fibres adhere to the rough surface of the roller and are carried in between the fixed knife and the roller and gripped between them. The oscillating knife beats the seeds and separates the fibres, which are gripped.
Ginning percentage (GP) or ginning outturn (GOT) is given by:
The ginning percentage for barbadense is 28-30, hirsutum 34-38 and desi coots 36-42. Hybrids have relatively higher ginning percentage.
Quality Evaluation:
Lint index: It is the weight of lint from 100 seeds.
Seed index:
It is the test weight, which is the weight of 100 seeds (g).
Seed indices (g) of cottons vary from 4.8 to 11.0 g as indicated below:
Arboreums 4.8-5.0
Herbaceums 5.5-6.0
Hirsutums 8.0-11.0
Barbadense 9.0-11.0
Oil Content:
It varies from 14.5 to 22.5 per cent in arboreums and herbaceums. In hersutums and barbadense, it ranges between 17.0 and 25.5 per cent. The main fatty acids are oleic and linolic with gossypol.
High Standard Counts (HSC):
It is expressed as hanks, each of 840 yards. Forties (40s) means that a pound of cotton gives 40 hanks of 840 yards. The metric yarn count is the number of km making up 1.00 kg of yam. This metric count is 1.693 times the English count.
Colour:
In the laboratory, the colour is estimated using Nickerson Hunter Colorimeter.
Thrash Content:
Trash content is estimated in the laboratory using Shriely Analyser.
Staple Length (fibre length):
It is the normal length by measurement without regard to quality or value at 65 per cent RH and 21°C.
Holo Length:
It is the overall length of the lint without the fibre taken out of seed. Holo length Disc, Bolls sorter, Baer Sorter or Fibrograph are used for measuring holo length. While, 2.5 per cent span fibre length is the distance in mm spanned by longest 2.5 per cent fibres in test specimen, 50 per cent span fibre length is the distance in mm spanned by 50 per cent of the fibres in a test specimen.
Micronaire:
A measure of airflow through a compressed specimen of fibre that relates to fibre fineness and/or maturity. It is expressed in terms of weight per unit length of fibre (10-6 g cm-1 or millitex).
Millitex is the weight in mg of a km length of fibre. Micronaire (fibronaire) reading is determined by an air flow instrument. It is a measure of maturity and cell wall development.
Micronaire is equal to the average weight of the fibre in micrograms (µg) and the fineness in cotton is graded as:
Very fine – less than 3.0
Fine – 3.0 to 3.9
Average – 4.0 to 4.9
Coarse – 5.0 to 5.9
Fibre Maturity:
Immature fibres weigh less and offer less resistance to the flow of air. Immature cottons produce neps, weak thread and irregular dying. Fibres are treated with 18 per cent caustic soda and count the number of mature fibres (N), immature fibres (I) and dead fibres (D) are measured Maturity ratio is calculated as:
M = (%N – %D) /200 + 0.70
Fibre Strength:
A sample of cotton lint is combined into a flat bundle of fibres and gripped by a pair of clamps in a machine called Pressely Tester or Stelometer. Weight is applied till the bundle breaks. At the breaking point, the weight is read on the scale which indicates the strength in lbs inch-2 of fibre or kg cm-2.
Grading system is:
Very strong – > 95
Strong – 86 – 95
Average – 76 – 85
Fair – 66 – 75
Weak – < 66
Nippiness:
It describes the lint that is rough and lumpy.
Neps:
These are tangled knots of fibre or lumps caused by mechanical processing.
Cavitoma:
Describes cotton damaged by microbes.
Count-Strength-Product (CSP):
Yarn quality is usually assessed in terms of CSP, which is the product of the count of yarn and the breaking strength in pounds of one lea (120 yards) of that yarn.