Evaluation of bio-fertilization and pre-sowing seeds’ magnetization on the quality and productivity of Roselle (Hibiscus sabdariffa L.) cultivars and on the soil fertility

The aim of this study is to assess the effect of seeds' magnetization time before sowing combined with the bio-fertilization at different rates of mineral N fertilization on the quality and productivity of roselle (Hibiscus sabdariffa L.) cultivars and on the soil fertility. Bright and dark red calyces of roselle cultivars were cultivated in two split-plot field experiments during the successive summers of the years 2022 and 2023. The main plots were the applied mineral N fertilization rates (0, 35, 50, and 70 kg N fed-1), while the times of pre-sowing seeds' magnetization (0, 15, 30 and 60 min) were the sub-plots. All treatments were triplicated. A bacterium culture contains two types of bacteria (1st type: FMw 879336, 2nd type: Pseudomonas Sp.) plus liquid vinasse as a carrier were used as the bio-fertilizer that was foliar-applied (30 L fed-1) before transplanting, on soil before planting and at 25, 45 and 65 days after sowing on soil and plant. The results indicated that the 50 kg N fed-1 application combined with 30 min magnetization time of seeds before cultivation and bio-fertilization has significantly decreased the soil EC by 38.5% (from 4.88 to 3.0 dS m-1) and increased the soil organic matter OM by 26.2% relative to the same treatment without bio-fertilizer or without magnetization (from 0.65 to 0.82%). The soil available N, P, Fe, Mn and Zn were significantly increased by 49.4, 22.5, 29.2, 87.7, and 26.9%, respectively, with the same treatment. The plant growth components, protein, carbohydrate, Anthocyanin, and chlorophyll were improved.