NK combinations do not alleviate the effects of salt stress on gas exchange, photosynthetic pigments and growth of cotton (Gossypium hirsutum L.)

Abstract

The water resources in the semi-arid region of Northeast Brazil commonly have high concentrations of salts, compromising the quality of the water used in irrigation. Thus, it is necessary to study the feasibility of using these resources in agriculture. The present study aimed to evaluate gas exchanges, photosynthetic pigments and growth of white cotton cv. BRS 368 RF using irrigation water of different salinity levels and fertilization with combinations of nitrogen and potassium, under greenhouse conditions in the municipality of Campina Grande-PB, Brazil. Treatments were arranged in randomized blocks in a 5 x 4 factorial scheme, with five levels of electrical conductivity of water–ECw (0.7, 2.2, 3.7, 5.2 and 6.7 dS m-1) and four combinations of fertilization with nitrogen and potassium (70/50, 100/75, 130/100, 160/125% of the recommended dose), with three replicates. There was degradation in chlorophyll a and b levels and in cotton growth, but the cultivar BRS 368 RF markedly increased carotenoid biosynthesis at 75 days after sowing. Nitrogen and potassium application in the combination of 100/75% of their respective recommendations led to increase in plant height. The supply of nitrogen in combination with potassium did not alleviate the deleterious effects of salt stress on gas exchange, photosynthetic pigments and growth of cotton.