Gas exchanges and production of colored cotton under salt sress and nitrogen fertilization

Abstract

This study was conducted with the objective of evaluating the gas exchanges and production components of colored-fiber cotton as a function of irrigation with water of different saline levels and nitrogen (N) doses. The experiment was carried out in drainage lysimeters, filled with eutrophic Regolithic Neosol of sandy loam texture, in the municipality of Campina Grande-PB, Brazil. The statistical design was randomized blocks and the treatments resulted from the combination of five levels of irrigation water electrical conductivity - ECw (5.1, 6.1, 7.1, 8.1 and 9.1 dS m^-1) and five N doses - ND (65; 100; 135; 170; 205 mg of N kg^-1 of soil) in a 5 x 5 factorial scheme, with three replicates. The interaction between the saline levels of the irrigation water and the N doses did not influence significantly any of the analyzed variables. The gas exchanges and production components of the cotton cultivar 'BRS Rubi' were negatively affected by the ECw higher than 5.1 dS m^-1; the CO₂ assimilation rate and total number of seeds per plant were the variables most sensitive to the effects of salt stress; N doses above 65 mg kg^-1 led to decrease of stomatal conductance in the cotton crop.