A greenhouse experiment was carried out during two successive seasons (2015/2016 and 2016/2017) on
sweet basil plants (Ocimum basilicum, L.) grown, in sandy soil, under salinity stress to study the effect of spraying
seaweed extract on growth, leaf chemical composition and essential oil percentage of basil plants. The experiment
was conducted under controlled conditions in greenhouse, with temperature fixed at 25 ± 3C°, relative humidity
between 75 – 85% and 14 hours light exposure. The Spraying seaweed extract exhibited higher tolerance to high
salinity as compared to unsprayed plants. Under high level of salinity (2000 and 4000 ppm NaCl), the plants
received seaweed extract at High concentrations (100 and 200 ppm) present higher values of plant height, shoot
length, branch numbers/plant and chlorophyll contents and carotenoids as compared to unsprayed plants or those
sprayed with lowest seaweed concentration (50 ppm). The chemical analysis of mature leaves of plant sprayed with
higher seaweed extract (100 and 200 ppm) showed significantly higher ratio of N, P and K than those sprayed with
lower concentrations or those untreated plants. However, N, P and K contents decreased significantly as a result of
increasing NaCl concentration in nutrient solution from 500 to 4000 ppm. However, gradual and significant increase
in leave calcium % due to increasing NaCl level in the nutrient solution from 500ppm to 3000ppm.