Effect of sowing date and plant density on yield and yield components of black cumin (Nigella sativa L.) in Gorgan, Golestan province

Black cumin is one of the most medicinal plants in the world, which is used in large quantities every year in the pharmaceutical, health and food industries. Planting date and suitable climatic conditions are one of the most important factors in plant establishment and achieving the desired economic yield, so that, the vegetative and reproductive stages of plants are adapted to the desired environmental conditionsin planting date and suitable environmental conditions (Mehta et al, 2009). To make maximum use of natural resources during the growing season, it is needed to choosed right planting date. In very early planting, low soil temperature and frost damage cause poor plant establishment in spring (Koocheki et al, 2017). Delay in planting date due to shortening of plant growth period and the possibility of occurrence of flowering time with high temperatures had adverse effects on plant growth and development. Hence, the objective of the present study was to evaluate the effect of sowing date and plant density on yield and yield components of black cumin in Gorgan region.
Materials and Methods
In order to investigate the effect of sowing date and plant density on yield and yield components of black cumin, an experiment was conducted in a split plot arrangement base on a randomized complete block design with three replications in Agriculture Reseach and Education center of Golestan during growing season of 2020-2021. In this experiment, main plot was four sowing dates (5 October, 5 November, 5 December and 5 January) and subplot was plant density at four levels (40, 80, 120 and 160 plant.m-2). In the physiological maturity was measured the morphological abd yield components such as plant height, number of lateral branches, number of capsules per plant, number of seeds per capsule, 1000-seed weight, biological yield and grain yield in plant.
Results and Discussion
The results showed that there was a significant different effect on yield and its components by delaying sowing date, so that the grain yield, number of capsules per plant, number of seeds per capsule and 1000-seed weight was decreased 64, 40, 32 and 22%, respectively.One of the main reasons is that the delay in planting date due to induction temperature stress has caused the sterile flowers and fall off., which leads to a reduction in the production potential of capsules and other yield components. Also, the above traits had increasing trend with increasing density from 40 to 120 plant.m-2, but further increase in density to 160 plant.m-2, these traits was reduced except plant height and biological yield. The interaction effect of sowing date and density except for 1000-seed weight on all traits was significant, so that the highest grain yield (1455 kg.ha-1) was obtained on November 6 and a density of 120 plant.m-2, which there was no significant difference with a density of 80 plant.m-2. It appears that the increase in seed yield with the increase in plant density was a result of higher leaf area, effective utilization of solar radiation during growth period and enhanced photosynthetic capacity and production of more pods per unit area. The lowest grain yield (650 kg.ha-1 ) was obtained on January 5 and the density of 40 plant.m-2, which decreased by 42% compared to November 6. Also, the highest biological yield (5376 kg.ha-1) was obtained on November 6 with a density of 160 plant.m-2. The results of correlation coefficients showed that grain yield had the highest significant positive correlation with the number of lateral branches (r = 0.89 *) and the number of capsules per plant (r = 0.94 **).
Conclusions
The results of this study showed the highest (1450 kg.ha-1) and lowest (525 kg.ha-1) grain yield was produced from planting date in November 6 and in January 6 , respectively. Therefore, in order to achieve the desired economic yield in the cultivation of black cumin plant, early cultivation (preferably the oneth decade of November) with 80 plants per square meter can be recommended for Gorgan region.