Effect of nitrogen application rate on nitrogen use efficiency in barley cultivars in Mashhad and Damghan conditions

Barely (Hordeum Vulgare L.) is one of the major grain crops from cereal family, which is the world`s fourth most important crop in terms of cultivation area and yield production after wheat, corn and rice. Iran`s share of world barely production is 2.7 million hectares, representing almost 1.86 % of total global barley production, according to Ministry of Agriculture Jihad statistics (2013). Nitrogen is one of the most important nutritional elements with a high consumption rate, which plays a pivotal role in the vital processes of plants. Lack of nitrogen is associated with the more significant limitation in producing crops compared to the other natural elements. Over-consumption of nitrogen fertilizer harms the environment, while it also has an intense restrictive effect on microorganism diversity and yield of the crops’ roots. Furthermore, less consumption of nitrogen than the required amount might be associated with the diminished yield of the crops (Beatty et al., 2010). To increase the efficiency of nitrogen consumption, we need nitrogen management strategies, traditional methods of plant breeding and biotechnology. The aim of this study was to evaluate the effects of different levels of nitrogen fertilizer on nitrogen use efficiency and yield of old and new barely cultivars in the two regions of Mashhad and Damghan.
The study was conducted at the research farms of Ferdowsi University of Mashhad and university of Agricultural Sciences of Damghan, Iran in the crop year of 2014-2015, using a factorial design based on completely random blocks with three replicas. Experimental treatments were combination of barley cultivars (five new cultivars: Fajr 30, Nosrat, Behrokh, Yousef and Nik, and five old cultivars: Reyhan, Eram, Afzal, Nimrooz and Karoon) and different levels of nitrogen fertilizer based on soil test from depth of 0-30 cm (the consumption of normal fertilizer, 50% less and 50% more than the recommended amount of nitrogen for barely). In this experiment, in addition to yield attributes, traits such as nitrogen use efficiency, nitrogen uptake efficiency, nitrogen productivity, nitrogen harvest index and seed nitrogen content were measured.
Result and The results of combined analysis of variance indicated that the effect of nitrogen fertilizer and cultivar was significant on the all studied traits. While the interaction of the location and cultivar was significant for nitrogen use efficiency, nitrogen productivity and yield, the other interactions were not found to be significant. The lower application of nitrogen than normal was compared with its excessive consumption, which indicated a reduction in the nitrogen utilization efficiency, uptake efficiency, productivity, harvest index, and nitrogen seed content in all the studied barely cultivars. The new barely cultivars exhibited higher nitrogen use efficiency than the old cultivars. Furthermore, maximum and minimum nitrogen use efficiency were respectively recorded for Behrokh cultivar at Mashhad region and Afzal cultivar at Damghan region, where nitrogen use efficiency of new cultivar of Behrokh was 57 % more than that of Afzal old cultivar. Accordingly, level of nitrogen use efficiency under the climate of Mashhad was approximately 33% higher than Damghan. The highest nitrogen uptake efficiency and harvest index were observed in Behrokh and Eram cultivars, respectively. In addition, maximum and minimum content of nitrogen in the seeds were registered for the cultivars of Nik and Afzal, respectively, so that the seed nitrogen content of Nik new cultivar was 22% higher than Afzal old cultivar. Comparison of average grain yield across the regions showed that the old cultivars consistently produced lower grain yield as compared to new ones where Yousef new cultivar gave the highest grain yield (6573 kg ha-1) in Mashhad and old Afzal cultivar had the lowest grain yield (3152 kg ha-1) in Damghan. Superiority of new cultivars compared to old cultivars could be attributed to their genetic enhancement in terms of yield production (Gabriella et al., 2003). It is also notable that all the studied features in the current research had significant positive associations with seed yield performance. Given the variable response of the cultivars in Mashhad and Damghan, different cultivars should be tested to identify those cultivars that are adapted to the climatic conditions of each region.