Effect of Sowing Date and Nitrogen Fertilizer on the Growth and Yield of Roselle (Hibiscus sabdariffa l.) in Mubi North, Guinea Savannah Nigeria

The field experiment was conducted during 2024 rain fed cropping season at the Teaching and Research Farm of the Department of Crop Science, Adamawa State University, Mubi to determine the most suitable sowing date and nitrogen level that can give optimum growth and yield of roselle (Hibiscus sabdariffa L.) in Mubi Northern Guinea Savannah. The treatments consisted of three (3) different sowing dates of ten (10) days interval: SD1 (21/07/2024), SD2 (31/07/2024) and SD3 (10/08/2024) and four levels of nitrogen fertilizer: N1 (0 kg N/ha), N2 (50 kg N/ha), N3 (100 kg N/ha) and N4 (150 kg N/ha) respectively. The experiment was laid out in a split plot design replicated three times. Sowing date was allocated to main plots and nitrogen levels to sub-plots. Data were taken on plant height, number of branches, days to first flowering, days to 50 % flowering, fresh calyx weight, dry calyx weight and dry seed weight. Data collected were subjected to analysis of variance (ANOVA) and mean were separated using Duncan Multiple Range Test at 5 % level of probability. Result obtained shows that effect of sowing date was significant (p 0.05) on the parameters measured except on number of branches and days to flowering (first and 50 %). Similarly, nitrogen levels were also significant (p 0.05) on the parameters measured except on number of days to flowering and dry calyx weight. Sowing on 21/07/2024 (SD1) was found to be the best for fresh calyx weight (125.6 g), dry calyx weight (23.30 g) and dry seed weight (18.23 g) per plant. Similarly, application of 150 kg N/ha (N4) produced better fresh calyx weight (169.97 g) and dry seed weight (26.95 g) per plant. Based on the result of the study, early sowing (SD1) and 150 kg N/ha (N4) gave optimum performance and seed yields (27.80 g) and are hereby recommended for the study area.