Pedosphere 17(4): 445--456, 2007
ISSN 1002-0160/CN 32-1315/P
©2007 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Nitrogen runoff and leaching losses during rice-wheat rotations in taihu lake region,China
TIAN Yu-Hua1,2, YIN Bin1, YANG Lin-Zhang1, YIN Shi-Xue3 and ZHU Zhao-Liang1
1 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing 210008 (China). E-mail: yhtian@issas.ac.cn
2 Graduate College of the Chinese Academy of Sciences, Beijing 100049 (China)
3 College of Environmental Science and Engineering, Yangzhou University, Yangzhou 225009 (China)
ABSTRACT
      Although nitrogen (N) loss through runoff and leaching from croplands is suspected to contribute to the deterioration of surrounding water systems, there is no conclusive evidence for paddy soils to prove this hypothesis. In this study, field plot experiments were conducted to investigate N losses through runoff and leaching for two consecutive years with 3 N fertilization rates in rice (Oryza sativa L.) -wheat (Triticum aestivum L.) rotations in the Taihu Lake region, China. A water collection system was designed to collect runoff and leachates for both the rice and wheat seasons. Results showed that dissolved N (DN), rather than particulate N (PN), was the main form of N loss by runoff. The NO3--N concentration in runoff was between 0.1 and 43.7 mg L-1, whereas the NH4+-N concentration ranged from below detection limit to 8.5 mg L-1. Total N (TN) loads by runoffwere 1.0-17.9 and 5.2-38.6 kg ha-1 during rice and wheat seasons, respectively, and the main loss occurred at the early growing stage of the crops. Nitrogen concentrations in leachates during the rice seasons were below 1.0 mg L-1 and independent of the N application rate, whereas those during the wheat season increased to 8.2 mg L-1 and were affected by the fertilizer rate. Annual losses of TN through runoff and leaching were 13.7-48.1 kg ha-1 from the rice-wheat cropping system, accounting for 5.6%-8.3% of the total applied N. It was concluded that reduction in the N fertilization rate, especially when the crop was small in biomass, could lower the N pollution potential for water systems.
Key Words:  leaching, N fertilization rate, N loss, paddy soil, runoff
Citation: Tian, Y. H., Yin, B., Yang, L. Z., Yin, S. X. and Zhu, Z. L. 2007. Nitrogen runoff and leaching losses during rice-wheat rotations in taihu lake region,China. Pedosphere. 17(4): 445-456.
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