A comparative study of urea application in split with sulfur coated and nitrification inhibitor on nitrogen productivity and yield of rice (Oryza sativa L.) in two different paddy soils

Despite of nitrogen is an influential factor in rice production, but its use efficiency is usually lower in paddy rice than in upland crops. To determine the effects of split application urea, sulfur coated urea and nitrification inhibitor on yield, uptake and nitrogen use efficiency in rice (Oryza sativa L.) cv. Khazar, an experiment was conducted using six different treatments based on randomized complete block design with three replications at two agricultural research fields with different soils (Kisum and Soil and Water Stations), Rice Research Institute of Iran. In this experiment, the effects of coated urea fertilizer and nitrification inhibitor (2,5- dimethyl parabanzo quionon) together with urea and urea splitting methods at two and three times was studied. The results showed that the straw yield, grain and straw N uptake and total N uptake by plant were significantly influenced by different nitrogen application methods in Kisum station with light soil texture. In this field, the maximum grain and straw N uptake and total N uptake were obtained using 90 kg net N per ha from urea source at three equal splitting, one-third at each transplanting, tillering and panicle initiation stage (T5 treatment), while the maximum grain yield was observed for 90 kg net N per hafrom coated urea at transplanting stage (T2 treatment). In Soil and Water station, the effects of treatments on grain and straw yield and grain and straw N uptake were significant at 1% probability level, so that the highest grain and straw yield and N uptake were observed in T5 treatment. The results of this research indicated that for high yielding and long growth duration variety, Khazar, urea splitting at three stages in soils with moderate to heavy textures and use of sulfur coated urea together with splitting method in soils with light to moderate textures is the most appropriate method of nitrogen application.