Crescimento, trocas gasosas e produção do algodoeiro sob déficit hídrico nas fases fenológicas.

Abstract

The cotton crop (Gossypium hirsutum L.) has great economic importance in Brazil. The hydric limitations in the semi-arid region make the efficient use of irrigation of fundamental importance for the cultivation of species, especially cotton, one of the alternatives is to identify the periods when the crop is susceptible to lack of water to reduce yield losses. The objective of this study was to evaluate the effect of the water deficit applied in different phases of the cotton phenological cycle, under growth, physiological and productivity parameters of two cultivars of white cotton herbaceous cotton. The experiment was conducted under field conditions, in the experimental area located in the Center of Science and Technology Agrifood (CSTA), belonging to the Federal University of Campina Grande, campus of Pombal, PB. The treatments were made based on a factorial scheme of 6 x 2, related to six conditions of water regime, five periods of water deficit (E1 = water deficit in the initial growth phase, E2 = water deficit in the appearance phase of the first Flower bud, E3 = water deficit in the first flower appearance phase, E4 = water deficit in the appearance phase of the first apple and E5 = water deficit in the appearance phase of the first open bud) and a control (100 of available soil water ). Applied in two cultivars (BRS 286 and BRS 336), distributed in a randomized complete block design with subdivided plots and four replicates. The hydric deficit applied in each phase, according to treatments, corresponded to the suspension of the irrigation for a period of 14 days, with irrigations with a leaf equivalent to the control in the other phases of the crop. Irrigations were carried out with fixed irrigation shifts of 2 days, always in the morning, based on the availability of water in the soil to the plants, using a localized irrigation system with drip tapes. At the end of the bean formation phase, growth, gas exchange, and yield of the plants were evaluated. The results were submitted to analysis of variance (Test F) and the means were compared by the Tukey test at 5% probability by the statistical program Sisvar. Based on the gas exchange, the BRS 286 variety has greater potential for recovery after stress. The cultivars have similar growth, even under stress. Higher productivity in the condition of ideal water availability was the BRS 336 cultivar. Stress in the initial growth phase and in the bole, although reducing production, allows a satisfactory productivity in relation to the national average. The phases of flower and apple are the most sensitive to water deficit, having the lowest yield.