Improving the Growth and Productivity of the Nigella sativa L. Plant by Using Some Natural Stimulants

Recently, there is a growing global trend to reduce the use of chemical fertilizers in agriculture due to their negative effects on soil quality, environmental health, and rising production costs. Therefore, recent agricultural strategies focus on integrating natural growth stimulants and eco-friendly inputs. Accordingly, this study was conducted during the 2021/2022 and 2022/2023 seasons at El Barmoon Farm, Mansoura Horticultural Research Station, Dakahlia Governorate, Egypt, to evaluate the response of Nigella sativa L. plants to reduced mineral fertilization combined with potassium humate as a soil amendment, along with natural foliar stimulants. The main plot treatments included three fertilization levels: 100% of the recommended NPK dose, 75% NPK plus potassium humate at 2 kg/fed, and 50% NPK plus potassium humate at 2 kg/fed. The subplot treatments involved five foliar applications: no spray, seaweed extract at 0.5 mL/L, compost tea at 20 L/ha, sodium selenite at 8 g/L, and potassium silicate at 4 mL/L. The results showed that mineral fertilizers can be safely reduced to 75% and even 50% of the recommended dose when combined with potassium humate as a soil amendment, without compromising plant performance. All foliar treatments significantly improved the studied characteristics. The compost tea foliar application was the most effective. The interaction between 75% NPK plus potassium humate combined with foliar application of compost tea achieved the highest overall performance in vegetative growth, seed yield, and fixed oil productivity across both seasons. These findings confirm that combining natural soil amendments with eco-friendly foliar stimulants can effectively reduce the use of mineral fertilizers while maintaining high growth and productivity in Nigella sativa L.