Pedosphere 17(5): 568--579, 2007
ISSN 1002-0160/CN 32-1315/P
©2007 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Paddy soil stability and mechanical properties as affected by long-term application of chemical fertilizer and animal manure in subtropical China
LI Jiang-Tao1,2 and ZHANG Bin2
1 School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093 (China). E-mail: ljt7694@126.com
2 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
ABSTRACT
      Wet stability, penetration resistance (PR), and tensile strength (TS) of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization (CK), normal chemical fertilization (NPK), double the NPK application rates (2NPK), and NPK mixed with organic manure (NPK+OM). Compared with CK, fertilization increased soil organic carbon (SOC) and soil porosity. The results of soil aggregate fragmentation degree (SAFD) showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK+OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter (NMWD) (P ≤ 0.05), but the lowest PR and TS in both cultivated horizon (Ap) and plow pan. The CK and 2NPK treatments were measured with PR > 2.0 MPa and friability index < 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.
Key Words:  soil aggregate stability, chemical fertilization, organic matter, penetration resistance, tensile strength
Citation: Li, J. T. and Zhang, B. 2007. Paddy soil stability and mechanical properties as affected by long-term application of chemical fertilizer and animal manure in subtropical China. Pedosphere. 17(5): 568-579.
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