Effects of Nitroxin Biofertilizer on Morpho-Physiological Characteristics of Blackseed (Nigella sativa L.) Ecotypes under Drought Stress

Following climate change, drought stress has become the most important limiting factor for crop production and. Plants become under dry when the water available to the roots is limited or the water loss through transpiration is very high. Decreased photosynthetic active radiation absorption, impaired light consumption efficiency and reduced harvest index are the most important factors reducing yield in soil moisture deficit conditions. On the other hand, the adverse effects of the use of chemical drugs in recent years have led to much attention to the cultivation of medicinal plants, which with the increase in their use requires the development of cultivation, management and proper planning. Bio-fertilizers as an alternative in some cases and in most cases as a complement to chemical fertilizers can help to ensure the sustainability of agricultural production systems.

 The study was aimed to evaluate the effect of nitroxin biological fertilizer on ecotypes of black cumin under drought stress. The experiment was conducted as a split-split plot with three replicates at Ilam University during growing season of in 2018. Drought stress levels including no stress (Irrigation based on 100% of plant water needs), moderate stress (Irrigation based on 50% of plant water needs) and severe stress (Irrigation based on 35% of plant water needs) as main plot, nitroxin fertilizer treatments including no nitroxin (control) and application of 1 liter ha-1 nitroxin as sub plot and ecotype treatments including Neyshabour, Mashhad, Semirom and Isfahan Sub-plots were considered as sub-plots. Measured traits included plant height, number of sub-branches, yield, grain yield components (number of follicle and number of seeds per follicle), relative leaf water content, ion leakage and photosynthetic pigments.

 The results showed that the main effect of drought stress, nitroxin and ecotype on all treats were significant (p≤0/01). The highest plant height and the first sub-branch height of Mashhad ecotype were obtained under Irrigation based on 100% of plant water needs conditions under moderate stress. The highest number of branches per-plant of Neyshabur ecotype was obtained under nitroxin under drought stress conditions. The highest number of capsules per plant was obtained from Mashhad ecotype treatment with no nitroxin and Irrigation based on 100% of plant water needs. The highest number of seeds in main capsule, seed yield and harvest index were obtained from Semirom ecotype under nitroxin under Irrigation based on 50% of plant water needs. The highest biological yield was obtained in Isfahan ecotype, nitroxin consumption and Irrigation based on 50% of plant water needs.The results of this study showed that drought stress caused a significant reduction (p≤0.01) in the values of chlorophyll a, b and total chlorophyll traits and relative moisture content of leaves Meanwhile, the use of nitroxin biological fertilizer in most cases improved these traits in different ecotypes, which can be due to the positive effects of biological fertilizer in helping to better absorb water and nutrients under drought stress and reduce the negative effects of water deficiency on Physiological traits of the plant.

 Since better absorption of nutrients depends on the existence of an extensive root system, it seems that the lack of expansion of the plant root system under drought stress and the lack of use of chemical fertilizers, the ground for the activity of microorganisms. This has led to the improvement of the root system and consequently better absorption of water and nutrients needed by the plant in conditions of moisture stress. In general, the results of this study indicate that the application of biological fertilizers may have had a positive effect on improving the yield and quantitative properties of the herbicide under drought stress conditions, however, this issue needs further investigation. From the results it can be concluded that moderate drought stress can be applied in weather conditions Ilam province in addition to reducing water consumption will lead to better outcomes.