Effect of nitrogen supplying sources on nitrogen use efficiency in rice (Oryza sativa L. cv. Shiroudi)

The use of nitrogen fertilizer has a key role in enhancing agricultural productivity worldwide. In order to achieve an effective approach to enhance nitrogen use efficiency in rice, a field experiment was conducted in a randomized complete block design with three replications and 13 treatments on Shiroudi, a high yielding rice cultivar in Rice Research Institute of Iran (Amol) in 2015 and 2016. Treatments were included: N0: Without N fertilizer (Control), N1: split application of 115 kg.ha-1, (N2, N3), (N4, N5) and (N6, N7) application of 115 and 57.5 kg.ha-1 N from Sulfur Coated Urea (SCU), Urea Super Granule (USG) and Ammonium Sulfate (AS) sources, respectively. Nitrogen nanofertilizer+ 50% of recommended N fertilizer (N8), application of Azospirillium, Azotobacter and Azospirillium + Azotobacter (N9, N10 and N11), farmers nitrogen fertilizer practice (115 kg.ha-1 from source of urea) (N12). Results showed that the effect of nitrogen fertilizer treatments on grain yield, dry matter, harvest index, grain and straw N content, total N uptake, N harvest index and all N use efficiency indices were significant. The highest grain yield (7869 kg.ha-1) was obtained from N6 (115 kg.ha-1 N from source of ammonium solfate). The highest rates of PFP (136.2 kg.kg1), AEN (38.1 kg.kg-1), REN (90.8 %), PEN (42 kg.kg-1) and IEN (54.2 kg.kg-1) were obtained from N5 (USG) treatment. Based on the results of this experiment, deep placement of USG fertilizer due to higher N uptake may led to reduce N losses and has relative advantage campared to other N fertilizer sources in rice production.