Influence of nitrogen on the growth and yield of cotton under salinity stress

Mineral nutrient supplementation is a vital strategy to detoxify the lethal effects of salinity stress induced by sodium chloride. To explore the role of mineral nutrition (nitrogen), a hydroponic experiment was carried out for the whole growing season to find out the effects of different levels of nitrogen (0.25, 2.5, and 5 mmol·L−1 N) on the growth and yield of upland cotton genotypes (salt-tolerant, ST, Z9807 and salt-sensitive, SS, Z0102) exposed to salt stress (200 mmol·L−1 NaCl). Salt stressed cotton genotypes exhibited a marked reduction in growth traits and dry biomass accumulation. Nitrogen confirmed its positive role by ameliorating the detrimental effects of salt stress on significant levels when supplied at 2.5 mmol·L−1 as compared to 5 mmol·L−1. Nitrogen application at 5 mmol·L−1 concentration suggestively increased all the morphological and physiological traits under the non-saline environment. Nitrogen at 2.5 mmol·L−1 progressively improved the root morphology of both tolerant and sensitive genotypes and ensured better nitrogen uptake under saline conditions. Besides, nitrogen supplementation at 2.5 mmol·L−1 proved beneficial in positively enhancing the photosynthetic pigment biosynthesis (3.05- and 4.14-fold for TChl, 1.72- and 2.06-fold for Car, and 2.84- and 2.96-fold for An for ST and SS), nitrogen content (9.26- and 11.19- fold for ST and SS), and the seed cotton yield (7.20 times in ST and 7.25 times in SS) of cotton genotypes as compared to the salinity treatment alone. Conclusively, the study results evidenced that nitrogen at moderate concentration can be advantageous in preventing NaCl induced damage.