NPK and sodium content in sesame under salt stress and nitrate/ammonium fertilization

Abstract

This study aimed to evaluate the effects of saline water irrigation and fertilization with different nitrate/ammonium proportions on the contents of nitrogen (N), phosphorus (P), potassium (K⁺) and sodium (Na⁺) and Na⁺/K⁺ ratio in the sesame cv. CNPA G3, through an experiment conducted in drainage lysimeters under greenhouse conditions, in eutrophic Regolithic Neosol with sandy loam texture, in the municipality of Campina Grande-PB, Brazil. Treatments were distributed in randomized blocks, in 5 x 5 factorial scheme, with three replicates, relative to five levels of irrigation water salinity - ECw (0.6; 1.2; 1.8; 2.4 and 3.0 dS m^-1) and five nitrate/ammonium proportions - NAP (200:0, 150:50, 100:100, 50:150, 0:200 mg kg^-1 of NO₃^--N/NH₄⁺-N). Increasing ECw levels caused increment in Na⁺ contents and reduction in N, P and K⁺ contents in leaf and stem tissues of the sesame cv. CNPA G3. The increase in the Na⁺/ K⁺ ratio in leaves and stem of sesame under irrigation with ECw water up to 3.0 dS m^-1 can be considered as a mechanism of tolerance to salt stress. There was interaction between the factors (ECw x NAP) for the N content in the leaf tissues, and its highest accumulation was obtained with ECw of 0.6 dS m^-1 and NO₃^--N/NH₄⁺-N proportion of 200:0 mg kg^-1.