Chapter 22 - Cotton

Abstract

Cotton is an indeterminate, perennial plant of tropical origin, which limits production to locations with relatively long, warm growing seasons. Amongst the four species of domesticated cotton grown for their economically valuable seed-coat fibres, Gossypium hirsutum accounts for 95% of global production. Because of its indeterminate growth habit, reproductive growth is inextricably linked to vegetative growth. Thus efforts to maximise seedling vigour and minimise stress during canopy development are essential. However, due to its perennial nature, excess water, and nutrients favour vegetative growth and penalise fruit retention, requiring crop monitoring and growth management to maintain vegetative-to-reproductive balance. Cotton canopies are efficient at radiation capture due to planophile leaf orientation and diaheliotropic leaf movements. This chapter discusses canopy characteristics that can be used to improve estimates of canopy radiation use efficiency in future climate scenarios. Improvements in water use efficiency (WUE) will also be essential for sustainable cotton production, and carbon isotope discrimination, dark-adapted conductance and night-time transpiration warrant further research as screening tools for improved WUE in cotton. Nitrogen use efficiency (iNUE) varies substantially with yield environment, and improvements in lint yield have also improved iNUE. Genetic yield improvement has occurred steadily at a rate of 2±1% y− 1, largely by increasing lint percent. However, negative genetic association exists between lint yield and fibre quality, and breaking this linkage remains one of the more important goals of modern cotton breeding. Environment also influences yield and fibre quality parameters, where boll density primarily drives environment-induced yield loss and environments conducive to high yields also positively impact fibre quality.