Interaction between soil salinity and nitrogen on growth and gaseous exchanges in guava

Abstract

This study evaluated the growth and gas exchanges of guava, cv. ‘Paluma’ cultivated in salinized soil and subjected to different nitrogen (N) doses in a protected environment in the municipality of Campina Grande-PB. The experimental design was randomized blocks, in a 5 x 4 factorial arrangement with three replicates, and the treatments resulted from the combination of five salinity levels in the soil saturation extract - ECse (2.15, 3.15,4.15, 5.15 and 6.15 dS m^-1) and four N doses (70, 100, 130 and 160% of the recommended N dose). The dose referring to 100% of N corresponded to 541.1 mg of N dm^-3 of soil. At 120 and 180 days after (DAT), plant growth was evaluated based on stem diameter (SD), leaf area (LA) and number of leaves (NL). At 210 DAT, the following variables of leaf gas exchanges were evaluated: stomatal conductance (gs), internal CO₂ concentration (Ci), transpiration (E) and CO₂ assimilation rate (A). ECse above 2.15 dS m^-1 reduced stem diameter, leaf area, number of leaves, stomatal conductance, internal CO₂ concentration, transpiration and CO₂ assimilation rate, in both evaluation periods. N dose above 70% of the recommendation (378.7 mg N dm^-3 of soil) did not mitigate the deleterious effects caused by the salt stress on the growth and gas exchanges of guava plants.