Abstract:

【objective】 It is of great importance to study the effect of different water and nitrogen management strategies on the nitrogen balance and nitrate movement in soil profile. 【Method】 In a field experiment, the nitrogen balance and nitrate movement in soil profile of conventional irrigation + conventional N application, optimized irrigation + conventional N application, conventional irrigation + optimized N application, optimized irrigation + optimized N application were studied. 【Result】 The result showed that the optimized irrigation and fertilization strategy based on soil nitrate quick testing and soil moister measurement could dramatically reduce N losses from 163-294 kg?hm-2 to 19-87 kg?hm-2. Under conventional treatment, nitrate accumulation were greatly increasing in 60-200 cm soil profile after harvesting, and the ratio of nitrate accumulation amount to apparent N losses within 0.39-0.69. According to the results of nitrate movement process, nitrate accumulation become evident in soil profile of conventional N application, but not evident in optimized one. 【Conclusion】 Apparent N losses can be 52%-68% in conventional N application system, nitrate leaching out of root layer is one of important loss way. Optimized N application system in this experiment can dramatically reduce nitrate leaching.

Key words: cotton, nitrogen, water, nitrogen balance, nitrate