Irrigation with water enriched with seaweed extract to overcome effects of salinity in ‘New red fire’ leafy lettuce cultivation

ABSTRACT Lettuce (Lactuca sativa L.) is salt-sensitive, and salinity level can negatively affect yield. The study was conducted to investigate effect of water enriched with seaweed extract to overcome effects of salinity in ‘New Red Fire’ leafy lettuce cultivation. The highest and lowest leaf free proline content was in plants irrigated with saline water at EC 7 and 1.37 dS m−1. Increasing water EC level from 2.5 to 4 dS m−1 resulted in 9.3% increase in leaf total soluble solid content. The highest leaf vitamin C content was in plants treated by Chlorella vulgaris seaweed solution. Salinity levels could be classified into three groups: 1.37 and 2.5 dS m−1 (least damaging), 4 and 5 dS m−1 (tolerance threshold) and 7 dS m−1 (most damaging). Chlorella vulgaris seaweed solution appeared to neutralize adverse effects of salinity on plant fresh weight, free proline content, total soluble solid content, photosynthetic pigments content, radical scavenging activity, anthocyanin content, phenol and flavonoid content, peroxidase enzyme activity and leaf vitamin C content. Irrigation ‘New Red Fire’ with water enriched with Chlorella vulgaris seaweed extract is strongly recommended to overcome effects of salinity on lettuce morphological and physiological characteristics. Salinity levels higher than 5 dS m−1 can seriously damage ‘New Red Fire’ qualitative and quantitative properties.