Effect of sowing date on yield and yield components of different varieties of black cumin (Nigella sativa L.) in Gorgan climatic conditions

Black cumin is a medicinal and widely used plant worldwide. The seeds of this plant have significant economic value and contain compounds such as thymoquinone, thymol, tocopherol, trans-retinol, and selenium, which have multipurpose applications. Studies have shown that the delay in cultivation hurts the growth and performance of this plant. Since the sowing date is effective on plant establishment, control of weeds, diseases and pests, harvest time, and product quality, it is important to know the proper sowing date in each region to improve the quality and quantity of the product.

Therefore, to investigate the effect of sowing date and different varieties of black cumin on the yield and yield components, a field experiment was conducted in the agricultural year 2021–22 at the Golestan Agriculture and Natural Resources Research and Education Center. This experiment was factorial with a randomized complete block design with 4 replications. The treatments included the sowing date in three levels (6 November, 6 December, and 5 January) and the black cumin variety in three levels (Iranian, Syrian, and Indian). In this study, the traits studied include the number of sub-branches, capsules per plant, the number of pods per plant, the number of seeds per capsule, the number of follicles, the weight of capsules, the weight of 1000 seeds, seed yield, dry weight of a single plant, and biological yield.

The results showed that the effect of sowing date, varieties, and their mutual effect on most studied traits was significant at the probability level of 1%. Based on the results, the highest number of healthy pus capsules and the highest number of follicles were observed in the Iranian variety. Also, the highest capsule weight, 1000 seed weight, and maximum seed yield were assigned to the Indian variety on the first sowing date with an average of 0.288, 2.38 g, and 994.75 kg/ha, respectively. In general, among the investigated varieties, the Indian variety had the highest value in most of the functional traits compared to the other two varieties due to its adaptability to the climatic conditions of the region.

In this research, the delay in sowing dates (December and January) caused a significant decrease in traits related to yield and yield components, and the first sowing date (2021/11/06) had the most positive effect on all three varieties. Therefore, the most suitable sowing date for black cumin in Gorgan climatic conditions is planting in November, which achieves the maximum grain yield in black cumin varieties, especially the Indian variety. As a result, to achieve maximum yield, this sowing date is recommended in the climatic conditions of Gorgan city.