Document Type : Research Article
Authors
Department of Plant Production and Genetics, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
10.22067/jcesc.2025.90916.1360
Abstract
Introduction: Nigella (Nigella sativa L.) is a medicinal crop in the Ranunculaceae family, a dicotyledonous, herbaceous and annual plant. Nigella sativa is one of the eight species of this genus that can be cultivated naturally in different parts of Iran. Grains of nigella contains about 40% oil and 1.4% essential oil. The main fatty acids in nigella grain are oleic acid, linoleic acid and palmitic acid. In dry and semi-dry regions, such as west of Iran, water deficit is the most important factor that reduce the growth and production of crops. Plant's growth depends on the adequate amount of nutrients in the rhizosphere. Among nutrients, nitrogen has a particular importance. Because nitrogen plays a role in the formation of amino acids, proteins, nucleic acids and other cell compounds. Using the correct methods of mineral nutrition in plants reduces the effects of drought stress. Silicon is one of these elements. Although silicon is not an essential element for plant growth, it plays an important role in reducing the harmful effects of drought stress. The aim of this experiment was to investigate the effects of silicon foliar application and nitrogen fertilizer in modulating the negative impacts of drought stress on growth, grain yield and phonologic stages of nigella.
Materials and methods: This experiment was carried out in the research farm of Razi University during two crop years, 2020-21 and 2021-22. The research was done in the form of two separate experiments, one under non-drought conditions and the other under drought stress conditions. Each experiment was laid out as a split plot in the form of a randomized complete blocks design (RCBD) in three replications. The main factor was the amount of nitrogen fertilizer in three levels (0, half, and equivalent to the recommended amount, respectively contain 0, 125 and 250 kg urea ha-1) and the sub-factor including silicon foliar spraying in four concentrations (0, 3, 6 and 9 mM). The measured traits were included grain yield, HI, biomass, capsules per plant, grains per capsule, 1000 grain weigh, grains per plant, days to flowering, days to physiologic ripening, grain filling period and grain filling rate. To analysis of variance of the data, the combined analysis model was used with SAS, 9.4 software. The Bartlett test was used to confirm the homogeneity of variances. In combined analysis, year was considered as a random effect and nitrogen and silicon as fixed effects. The means comparison was performed by LSD test at the probability level of 5%.
Results and Discussion: In normal moisture conditions and without silicon spraying, the application of 250 kg.ha-1 urea was more suitable for the investigated traits. So that the highest values of grain yield (1453 kg.ha-1), number of capsules per plant (33.6 capsules), number of grains per capsule (73.8 grains), number of grains per plant (2514 grains), days to physiological maturity (106.6 days) and grain filling rate (125.7 mg.day-1) were obtained at 250 kg.ha-1 urea. In the absence of nitrogen, silicon was not effective. But with nitrogen application, 6 and 9 mM silicon foliar spraying were effective. In general, under without drought stress conditions, the interaction effect of 250 kg.ha-1 nitrogen × 6 mM silicon was found as the superior treatment. Under drought stress conditions and without silicon spraying, 125 kg.ha-1 nitrogen was more suitable than 250 kg.ha-1 nitrogen and also the no-nitrogen treatment. But in silicon spraying treatments, the use of 250 kg.ha-1 nitrogen achieved better results. At 125 kg.ha-1 nitrogen, foliar spraying of silicon 6 mM was more suitable. But at 250 kg.ha-1 nitrogen, foliar spraying of 9 mM silicon was better. According to the obtained results, under drought stress conditions, the consumption of 250 kg.ha-1 nitrogen × silicon foliar application of 9 mM was determined as the best treatment.
Conclusion: In general, the results of this experiment showed that silicon foliar spraying was able to significantly reduce the negative effects of water deficiency in nigella sativa. Therefore, in order to increase the yield of nigella, along with the application of nitrogen fertilizer as much as the recommended amount, it is recommended to foliar spraying of 6 mM silicon under normal moisture conditions and 9 mM under drought stress conditions.
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