Evaluation of the effect of nitrogen foliar application on some physiological and agronomic characteristics of three barley (Hordeum vulgare L.) varieties under different humidity conditions

Barley (Hordeum vulgare L.) It is one of the most important grains and belongs to the genus of wheat. It is cultivated in more than one hundred countries of the world as a profitable crop. Barley is mostly used for grain production, for animal feed and fermentation industries. Among the grains, Barley had the highest production after wheat, rice and corn and accounts for nearly 91% of the world's grain production. In order to investigate the effects of urea foliar application on some physiological and agronomic characteristics of three barley cultivars under normal irrigation conditions and drought stress at the end of the season, a factorial experiment in the form of a randomized complete block design with three replications, during two years of cultivation 2017-2018 and 2018-2019 was carried out in the research farms of the Agricultural Research and Training Center of East Azerbaijan Province.

This study is a two separate experiment with optimal irrigation and drought stress at the end of the season was done with similar plans. Irrigation was stopped at the stage of spike emergence. Urea foliar application levels include non-foliar application and once foliar application after spiking was determined as the first factor and barley cultivars as the second factor. Barley cultivars included Mahtab, Jolgeh and Makuei. Measured traits included; Grain yield, 1000-seed weight, flag-leaf area, flag-leaf chlorophyll content and flag-leaf proline.

Drought stress reduces the value of all traits except flag-leaf proline and increased flag-leaf proline content in all cultivars. However, urea foliar application was able to mitigate the adverse effects of water stress. For the trait of grain yield, Mahtab cultivar with 4710.4 kg/ha at the control level and 5496.41 kg/ha at the level of urea foliar application, had the highest grain yield among cultivars under drought stress conditions. For the trait of 1000-seed weight, Mahtab cultivar with 34.15 g at the control level and 37.33 g at the level of urea foliar application, had the highest grain yield among cultivars under drought stress conditions. For the trait of flag-leaf area, Makuei cultivar with 13.95 cm2 at the control level and Jolgeh cultivar with 14.27 cm2 at the level of urea foliar application, had the highest flag-leaf area among cultivars under drought stress conditions. For the trait of flag-leaf chlorophyll, Makuei cultivar with 44.4 units at the control level and Jolgeh cultivar with 46.48 units at the level of urea foliar application had the highest flag-leaf chlorophyll among cultivars under drought stress conditions. For the trait of flag-leaf proline content, Mahtab cultivar with 5.4 units at the control level and 3.12 units at the level of urea foliar application had the highest flag-leaf proline content among cultivars under drought stress conditions. In general, Mahtab cultivar, compared to other cultivars, had a smaller decrease in the amount of studied traits under drought stress conditions that indicates its greater resistance and adaptation to water shortage stress.

In general, the results showed that the cessation of irrigation at the stage of spike emergence in the used cultivars caused a significant reduction in the studied traits in both years of the experiment. However, urea foliar application was able to mitigate the adverse effects of water stress. So that the application of this element had a positive role in the studied traits barley cultivars especially in water shortage stress conditions. Study traits in used cultivars decreased in water shortage stress conditions that indicates the sensitivity of the studied cultivars to water shortage. Mahtab cultivar compared to other cultivars, was less reduction in the amount of studied traits under drought stress conditions. And also compared to other cultivars, was a further increase in flag-leaf proline content under drought stress conditions that indicates its greater resistance and adaptation to water shortage stress.