Abstract:Taking the rice vatieties of Jinyou 253 and Guihan 1 as the material, pot experiments were conducted to evaluate the differences of nitrogen utilization by rice using 15N tracer techniques in the early and late seasons of 2008. Experiment was carried out under three water management modes (Wetting irrigation, alternation irrigation and water layer irrigation) and two soil tillages patterns (no tillage and conventional tillage). The results showed that: (1) Wetting irrigation reduced the nitrogen uptake from fertilizer by rice plants under both soil tillage patterns, and the differences were significant for the basal and tillering fertilization. (2) More nitrogen from fertilizer was absorbed by rice plants and less was reserved in soil under wetting irrigation condition. (3) Nitrogen uptake by rice plants under wetting irrigation condition was obvious lower than that of rice with alternation or water layer irrigation under the conventional tillage pattern, but the influence of wetting irrigation on nitrogen uptake was less under no tillage pattern. (4) Grain yield and nitrogen grain production efficiency were reduced under Wetting irrigation condition.