Effect of irrigation interval and nitrogen fertilizer rate on grain yield and yield components of rice (Oryza sativa L.) cv. Hashemi

Irrigation water deficit is an important factor that affect rice production in the world as well as Guilan province in Iran. Intermittent irrigation method can be applied to compensate for the water shortage in rice growing areas, however, it would affect other crop mangement practices such as fertilizer application and mangement. Therefore, this experiment was conducted to determine optimum fertilizer nitrogen requirement in different irrigation regimes using split plot arrangements in randomized complete block design with three replications in Rice Research Institute, Iran in 2015 and 2016 growing seasons. Irrigation regimes included at five levels (permanent submergence, intermittent irrigation with 5, 8, 10 and 15 day intervals) were assigned to main plots and nitrogen fertilizer  at sixlevels (0, 30, 45, 60,75 and 90 kg Nha-1 from urea source) were randomized in sub-plots. Planting, crop husbandry and harvesting pratcices were done according to RRII recommendations. The results showed that effects of irrigation regime and nitrogen fertilizer application rates were significant on the grain yield, biological yield and most of the studied traits. Among irrigation regimes, intermittent irrigation of five days interval with 3278 kg.ha-1 had significantly higher grain yield. The highest grain yield (3388 kg.ha-1) was also obtained from application of 90 kg N.ha-1. The irrigation water consumption in intermittent irrigation with five days interval was 379 m3.ha-1 less than permanent submergence irrigation. Regarding to this fact, that highest grain yield (4335 kgha-1) and highest water productivity (688 g.m-3) beloged to intermittent irrigation with five days intervaland 90 kgN.ha-1 application. This combination of irrigation interval and N fertilizer application rates can be recommended for heavy textured soils of paddy fields in Guilan province.