Pedosphere 27(1): 112--120, 2017
ISSN 1002-0160/CN 32-1315/P
©2017 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Comparison of gross N transformation rates in two paddy soils under aerobic condition
LAN Ting1,2, HAN Yong2 and CAI Zu-Cong3
1College of Resources Science and Technology, Sichuan Agricultural University, Chengdu 611130 (China)
2State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
3School of Geography Science, Nanjing Normal University, Nanjing 210097 (China)
      Although to date individual gross N transformations could be quantified by 15N tracing method and models, studies are still limited in paddy soil. An incubation experiment was conducted using topsoil (0--20 cm) and subsoil (20--60 cm) of two paddy soils, alkaline and clay (AC) soil and neutral and silt loam (NSL) soil, to investigate gross N transformation rates. Soil samples were labeled with either 15NH4NO3 or NH415NO3, and then incubated at 25 oC for 168 h at 60% water-holding capacity. The gross N mineralization (recalcitrant and labile organic N mineralization) rates in AC soil were 1.6 to 3.3 times higher than that in NSL soil, and the gross N nitrification (autotrophic and heterotrophic nitrification) rates in AC soil were 2.4 to 4.4 times higher than those in NSL soil. Although gross NO3- consumption (i.e., NO3- immobilization and dissimilatory NO3- reduction to NH4+) rates increased with increasing gross nitrification rates, the measured net nitrification rate in AC soil was approximately 2.0 to 5.1 times higher than that in NSL soil. These showed that high NO3- production capacity of alkaline paddy soil should be a cause for concern because an accumulation of NO3- can increase the risk of NO3- loss through leaching and denitrification.
Key Words:  leaching, immobilization, mineralization, 15N tracing model, nitrification, NO3- loss
Citation: Lan, T., Han, Y. and Cai, Z. C. 2017. Comparison of gross N transformation rates in two paddy soils under aerobic condition. Pedosphere. 27(1): 112-120.
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