Effect of irrigation interval and biological and nitrogen fertilizers on grain yield and water use efficiency of rice cultivars

Management of plant nutrition using fertilizers is an approach to deal with drought and increase water productivity in paddies. The effects of different irrigation regimes and the application of biological and chemical nitrogen fertilizers were studied on yield, yield components, and water use efficiency of rice cultivars in a field experiment at the Rice Research Institute of Iran, Rasht, in 2018–2019 crop years. The study was split-split plots based on the complete randomized block design with three replications. The main plot was assigned to irrigation interval at three levels of full flood irrigation and irrigation intervals of 10 and 15 days, the sub-plot was assigned to fertilizer type at three levels of seedling root inoculation with biofertilizer, seedling root inoculation with biofertilizer + chemical N fertilizer to meet 50% of plant N requirement, and chemical N fertilizer (as urea) to meet 100% of plant N requirement, and the sub-sub-plot was assigned to rice cultivar at two levels of 'Hashemi' and 'Gilaneh'. The results of analysis of variance showed that the grain yields in the treatments of 10-day and 15-day irrigation interval were 28% and 42% lower than that in the treatment of full flood irrigation, respectively. The number of unfilled grains per panicle was 20% higher in the treatment of 100% chemical N fertilizer than in the combined application of the biological and chemical fertilizers. The irrigation interval of 15 days with the combined application of the fertilizers consumed less water in both cultivars than the other treatments. The application of biofertilizer with chemical fertilizer significantly influenced productivity, thereby reducing chemical fertilization by 50% and alleviating environmental pollution.