Pedosphere 17(6): 721--731, 2007
ISSN 1002-0160/CN 32-1315/P
©2007 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Groundwater contamination with NO3-N in a wheat-corn cropping system in the North China Plain |
ZHAO Bing-Zi1, ZHANG Jia-Bao1 , M. FLURY2, ZHU An-Ning1, JIANG Qi-Ao1 and BI Jin-We1 |
1 State Experimental Station for Agro-Ecology, State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2 Department of Crop and Soil Sciences, Center for Multiphase Environmental Research, Washington State University, Pullman, WA 99164 (USA) |
| ABSTRACT |
| The North China Plain, where summer corn (Zea mays L.) and winter wheat (Triticum aestivum L.) are the major crops grown, is a major agricultural area in China. Permeable soils make the region susceptible to groundwater pollution by NO3-N, which is applied to fields in large amounts of more than 400 kg NO3-N ha-1as fertilizer. A field experiment was established in 2002 to examine the relationship among N fertilization rate, soil NO3-N, and NO3-N groundwater contamination. Two adjacent fields were fertilized with local farmers' N fertilization rate (LN) and double the normal application rate (HN), respectively, and managed under otherwise identical conditions. The fields were under a traditional summer corn/winter wheat rotation. Over a 22-month period, we monitored NO3-N concentrations in both bulk soil and soil pore water in 20-40 cm increments up to 180 cm depth. We also monitored NO3-N concentrations in groundwater and the depth of the groundwater table. No significant differences in soil NO3-N were observed between the LN and HN treatment. We identified NO3-N plumes moving downward through the soil profile. The HN treatment resulted in significantly higher groundwater NO3-N, relative to the LN treatment, with groundwater NO3-N consistently exceeding the maximum safe level of 10 mg L-1, but groundwater NO3-N above the maximum safe level was also observed in the LN treatment after heavy rain. Heavy rain in June, July, and August 2003 caused increased NO3-N leaching through the soil and elevated NO3-N concentrations in the groundwater. Concurrent rise of the groundwater table into NO3-Nrich soil layers also contributed to the increased NO3-N concentrations in the groundwater. Our results indicate that under conditions of average rainfall, soil NO3-N was accumulated in the soil profile. The subsequent significantly higherthan-average rainfalls continuously flushed the soil NO3-N into deeper layers and raised the groundwater table, which caused continuous groundwater contamination with NO3-N. The results suggest that under common farming practices in the North China Plain, groundwater contamination with NO3-N was likely, especially during heavy rainfalls, and the degree of groundwater contamination appeared to be proportional to the N application rates. Decreasing fertilization rates, splitting fertilizer inputs, and optimizing irrigation scheduling had potential to reduce groundwater NO3-N contamination. |
| Key Words: field experiment, groundwater contamination, NO3-N, wheat-corn cropping system |
| Citation: Zhao, B. Z., Zhang, J. B., Flury, M., Zhu, A. N., Jiang, Q. A. and Bi, J. W. 2007. Groundwater contamination with NO3-N in a wheat-corn cropping system in the North China Plain. Pedosphere. 17(6): 721-731. |
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