Pedosphere 15(5): 554--562, 2005
ISSN 1002-0160/CN 32-1315/P
©2005 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Changes in soil C and N contents and mineralization across a cultivation chronosequence of paddy fields in subtropical China |
LI Zhong-Pei1 , ZHANG Tao-Lin1, HAN Feng-Xiang2 and P. FELIX-HENNINGSEN3 |
1 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China). E-mail: zhpli@issas.ac.cn;
2 Diagnostic Instrumentation and Analysis Laboratory, Mississippi State University, Starkville MS 39759 (USA);
3 Institute of Soil Science and Soil Conservation, Justus-Liebig-University, Giessen D-35392 (Germany) |
| ABSTRACT |
| Dynamics of soil organic matter in a cultivation chronosequence of paddy fields were studied in subtropical China. Mineralization of soil organic matter was determined by measuring CO2 evolution from soil during 20 days of laboratory incubation. In the first 30 years of cultivation, soil organic C and N contents increased rapidly. After 30 years, 0-10 cm soil contained 19.6 g kg-1 organic C and 1.62 g kg-1 total N, with the corresponding values of 18.1 g kg-1 and 1.50 g kg-1 for 10-20 cm, and then remained stable even after 80 years of rice cultivation. During 20 days incubation the mineralization rates of organic C and N in surface soil (0-10 cm) ranged from 2.2% to 3.3% and from 2.8% to 6.7%, respectively, of organic C and total N contents. Biologically active C size generally increased with increasing soil organic C and N contents. Soil dissolved organic C decreased after cultivation of wasteland to 10 years paddy field and then increased. Soil microbial biomass C increased with number of years under cultivation, while soil microbial biomass N increased during the first 30 years of cultivation and then stabilized. After 30 years of cultivation surface soil (0-10 cm) contained 332.8 mg kg-1 of microbial biomass C and 23.85 mg kg-1 of microbial biomass N, which were 111% and 47% higher than those in soil cultivated for 3 years. It was suggested that surface soil with 30 years of rice cultivation in subtropical China would have attained a steady state of organic C content, being about 19 g kg-1. |
| Key Words: cultivation chronosequence, mineralization, paddy fields, soil C, soil N |
| Citation: Li, Z. P., Zhang, T. L., Han, F. X. and Felix-henningsen, P. 2005. Changes in soil C and N contents and mineralization across a cultivation chronosequence of paddy fields in subtropical China. Pedosphere. 15(5): 554-562. |
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