EFFECT OF IRRIGATION INTERVAL AND BIOLOGICAL AND NITROGEN FERTILIZERS ON GRAIN YIELD AND YIELD COMPONENTS OF RICE CULTIVARS

The effects of different irrigation regimes and the application of biological and chemical nitrogen (N) fertilizers on yield and yield components of rice cultivars in a field experiment at the Rice Research Institute of Iran, Rasht in 2018- 2019 crop years were studied. The study was split-split plots based on the complete randomized block design with three replications. The main experimental factor was irrigation interval at three levels (flood irrigation and irrigation at intervals of 10 and 15 days), the second factor was fertilizer type at three levels [seedling root inoculation with Nitroxin biofertilizer, seedling root inoculation with Nitroxin 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 third factor was cultivar at two levels (rice varieties 'Hashemi' and 'Gilaneh'). The results showed that the combined application of the biological and chemical fertilizer (100% N) did not cause any significant differences in the yield of the rice cultivars. The flood irrigation produced 27.7% and 41.6% higher grain yield than the irrigation at intervals of 10 and 15 days, 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 combined application of Nitroxin and chemical fertilizer not only was appropriate for yield and yield components, but it also decreased the effect of chemical N fertilizer application by 50%.