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Effects of cropping patterns on the content, composition and migration of soluble nitrogen in cropland soil in karst region.

YANG Cheng1*, MENG Fan-fei1, PENG Yan1, CUI Li-fang1, LIU Tao-ze2, LUO Xu-qiang3   

  1. (1College of Eco-Environmental Engineering, Guizhou Minzu University, Guiyang 550025, China; 2State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China; 3School of Geography and Resources, Guizhou Education University, Guiyang 550018, China).
  • Online:2019-10-10 Published:2019-10-10

Abstract: We examined the effects of six different cropping patterns on the content, composition and migration of soluble nitrogen in cropland soils in Guizhou karst region. The results showed that the contents of soil soluble inorganic nitrogen (SIN),  soluble organic nitrogen (SON) and  soluble total nitrogen (TSN) ranged from 3.75 to 95.15 mg·kg-1, 21.17 to 155.91 mg·kg-1 and 28.76 to 188.95 mg·kg-1, with a mean value of 26.49, 59.76 and 86.25 mg·kg-1, respectively. The contents of SIN under different cropping patterns were as the following order: chive-ginger rotation land> chive-maize rotation land> chive-waterlogged and fallowed land> chive-chive continuous cultivation land> chivefallowed land> chive-rice rotation land. For SON, the order was: chive-chive continuous cultivation land> chive-ginger rotation land> chive-maize rotation land> chivewaterlogged and fallowed land> chive-fallowed land> chive-rice rotation land. For TSN, the order was: chive-ginger rotation land> chive-chive continuous cultivation land> chive-maize rotation land> chive-waterlogged and fallowed land> chive-fallowed land> chive-rice rotation land. SON and NH4+-N were the main components of soil soluble nitrogen. The SON/TSN ratios were more than 60%, with the highest of 82.4%. The contents of SIN and SON decreased with soil depth at 0-60 cm layers. Our results indicate that cropping patterns have significant impacts on the content and composition of soluble nitrogen in cropland soil. SON is the major form of nitrogen loss from cropland soil, which should be paid attention to.

Key words: alkaline fertilizer, Cd pollution, rice, Cd concentration of rice.