Gas exchange and production of sunflower (Helianthus annuus L.) irrigated with water of different salinity, cationic nature and nitrogen doses

Abstract

This study aimed to evaluate the gas exchanges and production components of sunflower, cv. BRS 324, as a function of irrigation with water of different salinity levels and cationic nature associated with doses of nitrogen (N). The study was conducted in pots adapted as lysimeters, under field conditions, in an eutrophic Grey Argisol of sandy loam texture. The experimental design was randomized blocks, in 5 x 5 factorial scheme, with three replicates, corresponding to five combinations of water salinity and cationic nature - S (S1- Control; S2- NaCl; S3- CaCl2; S4 - KCl and S5 - NaCl+CaCl2+MgCl2) and five N doses (50; 75; 100; 125 and 150 mg of N kg-1 of soil). Irrigation was applied using water with electrical conductivity - ECw of 0.5 dS m-1 for the control (S1) and 5.0 dS m-1for the other treatments (S2; S3; S4 and S5). Gas exchange through stomatal conductance, transpiration, CO2 assimilation rate, internal CO2 concentration and intrinsic water use efficiency were evaluated and the production components were determined by the internal diameter of the capitulum, the phytomass of the capitulum with achenes and dry matter of the capitulum. The gas exchange of sunflower cv. BRS 324 were significantly influenced, being the biggest decrease due to the variation in the ECw when compared with the cationic nature of irrigation water. Among the evaluated cations, potassium promoted the highest value of stomatal conductance and CO2 assimilation rate. Irrigation with saline water negatively affected the production components of sunflower, regardless of the cation present in the irrigation water.