Pedosphere 25(1): 93--102, 2015
ISSN 1002-0160/CN 32-1315/P
©2015 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Dissolved organic nitrogen leaching from rice-wheat rotated agroecosystem in southern China
SONG Ge1,2,3, ZHAO Xu1,2, WANG Shen-Qiang1,2, XING Guang-Xi1 and ZHU Zhao-Liang1
1State Key Laboratory of Soil and Sustainable Agriculture, Changshu National Agro-Ecosystem Observation and Research Station, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2University of Chinese Academy of Sciences, Beijing 100049 (China)
      The rice-wheat rotation in southern China is characterized by frequent flooding-draining water regime and heavy nitrogen (N) fertilization. There is a substantial lack of studies into the behavior of dissolved organic nitrogen (DON) in the intensively managed agroecosystem. A 3-year in situ field experiment was conducted to determine DON leaching and its seasonal and yearly variations as affected by fertilization, irrigation and precipitation over 6 consecutive rice/wheat seasons. Under the conventional N practice (300 kg N ha-1 for rice and 200 kg N ha-1 for wheat), the seasonal average DON concentrations in leachate (100 cm soil depth) for the three rice and wheat seasons were 0.6–1.1 and 0.1–2.3 mg N L-1, respectively. The cumulative DON leaching was estimated to be 1.1–2.3 kg N ha-1 for the rice seasons and 0.01–1.3 kg N ha-1 for the wheat seasons, with an annual total of 1.1–3.6 kg N ha-1. In the rice seasons, N fertilizer had little effect (P > 0.05) on DON leaching; precipitation and irrigation imported 3.6–9.1 kg N ha-1 of DON, which may thus conceal the fertilization effect on DON. In the wheat seasons, N fertilization had a positive effect (P < 0.01) on DON. Nevertheless, this promotive effect was strongly influenced by variable precipitation, which also carried 1.8–2.9 kg N ha-1 of DON into fields. Despite a very small proportion to chemical N applied and large variations driven by water regime, DON leaching is necessarily involved in the integrated field N budget in the rice-wheat rotation due to its relatively greater amount compared to other natural ecosystems.
Key Words:  irrigation, N fertilization, paddy soil, precipitation, seasonal variation
Citation: Song, G., Zhao, X., Wang, S. Q., Xing, G. X. and Zhu, Z. L. 2015. Dissolved organic nitrogen leaching from rice-wheat rotated agroecosystem in southern China. Pedosphere. 25(1): 93-102.
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