Pedosphere 13(4): 367--374, 2003
ISSN 1002-0160/CN 32-1315/P
©2003 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Nitrate accumulation in soil profile of dry land farming in northwest China |
FAN Jun1 , HAO Ming-De1 and SHAO Ming-An |
| State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, the Chinese Academy of Sciences, Yangling 712100 (China). E-mail: erfan0278@sina.com |
| ABSTRACT |
| A long-term fertilizer experiment on dry land of the Loess Plateau, northwest China, has been conducted since 1984 to study the distribution and accumulation of NO3-N down to a depth of 400 cm in the profile of a coarse-textured dark loessial soil after continuous winter wheat cropping. Thirteen fertilizer treatments consisted of four levels of N and P applied alone or in combination. Annual N and P (P2O5) rates were 0, 45, 90, 135 and 180 kg ha-1. After 15 successive cropping cycles, the soil samples were taken from each treatment for analysis of NO3-N concentration. The results showed that NO3-N distribution in the soil profile was quite different among the treatments. The application of fertilizer N alone resulted in higher NO3-N concentration in the soil profile than the combined application of N and P, showing that application of P could greatly reduce the NO3-N accumulation. With an annual application of 180 kg N ha-1 alone, a peak in NO3-N accumulation occurred at 140 cm soil depth, and the maximum NO3-N concentration in the soils was 67.92 mg kg-1. The amount of NO3-N accumulated in the soil profile decreased as the cumulative N uptake by the winter wheat increased. Application of a large amount of N resulted in lower N recoveries in winter wheat and greater NO3-N accumulation in soil profile. NO3-N did not enter underground water in the study region; therefore, there is no danger of underground water pollution. Amount of NO3-N accumulation can be predicted by an equation according to annual N and P rates based on the results of this experiment. |
| Key Words: dry land, long-term fertilizer experiment, NO3-N accumulation, wheat |
| Citation: Fan, J., Hao, M. D. and Shao, M. A. 2003. Nitrate accumulation in soil profile of dry land farming in northwest China. Pedosphere. 13(4): 367-374. |
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