Effects of Interval Irrigation and Nitrogen Fertilizer at Different Stages of Growth on Yield and Yield Components of Rice

In this study, effects of nitrogen (N) fertilizer at different levels and irrigation interval at different growth stages of Hashemi rice were investigated on the yield and yield components in a factorial experiment based on a randomized complete block design with three replications during the crop years 2017 and 2018 in the Rice Research Institute of Iran, Rasht City. Studied factors were irrigation intervals (permanent waterlogging and irrigation once a week and once every 2 weeks) and different levels of N fertilizer (40, 60, and 80 kg ha-1 ) in both vegetative and reproductive stages. The studied traits were plant height, panicle length, number of panicles per plant, number of spikelet per main cluster, number of full grains per panicle, panicle fertility percentage, number of empty grains per panicle, 1000-grain weight, and grain yield. Results of the analysis of variance table showed that grain yield (GY) was significantly influenced by simple and interaction effects of the experimental treatments. The interactions of growth period, N fertilizer, and irrigation cycle were significant on this trait at a level of 1% during the two years. Grain yield and yield components increased significantly with N fertilizer application under optimal irrigation conditions. Among the treatments, the highest and lowest GYs belonged to the waterlogged irrigation treatment with 80 kg ha-1 of N fertilizer in the vegetative period in 2018 and irrigation treatment of once every 14 days with 40 kg ha-1 of N fertilizer in the reproductive period in 2017, respectively. In the presence of sufficient water, nitrogen plays an undeniable role in the yield. Although equal nitrogen use and management of permanent waterlogged irrigation and irrigation intervals have no effects on the yield, higher water use strongly reduces water use efficiency.