Pedosphere 9(2): 185--188, 1999
ISSN 1002-0160/CN 32-1315/P
©1999 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Difficultly extractable fixed ammonium in some soils of China |
| CHEN Bi-Yun, CHENG Li-Li and WEN Qi-Xiao |
| Institute of Soil Science, the Chinese Academy of Sciences, Nanjing 210008 (China) |
| ABSTRACT |
| Ninety-three soil samples and 19 sedimentary rock samples collected from 21 provinces of China were analyzed for their contents of fixed ammonium and total N by Kjeldahl-HF method. Results showed that amount of difficultly extractable fixed ammonium (the fixed ammonium that is not determinable by Kjeldahl procedures commonly used for soils) in soils ranged from 0 to 202 mg kg-1. It was generally more than 50 mg kg-1 in soils in Changji and Turpan districts, Xinjiang, accounting for 3.2%~36.8% with an average of 13.9% of the total N. For some Orthents derived from purple shale and purple sandstone in Sichuan and Hunan provinces and Chao soils derived from secondary loess in Henan Province and Ningxia Autonomous Region it was generally around 30 mg kg-1, accounting for 4%~7% of the total soil N, and for most of the rest of soils studied, with the exception of some subsoils, no or trace difficultly extractable fixed ammonium could be detected. It was suggested that the difficultly extractable fixed ammonium was originated from parent rock, and for slightly weathered soils derived from parent materials rich in this form of N the Kjeldahl method might give underestimation of total soil N. |
| Key Words: difficultly extractable fixed ammonium, fixed ammonium, parent rock |
| Citation: Chen, B. Y., Cheng, L. L. and Wen, Q. X. 1999. Difficultly extractable fixed ammonium in some soils of China. Pedosphere. 9(2): 185-188. |
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