The Effect of Combined Use of Nitrogen Fertilizer and Seaweed on Yield Components and Grain Yield of Rice (Oryza sativa L.) Variety Hashemi

IntroductionRice (Oryza sativa L.) is the staple food of half of the world's population, providing 21% of the energy and 15% of the protein of residents of rice-growing regions. Compared to other essential elements, rice needs more nitrogen. Therefore, for higher plant growth and productivity, nitrogen is used excessively. Nitrogen plays a vital role in the growth and development of rice and is an important part of enzymes, chlorophyll, nucleic acids, storage proteins, cell walls, and other cellular components. Excessive nitrogen application has resulted in many adverse effects such as increased nitrogen oxide emissions, reduced nitrogen use efficiency (NUE), and poor economic returns. Combining chemical fertilizers with biological and organic fertilizers is one of the ways to reduce the excessive consumption of chemical fertilizers. The use of seaweed as fertilizer in recent years has led to an increase in the quantity and quality of agricultural products due to its bioactive compounds. The purpose of this experiment was to investigate the effect of different levels of nitrogen fertilizer and seaweed foliar application on yield components, biomass, and grain yield of Hashemi rice cultivar in the Rudsar region.Materials and MethodsIn order to determine the appropriate level of nitrogen fertilizer and seaweed extract on the yield and yield components of Hashemi cultivar, an experiment was conducted, in Kishakjan village, Rudsar city, in Guilan province in 2022 and 2023. The experiment used the split plots in the form of randomized complete block design with three replications, the main factor being nitrogen fertilizer from the urea source at five levels (zero (control: without fertilizer use), 25, 50, 75 and 100 percent of nitrogen needed by the plant) and the sub factor of foliar spraying of fertilizer containing seaweed extract at four levels (zero (control: without seaweed use), 0.5, 1 and 1.5 liters per hectare) were considered.Results and DiscussionThe results showed that the application of nitrogen fertilizer levels and seaweed foliar application was significant on the investigated characteristics. So that the highest number of chlorophyll content (35), spike length (29.3 cm), thousand grain weight (26.3 g), grain yield (4014 kg ha-1), biological yield (7690.8 kg ha-1) and the harvest index (59.5%) was obtained in the application of 75% nitrogen fertilizer. In addition, the highest amount of the characteristics expressed in foliar spraying of seaweed fertilizer with a concentration of 1 lit ha-1 was obtained, which was not significantly different from the concentration of 1.5 1 lit h-1. The results of the interaction of experimental treatments also showed that the highest plant height (150 cm), the number of spike (29), the number of full seeds (132.4), respectively, were related to the application of 100% nitrogen fertilizer* 1 lit ha-1 of seaweed and 75% nitrogen fertilizer* 1 lit ha-1 of seaweed. The lowest number of unfilled seeds (4.2) and percentage of unfilled seeds (3.5) were recorded for the application of 75% nitrogen fertilizer*no use of seaweed fertilizer and 75% nitrogen fertilizer*1 lit ha-1of seaweed fertilizer, respectively.ConclusionNowadays, due to the high environmental and economic costs of chemical fertilizers, the use of fertilizers of biological and organic origin has received more attention than ever before. Based on the results of this study, foliar application of seaweed fertilizer in combination with nitrogen fertilizer significantly increased plant height, number of panicles, number of grain per panicle, and number of full grain per panicle. Nitrogen fertilizer application and foliar application of seaweed extract also increased chlorophyll content, panicle length, and 1000-grain weight, improving paddy yield and biological yield of Hashemi rice cultivar. In general, foliar application of one liter per hectare of seaweed and use of 50 and 75% nitrogen fertilizer was the best treatment to increase yield and yield components of Hashemi variety in the study region.