Evaluation of the salinity tolerance of cotton trees under saline stress on two substrates

The aim of this study was to evaluate the salinity tolerance of cotton plants grown under saline stress in two substrates. The experiment was carried out in an experimental area at the Centec Cariri School of Technology (FATEC Cariri), located in the city of Juazeiro do Norte, Ceará state. A completely randomized design was applied, using a 4 x 2 factorial scheme consisting of four irrigation water salinity levels (0.5; 3.0; 5.0, and 10 dS m-1) and two substrates (0 - 20 cm soil layers and earthworm humus) with four replications. To assess the tolerance of cotton plants to salinity, the methodology proposed by Fageria (1985) was used. The percentage reductions in plant height, absolute growth rate, stem diameter, number of leaves, and leaf area of cotton plants submitted to different levels of irrigation with saline water in the two substrates were quantified, comparing them to the control (plants cultivated with water whose electrical conductivity is equal to 0.5 dS m-1). Based on the found results, it was found that the used type of substrate changed the classification of cotton salinity tolerance, especially at the highest salinity levels tested (5.0 and 10 dS m-1). When considering the data of stem diameter and leaf area, cotton plants grown in soil substrate showed greater tolerance to salinity. However, from the data regarding absolute growth rate and number of leaves, cotton plants grown in earthworm humus substrate were more tolerant to salinity.