Two field experiments were conducted during the two successive winter seasons 2019/2020 and 2020/2021 at the Faculty of Agriculture Azhar University Farm, Assiut Governorate, Egypt, to study the effect of foliar spraying with different concentrations of algae extract and nitrogen fertilizer rates on growth, yield and quality of onion plants. The results proved that algae spraying led to an increase in the growth, productivity and quality of onions grown in loamy soil in Upper Egypt.
The highest yield was obtained by foliar spraying of algae at a concentration of 4.0 g l–1. In addition to fertilizing the soil with 90 kg nitrogen / fed., spraying onion plants after 30 and 45 days of cultivation with algae extract at a concentration of 4.0 g l–1 led to an increase in the total yield by (16.21 and 20.74%.) and the weight of the onion (22.69 and 27. (and the onion and onion diameter (16.20 and 19.02%) compared to the control treatment in the first and second seasons, respectively. In addition, despite the superiority of the soil fertilization treatment at a rate of 120 kg per fed., the improvement rates were not significant. Therefore, the mineral fertilization treatment at a rate of 90 kg per fed., with algae spraying is considered the best economically.