Rice is staple diet for more than fifty percent of the world population and nitrogen (N) deficiency is one of the major yields limiting constraints in most of the rice producing soils around the world. The lowland rice N recovery efficiency is <50% of applied fertilizers in most agro-ecological regions. The low N efficiency is associated with losses caused by leaching, volatilization, surface runoff, and denitrification. Hence, improving N use efficiency is crucial for higher yields, low cost of production, and reduced environmental pollution. Adequate N supplies, as crop demands is one of the most effective practices for improving N use efficiency. Based on experimental results, on an average, the N rate for maximum economic rice yield (6500 to 7000 kg ha-1) varied from 90 to 140 kg ha-1. The application timing also varied from total required amount applied at sowing to split in up to two or three applications during crop growth cycle. However, most appropriate or economic results could be expected when half of the required N is applied at sowing and remaining half at active or mid-tillering growth stage. The N applied at booting and flowering did not improve grain yield. Urea and ammonium sulfate are dominant N sources of N for annual crops, including rice, especially in developing countries. Results obtained under field and greenhouse conditions show that ammonium sulfate is better source of N for lowland rice compared to urea under Brazilian conditions.