The study looked at how different amounts of nitrogen fertilizer affect the yield of different rice varieties. They tested four levels of nitrogen and three rice types in Iran. Results showed that increasing nitrogen led to higher seed yield and nitrogen in the plants, but lower nitrogen recovery efficiency. One rice type, Khazar, had the best results with high yield and efficient nitrogen use. Overall, growing Khazar rice with 90 kg of nitrogen per hectare gave the best production with the least nitrogen waste.