Impact of Soil Additions Fertilizers and Foliar Chlorella Vulgaris Extract on Soil Properties and productivity of Lettuce Plant Grown Under Saline Soil Conditions

Sustainable agriculture is essential for addressing global challenges such as climate change, food insecurity, and environmental degradation. This study, conducted at Fayoum University’s Demo Farm in Egypt, investigated the effects of mineral and organic amendments, combined with foliar application of Chlorella vulgaris extract, on soil properties and lettuce productivity in salt-affected soils during the 2022/2023 and 2023/2024 winter seasons. Treatments included compost (C), biochar (B), a compost-biochar blend (CB-blend), and mineral fertilizers, with or without Chlorella vulgaris extract foliar spray. Results revealed that the CB-blend significantly enhanced soil properties, including bulk density, hydraulic conductivity, organic matter, nutrient availability, and microbial activity. The combination of CB-blend (5 t fad ^− 1 of compost + 5 t fad ^− 1 of biochar were mixed) and a chlorella vulgaris extract (CVextr) 10% foliar spray increased lettuce yield by 194.68% compared to untreated soil, demonstrating improved growth parameters such as head weight, circumference, and leaf area. These findings highlight the synergistic benefits of organic amendments and bio-stimulants in improving soil health, crop resilience, and productivity under saline conditions. The study advocates for the adoption of compost, biochar, and chlorella vulgaris extract (CVextr) 10% foliar spray as sustainable alternatives to synthetic fertilizers, offering a viable strategy for organic farming systems to mitigate saline stress and promote environmental sustainability.