Interactive effects of plant compost and natural biostimulants on growth, yield, and oil content of white mustard under drip irrigation in sandy soil

The expansion of white mustard ( Sinapis alba L.) cultivation onto low-fertility sandy soils necessitates to enhance oil productivity and establishing environmentally friendly soil relations as part of a sustainable development strategy. Combining organic soil amendments with natural biostimulants could offer an integrated solution by improving both the root zone environment and plant physiological performance. A two-year field study (2023/2024-2024/2025) employed a split-plot design to investigate the effects of plant compost (0, 5, 10, 15 tons per hectare) as a main plot and foliar biostimulants (seaweed extract at 2, 4 ml L −1 ; moringa leaf extract at 15, 30 %; active yeast at 6, 12 ml L −1 ) as sub-plots on white mustard grown under drip irrigation. All compost and biostimulant treatments significantly improved growth, yield, and biochemical parameters relative to the control. Compost rate at 15 t ha −1 yielded the highest values for vegetative growth (e.g., plant height, leaf area), yield components (pod number, seed yield), and fixed oil production. Among biostimulants, seaweed extract at 4 ml L −1 was most effective. A significant interaction was observed, with the combination of 15 t ha −1 compost and 4 ml L −1 seaweed extract producing the most pronounced results, increasing seed yield per hectare and oil yield by approximately 305 % and 875 %, respectively, compared to the untreated control. This treatment also maximized photosynthetic pigments and NPK content in plant tissue. The integrated application of 15 t ha −1 plant compost and 4 ml L −1 seaweed extract is a highly effective, sustainable cultivation strategy for maximizing growth, seed yield, and oil content of white mustard in sandy soils.