Assess the Regression and Correlation Relationships between the Traits Affecting the Seed Yield of Black Cumin (Nigella sativa L.) Cultivars Affected Different Planting Dates and Combined Nutrition

Choosing the right planting date, managing plant food sources and identifying traits that increase yield are the most important factors of success in increasing agricultural production. To investigate the regression and correlation relationships among the factors affecting the yield of black cumin under the influence of planting date and different sources of nitrogen supply, a study was done. This research was conducted according factorial split plots experiment based on randomized complete block design (RCBD) with three replications. Seven levels of nitrogen sources (including urea, manure fertilizer, Azotobacter, urea + manure fertilizer, urea + Azotobacter, Azotobacter + manure fertilizer, and urea + Azotobacter + manure fertilizer) as the first factor in the main plots. Additionally, two planting dates (November 22 and February 14) and two black cumin cultivars (Arak and Semirom) were considered as the secondary factors and were factorially assigned to the sub-plots. The number of seeds per plant showed the highest explanatory coefficient with a justification of 93.16% of the changes in seed yield, indicating its significant influence on seed production. Moreover, the correlation coefficients between seed yield and the number of seeds per plant, biological yield, and number of pod per plant were found to be 0.997, 0.932 and 0.816, respectively. These strong correlation values suggest close relationships between these factors and seed yield. The Arak cultivar, planted on November 22 and treated with urea fertilizer, exhibited the highest seed yield with an average of 498.8kg.ha-1. This yield was not significantly different from the Semirom cultivar, which showed an average yield of 460.8 kg.ha-1 when subjected to combined nutrition (Urea + Azotobacter + manure fertilizer) and planted on February 14. It can be concluded the first planting date and traits such as number of seeds per plant, number of pod per plant and biological yield are essential factors that researchers should consider to enhance seed yield in black cumin cultivation.