The level of water management influenced the efficiency of N-Urea fertilization for rice plants because rice plants could utilize only about 30-40% of the N fertilizer and the rest would be lost.The use of 15N isotope was one method to predict the movement of nitrogen from fertilizers. The objectives of this study were to study the dynamics of N nutrients in soil and plants with Nisotopes and to calculate the efficiency of water use in upland rice plants. This study used a Split Plot Design

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... the first factor level of water management and the second was N dose level. The N fertilizer was Urea fertilizer which was given an N15 tracer. P and K doses were determined based on soil nutrient status. The rice plants were Situpatenggang and DT15 Batan. The results of the study showed that soil water management with conventional irrigation was significantly better than cut irrigation. The maximum dose of N fertilizer in interrupted irrigation was reached at a dose of 228 kg/ha, and conventional irrigation doses reached 180 kg N/ha . Whereas the maximum dosage of N fertilizer in interrupted irrigation treatment was 198 kg/ha and conventional irrigation treatment was 159 kg N/ha.