Effect of different deficit irrigation levels and nutritional recourses on some quantitative and qualitative characteristics of black cumin (Nigella sativa L.) in Bardsir climate

Introduction Drought stress is one of the most important environmental stresses that disorder plant growth and development, and limit its production. Plants have different mechanisms to avoid the water deficit (Ali et al., 2007). However, some plants can’t tolerant and avoid of drought stress and need used some method and material e.g soil moisture absorbance material, organic and mineral fertilizer and osmotic regulator as salisylic acid, ascorbic acid and etc (Ashraf et al., 2007). Fertilization is one of the most important managements of agriculture which has significant effects on quantitative and qualitative increasing of agricultural plants. One of the aspects of sustainable agriculture to improve and maintain soil fertility and quality skins, through the use of organic fertilizers and fertilizer consumption balancing and consumption the product is developed. Application of cow manure could improve the mean weight diameter of aggregates, total porosity and water holding capacity of soils. Use of renewable sources of plant and animal life instead of chemical resources can play an important role in maintaining fertility and soil biological activities improve the quality of agricultural production and make ecosystem healthy. Nigella sativa (Black cumin) is an annual flowering plant, native to southwest Asia and used widely in traditional and industrial pharmacology (Salehi et al., 2014). Detailed investigations on medicinal plants have been less frequent than on agricultural crops especially under drought stress; therefore, their tolerance as-assessment for cultivation in arid and semi-arid areas is very important. The aim of the study was the applying some organic and mineral fertilizers as a strategy for holding moisture in soil and helping plant for avoiding drought stress. Materials and methods In order to investigate the effects of cow manure and chemical fertilizers interaction on some quantitative and qualitative characteristics of Nigella sativa L., an experiment was conducted as split-plot arranged based on randomized complete block design with three replications at experiment station of the Agricultural Faculty of Bardsir, Shahid Bahonar University of Kerman in 2015. Treatments were deficit irrigation levels (90%, 50% and 25% of the field capacity) assigned to main plot and nutritional resources (1- control, 2- NPK (200, 150 and 100 kg/ha, respectively), 3- cow manure (20 t/ha) and 4- NPK + cow manure) as subplot. The seedbed preparation was made based on common practices at the location. Plots size under the trial was 4 × 3 m so as to get 30 cm inter row spacing in six rows. Seeds were planted by hand. Drought treatments were start 10 days after plant establishment, and were performed by Time Domain Reflectmeter (TDR). In maturity stage, the traits of plant height, dry matter, branch number, follicles per plant, 1000 seed weight, harvest index, biological and seed yield, essential oil percentage and yield, and oil percentage and yield was estimated. Determination of essential oil and oil were done by Clevenger (Clevenger, 1928) and Soxhlet, respectively. Data were subjected to two-way analysis of variance (ANOVA) and the difference between treatment means was separated using Duncan test. A significance level of 95% was applied. Results and discussion: The results showed that irrigation treatments had a significant effect on plant height, branches number, follicles per plant, seed yield, biological yield, essential oil yield, oil percentage, oil yield, HI, essential oil percentage, seed per follicles. 1000-seed weight showed a non-significant effect as affected by the treatments. The traits were significantly reduced by decrease in field capacity. Nutritional resources showed also a significant effect (P< 0.01) on all the studied traits except oil and essential oil percentage. The highest values of seed yield (648.8 kg/ha), HI (32.72%), oil yield (177.1 kg/ha) and essential oil yield (8.3 kg/ha) were assigned to NPK+cow manure treatment. Interaction of irrigation levels and nutritional resources had significant effect on branch number, seed yield, essential oil yield and oil yield. Application of all the nutritional resources improved all the mentioned traits. Nevertheless, the highest branch number (44), seed yield (817.3 kg/ha), essential oil yield (10.3 kg/ha) and oil yield (189.3 kg/ha) was related to NPK+cow manure treatment in both stress and non-stress conditions. Also, cow manure and NPK+cow manure treatments showed equal values of seed yield, essential oil yield and branch number at 50% and 25% of the field capacity. So, it seems that NPK+cow manure and cow manure treatments especially first treatment were the best treatment in both stress and non-stress conditions. Cow manure by improving the physical structure, balancing the chemical elements and increasing soil moisture contents capacity under drought stress conditions helps to providing water and nutritional require for plant. Also, NPK had beneficial roles in plant resistance to drought stress via improving nutritional supply. Conclusions Based on the results, it can be stated that application of NPK+cow manure had higher effect on all the quantitative and qualitative characteristics than other nutritional resources. It seems that in drought stress conditions, the role of cow manure in terms of their impact on the physical structures of the soil is more important than nutritional properties chemical fertilizers.