Pedosphere 20(2): 261--272, 2010
ISSN 1002-0160/CN 32-1315/P
©2010 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Dynamics of nitrogen speciation in horticultural soils in suburbs of Shanghai, China
GE Ti-Da1,2,3, HUANG Dan-Feng1, P. ROBERTS2, D. L. JONES2 and SONG Shi-Weisup>1
1 School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 201101 (China)
2 School of the Environment and Natural Resources, University of Wales, Bangor, Gwynedd LL57 2UW (UK)
3 Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan 410125 (China)
      Dissolved organic nitrogen (DON) represents a significant pool of soluble nitrogen (N) in soil ecosystems. Soil samples under three different horticultural management practices were collected from the Xiaxiyang Organic Vegetable and Fruit Farm, Shanghai, China, to investigate the dynamics of N speciation during 2 months of aerobic incubation, to compare the effects of different soils on the mineralization of 14C-labeled amino acids and peptides, and to determine which of the pathways in the decomposition and subsequent ammonification and nitrification of organic N represented a significant blockage in soil N supply. The dynamics of N speciation was found to be significantly affected by mineralization and immobilization. DON, total free amino acids, and NH4+-N were maintained at very low levels and did not accumulate, whereas NO3--N gradually accumulated in these soils. The conversion of insoluble organic N to low-molecular-weight (LMW) DON represented a main constraint to N supply, while conversions of LMW DON to NH4+-N and NH4+-N to NO3--N did not. Free amino acids and peptides were rapidly mineralized in the soils by the microbial community and consequently did not accumulate in soil. Turnover rates of the additional amino acids and peptides were soil-dependent and generally followed the order of organic soil > transitional soil > conventional soil. The turnover of high-molecular-weight DON was very slow and represented the major DON loss. Further studies are needed to investigate the pathways and bottlenecks of organic N degradation.
Key Words:  amino acids, dissolved organic N, mineralization, N transformation, peptides
Citation: Ge, T. D., Huang, D. F., Roberts, P., Jones, D. L. and Song, S. W. 2010. Dynamics of nitrogen speciation in horticultural soils in suburbs of Shanghai, China. Pedosphere. 20(2): 261-272.
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