|Cotton (Gossypium spp.)|
French: Coton; Italian: Cottone; Spanish: Algodon; German: Baumwolle; Portuguese: Algodao
Annual. Harvested part: seed, for fibre.
Important uses of by-products: cotton seed oil; cake, meal and hulls (for feeding); linters.
Cotton is a major world fibre crop. It is grown under a very broad range of climates, soils and cultural practices. For the most part, it is grown in tropical latitudes. However, it is cultivated as far north as 43° N in the USSR and 45° N in China. There are four separate domesticated species of cotton grown in various parts of the world which include G. arboreum L. (diploid), G. herbaceum L.(diploid), G. hirsutum L. (tetraploid) and G. barbadense L. (tetraploid). G. arboreum and G. herbaceum are commonly referred to as Old World diploids due to their ploidy condition and origins being traced to locations in the Old World. Both G. hirsutum and G. barbadense evolved in the New World and are referred to as allelotetraploids. There are literally hundreds of varieties of these various domesticated species which have been developed for production around the world. G. hirsutum is the most extensively developed species and represents approx. 90 % of total world production.
Sown at an average soil temperature of at least 18 °C; between April 1 and May 25 (Georgia, USA), spring (China), early spring (March/Egypt), from May/June to August/September (India, North to South).
Sowing by dibbling or in rows, 18 - 24 kg/ha (Brazil), 25 - 40 kg/ha (USA), upto 50 - 150 kg/ha (Egypt).
Plant density (depending on spacing of rows and plants within rows) 55 000 plants/ha (India), 45 000 - 67 500 plants/ha (China/Yellow and Yangtze River) to 120 000 - 150 000 plants/ha (North China, short season), 60 000 - 90 000 plants/ha (USA), 55 000 - 125 000 plants/ha (Brazil) and from 100 000 (Egypt, traditional) to 168 000 plants/ha (intensive, recommended).
Temperature: Mainly tropical, grown at temperatures 25 - 35 °C.
Adapted to semi-arid conditions; in Brazil nearly all the cotton area is unirrigated; in India 70 % is rainfed; in China and Egypt it is irrigated (10 - 12 irrigations at 15 day intervals), also in USA (e.g. water use in Arizona, desert Southwest, equivalent to 1 040 mm).
Preferably grown on light to medium soils, pH 6 - 8; highly sensitive to soil acidity and water or soil salinity:
Flowers with direct seeding 75 - 80 days (China) to 80 - 120 days (Egypt) after sowing.
Harvested 140-160 (China) to 210 days (Egypt) after sowing.
Depends on variety and location under both irrigated and rainfed conditions. G. arboreum requires less nutrients than G. hirsutum; hybrids require more than single varieties; short compact variety types are more efficient users of nutrients than tall late varieties.
Plant analysis data
Several analyses have been reported under different agroclimatic conditions and for different varieties. General sufficiency ranges for upland cotton (G. hirsutum) in the USA are given in the following tables:
Nitrate-N levels of the petioles at different growth stages in Western USA (Acala and other upland varieties) should be as follows:
Nutrient deficiency symptoms
N - lack of N reduces yield and quality; visible symptoms are light green plants, lower leaves yellow, drying to brownish colour.
P - deficient plants are short and small, growth is retarded, and maturity is postponed; typical symptoms include loss of chlorophyll and development of red discoloured leaves.
K - deficient plants are susceptible to stem blight leading to premature senescence; typical symptoms are bronzing and marginal necrosis of leaves adjacent to developing bolls; plants develop fully necrotic leaves and premature defoliation occurs.
Mg - typical symptoms are lower purplish red leaves with green veins.
S - deficient plants are dwarfed with green leaves.
Mn - deficient leaves are yellowish or reddish grey with green veins.
Zn - small leaves with interveinal chlorosis and shortened stems giving the plant a small bushy appearance; slow in development; leaves lose green colour and produce necrotic spots.
B - deficient plants will produce clittelums, and dieback of terminal buds which do not blossom and drop heavily in production; young leaves yellowish green, flower buds chlorotic.
Due to the extensive variability in the conditions under which cotton is produced (soils, climate, varieties, species, cultural practices, etc.) it is very difficult to generalize recommendations for cotton fertility management.
