Recently, there has been a rapid increase in the use of nitrogen fertilizers to increase the production of sugar beet crops, despite their negative impact on the environment and human health, and their higher cost. Therefore, the aim of the research is to partially replace nitrogen fertilizers with algae extract.
Two field experiments were conducted in the Experimental and Production Station of the National Research Center in Nubaria, Beheira Governorate, Egypt. Sugar beet (Beta vulgaris var. Ras poly) was grown in sandy soil with a sprinkler irrigation system to study the effect of different planting densities and foliar application with algae extract and nitrogen on yield, yield components and quality characteristics throughout the winter seasons in 2019/2020 and 2020/2021. The combined studies showed that nitrogen fertilizer + foliar application of algae extract and planting density had a significant impact on growth parameters. Decreasing planting density from 50000 plants/fed to 40000 or 30000 plants/fed. (hectare = 2.4 fed) significantly increased root length, root diameter and fresh root weight/plant. The highest values of growth characters measured by less plant density 30000 plant/fed and 100 kg/N + 1.5 g/L algae extract. At the greatest plant density (50000 plants/fed.), the top, root, and sugar production (ton/fed.) exhibited the highest value, whereas at the lowest plant density (30000 plants/fed.), the lowest value was recorded. The maximum percentages of sucrose, purity, and extractable sugar were achieved by applying 80 kg of nitrogen/fed, plant density (50000 plants/fed) and spraying 2.5 g/L of spirulina extract on beets.