Pedosphere 21(4): 522--531, 2011
ISSN 1002-0160/CN 32-1315/P
©2011 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Impact of long-term alfalfa cropping on soil potassium content and clay minerals in a semi-arid loess soil in China |
LI De-Cheng 1, B. VELDE2, LI Feng-Min3, ZHANG Gan-Lin1, ZHAO Ming-Song1 and HUANG Lai-Ming1 |
1 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2 Laboratoire de Géologie, CNRS UMR 8538, Ecole Normal Supérieure, 24 rue Lhomond, 75231 Paris (France)
3 Ministry of Education Key Laboratory of Arid and Grassland Ecology, Lanzhou University, Lanzhou 730000 (China) |
| ABSTRACT |
| Alfalfa cropping has been considered an efficient method of increasing soil fertility. Usually nitrogen increase in root nodules is considered to be the major beneficial effect. A 21-year time series (five sampling periods) of alfalfa cultivation plots on a loess soil, initially containing illite and chlorite, in Lanzhou of northwestern China was selected to investigate the relationships among alfalfa cropping, soil potassium (K) content and soil clay minerals. The results indicated that soil K significantly accumulated after cropping, with a peak value at about 15 years, and decreased afterwards. The accumulated K was associated with the K increase in the well-crystallized illite, which was not extracted by the traditional laboratory K extraction methods in assessing bioavailability. The steep decline in soil K content after 15-year cropping was in accord with the observed fertility loss in the alfalfa soil. Plant biomass productivity peaked at near 9 years of culture, whereas soil K and clay minerals continued to increase until cropping for 15 years. This suggested that K increased in the topsoil came from the deep root zone. Thus alfalfa continued to store K in clays even after peak production occurred. Nitrogen did not follow these trends, showing a general decline compared with the native prairie soils that had not been cropped. Therefore, the traditional alfalfa cropping can increase K content in the topsoil. |
| Key Words: illite, prairie soil, soil fertility |
| Citation: Li, D. C., Velde, B., Li, F. M., Zhang, G. L., Zhao, M. S. and Huang, L. M. 2011. Impact of long-term alfalfa cropping on soil potassium content and clay minerals in a semi-arid loess soil in China. Pedosphere. 21(4): 522-531. |
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