Produção e qualidade da fibra do algodoeiro herbáceo submetido a déficits hídricos nas fases fenológicas.

Abstract

Considering that irrigation is the main consumer activity of water on the planet and a major consumer of electricity, it is important to conduct studies that define the time to perform the irrigation. Most cotton breeding program aims to obtain cultivars with good agronomic and technological characteristics of the fiber, compatible with the requirements of the textile industry, which is why it was aimed to study the effect of periods of water stress applied at different phenological stages, under the components of production and fiber quality of upland cotton cultivars. Experiment conducted in a greenhouse (protected environment) located at Embrapa Cotton from November 2014 to April 2015, with treatments distributed in a completely randomized experimental design in a 4 x 2 factorial scheme, being the factors four periods of irrigation deficits applied in different phenological stages (D1 = irrigated control, D2 = deficit in the onset phase of the first bud, D3 = deficit in the onset phase of the first flower and D4 = deficit in the onset phase of the first apple) and 2 cultivars of upland cotton (C1 = BRS 286 and C2 = BRS 336) with four replications, resulted, by the combination of the factors, in 08 treatments. After applied the 14 days of deficit (without irrigation) for each treatment, they returned to be irrigated by the end of the crop cycle. Irrigated control (D1) was irrigated from beginning to end of the experiment. The variables analyzed for production components were number of bolls per plant, average weight of one boll, percentage of fiber and yield, and for quality of fiber were length uniformity, short fiber index, strength, elongation, micronaire and maturity of the fibers. The data of the studied variables were subjected to analysis of variance by F test, and the treatment means of the factors compared by Tukey test at 5% probability. The water deficits applied on the different phenological stages of upland cotton cultivars BRS 286 and BRS 336 affected number of bolls per plant, yield, micronaire, maturity and elongation of the fibers; The irrigated control promoted major bolls number and yield, and best quality fiber indexes for the upland cotton cultivars BRS 286 e BRS 336; The BRS 336 cultivar highlighted with the highest values of bolls number, fiber percentage and fiber quality indexes, on this last for almost all analysed variables, except micronaire.