Combined Effect of Biological and Nitrogen Fertilizers on Leaf Area Index and Rice (Oryza sativa L.)Yield under Different Irrigation Conditions

IntroductionRice (Oryza sativa L.) is one of the most important and valuable grains in the world, after wheat, and is the main source of food for more than 50% of the world's population. Proper water management in rice fields plays a key role in the usefulness of other production inputs. One way to improve the efficiency of nitrogen fertilizer application and reduce its losses is the simultaneous use of organic and biological fertilizers. Due to the conditions of Iran in terms of water resources and excessive consumption of nitrogen fertilizers, the use of less water in rice cultivation and reducing the use of chemical fertilizers can play a very important role in saving and wasting water by using biofertilizers will reduce the cost and pollution of chemical fertilizers.Materials and MethodsAn experiment in the experimental farm of Rice Research Institute of Iran (Rasht) performed over two years, 2017 and 2018, to evaluate the response of two rice cultivars to bio-chemical fertilizers at different irrigation levels on leaf area index, yield, components Water performance and efficiency were assessed. This experiment was performed in the form of double split plots based on a randomized complete block design with three replications. Accordingly, experimental factors including water management at three levels without stress (flooding) and irrigation intervals of 10 and 15 days as the main factor, fertilizer at three levels including inoculation of seedlings with nitroxin biofertilizer, inoculation of seedlings with nitroxin biofertilizer + 50% of nitrogen chemical fertilizer required by the plant (combined fertilizer treatment) and 100% of nitrogen chemical fertilizer required by the plant) as a secondary agent and rice cultivar at two levels including Hashemi and Gilaneh as a secondary agent. The dimensions of each plot were 3Ï3 meters. In this experiment, grain yield, grain yield components, leaf area index, and water use efficiency were examined.Results and DiscussionThe results of this experiment showed that there was no significant difference between the combined treatment of fertilizer (2.77 t/ha) and the treatment of 100% nitrogen chemical fertilizer (2.82 t/ha) on the yield of rice cultivars. The waterlogging treatment caused a 23% and 38% higher grain yield compared to 10-day and 15-day irrigation cycles, respectively. The highest leaf area index was observed in the Gilaneh cultivar with 100% chemical nitrogen fertilizer required by the plant and inoculation of seedling roots with the combined treatment of fertilizer during flooding, with values of 4.52 and 4.03, respectively, and the lowest value of 1.48 was observed in the Hashemi cultivar with seedling root inoculation with nitroxin biofertilizer and irrigation for 15 days. Water use efficiency in nitrogen and compound fertilizer treatments was higher in the Gilaneh cultivar than in the other treatments. The Gilaneh cultivar with 15-day irrigation treatment and 100% nitrogen fertilizer required by the plant showed the highest water use efficiency in two years, and the plant needs of this cultivar did not show a significant difference. The combined application of nitroxin biofertilizer and nitrogen chemical fertilizer, in addition to producing a good yield and improving water use efficiency, reduced the use of nitrogen chemical fertilizer by 50%.ConclusionBy increasing the intensity of stress, seedling root inoculation treatments with nitroxin biofertilizer + 50% chemical nitrogen fertilizer required by the plant and consumption of 100% nitrogen fertilizer required by the plant improved water use efficiency. Biofertilizer, along with nitrogen fertilizer increased the leaf area index and crop yield. Nitrogen fertilizer increased the number of empty seeds per panicle compared to biofertilizer. The Gilaneh cultivar was more successful than the Hashemi cultivar in the studied traits. The use of biofertilizers could be a suitable and desirable alternative to chemical fertilizers, in the long run, to minimize environmental pollution and achieve sustainable agriculture.