The effect of integrated management of organic and chemical fertilization on yield, oil, and essential oil of Black cumin (Nigella sativa L.) in different irrigation regimes

Lack of water is one of the main factors in the reduction of agricultural production at arid and semi-arid regions of the world. Most of the agricultural land of Iran was located in arid and semi-arid area and severe water deficit threaten the agriculture of these areas. Accordingly, any strategy to reduce the effects of drought on crop yields is necessary. Organic sourceses in combined with chemical fertilizer can lead to soil fertility and increase crop production. Thus it seems necessary investigate the effect of different nutritional systems (Organic, chemical and integrated) and drought stress on yield and yield components of Black cumin. This experiment was carried out as a split-plot based on randomized completely block design with three replications in Agricultural Education and Medicinal Plant Research Center of Isfahan province during 2017. Treatments included drought stress at 90, 70 and 50% field capacity (FC), as the main source and fertilizer source including control (no fertilizer), vermicompost (10 t ha-1(, chemical fertilizer (N80P40K30) and integration of vermicompost + chemical fertilizer served as the subplot. This experiment, traits were plant height, number of branches per plant, number of follicles per plant, number of seeds per follicle, 1000 seed weight, grain yield, biological yield, essential oil content, essential oil yield, oil percentage and oil yield were evaluated. The results showed that plant height, number of lateral branches, number of follicles per plant, grain yield, biological yield, essential oil yield, oil percentage and oil yield at 1% probability level, harvest index, essential oil percentage, number of seeds per follicle at the probability level of five percentages were significantly affected by different levels of dryness. The mentioned traits showed a significant decrease with increasing drought from 90 to 50% of crop capacity. The type of fertilizer had a significant effect on all traits except essential oil percentage and oil content. The highest grain yield (648.8 kg ha-1), harvest index (32.72%), oil yield (177.1 kg ha-1) and essential oil yield (3.8 kg ha-1) in vermicompost + fertilizer combination Was obtained. The results of analysis of variance of the interaction between fertilizer source and different levels of dryness on the number of branches, grain yield, essential oil yield and oil yield were significant. The highest number of branches (44), grain yield (817.3 kg ha-1), oil yield (189.3 kg ha-1) and essential oil (10.3 kg ha-1), using vermicompost + fertilizer combination fertilizer in Irrigation treatments with 90% FC were reduced by decreasing irrigation water by 50% FC by 25, 42, 25 and 40%, respectively. In irrigation treatments at 70 and 50% level, grain yield, essential oil yield and number of lateral branches in vermicompost alone were not significantly different with vermicompost + chemical fertilizer. In general, the results showed that the combined consumption of vermicompost + fertilizer had the most effect on the quantitative and qualitative yield of Black cumin compared to other fertilizer treatments under both stress and non stress conditions. Vermicompost fertilizer improves the water requirement as well as the nutritional requirements of the plant by improving the physical structure, maintaining the balance in the chemical sector, and increasing the moisture storage capacity in the soil under drought stress conditions. Also, chemical fertilizers played a major role in providing the nutritional needs of black currant to create drought resistance. However, in drought stress conditions, vermicompost fertilizer in many traits was also equal to the combination of vermicompost + chemical fertilizer. Therefore, it seems that in such a situation.