Manejo da irrigação através da evapotranspiração em estágios fenológicos do níger (Guizotia abyssinica)

Abstract

The objective was to evaluate the impact of water deficit during the phenological stages of Niger (Guizotia abyssinica). Two experiments were conducted at the State University of Western Paraná (UNIOESTE), in Cascavel, Paraná, Brazil: one in a protected environment and the other in open field conditions. The experimental design was completely randomized, with eight treatments and four replications (32 plots), as follows: T1-(Vegetative), T2-(Reproductive), T3-(Grain Formation), T4-(Vegetative and Reproductive), T5-(Vegetative and Grain Formation), T6-(Reproductive and Grain Formation), T7-(None of the Stages), and T8-(Vegetative, Reproductive, and Grain Formation). The substrate consisted of red soil and vermicompost humus placed in PVC pots. Irrigation was based on reference evapotranspiration (ETo), estimated using the Thornthwaite, Camargo, and Penman-Monteith methods adapted to the region. The cultivation in the protected environment was conducted under a high tunnel structure without temperature control. Irrigation was applied locally. In the field, sowing took place in an open area without climate control. In both environments, the plants’ water demand was adjusted using the crop coefficient (Kc), considering the phenological stages. The variables analyzed included plant height, number of leaves and capitula, stem and capitulum diameter, fresh and dry biomass (shoot and root), and yield. Statistical analysis was performed using the F test at a 5% significance level with the Sisvar software. In the greenhouse, T8 was significant for: root length (17 cm) and stem length (144.50 cm), fresh mass (3.49 g) and dry mass (1.80 g) of roots, fresh mass (40.37 g) and dry mass (8.89 g) of stems, stem diameter (8.85 mm), number of capitula (20.25), and number of leaves (35.50). Capitulum diameter showed no significant differences. Among the combined treatments, T4 stood out, and among the isolated ones, T1 was the most prominent. In the open field, T8 also showed the best results, particularly for: fresh mass (4.23 g) and dry mass (0.85 g) of roots, fresh mass (46.6 g) and dry mass (8.19 g) of stems, stem diameter (8.53 mm), number of capitula (33), and number of leaves (49). For certain variables, no significant differences were observed: stem and root length, number and weight of seeds, one thousand-grain weight, capitulum diameter, and productivity indicators. Among the combined treatments, T6 had the highest values. Among the isolated treatments, T3 showed the highest mean. T3 proved to be sensitive to water stress, and continuous irrigation enhanced growth and productivity. "This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001"