N - increases height of plants, their boll-bearing capacity and seed weight, and improves seed cotton yield. Excess N - e.g. if cotton follows a good crop of soybeans - may result in rank growth, poor fruiting, delayed maturity, difficult defoliation and boll rot.
The N requirement of N is less for Asiatic cotton types than for American types, but it is greater for hybrids. The response to N is better in irrigated than in rainfed cotton. For better N response - as well as for other nutrients - proper weed control, insect and disease control is essential.
To obtain the highest efficiency from N, one-half (or one-third) should be given at the time of sowing, and the remainder split between (i) square formation and (ii) peak flowering and boll development. Split applications (side-dressing) will better meet the crop's requirements and reduce nitrate loss.
N given before or at planting can be broadcast together with P and K and incorporated into the soil; but placement at a depth of 5 cm below and 5 cm away from the plant has given a better yield (India) than broadcasting or simple drilling.
It is also common to apply part of the N as a foliar spray (1.5 - 2.0 % urea solution) in combination with insecticides at the time of peak flowering and the boll development stage. Foliar application has been found most beneficial on rainfed cotton.
P - improves root development, water use efficiency, the energy balance and the weight, oil and protein contents of the seed as well as fibre quality. The response to P (as well as to K) is normally better if it is given in form of NPK fertilizer (e.g. in India with N:P2O5:K2O ratio 2:1:1 or 3:1:1), before or at planting, incorporated into the soil or placed 7.5 - 10 cm below the moist soil surface.
When not applied pre-planting, P (and K) should be given at the latest at thinning (in the bottom of the furrow before watering).
K - improves fibre fineness and strength, and results in early maturity of the crop. The response to K will always be better if is it applied with N and P at preplanting and incorporated into the soil. Only on sandy, permeable soils it is appropriate to give a split application of K, e.g. with a second dressing at the time of thinning.
Mg - if soil status is low apply 45 - 50 kg/ha MgO; where liming is recommended, dolomitic limestone may be used.
S - if the applied NPK fertilizer does not contain S, at least 12 - 15 kg/ha S should be given in addition (e.g. in ammonium sulphate).
Mn - on soils with pH above 5.6, application of 2.8 kg/ha elemental Mn is recommended.
Zn - soils are deficient when Zn (DTPA extraction) drops below 0.55 ppm; in this case 4.5 kg/ha of e.g. 36 % zinc sulphate should be given (possibly as foliar spray with insecticides).
B - where needed, apply 0.6 kg/ha B (if possible in two foliar applications at 0.3 kg/ha each, tankmixed with insecticide spray).
Liming - the crop is very sensitive to soil acidity. It has repeatedly shown a marked response to lime when applied to an acid soil, particularly if pH has dropped below approx. 5.5. For lasting results, lime must be applied periodically. Enough should preferably be applied some months before planting; in an emergency it can also be applied shortly before planting.
It should be thoroughly mixed with the soil. Split application may be necessary where the soil is very acid and correspondingly large quantities of lime are recommended; the first application should be disced into the soil, followed by mouldboard ploughing; this can be followed by a second application and another discing. Most fields should however be limed before the soil becomes so acid that yields are reduced.
(Attention: no reduced tillage practices should be used in cotton planting unless the soil has been well limed to a depth of 20 cm.)
Preferred nutrient forms
N - may be given in ammonium, nitrate or amide form (ammonium nitrate, ammonium sulphate, urea or NP or NPK fertilizer) containing N in ammonium or ammonium nitrate form.
P - water-soluble, or water- and citrate-soluble form (e.g. superphosphate, ammonium phosphate or ammonium nitrate phosphate, NP or NPK).
K - normally as potassium chloride in NPK fertilizers; also, where sulphur is lacking, as potassium sulphate.
Present fertilizer practices
Brazil (Sao Paulo)
At planting: 10 kg/ha N, 30 kg/ha S plus P2O5 and K2O (rates according to soil status, see below), applied in the furrows.
When the crop is thinned, 15 - 50 kg/ha N (rate depending on soil organic matter) sidedressed, together with 25 kg/ha K2O where required.
B is either applied at planting (0.5 - 1.5 kg/ha B) or as a sidedressing (1.2 - 1.5 kg/ha B).
Lime (usually as dolomitic limestone) is topdressed and incorporated (0 - 20 to 0 - 30 cm) at a rate to raise base saturation to 70 %.
Before sowing or transplanting 30 - 45 t/ha organic manure is given.
