Pedosphere 20(2): 209--216, 2010
ISSN 1002-0160/CN 32-1315/P
©2010 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Nitrate and ammonium leaching in variable- and permanent-charge paddy soils
XIONG Zheng-Qin1,2, HUANG Tai-Qing1, MA Yu-Chun1, XING Guang-Xi2 and ZHU Zhao-Liang2
1 College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095b (China)
2 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
ABSTRACT
      A variable-charge (VC) and a permanent-charge paddy soil (PC) were selected to study nitrate-N (NO3--N) and ammonium-N (NH4+-N) leaching with N isotopes for one consecutive year. An irrigation and intermittent drainage pattern was adopted to mimic natural occurrence of rainfall during the upland crop season and drainage management during the flooded rice season. Treatments to each soil type were no-N controls (CK), 15N-labeled (NH4)2SO4 (NS), and milk vetch (NV) applied at a rate equivalent to 238 kg N ha-1 to unplanted lysimeters, totaling six treatments in triplicates. Results indicated that the soil type dominated N leaching characteristics. In the case of PC, NO3--N accounted for 78% of the total leached inorganic N;NS was prone to leach three times more than the NV, being 8.2% and 2.4% of added 15N respectively;and > 85% of leached NO3--N came from native N in the soil. In the case of VC, NH4+-N made up to 92% of the total inorganic N in leachate. Moreover, NH4+-N leaching was detected throughout the whole incubation, and was particularly high during the flooded season. NO3--N leaching in VC occurred later at a lower rate compared to that in PC. The findings of this study indicate that NO3--N leaching during the drained season in permanent-charge paddy soils and NH4+-N leaching in variable-charge soils deserve more attention for regional environmental control.
Key Words:  drained/flooded rotations, fertilizer-derived nitrate, ion movement, lysimeter, 15N tracing technique
Citation: Xiong, Z. Q., Huang, T. Q., Ma, Y. C., Xing, G. X. and Zhu, Z. L. 2010. Nitrate and ammonium leaching in variable- and permanent-charge paddy soils. Pedosphere. 20(2): 209-216.
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