Cotton Agronomic Principles

The Plant

Cotton is grown in temperate regions around the gloge consisting of several species: 

• G. hirsutum L. – Upland cotton, constitutes 90% of total cultivated cotton
• G. arboreum L. – India, Pakistan, China and Thailand
• Others: G.barbadense L., G. aroboreum L. and G.herbaceum L

Gossypium hirsutum (L.) is the primary cotton species grown in North American production.

Cotton is grown for fiber and oil seed. The cotton plant is unique because it is a perennial with an indeterminate growth habit and has perhaps the most complex structure of any major field crop. Associated with this complex growth habit is an extreme sensitivity to adverse environmental conditions which causes excess fruit abscission. A better understanding of cotton growth and development in commercial production is important in the continuing efforts of growers to produce lint and seed yield more efficiently. 

From emergence to appearance of the first flower bud (square), the shoot growth is slow. At this stage, the cotton establishes a vigorous root system. Upon the appearance of the first flower (white), a plant with good yield potential should have 9-10 nodes above this flower. From the first square, the goal is to obtain a plant with maximum possible number of nodes and fruiting positions.

Growing Conditions

Cotton needs a period of 140 the 160 predominantly sunny days. Temperature has a high influence on the development of the plant, as it is native to tropical and sub-tropical warm humid climates. After the 130 days, the time must be relatively dry to guarantee the opening of the fruits and the quality of the harvested cotton.

Cotton is preferably grown on light to medium soils, with a pH of 6 – 7.5. The plant is highly sensitive to soil acidity. A low pH can cause low calcium availability and aluminium toxicity in cotton, hence acidity alleviation with lime is essential to achieve high crop yields. Areas under risk of flooding are also unfavorable for cotton production, as cotton plants do not tolerate water saturation causing low oxygen in root environment.

Cotton and Water

Plant nutrition depends on an adequate supply of water for uptake, translocation and metabolic functions for growth. Therefore drought stress and irrigation strongly affect the resulting growth and yield. Cotton responds to moisture and too little water can limit cotton yields. In the arid areas of the USA, irrigation is mandatory for production. In the humid south of the country, irrigation is critical for maintaining yields during drought. However cotton can adapt to semi-arid conditions. Cotton exhibits a large degree of drought tolerance compared to other crops because of various mechanisms including root growth, osmotic adjustment and selective fruit shedding.