N - part applied as basal dressing, the rest as a topdressing at flowering.
P, K, B and Zn - generally given as basal dressing: (B and Zn also as foliar spray at flowering).
On soils with adequate reserves of P and K according to soil analysis:
B - where needed, is generally applied at a rate of 12 kg/ha borax as a basal dressing; as foliar spray, 0.1 - 0.2 % borax solution is applied 2 - 3 times at 15 days intervals.
Zn - where needed, is generally applied as a basal dressing of 22 kg/ha zinc sulphate (Zn SO4.7 H2O = 23 % Zn); it is also sprayed - from the square stage - as 0.1 - 0.2 % zinc sulphate solution.
Where available well decomposed organic manure is applied and incorporated in the soil before planting.
Fertilizer rates (based on long term field experiments in the cotton belt):
- for provinces in the Nile Delta
N = 145 - 180 kg/ha (except for variety G77
receiving 160 - 200 kg/ha N)
- for provinces in Middle and Upper Egypt
N = 160 - 200 kg/ha
K may be added, where needed, at a rate of 55 - 60 kg/ha K2O.
N is given in 2 split applications
Generally recommended N rate:
N rate is used as a guide. Where cotton follows a good crop of soybeans N-rate is reduced by 20 - 30 kg/ha; where vegetative growth has been inadequate, N rate is increased by this amount.
Present practice in Southeastern USA
N - a basic rate of 65 kg/ha N is recommended for "average" loamy sand soils; this may be modified recording to residual N from previous crop, the possibility of irrigation, and the growth of cotton in the field in previous years.
On fields which have produced rank growth, the total N rate is reduced to 45 - 55 kg/ha. The petiole monitoring programme can help lower early season rates without yield reduction as a result of N deficiency. With weekly monitoring, N can be applied well before actual deficiencies may appear.
Desired pH = 6.0
N - on fields having previously produced plants with excess vegetation, reduce the N rate; reduce by 20 - 30 kg/ha when the crop follows soybeans or other legumes in the rotation. On fields where vegetative growth has been unsatisfactory, increase N rate by 20 kg/ha. With N rates higher than 110 kg/ha, insect control is essential. Split application of N, with one-quarter to one-third before or at planting and the rest as side-dressing, is recommended.
P - on new ground low in P, double the P2O5 rate.
K - for first year cotton following hay crops, pasture or soybeans and with soil K status low or medium, increase the K2O rate by 45 - 55 kg/ha.
With irrigation, the P2O5 and K2O rates are increased by 25 %.
Middle South USA
On sandy loam and silt loam soils the recommended N rate is 60 - 90 kg/ha N; on silty clay loams, silty clays and clays, 100 - 135 kg/ha N.
The P and K rates are based on soil analysis, soil texture, (K) and irrigation potential:
Preplant N fertilizer guidelines based on pre-season soil NO3-N levels (Arizona):
Split applications and/or water-run applications of N prior to the peak bloom period are recommended.
Western USA (California)
Western USA (Arizona)
DECKARD, E.I.; TSAI, C.Y.; TUCKER, T.C.: Effect of nitrogen nutrition on quality of agronomic crops. In: HAUCK, R.D. (ed.): Nitrogen in crop production. American Society of Agronomy, Madison, WI, USA (1984)
DOERGE, T.A.; ROTH, R.L.; GARDNER, B.R.: Nitrogen fertilizer management in Arizona. Report 191025, College of Agriculture, Univ. of Arizona, Tucson, AZ, USA (1991)
HAKE, K.; KERBY, T.: Cotton fertility guide. Univ. of California, Coop. Ext. #KC-8801, Bakersfield, CA, USA (1988)
KOHEL, R.J.; LEWIS, C.F. (ed.): Cotton. Agronomy No. 24, American Society of Agronomy, Madison, WI, USA (1984)
Author: J.C. Silvertooth, Extension Agronomist - Cotton, The University of Arizona, Tucson, USA
Contributors: E. Malavolta, Professor of Plant Nutrition, Universidade de Sao Paulo, Piracicaba, Brazil; Li Yun-ji, Cotton Research Institute (CAAS), Anyang, China; A. Momtaz, Director, Agriculture Research Center, Giza, Egypt; M. Singh, Professor, Division of Genetics, Indian Agricultural Research Institute, New Delhi, India