Cultivo de algodoeiro de fibra colorida sob restrição hídrica e aplicação de quitosana

Abstract

The semiarid region of Brazil stands out for the practice of cotton farming as a source of employment and income generation. However, the expansion of production areas has been affected by the occurrence of temporal and spatial variation in rainfall, which, together with other climatic factors, can result in a reduction in water resources available for irrigation, affecting the growth and development of agricultural crops. In this sense, there is a need to identify strategies to produce safely and mitigate the harmful effects of water restriction. Thus, the use of chitosan biopolymer is a promising alternative, which can contribute to improving the absorption of water and nutrients, reducing transpiration and acting on the antioxidant system of plants. In this sense, the objective of this study was to evaluate the effect of chitosan concentrations on the morphophysiology and production components of the colored fiber cotton ‘BRS Jade’ under water restriction. The plants were grown in drainage lysimeters under greenhouse conditions in Campina Grande - PB. A completely randomized design was used in a 2 × 4 factorial scheme, with two irrigation levels (100 and 50% of the crop's water requirement) and four with chitosan concentrations (0.0; 0.25; 0.50 and 0.75 g L-1) with three replicates. Foliar application of chitosan biopolymer at concentrations of 0.25 to 0.50 g L-1 mitigated the effects of water restriction on electrolyte leakage at the leaf blade, gas exchange, photosynthetic pigment synthesis, chlorophyll a fluorescence, growth in stem diameter and leaf area, and increased boll weight per plant, cotton lint weight, 100-seed weight, average boll weight, cotton seed weight, total dry matter of bolls, stem, leaves and shoots, and water use efficiency. Concentrations of 0.25 to 0.50 g L-1 improved fiber percentage, uniformity, maturity, elongation at break, fiber strength, and micronaire index. Chitosan did not show any benefits on the length or short fiber index of ‘BRS Jade’ cotton under water restriction at concentrations above 0.38 g L⁻¹. The results of this study validated the hypothesis that foliar application of chitosan attenuates the adverse effects of water restriction in colored fiber cotton cultivation.