Pedosphere 23(1): 59--69, 2013
ISSN 1002-0160/CN 32-1315/P
©2013 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Nitrate-nitrogen dynamics and nitrogen budgets in rice-wheat rotations in Taihu Lake region, China |
ZHANG Jun-Hua1,2, LIU Jian-Li1 , ZHANG Jia-Bao1, CHENG Ya-Nan1,3 and WANG Wei-Peng1,3 |
1 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2 State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006 (China)
3 University of Chinese Academy of Sciences, Beijing 100049 (China) |
| ABSTRACT |
| Nitrate-nitrogen (NO3--N) dynamics and nitrogen (N) budgets in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period. The experiment included four N rates for rice and wheat, respectively: N1 (125 and 94 kg N ha-1), N2 (225 and 169 kg N ha-1), N3 (325 and 244 kg N ha-1), and N0 (0 kg N ha-1). The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO3--N in sampled waters and the concentrations of NO3--N only showed a rising trend during the field drying stage. The NO3--N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons, particularly in the wheat seedling stage. In the wheat seedling stage, the NO3--N concentrations of leachates were significantly higher in N treatments than in N0 treatment and increased with increasing N rates. As the NO3--N content (below 2 mg N L-1) at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates, the high levels of NO3--N in the groundwater of paddy fields might not be directly related to NO3--N leaching. Crop growth trends were closely related to variations of NO3--N in leachates. A reduction in N application rate, especially in the earlier stages of crop growth, and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss. Above-ground biomass for rice and wheat increased significantly with increasing N rate, but there was no significant difference between N2 and N3. Increasing N rates to the levels greater than N2 not only decreased N use efficiency, but also significantly increased N loss. After two cycles of rice-wheat rotations, the apparent N losses of N1, N2 and N3 amounted to 234, 366 and 579 kg N ha-1, respectively. With an increase of N rate from N0 to N3, the percentage of N uptake in total N inputs decreased from 63.9% to 46.9%. The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore, the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall. |
| Key Words: above-ground biomass, Crop uptake, nitrate-nitrogen leaching, nitrogen mineralization, nitrogen transport |
| Citation: Zhang, J. H., Liu, J. L., Zhang, J. B., Cheng, Y. N. and Wang, W. P. 2013. Nitrate-nitrogen dynamics and nitrogen budgets in rice-wheat rotations in Taihu Lake region, China. Pedosphere. 23(1): 59-69. |
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